U.S. patent application number 11/239557 was filed with the patent office on 2006-06-08 for media servowriting system.
Invention is credited to Matt Bellis, Tom Carr, Harald Hess, Dan L. Kilmer, Patrick Rodney Lee, Alex Moraru, Gustavo A. Pinto, Franklin Tao, Teodor Zanetti, Jun Zhu.
Application Number | 20060119977 11/239557 |
Document ID | / |
Family ID | 28675313 |
Filed Date | 2006-06-08 |
United States Patent
Application |
20060119977 |
Kind Code |
A1 |
Zhu; Jun ; et al. |
June 8, 2006 |
Media servowriting system
Abstract
A system and methods for efficiently performing media writing
functions is disclosed. The system and methods include: detecting
media movement with respect to a base and heads during reading and
writing, and moving the heads in response; using an interferometer,
such as a dual beam differential interferometer, to dynamically
monitor disk position and address perceived errors; and minimizing
repeatable and non repeatable runout error by writing data, such as
servo bursts, in multiple revolutions to average adverse runout
conditions. The present system has the ability to use an
interferometer to enhance media certification and perform on line,
in situ monitoring of the media, and includes shrouding, head
mounting, disk biasing, and related mechanical aspects beneficial
to media writing.
Inventors: |
Zhu; Jun; (Palo Alto,
CA) ; Moraru; Alex; (Aptos, CA) ; Zanetti;
Teodor; (Sunnyvale, CA) ; Tao; Franklin;
(Union City, CA) ; Kilmer; Dan L.; (Seiad Valley,
CA) ; Hess; Harald; (La Jolla, CA) ; Carr;
Tom; (Leucadia, CA) ; Bellis; Matt; (Santa
Rosa, CA) ; Pinto; Gustavo A.; (Belmont, CA) ;
Lee; Patrick Rodney; (San Diego, CA) |
Correspondence
Address: |
SMYRSKI LAW GROUP, A PROFESSIONAL CORPORATION
3310 AIRPORT AVENUE, SW
SANTA MONICA
CA
90405
US
|
Family ID: |
28675313 |
Appl. No.: |
11/239557 |
Filed: |
September 28, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10395051 |
Mar 22, 2003 |
6977791 |
|
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11239557 |
Sep 28, 2005 |
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60367046 |
Mar 23, 2002 |
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Current U.S.
Class: |
360/77.03 ;
360/31; 360/75; G9B/5.222 |
Current CPC
Class: |
G11B 5/59633
20130101 |
Class at
Publication: |
360/077.03 ;
360/075; 360/031 |
International
Class: |
G11B 5/596 20060101
G11B005/596; G11B 21/02 20060101 G11B021/02; G11B 27/36 20060101
G11B027/36 |
Claims
1. A method for tracking and controlling media read/write
characteristics, comprising: creating media having a predetermined
expected baseline configuration; reading said media having the
predetermined expected baseline configuration; determining whether
said media has moved from an expected position based on the media
reading of the predetermined expected baseline condition; and
correcting data hardware based on determining whether said media
has moved from said expected position.
2. The method of claim 1, wherein said predetermined baseline
configuration comprises media organization structure.
3. The method of claim 2, wherein media organization structure
comprises data track structure and said media is a computer hard
disk.
4. The method of claim 2, wherein media organization structure
comprises servo data track structure and said media is a computer
hard disk.
5. The method of claim 1, wherein said determining comprises
utilizing a non-contact radiation detection system interacting with
the media to detect alterations in the predetermined expected
baseline configuration and hardware coupled to said media.
6. The method of claim 1, said media having two sides, wherein said
reading comprises reading more than one side of the media.
7. The method of claim 1, wherein said correcting comprises
determining deviations in media position based on the predetermined
expected baseline condition and moving data hardware to align said
data hardware with the media.
8. A method for dynamically tracking and controlling errors in
media operation, comprising: producing an ideal disk using
patterning technology; and utilizing a non-contact radiation
detection system with said ideal disk to detect media movement;
wherein data from the media is fed back to hardware and/or software
to compensate for position errors during reading and/or writing to
the media.
9. The method of claim 8, wherein producing the ideal disk
comprises producing a disk having data track structure information
located thereon.
10. The method of claim 9, wherein producing the ideal disk
comprises using lithography methods.
11. The method of claim 9, wherein producing the ideal disk
comprises writing tracks using at least one electron beam.
12. The method of claim 9, wherein producing the ideal disk
comprises providing the ideal disk with a media organization
structure.
13. The method of claim 12, wherein media organization structure
comprises data track structure.
14. The method of claim 12, wherein media organization structure
comprises servo data track structure.
15. The method of claim 9, wherein said utilizing comprises
interacting with the ideal disk to detect alterations in the
patterning technology and hardware coupled to said ideal disk.
16. The method of claim 9, said ideal disk having two sides,
wherein said utilizing comprises reading from the two sides of the
ideal disk.
17. A method of dynamically tracking and controlling errors in
media operation, comprising: creating an ideal magnetic disk to
detect media movement; placing said ideal magnetic disk in
association with at least one other media; monitoring said ideal
magnetic disk for electromagnetic variations in media position; and
correcting hardware positioning based on said monitoring
results.
18. The method of claim 17, wherein creating the ideal disk
comprises producing an ideal disk having disk track structure
information located thereon.
19. The method of claim 17, wherein creating the ideal disk
comprises using lithography methods.
20. The method of claim 17, wherein creating the ideal disk
comprises writing tracks using at least one electron beam.
21. The method of claim 17, wherein creating the ideal disk
comprises providing the ideal disk with a media organization
structure.
22. The method of claim 17, wherein media organization structure
comprises data track structure.
23. The method of claim 17, wherein media organization structure
comprises servo data track structure.
24. The method of claim 17, wherein said monitoring comprises
employing non-contact methods to detect alterations in the
patterning technology and hardware coupled to the ideal disk.
25. The method of claim 17, said ideal disk having two sides,
wherein said monitoring comprises reading from the two sides of the
ideal disk.
26. In a system for writing to at least one magnetic disk, the
system comprising at least one head, a method for interfacing with
at least one magnetic disk comprising: creating at least one
reference medium comprising reference data; reading reference data
from the at least one reference medium using at least one head;
determining relative movement between the reference medium and the
head using reference data received from said reading; and reducing
relative movement in response to a determination of relative
movement between the reference medium and the head.
27. The method of claim 26, wherein said interfacing comprises
reading from the at least one magnetic disk.
28. The method of claim 26, wherein said interfacing comprises
writing to the at least one magnetic disk.
29. The method of claim 26, wherein creating comprises making a
reference magnetic disk and reading reference data comprises
reading magnetic reference data.
30. The method of claim 26, wherein creating comprises producing a
disk using one from a group comprising: patterning technology;
lithography; and writing using an electron beam.
31. The method of claim 30, wherein reading comprises one from the
group comprising: reflecting light energy from the disk; refracting
light energy; and transmitting light energy.
32. The method of claim 26, wherein reducing relative movement
comprises moving the spindle.
33. The method of claim 26, wherein reducing relative movement
comprises moving the head.
34. The method of claim 32, wherein moving the spindle comprises
one from a group comprising: using an air pulse to alter spindle
position; utilizing a mechanical centrifugal device; varying an
internal magnetic field within an electromotor associated with the
spindle; and varying an external magnetic field surrounding the
spindle.
35. The method of claim 33, wherein moving the head comprises one
from the group comprising: moving a tip of an arm attached to the
head, wherein each arm is jointed and has an individual actuator
associated therewith; and moving an arm attached to the head.
36. A method of dynamically tracking and controlling errors on
media disks, comprising: forming an ideal disk having predetermined
characteristics located thereon; and operating said ideal disk in
association with at least one media disk; wherein said operating
comprises determining whether said at least one media disk has
moved from an expected position based on reading the ideal disk and
the predetermined characteristics thereon.
37. The method of claim 36, wherein said predetermined
characteristics comprise media organization structure.
38. The method of claim 37, wherein media organization structure
comprises data track structure and said media disks are computer
hard disks.
39. The method of claim 37, wherein media organization structure
comprises servo data track structure and said media disks are
computer hard disks.
40. The method of claim 36, wherein said operating comprises
utilizing a non-contact radiation detection system interacting with
the media to detect alterations in the predetermined
characteristics and hardware coupled to at least one media
disk.
41. The method of claim 36, said ideal disk having two sides,
wherein said operating comprises reading more than one side of the
ideal disk.
42. The method of claim 36, further comprising correcting for
perceived errors, wherein said correcting comprises determining
deviations in media disk position based on the predetermined
expected baseline condition and moving data hardware to align said
data hardware with the media disk.
43. A method for minimizing likelihood of a head within a
servowriting apparatus contacting a disk located therein,
comprising: sensing sound intensity in a predetermined frequency
range from a first sensor positioned at a first location within the
servowriting apparatus; determining the existence of a pending head
crash based on the sound intensity; and moving an element of the
servowriting apparatus upon determining the existence of the
pending head crash.
44. The method of claim 43, wherein moving the element causes the
head to move away from the disk.
45. The method of claim 43, further comprising: additionally
sensing sound intensity from a second sensor positioned at a second
position within the servowriting apparatus.
46. A method of preserving disk integrity in a media servowriter,
comprising: receiving acoustic signals; identifying acoustic
signals falling within a predetermined range; assessing the
probability signals within the predetermined range constitute a
likely failure event; and retracting equipment within the
servowriter to prevent contact between devices within the
servowriter and the disk.
47. The method of claim 46, wherein said receiving acoustic signals
comprises receiving signals at a plurality of locations within the
media servowriter.
48. The method of claim 46, wherein said retracting equipment
causes a head to move away from a disk located within the media
servowriter.
49. The method of claim 46, wherein assessing comprises determining
whether at least one from a group of attributes is outside a
predetermined boundary, the group of attributes comprising:
amplitude; frequency; and intensity.
50. An apparatus for decreasing likelihood of a head contacting a
disk in a servowriting system, comprising: a sensor capable of
detecting a presence of sound intensity at a predetermined
intensity range; a computing device programmed to determine the
presence of an undesired event; and retraction apparatus for
retracting said head from said disk when the computing device
determines the presence of the undesired event.
51. The system of claim 50, further comprising at least one
additional listening device for detecting a presence of sound
intensity at a plurality of points within the system.
52. The system of claim 50, wherein the undesired event comprises
an impending head crash.
53. The system of claim 50, wherein the undesired event comprises a
head crash.
54. A method of preserving disk and head integrity in a media
servowriter, comprising: receiving sound signals falling within a
certain intensity range; determining whether the sound signals may
constitute a failure event; and retracting the head away from the
disk when the sound signals are determined to constitute the
failure event.
55. The system of claim 54, wherein said receiving comprises
detecting a presence of sound intensity at a plurality of points
within the media servowriter.
56. The system of claim 50, wherein the failure event comprises an
impending head crash.
57. The system of claim 50, wherein the failure event comprises a
head crash.
58. An apparatus for determining failure in connection with a
servowriting system, comprising: means for detecting sounds made by
the servowriting system; and means for determining whether detected
sounds constitute a servowriting system failure.
59. The apparatus of claim 58, wherein said detecting means
comprise an acoustical sensor.
60. The apparatus of claim 59, wherein the detecting means further
comprise an additional acoustical sensor positioned remotely from
the acoustical sensor.
61. The apparatus of claim 58, wherein said determining means
determine the presence of an impending head crash.
62. The apparatus of claim 58, wherein said determining means
determine the existence of a head crash.
63. The apparatus of claim 58, wherein the determining means
monitor at least one characteristic from a group comprising
amplitude, frequency, and intensity of the sounds, and wherein the
determining means determines the servowriting system failure when
the monitored characteristic performs outside a predetermined
expected value.
64. An apparatus for controlling airflow over rotating media,
comprising: at least one baffle covering the media, the at least
one baffle comprising at least one cavity shielding at least a
portion of the rotating media; wherein the at least one baffle
provides the ability to inhibit turbulent flow when the rotating
media rotates.
65. The apparatus of claim 64, wherein the apparatus operates and
rotating media rotates in the presence of a pressure reduced from
atmospheric pressure.
66. The apparatus of claim 64, wherein the apparatus operates and
rotating media rotates in the presence of vacuum conditions.
67. The apparatus of claim 64, further comprising a second baffle
covering the rotating media, wherein the two baffles shield
substantially all of the rotating media save for mechanical
components interacting with the rotating media.
68. The apparatus of claim 67, wherein each baffle contains a
plurality of cavities, the plurality of cavities corresponding to
the quantity of rotating media able to be placed in the
apparatus.
69. The apparatus of claim 64, further comprising media access
equipment and a second baffle, wherein said baffle, said second
baffle, and said media access equipment substantially shield the
rotating media.
70. An apparatus for controlling airflow over rotating media, said
rotating media associated with a head positioner, comprising: a
baffle arrangement shielding a non-insubstantial of the rotating
media formed such that head positioner hardware has access to a
non-insubstantial portion of the rotating media, said baffle
arrangement comprising at least one baffle having openings formed
to enclose individual rotating media therein.
71. The apparatus of claim 70, wherein the apparatus operates and
rotating media rotates in the presence of a pressure reduced from
atmospheric pressure.
72. The apparatus of claim 70, wherein the apparatus operates and
rotating media rotates in the presence of vacuum conditions.
73. The apparatus of claim 70, wherein the baffle arrangement
further comprises a second baffle covering the rotating media,
wherein the two baffles shield substantially all of the rotating
media save for the head positioner hardware interacting with the
rotating media.
74. The apparatus of claim 73, wherein each baffle contains a
plurality of cavities, the plurality of cavities corresponding to
the quantity of rotating media able to be placed in the
apparatus.
75. An apparatus for controlling airflow over rotating media, said
rotating media intermittently being in contact with at least one
head, said at least one head being associated with head maintaining
hardware, comprising: a shroud having at least one relief cut for
holding the at least one head and the head maintaining hardware
over the rotating media, wherein the shroud tends to decrease
airflow contacting the at least one head.
76. The apparatus of claim 75, wherein the apparatus operates and
rotating media rotates in the presence of a pressure reduced from
atmospheric pressure.
77. The apparatus of claim 75, wherein the apparatus operates and
rotating media rotates in the presence of vacuum conditions.
78. The apparatus of claim 75, further comprising a second shroud
covering the rotating media, wherein the two shrouds shield
substantially all of the rotating media save for the head
maintaining hardware interacting with the rotating media.
79. The apparatus of claim 78, wherein each shroud contains a
plurality of cavities.
80. The apparatus of claim 75, further comprising an additional
shroud, wherein the two shrouds cover the at least one head while
allowing for free operation of head maintaining hardware and
simultaneously enable reduced airflow over the rotating media.
81. An apparatus for controlling airflow over rotating media,
comprising: a plurality of baffles covering the rotating media,
each baffle comprising: a plurality of cavities, each cavity
covering at least a portion of a subset of the rotating media,
wherein the baffle and plurality of shrouds tend to inhibit
turbulent airflow during rotation of the rotating media.
82. The apparatus of claim 81, wherein the apparatus operates and
rotating media rotates in the presence of a pressure reduced from
atmospheric pressure.
83. The apparatus of claim 81, wherein the apparatus operates and
rotating media rotates in the presence of vacuum conditions.
84. The apparatus of claim 81, said plurality of baffles comprising
two baffles, wherein the two baffles shield substantially all of
the rotating media save for mechanical components interacting with
the rotating media.
85. The apparatus of claim 81, wherein the plurality of cavities
correspond to the quantity of rotating media able to be placed in
the apparatus.
86. A method for changing a head assembly employed in a media
writing device, comprising: providing a head mount assembly having
a bore passing therethrough; positioning the head assembly adjacent
the head mount; aligning the head assembly with the head mount; and
press fitting the head assembly to the head mount.
87. The method of claim 86, wherein the aligning comprises passing
a first relatively narrow device through the head assembly to fix
head assembly position.
88. The method of claim 87, wherein the aligning further comprises
passing a second relatively narrow device through the head assembly
and the bore of the head mount to align the head assembly with the
head mount.
89. The method of claim 86, wherein said positioning comprises
fixedly mounting the head mount to an assembly tool and locating
said head assembly adjacent to the fixedly mounted head mount.
90. The method of claim 89, wherein the press fitting comprises
compressing the assembly tool, thereby pressing the head assembly
against the fixedly mounted head mount.
91. The method of claim 89, wherein said assembly tool comprises a
plurality of sections, and said sections employ a spring to draw
said sections together and hold said head assembly and said fixedly
mounted head mount.
92. A method for replacing drive heads, comprising: abutting a head
maintenance arrangement to a mounting device, said head maintenance
arrangement having an ability to receive a drive head; and press
fitting the head maintenance arrangement to the mounting device
free of staking.
93. The method of claim 92, further comprising: removing the head
from the head maintenance arrangement prior to said abutting.
94. The method of claim 92, wherein said head maintenance
arrangement comprises a head assembly.
95. The method of claim 92, further comprising providing the
mounting device with a bore passing therethrough prior to said
abutting.
96. The method of claim 95, further comprising aligning the head
maintenance arrangement with the mounting device.
97. The method of claim 96, wherein the aligning comprises passing
a first relatively narrow device through the head maintenance
device to relatively fix head maintenance device position.
98. The method of claim 97, wherein the aligning further comprises
passing a second relatively narrow device through the head
maintenance device and the bore of the mounting device to align the
head maintenance device with the mounting device.
99. The method of claim 92, wherein said abutting comprises fixedly
mounting the mounting device to an assembly tool and locating said
head maintenance device adjacent to the fixedly mounted mounting
device.
100. The method of claim 99, wherein the press fitting comprises
compressing the assembly tool, thereby pressing the head
maintenance device against the fixedly mounted mounting device.
101. The method of claim 99, wherein said assembly tool comprises a
plurality of sections, and said sections employ a compression
device to draw said sections together and hold said head
maintenance device and said fixedly mounted mounting device.
102. A system for replacing a drive head in a media writer,
comprising: an assembly tool having a plurality of component parts;
a clamping device for receiving the assembly tool; a drive head
maintenance apparatus for maintaining the drive head; and a mount;
wherein the assembly tool has the ability to hold the drive head
maintenance apparatus adjacent the mount and the clamping device
has the ability to compress the assembly tool, thereby press
fitting the drive head maintenance apparatus to the mount.
103. The system of claim 102, further comprising at least one
alignment pin for aligning the mount with the drive head
maintenance apparatus in connection with the assembly tool.
104. The system of claim 102, wherein said assembly tool further
comprises at least one compression device for applying pressure
between the component parts to maintain the mount and drive head
maintenance apparatus.
105. The system of claim 103, wherein said mount comprises a bore,
and at least one alignment pin passes through the drive head
maintenance apparatus and the bore in the mount.
106. A drive head change apparatus, comprising: a head assembly
having the ability to support hardware comprising at least one
drive head; and a head mount tab for adjoining the head assembly to
positioning hardware, wherein said head assembly is affixed to said
head mount tab in a removable manner thereby minimizing potential
damage to said mounting tab.
107. The apparatus of claim 106, further comprising at least one
alignment pin for aligning the head mount tab with the head
assembly prior to press fitting the head assembly to the head mount
tab.
108. The apparatus of claim 107, wherein said head mount tab
comprises a bore, and at least one alignment pin passes through the
head assembly and the bore in the head mount tab.
109. The apparatus of claim 106, further comprising an assembly
tool for holding the head mount tab.
110. The apparatus of claim 109, wherein the assembly tool has the
ability to hold the head assembly adjacent the head mount tab.
111. The apparatus of claim 110, further comprising a clamping
device having the ability to compress the assembly tool, thereby
press fitting the head assembly to the head mount device.
112. The apparatus of claim 109, wherein said assembly tool further
comprises at least one compression device for applying pressure
between the component parts to maintain the mount and drive head
maintenance apparatus.
113. A system for detecting movement of a plurality of disks
mounted to a spindle, comprising: a transmitter/receiver capable of
emitting a first beam of energy toward said spindle and receiving
energy from said spindle; and an error calculator determining
differences between actual head position based on said reflective
element position and orientation of the spindle.
114. The system of claim 113, wherein said transmitter/receiver
comprises an interferometer, and said energy comprises light
energy.
115. The system of claim 113, wherein the transmitter/receiver
comprises a laser diode and an optical detector.
116. The system of claim 113, wherein the spindle is polished to
provide a high degree of reflectivity.
117. The system of claim 113, wherein the spindle is at least
partially covered with a reflective material.
118. The system of claim 114, wherein the interferometer comprises
a dual beam interferometer, and the transmitter/receiver further
comprises a plurality of optical detectors.
119. The system of claim 113, wherein the spindle has a
circumference and where the spindle comprises elements regularly
spaced around the circumference of the spindle.
120. The system of claim 113, further comprising a lensing
arrangement for receiving light energy and converting said received
light energy into collimated light energy.
121. A system for positioning a head over a disk, said disk mounted
to a spindle, comprising: a transmitter/receiver capable of
emitting a first beam of energy toward said spindle and receiving
energy from said spindle; a reflective element positionally
emulating the head and oriented to receive a second beam of light
energy from said transmitter/receiver and reflect the second beam
back toward said transmitter/receiver; and an error calculator
determining differences between actual head position based on said
reflective element position and orientation of the spindle.
122. The system of claim 121, wherein said transmitter/receiver
comprises an interferometer, and said energy comprises light
energy.
123. The system of claim 121, wherein the transmitter/receiver
comprises a laser diode and an optical detector.
124. The system of claim 121, wherein the spindle is polished to
provide a high degree of reflectivity.
125. The system of claim 121, wherein the spindle is at least
partially covered with a reflective material.
126. The system of claim 122, wherein the interferometer comprises
a dual beam interferometer, and the transmitter/receiver further
comprises a plurality of optical detectors.
127. The system of claim 121, wherein the spindle has a
circumference and where the spindle comprises elements regularly
spaced around the circumference of the spindle.
128. The system of claim 121, further comprising a lensing
arrangement for receiving light energy and converting said received
light energy into collimated light energy.
129. A method for positioning a head above a disk rotating about a
spindle, comprising: transmitting a first light energy beam to said
spindle and receiving light energy reflected off the spindle;
transmitting a second light energy beam to a reflective element
positioned to substantially emulate head position; receiving light
energy from said transmitting that is reflected off the reflected
element; computing an error signal based on positional differences
between said spindle, said emulated head, and disk orientation; and
altering head position based on the computed error signal.
130. The method of claim 129, wherein the reflective element
comprises a corner cube mounted to an e-block.
131. The method of claim 129, wherein the first light energy
transmitting beam and second light energy transmitting beam emanate
from a dual beam interferometer.
132. The method of claim 129, wherein the second light energy beam
is collimated.
133. The method of claim 129, further comprising transmitting a
third light energy beam to the disk to provide z-axis measurement
and provide tilt data.
134. The method of claim 129, wherein orientation of the first
light energy beam is approximately 90 degrees different from
orientation of the second light energy beam.
135. The method of claim 129, wherein orientation of the first
light energy beam is greater than approximately 45 degrees from
orientation of the second light energy beam.
136. A system for accurately positioning a head over a media disk,
said media disk rotating about a spindle, comprising: a dual beam
interferometer emitting a first beam of light energy toward said
spindle and receiving reflected light energy from said spindle; a
reflective element positionally emulating the head and oriented to
receive a second beam of light energy from said dual beam
interferometer and reflect the second beam back toward said dual
beam interferometer; an error calculator determining differences
between actual head position based on said reflective element
position and orientation of said spindle.
137. The system of claim 136, further comprising a lensing
arrangement for receiving light energy transmitted from the dual
beam interferometer and converting said light energy into
collimated light energy.
138. The system of claim 136, wherein the reflective element
comprises a corner cube mounted to an e-block.
139. The system of claim 136, wherein the second light energy beam
is collimated.
140. The system of claim 136, further comprising transmitting a
third light energy beam toward the spindle to provide z-axis
measurement and provide tilt data.
141. A method for efficiently positioning a head above a media disk
rotating about a spindle, comprising: transmitting a first light
energy beam to said spindle and receiving light energy reflected
off the spindle; transmitting a second light energy beam to a
reflective element positioned to substantially emulate head
position and receiving light energy reflected off the reflective
element; computing an error signal based on positional differences
between said spindle, said emulated head, and disk orientation; and
altering head position based on the computed error signal.
142. The method of claim 141, wherein the reflective element
comprises a corner cube mounted to an e-block.
143. The method of claim 141, wherein the first light energy
transmitting beam and second light energy transmitting beam emanate
from a dual beam interferometer.
144. The method of claim 141, wherein the second light energy beam
is collimated.
145. The method of claim 141, further comprising transmitting a
third light energy beam to the disk to provide z-axis measurement
and provide tilt data.
146. The method of claim 141, wherein orientation of the first
light energy beam is approximately 90 degrees different from
orientation of the second light energy beam.
147. The method of claim 141, wherein orientation of the first
light energy beam is greater than approximately 45 degrees from
orientation of the second light energy beam.
148. A system for accurately positioning a head over rotating
media, said rotating media able to spin about a center axis,
comprising: an interferometer having the ability to emit light
energy and measure an effective distance between said head and said
spindle; and means for computing a correction factor to be applied
to said spindle to correct for any perceived distance errors
related to said head measurement.
149. A system for determining spindle orientation inaccuracies,
comprising: an interferometer having the ability to emit light
energy and measure an effective distance between said
interferometer and said spindle; and means for computing a
correction factor for application to the spindle to correct for
perceived errors.
150. The system of claim 149, wherein the interferometer comprises
a tri coupler.
151. The system of claim 149, wherein the light energy emitted from
the interferometer is collimated.
152. The system of claim 149, further comprising transmitting an
additional energy beam toward the spindle to ascertain z-axis
performance and tilt data.
153. The system of claim 149, wherein orientation of the light
energy is approximately 90 degrees different from orientation of
the additional light energy beam.
154. The method of claim 149, wherein orientation of the light
energy is greater than approximately 45 degrees from orientation of
the additional light energy beam.
155. A method for minimizing media writing errors in a computing
device, comprising: writing a portion of a data burst on a first
pass; and writing additional portions of the data burst on
subsequent passes.
156. The method of claim 155, wherein the data burst comprises a
number of dipulses, and wherein writing the portion of the data
burst comprises writing one dipulse on the first pass and all
remaining dipulses on the second pass.
157. The method of claim 156, further comprising computing an
energy value for multiple bursts written using the multiple
passes.
158. The method of claim 157, further comprising evaluating the
computed energy value and rewriting the portion and additional
portions if the energy value exceeds a predetermined threshold.
159. A method for increasing magnetic disk yield during the
manufacturing process, comprising: initially writing a first
complete set of servo data to a magnetic disk; subsequently writing
at least one additional set of servo data to the magnetic disk;
evaluating the quality of the servo data written; and removing the
lowest quality servo data and retaining the highest quality servo
data.
160. The method of claim 159, wherein said initially writing and
said subsequently writing comprises writing the first complete set
and the at least one additional set to a substantially identical
region on the magnetic disk.
161. The method of claim 159, wherein the evaluating comprises
averaging the qualities of servo data written.
162. The method of claim 159, further comprising assessing head
quality based on said evaluating.
163. The method of claim 162, further comprising removing heads of
inferior quality indicated by said evaluating and said
assessing.
164. The method of claim 159, wherein said initially writing
comprises: partitioning the first set of servo data into multiple
overlapping contiguous segments and a first predetermined quantity
of the overlapping contiguous segments are written during a first
pass.
165. The method of claim 164, wherein the subsequently writing
comprises writing a second predetermined quantity of the
overlapping contiguous segments to the disk.
166. The method of claim 159, wherein said evaluating comprises
determining energy perceived by reading the first complete set and
the additional set of servo data.
167. The method of claim 166, wherein the energy comprises a
difference between the first complete set of servo data and one
additional set of servo data divided by the sum of the first
complete set of servo data and the one additional set of servo
data.
168. The method of claim 166, wherein initial and subsequent
writing is determined unsatisfactory if the energy exceeds a
predetermined threshold.
169. A method of writing to a disk, comprising: writing data to the
disk; rewriting said data to the disk at locations offset from data
previously written to the disk; and removing data having lowest
quality from the disk.
170. The method of claim 169, wherein the data comprises servo
data.
171. The method of claim 170, wherein the servo data comprises one
set of servo data and at least one additional set of servo
data.
172. The method of claim 171, wherein said writing and said
rewriting comprise writing the first complete set and the at least
one additional set to a substantially identical region on the
magnetic disk.
173. The method of claim 170, further comprising evaluating quality
of servo data written to the disk.
174. The method of claim 173, further comprising assessing head
quality based on said evaluating.
175. The method of claim 174, further comprising removing heads of
inferior quality indicated by said evaluating and said
assessing.
176. The method of claim 170, wherein said writing comprises:
partitioning the first set of servo data into multiple overlapping
contiguous segments and a first predetermined quantity of the
overlapping contiguous segments are written during a first
pass.
177. The method of claim 176, wherein the rewriting comprises
writing a second predetermined quantity of the overlapping
contiguous segments to the disk.
178. The method of claim 173, wherein said evaluating comprises
determining energy perceived by reading the first complete set and
the additional set of servo data.
179. The method of claim 178, wherein the energy comprises a
difference between the first complete set of servo data and one
additional set of servo data data and the one additional set of
servo data.
180. The method of claim 178, wherein initial and subsequent
writing is determined unsatisfactory if the energy exceeds a
predetermined threshold.
181. A servo data writing apparatus, comprising: means for writing
data to a disk; means for rewriting said data to the disk at
locations offset from data previously written to the disk; and
means for removing data having lowest quality from the disk.
182. The apparatus of claim 181, wherein the data comprises one set
of data and at least one additional set of data.
183. The apparatus of claim 182, wherein said writing and said
rewriting comprise writing the first complete set and the at least
one additional set to a substantially identical region on the
disk.
184. The apparatus of claim 182, wherein said writing and said
rewriting comprise writing the first complete set and the at least
one additional set to substantially different regions on the
disk.
185. The apparatus of claim 181, further comprising means for
evaluating quality of data written to the disk, said evaluating
means providing an evaluation to said removing means.
186. The apparatus of claim 185, wherein said evaluating means
determines energy perceived by reading the first complete set and
the additional set of data. divided by the sum of the first
complete set of servo
187. The apparatus of claim 186, wherein said evaluating means
determines writing and rewriting is unsatisfactory if the energy
exceeds a predetermined threshold.
188. A method of assessing track writing performance on a media,
comprising: monitoring spindle axis position with respect to a
reference position; and providing said spindle axis position with
respect to a reference position to a processor.
189. The method of claim 188, wherein said monitoring comprises
evaluating spindle axis position using a sensing device.
190. The method of claim 189, wherein the sensing device comprises
an interferometer.
191. The method of claim 190, wherein the interferometer comprises
a differential interferometer.
192. The method of claim 188, wherein said monitoring comprises
evaluating spindle axis position using a capacitance probe.
193. The method of claim 188, wherein the monitoring comprises
evaluating spindle axis position using an inductive sensor.
194. The method of claim 188, wherein the monitoring comprises
evaluating spindle axis position using an alternate position
optical sensor.
195. A method of computing a media track writing performance
metric, comprising at least one from the group including: computing
a standard deviation of an observed track write radius from a
desired track write radius and decomposing the standard deviation
into repeatable and nonrepeatable components; computing time
dependent servo mark positions; and computing optically inferred
spindle axis positions.
196. A method of computing a performance metric for media track
writing, comprising: monitoring position of a rotating component of
a holder maintaining said media; computing a topological radius of
a surface of said rotating component; and determining a difference
between the rotating component position and the topological radius,
wherein said difference equals rotating component wobble.
197. The method of claim 196, further comprising separating wobble
into a repeatable part and a nonrepeatable part.
198. The method of claim 197, wherein the nonrepeatable part
comprises nonharmonic components.
199. The method of claim 197, wherein the repeatable part comprises
harmonics of a rotational rate of said rotating component.
200. A method for biasing at least one disk fixedly attached to a
spindle, comprising: applying a biasing lateral force to a first
disk fixedly attached to said spindle thereby tightly interfacing
said disk with the spindle at one portion of the disk; and applying
a differently oriented biasing lateral force to any second disk
fixedly attached to said spindle.
201. A method for biasing a disk attached to a spindle, comprising:
applying a biasing lateral force to the disk fixedly attached to
said spindle thereby tightly interfacing said disk with the spindle
at one portion of the disk.
202. A system for maintaining media, comprising: a cap; at least
one spring holding the cap; and a fluid release ball bearing
arrangement having the ability to slidably engage and release said
cap using force generated by the at least one spring.
203. A device for maintaining media, comprising: a fluid release
arrangement having the ability to slidably engage and release a
cover.
204. A device for holding a rotating hub, comprising: a chuck clamp
housing; a mounting plate fixedly mounted to the chuck clamp
housing; a spindle within the chuck mounting plate; a chuck clamp
surrounding the chuck mounting plate and having the ability to
engage the hub, wherein said chuck clamp comprises a plurality of
finger elements.
205. The device of claim 204, further comprising a Belleville
spring and a fluid release system providing the ability to attach
and release said device and said hub.
Description
[0001] This application claims the benefit of U.S. Provisional
Patent Application Ser. No. 60/367,046, filed Mar. 23, 2002.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to the field of data
storage media, and more specifically to systems and methods for
efficiently initializing, certifying or otherwise reading data from
or writing data to such media.
[0004] 2. Description of the Related Art
[0005] Disk drives are magnetic recording devices used for the
storage of digital information. The digital information is recorded
on substantially-concentric tracks on either surface of one or more
magnetic recording disks. The disks are rotatably mounted on a
spindle motor, and information is accessed by read/write heads
mounted to actuator arms rotated by a voice coil motor. The voice
coil motor rotates the pivoting arms and moves the heads radially
over the surface of the disk or disks. During servowriting and/or
initialization of a disk, the read/write heads must generally be
accurately positioned on the disk to ensure proper reading and
writing of servo information that will define the data storage
tracks. After the servo writer writes the servo patterns on the
disks, the control system is added to the hard drive assembly.
[0006] Movement of the pivoting arms is controlled by a servo
system, which utilizes servo information recorded on one or more of
the disks to center the head on a particular track. Servo
information is utilized to determine an actual position of the
heads. A voice coil motor (VCM) moves the heads if the actual head
position deviates from a desired head location. Head position is
typically controlled by a closed loop servo system.
[0007] The servo information in the servo tracks is often written
with timing derived from a master clock track in the servo writing
system. Writing of servo information must be precise. Servo
information is typically recorded by special instruments containing
precise mechanical positioners, positioned using highly accurate
feedback devices such as optical encoders or laser
interferometers.
[0008] A media servowriter is a device dedicated primarily to the
servo data writing function. It can also perform other functions
related to hard disk preparation for insertion into a hard disk
drive. In operation, a media servowriter writes multiple disks in
preparation for their placement in an HDD, with the goal being
minimal further disk preparation once each disk is located in the
HDD. Media servowriters can thus be housed in one location while
hard disk assembly including completed disks may be performed at
another location with the knowledge that the servowritten disks
have been tested and approved for certain parameters.
[0009] Previously available servowriters suffer from a variety of
shortcomings and system performance issues. An example of known
system performance issues is that of system positioning accuracy:
positioning heads over tracks to accurately read and write
information at high speeds is an ongoing performance consideration
that can always be improved or enhanced. Most, if not all, of the
previously available systems suffer from an inability to support
custom read/write heads, or provide accurate micro-move and settle
times or track holding accuracy.
[0010] One particular problem with currently available disk drives
and servowriters is the complexity associated with knowing the
location of a head over a disk, and detecting and utilizing
relative movements of disks, positioners, heads, and related
equipment with respect to a reference point or plane. In current
servowriters, no action occurs during normal operation to track or
control disk or spindle position with respect to the drive base.
Instead, the system tracks and controls head position with respect
to some servowriter structural reference point, with the implicit
assumption that disk position is sufficiently well known and
stationary. In actual operation, however, the disks and spindle may
shift, vibrate, deform, or otherwise alter their position in space
with respect to the structural reference point. Current systems do
not physically track disk position nor compensate for movement or
irregularities resulting from real world conditions, including the
aforementioned conditions and non-repeatable run out movement. A
servowriter without the ability to track disk position and
compensate for positional or movement irregularities may introduce
or otherwise suffer from errors while heads are reading from or
writing to the disks. This error introduction may limit the spin
rate and/or track density of the disks.
[0011] It would be beneficial if one could track and compensate for
media movement during the read and write process, thereby
decreasing the risk of reading from or writing to incorrect
locations on the media surface.
[0012] Another problem with currently available disk drives and
servowriters is that of accurate head positioning. During the
process of writing servo tracks on magnetic media, servo patterns
must be positioned with high accuracy on different radial tracks.
The traditional method of locating servo patterns on disks is to
use a read/write head flying over a spinning media disk. The
read/write head is attached to a rotary positioning device
comprising a voice coil, associated voice coil motor, and a rotary
optical encoder for closed loop positioning purposes. The rotary
positioning device is used to hold the read/write head and swing
the head over the spinning media disk. Errors in servo track
accuracy can occur whenever the system does not maintain head
position in a controlled radius as the media disk spins below the
head. In certain circumstances the axis of the spinning media disk
can translate laterally in the plane of rotation or the axis can
wobble, tilting about a pivot point not coincidence with the media
disk plane, thereby also translating the disk with respect to the
head. Head position errors may also occur if the entire optical
encoder fails to precisely track head position. The entire
positioning device can translate or vibrate with respect to the
spinning disk, or flexing of any components connecting the head to
the optical encoder can produce positional errors.
[0013] Previous systems have employed a rigid mechanical connection
between the optical encoder and the heads as well as a stable
mechanical reference between the optical encoder and the axis of
the spinning disk. In a disk having a track pitch below one micron,
the rigid positional linkage performance between the optical
encoder and the head as well as the optical encoder and spindle
axis can be compromised by various factors, such as wobble or
translation of the spindle axis within its bearing mount, causing
radial runout. Other potentially problematic factors may include
tiny distortions of the shape of any hardware that mechanically
references the head to the spindle axis. External vibrations,
vibrations from the spindle motor, temperature fluctuations or
flutter from the disk can all contribute nanometer fluctuations and
errors in positioning the head at constant track radius.
[0014] It would be beneficial to have a servo system that minimizes
the dependence on the idealized mechanical references connecting
spindle axis position to head position, thereby minimizing errors
and fluctuations in the radius of servo data, or marks.
[0015] Another example of known system performance issues is that
of system positioning accuracy: positioning heads over tracks to
accurately read and write information at high speeds is an ongoing
performance consideration that can always be improved or enhanced.
One particular problem with currently available servowriters is the
equipment used to format a disk writes a set of servo sectors to
the disk, and the presence of relatively significant servo sector
errors can cause the servowriter to indicate the disk is bad during
verification testing. Alternately, when writing to a formatted
disk, the presence of relatively significant errors in the servo
sectors causes the disk drive to mark those sectors as unusable for
data storage, either by detecting excessive servo errors while
track following or excessive errors detected during data writing
and reading, with the result that the data storage capacity of the
disk would be reduced. Thus the downside of the old method of
writing servo sectors or data sectors and monitoring the written
data for errors would be discarded disks or unusable disk area.
These drawbacks decrease yield and reduce available storage
capacity.
[0016] It would be beneficial to have a method of writing data,
including servo data, that would reduce the risk of decreased
yields and/or storage capacity of hard disks as compared with
previously known systems.
[0017] Furthermore, most, if not all, of the previously available
systems suffer from an inability to support custom read/write
heads, or provide accurate micro-move and settle times or track
holding accuracy.
[0018] Disk drive heads are replaced periodically due to wear and
tear. Instead of staking, wherein the head suspension and the head
mount tab 3501 may suffer permanent deformation, it would be
beneficial to offer a design that does not encounter permanent
mechanical deformation during assembly or reassembly. In a
particular hardware implementation, staking has required mounting a
tab replacement or head arm or E-block after only two or three head
replacements due to permanent deformation of the boss receiving
bore of the head mount. It would be preferable to offer a design
that can impart less distortion to the interface between the HGA
and the mating head mount bore, increasing the number of reuses of
the head mount tab before replacement is indicated.
[0019] Further, hard disk drives rely heavily on position reference
information "written" or recorded as concentric bands of tracks
onto disk surfaces. The operation of creating those tracks, known
as servo track writing, requires precise record-phase head
positioning and spindle mechanisms, as well as accurate timing and
control electronics. The servo track writing process traditionally
has been performed after disks have been installed into a "hard
disk assembly", or HDA. At the stage where disks are located in an
HDA, the disks have been positioned on a spindle within the HDA.
The HDA read-write heads have been loaded onto the disk or disks.
An operator has traditionally placed the HDA onto a Servo Track
Writer device that provides head positioning and servo pattern
information to the HDA to enable proper recording of the servo
tracks onto the disk or disks. This traditional technique is
especially useful when multiple disks are used within the HDA.
[0020] However, as disk areal data density has increased, many Hard
Disk Drives today utilize only one disk, decreasing the usefulness
of the aforementioned technique. Further, increased areal data
density is frequently accompanied by an increase in track density,
which requires that the HDA write additional servo tracks. With at
least two servo tracks for every data track, the number of servo
tracks has increased at twice the rate of data tracks for a disk of
fixed size or area. This increased number of tracks results in a
dramatic increase in the time required to write the servo tracks.
Servo writing, which previously took a few minutes can now easily
exceed a half hour or more, depending on STW machine parameters,
disk size, rotational speed (RPM), and total number of servo
tracks. This time increase, coupled with the fact that many disk
drives today use only a single disk, has created a demand for a
media track writer, or MTW, that can simultaneously record servo
tracks on multiple disks prior to installation into an HDA.
[0021] One aspect of the MTW that is particularly noteworthy is the
mechanical clearance between the disk inside diameter, and the hub
or chuck outside diameter, namely the disk opening and the hub that
fills the opening. A significant clearance dimension is necessary
to enable fast and reliable disk installation on and off the hub
and to accommodate disk and hub manufacturing tolerances. If this
clearance is too large, the disk or disks will move laterally and
possibly axially during high RPM rotation. A finite clearance value
exists under any set of dimensions. This clearance, if not
addressed in some manner, creates an uncertainty with regard to the
concentricity of servo tracks to disk ID, and can in certain
circumstances result in significant eccentricity errors introduced
when removing disks from the MTW and installed into a disk drive
HAD. If uncontrolled, these errors can in certain circumstances
exceed 4000 microinches, or millionths of an inch. Excessive
eccentricity, or servo track "runout", can cause servo capture and
performance problems for the HDD, in that the head can be
mislocated above the disk and can run outside a track, or begin in
one track and end in another.
[0022] An additional aspect of a media servowriter is holding a
hub, specifically a hub of a disk stacking cylinder employed to
hold multiple disks during disk servowriting and certification.
Previously available hub holding devices used some type of
mechanical "jaws" that gripped the exterior of the hub and/or the
notch formed between the hub and the main cylinder. The jaws were
formed of some type of metal and were metal pieces used to pin the
hub down and hold it in position by applying pressure to the upper
side of the hub. These jaw-type locking devices tend to be
imprecise in holding the hub or other cylindrical piece. At
significantly high RPMs, such as in excess of 10,000 to 20,000
RPMs, centrifugal force works to pry these devices open, and many
jaw type devices are pried open or move the piece as a result of
high forces applied thereto. This prying tends to damage the hub
and/or maintaining device and is generally unacceptable. Thus the
previous devices could be characterized as easily pried open, with
poor repeatability, and highly subject to movement of the
piece.
[0023] It would be beneficial to provide a system overcoming these
drawbacks present in previously known systems and provide an
improved media servowriter, disk writer, and/or other device having
improved functionality over devices exhibiting those negative
aspects described herein.
SUMMARY OF THE INVENTION
[0024] According to one aspect of the present design, there is
provided a method for tracking and controlling media read/write
characteristics. The method comprises creating media having a
predetermined expected baseline configuration, reading the media
having the predetermined expected baseline configuration,
determining whether the media has moved from an expected position
based on the media reading of the predetermined expected baseline
condition, and correcting data hardware based on determining
whether the media has moved from the expected position.
[0025] According to a second aspect of the present design, there is
provided a method for minimizing likelihood of a head within a
servowriting apparatus contacting a disk located therein. The
method comprises sensing sound intensity in a predetermined
frequency range from a first sensor positioned at a first location
within the servowriting apparatus, determining the existence of a
pending head crash based on the sound intensity; and moving an
element of the servowriting apparatus upon determining the
existence of the pending head crash.
[0026] According to a third aspect of the present design, there is
provided an apparatus for controlling airflow over rotating media.
The apparatus comprises at least one baffle covering the media, the
at least one baffle comprising at least one cavity shielding at
least a portion of the rotating media; wherein the at least one
baffle provides the ability to inhibit turbulent flow when the
rotating media rotates.
[0027] According to a fourth aspect of the present design, there is
provided a method for changing a head assembly employed in a media
writing device. The method comprises providing a head mount
assembly having a bore passing therethrough, positioning the head
assembly adjacent the head mount, aligning the head assembly with
the head mount, and press fitting the head assembly to the head
mount.
[0028] According to a fifth aspect of the present design, there is
provided a system for detecting movement of a plurality of disks
mounted to a spindle. The system comprises a transmitter/receiver
capable of emitting a first beam of energy toward the spindle and
receiving energy from the spindle and an error calculator
determining differences between actual head position based on the
reflective element position and orientation of the spindle.
[0029] According to a sixth aspect of the present design, there is
provided a system for positioning a head over a disk, the disk
mounted to a spindle. The system comprises a transmitter/receiver
capable of emitting a first beam of energy toward the spindle and
receiving energy from the spindle, a reflective element
positionally emulating the head and oriented to receive a second
beam of light energy from the transmitter/receiver and reflect the
second beam back toward the transmitter/receiver, and an error
calculator determining differences between actual head position
based on the reflective element position and orientation of the
spindle.
[0030] According to a seventh aspect of the present design, there
is provided a system for accurately positioning a head over
rotating media, the rotating media able to spin about a center
axis. The system comprises an interferometer having the ability to
emit light energy and measure an effective distance between the
head and the spindle, and means for computing a correction factor
to be applied to the spindle to correct for any perceived distance
errors related to the head measurement.
[0031] According to an eighth aspect of the present design, there
is provided a system for determining spindle orientation
inaccuracies. The system comprises an interferometer having the
ability to emit light energy and measure an effective distance
between the interferometer and the spindle, and means for computing
a correction factor for application to the spindle to correct for
perceived errors.
[0032] According to a ninth aspect of the present design, there is
provided a method for increasing magnetic disk yield during the
manufacturing process. The method comprises initially writing a
first complete set of servo data to a magnetic disk, subsequently
writing at least one additional set of servo data to the magnetic
disk, evaluating the quality of the servo data written, and
removing the lowest quality servo data and retaining the highest
quality servo data.
[0033] According to a tenth aspect of the present design, there is
provided a method of assessing track writing performance on a
media. The method comprises monitoring spindle axis position with
respect to a reference position, and providing the spindle axis
position with respect to a reference position to a processor.
[0034] According to an eleventh aspect of the present design, there
is provided a method of computing a media track writing performance
metric. The method comprises at least one from the group including
computing a standard deviation of an observed track write radius
from a desired track write radius and decomposing the standard
deviation into repeatable and nonrepeatable components, computing
time dependent servo mark positions, and computing optically
inferred spindle axis positions.
[0035] According to a twelfth aspect of the present design, there
is provided a method of computing a performance metric for media
track writing. The method comprises monitoring position of a
rotating component of a holder maintaining the media, computing a
topological radius of a surface of the rotating component, and
determining a difference between the rotating component position
and the topological radius, wherein the difference equals rotating
component wobble.
[0036] According to a thirteenth aspect of the present design,
there is provided a method for biasing at least one disk fixedly
attached to a spindle. The method comprises applying a biasing
lateral force to a first disk fixedly attached to the spindle
thereby tightly interfacing the disk with the spindle at one
portion of the disk and applying a differently oriented biasing
lateral force to any second disk fixedly attached to the
spindle.
[0037] According to a fourteenth aspect of the present design,
there is provided a method for biasing a disk attached to a
spindle, comprising applying a biasing lateral force to the disk
fixedly attached to the spindle thereby tightly interfacing the
disk with the spindle at one portion of the disk.
[0038] According to a fifteenth aspect of the present design, there
is provided a system for maintaining media, comprising a cap, at
least one spring holding the cap, and a fluid release ball bearing
arrangement having the ability to slidably engage and release the
cap using force generated by the at least one spring.
[0039] According to a sixteenth aspect of the present design, there
is provided a device for holding a rotating hub, comprising a chuck
clamp housing, a mounting plate fixedly mounted to the chuck clamp
housing, a spindle within the chuck mounting plate, and a chuck
clamp surrounding the chuck mounting plate and having the ability
to engage the hub, wherein the chuck clamp comprises a plurality of
finger elements.
[0040] These and other objects and advantages of the present
invention will become apparent to those skilled in the art from the
following detailed description of the invention and the
accompanying drawings.
DESCRIPTION OF THE DRAWINGS
[0041] FIG. 1 is a general conceptual representation of the
servowriting system according to one aspect of the current
invention;
[0042] FIG. 2 represents the mechanics of the servo writing device
of one aspect of the current invention;
[0043] FIG. 3 is the multiple disk and spindle arrangement used in
accordance with one aspect of the current invention;
[0044] FIG. 4 presents a single multiple read/write head positioner
arrangement that may be utilized in accordance with one aspect of
the current invention;
[0045] FIG. 5 presents an alternate view of the servowriting device
with media cover and in-place positioner according to one aspect of
the current invention;
[0046] FIG. 6 is a conceptual view of the optical inspection system
according to one aspect of the current invention;
[0047] FIG. 7 shows ideal operation of writing bursts to a
track;
[0048] FIG. 8 illustrates a more typical operation of burst writing
observed under certain typical conditions;
[0049] FIG. 9 shows a conceptual illustration of the sinusoidal
dipulse writing of a burst;
[0050] FIG. 10 presents multiple dipulse writing over multiple
passes in accordance with an aspect of the present invention;
[0051] FIG. 11 represents one aspect of the inventive device
disclosed herein;
[0052] FIG. 12 represents the relationship between a single data
sector and an associated servo sector;
[0053] FIG. 13 shows the disposition of servo sectors at
substantially regular angular offset positions around the disk
according to one aspect of the current invention;
[0054] FIG. 14 is a schematic cross-sectional view at some point
along the length of a fiber optical tri-coupler such as used in an
interferometer according to one aspect of the current
invention;
[0055] FIG. 15 is a schematic of an embodiment of an interferometer
according to the present invention;
[0056] FIG. 16 is a schematic of an alternate embodiment of an
interferometer according to the present invention;
[0057] FIG. 17 is a graph showing the output signals from
photodetectors on the interferometer versus the input
phase-difference between the input beams according to one aspect of
the current invention;
[0058] FIG. 18 represents a conceptual top view of an acoustic
sensor implemented in one aspect of the present invention;
[0059] FIG. 19 illustrates a perspective view of the left baffle
shroud according to one aspect of the present invention;
[0060] FIG. 20 is a perspective view of an eleven-shroud right
baffle according to one aspect of the present invention;
[0061] FIG. 21 represents the hardware associated with the servo
writing device according to one aspect of the current
invention;
[0062] FIG. 22 is a top cutaway view of the left baffle shroud
according to one aspect of the current invention;
[0063] FIG. 23 presents a side cutaway view of the left baffle
shroud according to one aspect of the current invention;
[0064] FIG. 24 shows a bottom view of the left baffle shroud
according to one aspect of the current invention;
[0065] FIG. 25 illustrates a side view of the right baffle shroud
according to one aspect of the current invention;
[0066] FIG. 26 is an alternate perspective view of the right baffle
shroud according to one aspect of the current invention;
[0067] FIG. 27 shows a bottom view of the right baffle shroud
according to one aspect of the current invention;
[0068] FIG. 28 is a perspective view of the clock shroud according
to another aspect of the current invention;
[0069] FIG. 29 presents a top view of the clock shroud of FIG. 28
according to one aspect of the current invention;
[0070] FIG. 30 is a rotary voice coil motor design according to one
embodiment of the current invention;
[0071] FIG. 31 presents a coil housing according to one embodiment
of the current invention;
[0072] FIG. 32 presents a front and side view of a coil according
to one embodiment of the current invention;
[0073] FIG. 33 shows a scale holder and shaft used to maintain and
rotate the positioner, E-block, and related components according to
one embodiment of the current invention;
[0074] FIG. 34 shows the E-block assembly, including a plurality of
heads attached thereto on head assemblies according to one
embodiment of the current invention;
[0075] FIG. 35 shows an example of a mounting tab that may be
mounted to the E-block and that may operate in accordance with the
present invention according to one embodiment of the current
invention;
[0076] FIG. 36 shows a top view of the E-Block bifurcated by a
centerline and particularly highlighting the slots for receiving
the dowels or pins of the mounting tab according to one embodiment
of the current invention;
[0077] FIG. 37 is an exploded view of one aspect of an assembly
tool that may be used in accordance with the present invention;
[0078] FIG. 38A shows front and side views of one aspect of a left
section of an assembly tool according to one embodiment of the
current invention;
[0079] FIG. 38B illustrates front, rear, and side views of one
aspect of a center section of an assembly tool according to one
embodiment of the current invention;
[0080] FIG. 38C represents front and side views of one aspect of a
right section of an assembly tool according to one embodiment of
the current invention;
[0081] FIG. 39 shows various components that may be employed in the
inventive press fit method disclosed herein according to one
embodiment of the current invention;
[0082] FIG. 40 shows one detailed aspect of a head assembly
according to one embodiment of the current invention;
[0083] FIG. 41 is a view of an assembly tool maintaining a mounting
tab and head assembly prior to press fitting with an alignment pin
inserted therethrough according to one embodiment of the current
invention;
[0084] FIG. 42 illustrates an assembly tool maintaining a mounting
tab and head assembly prior to press fitting with a second
alignment pin inserted therethrough according to one embodiment of
the current invention;
[0085] FIG. 43 shows an assembly tool maintaining a mounting tab
and head assembly and press fitting the components together using a
vise or clamping device according to one embodiment of the current
invention;
[0086] FIG. 44 is an aspect of the locking cap arrangement of a
system according to one aspect of the current invention;
[0087] FIG. 45 is a close view of a locking cap according to an
aspect of the present invention;
[0088] FIG. 46 is an aspect of the locking cap arrangement with
bearings released and in release position according to one
embodiment of the current invention;
[0089] FIG. 47 is a close view of the locking cap arrangement with
bearings released and in release position according to one
embodiment of the current invention;
[0090] FIG. 48 illustrates the finger gripping arrangement used to
grip a hub holding one or more disks according to one embodiment of
the current invention;
[0091] FIG. 49 is an alternate view of the finger gripping
mechanism according to one embodiment of the current invention;
and
[0092] FIG. 50 is another alternate view of the finger gripping
mechanism according to one embodiment of the current invention.
DETAILED DESCRIPTION OF THE INVENTION
[0093] According to the present invention, there is provided an
enhanced media servowriter having several aspects constituting
improvements over previously known designs. An aspect of the
present invention is a system and method for tracking disk and
spindle position, typically in a multiple media disk arrangement,
whereby data from the disks or spindle are fed back to hardware
and/or software to compensate for position errors during reading
and/or writing to the media.
[0094] In a particular aspect of the present invention, a
non-contact radiation detection system cooperates with an ideal
disk produced using patterning technology to detect movement of
disks mechanically coupled to a spindle. The system further
utilizes an ideal magnetic disk to detect movement of disks
mechanically coupled to a spindle. Further, the system and method
disclosed herein detect spindle and disk (or disks) movement with
respect to a common base by detecting radiation reflected by a
rotating part of the spindle.
[0095] A particular implementation measures and calculates the
distance between the spindle axis position and an emulated head
position and uses this distance to more accurately position the
head. The system may employ a dual channel interferometer, such as
a multiphase or guided wave interferometer, to reflect energy beams
off the spindle holding the rotating media by using a retro
reflector emulating head position and a lensing arrangement. The
interferometer determines actual distance from the head to the
spindle using the emulated head position and the system utilizes a
digital signal processor or other computing device to compare that
distance to any topological shift in the spindle position to find
an overall error. The system then applies the overall error to the
voice coil to correct head position. Alternate aspects of the
invention employ interferometers in the z (vertical) direction or
in the y direction to determine and compensate for tilt, vibration,
or other undesirable media and/or head shifting.
[0096] In one aspect, the interferometer operates by reflecting
light off the polished chuck holding the disks, which is part of
the rotating portion of the spindle and thus accurately emulates
spindle axis position and orientation. Due to errors in the spindle
chuck (not perfectly cylindrical, tilted or otherwise
computationally off desired orientation) the system determines the
topological offset of the chuck and uses this value in combination
with the raw distance between the head and the chuck and/or spindle
to determine an overall positional error rate signal. The DSP
processes this error signal to produce a corrective positional
signal, which the DSP applies to the voice coil or other control
device. The result is a compensation for angular tilt and/or shifts
in orientation and/or the relationship between the head or the
media. The retro reflector may be a corner cube or cat's eye or any
other optical element having beneficial functionality in this
interferometer-emulated head position arrangement.
[0097] The devices and methods disclosed herein may be employed in
servowriting and/or data writing systems, and may be used in other
systems employing a device such as a head to write or read data to
or from rotating media.
[0098] A further aspect of the present invention includes a method
for increasing the yield of magnetic disks during the manufacturing
process. According to an aspect of the present invention, once the
system has written the set of servo sectors to the disk, the
servowriter verifies data written in the servo sectors to validate
the disk. If the data written within the servo sectors exhibits
sufficient integrity, the servowriting process is considered
successful, and data sectors corresponding to the servo sectors are
produced and validated. The data sectors may store data
subsequently written to the disk.
[0099] Another aspect of the invention utilizes the writing and
reading concepts disclosed above to increase the data storage
capacity of a hard disk drive by writing multiple duplicate
versions of data to the disk in different data sectors around the
disk, and then retaining only the data exhibiting a sufficient
degree of integrity. In this aspect of the invention, similar to
the servowriting aspect outlined above, more than one set of data
sectors is written to the media disk during normal operation,
preferably during the same revolution. As a result, instead of a
single set of data sectors disposed at predetermined positions
around the disk based on available space on the disk, this aspect
of the method disclosed herein produces one or more additional sets
of data sectors, each of these data sectors being disposed at
predetermined positions around the disk with respect to other data
sectors. Once written, the HDD determines the set of data having
the highest data integrity by comparing all data sets against
original or baseline data. The system may then erase lower quality
or duplicate data.
[0100] A further aspect of the present invention is tracking disk
and spindle position, typically in a multiple media disk
arrangement, whereby data from the disks or spindle are fed back to
hardware and/or software to compensate for position errors during
reading and/or writing to the media. This aspect of the invention
may or may not be used with the hardware disclosed. A non-contact
radiation detection system cooperates with an ideal disk produced
using patterning technology to detect movement of disks
mechanically coupled to a spindle. Another aspect of the present
invention utilizes an ideal magnetic disk to detect movement of
disks mechanically coupled to a spindle. An aspect of the invention
provides a system and method for detecting spindle and disk (or
disks) movement with respect to a common base by detecting
radiation reflected by a part of the spindle.
[0101] Media Servowriter
[0102] FIG. 1 is a general conceptual representation of the
servowriting system in which the present invention may be employed.
From FIG. 1, the system controller 102 controls clock pattern 103,
robotics control 104, position servo 105, and PES and verify block
106. Robotics control 104, position servo 105, and PES and verify
blocked 106 perform functions related to the present invention. For
example, robotics control 104 provides commands to drive the motors
and sensors interacting with the spindle and air bearing to drive
the multidisk spindle and air bearing arrangement.
[0103] In one embodiment, clock pattern circuit 103 generates a
clocking signal and establishes the pattern generated on the disk
surface. System controller 102 provides an indication to clock
pattern circuit 103 to initiate a pattern on the disk surface when
appropriate, such as during disk processing routines when it is
appropriate for certification and servowriting to occur. Pattern
read/write block 107 provides signals for reading and writing the
pattern established by the clock pattern circuit 103. This pattern
is the pattern used for this certification as described herein,
which is written to and read from the media. Clock pattern circuit
103 also issues commands for servo/clock writing to servo clock
read/write circuit 108. Servo clock read/write circuit 109 writes
servo clock information to the disk and reads that clocking
information to assess the validity of the servo data.
Servo/certification module 110 determines the proper time, data,
and pattern for servowriting for the multiple head/multiple disk
arrangement of the present invention.
[0104] Operation of servo/certification module 110 in one
embodiment is described below. Servo certification module 110
receives data from pattern read/write block 107 and servo clock
read/write circuit 108. Servo certification module 110 transmits
appropriate data and receives relevant data at multiple data
preamps 111a through 111n, where n is the total number of preamps
used to write to multiple disks. For example, but without
limitation, a system may employ ten disks and twenty heads in
connection with four preamps. Uniform correspondence in preamp to
disk ratio between data preamps is not required, and one data
preamp may write to one disk while another may write to several
media disks in the same configuration. Multiple data preamp and
disk arrangements may be employed while still within the course and
scope of the present invention. Servo clock read/write circuit 108
also transmits and receives relevant data at clock preamp 112.
These preamps filter and amplify data received from the various
circuits and transmit the amplified signals to the appropriate
read/write heads 113a-n.
[0105] In association with one possible implementation of the
present invention, media disks are located on spindle 120 and
read/write heads 113a-n positioned proximate the disk surface using
the head stack assembly. The spindle 120 preferably rides on an air
bearing 122, thereby operating to rotate the disks in an efficient
manner while multiple heads engage the media 121, such as multiple
hard disks 121a-n, in order to read and write appropriate
information. The system writes patterns, including servo patterns,
to each disk using the read/write heads. As reading and writing
using multiple heads may involve simultaneous processing, reduced
processing requirements and time sharing could result in
significant cost savings. The system writes servo data and performs
certification in a timely and cost effective manner using the
spindle 120 and head stack assembly arrangement.
[0106] Compensation for Head and Disk Movement
[0107] One aspect of the invention disclosed herein detects
movement (other than spinning) of the spindle and/or media, such as
computer disks, with respect to a reference location, such as a
granite base to which disk drive or servowriter hardware is
attached, or directly with respect to a head interacting with the
media. The present invention comprises methods and systems for
compensating for such movement. The result of this aspect of the
invention is to in most cases decrease the relative movement (other
than spinning) between the heads and disks during normal disk drive
or servowriting operation.
[0108] Four aspects and various related embodiments of the current
invention are specifically disclosed herein for detecting movement
of media disks and/or the spindle holding the media with respect to
the base. These four aspects compensate movement with respect to
the base and/or heads. The first aspect is a non-contact radiation
detection system combined with an ideal disk produced using
patterning technology. The second aspect is an ideal magnetic disk
serving as a reference for a head reading information from the
ideal magnetic disk. The third aspect is a non-contact radiation
detection system that bounces radiation off one or more parts of
the spindle. The fourth aspect is a non-contact radiation detection
system that bounces radiation off both a part of the spindle and
one or more parts of one or more heads.
1. Non-Contact Radiation Detection System Combined with an Ideal
Disk Produced Using Patterning Technology
[0109] In a first aspect of the current invention, a non-contact
radiation detection system cooperates with an ideal disk produced
using patterning technology to detect movement of disks
mechanically coupled to a spindle.
[0110] From FIG. 2, the current system comprises a base 201, having
a mounting block (not shown) or other holding device affixed
thereto. The mounting block is fixedly mounted to a spindle 202.
The rotating spindle may maintain a plurality of media disks 204
(a) through (n), illustrated in further detail in FIG. 3, but may
maintain a single disk or virtually any number of disks. In the
configuration shown, ten disks are employed and are secured by
locking cap 302 and chuck clamp 303. Positioner 401 of FIG. 4
maintains a series of heads 403(a) through (n), typically
individual read/write heads that perform both reading and writing
functions, where each head flies over the surface of the media
204(a) through (n), which are typically hard disks. A depiction of
the entire system is presented in FIG. 5, wherein the positioner
401 is closely associated with the disk stack and a VCM motor 502
to read from and write to the disks.
[0111] In the current aspect of the present invention, an ideal
disk (not shown) comprising positional guiding information, such as
a particular data and/or servo data track structure, is produced
possibly separate and apart from the configuration illustrated in
FIG. 3. The ideal disk may be produced using the FIG. 2 through 5
configuration, but it is typically not produced in the same
multi-disk situation as illustrated in FIG. 3.
[0112] According to an aspect of the invention, the ideal disk is
produced using patterning technology. In one case, the ideal disk
is produced using lithography methods, as employed in the
semiconductor industry. In another case, the ideal disk is produced
using an electron beam (e.g., the tracks on the disk are written
using an electron beam). This ideal disk is used as a reference for
the subsequent media reading and writing functions performed by the
system of FIG. 1. If the ideal disk is a magnetic disk, the system
reads magnetic reference data. If the ideal disk is produced using
patterning technology, lithography, or an e-beam, reading reference
data from the disk may include employing a device such as a laser
positioning system employing, for example, reflection, refraction,
or transmission, such as in the case where physical holes are
placed in the ideal disk.
[0113] In one embodiment, the ideal disk produced using methods
disclosed herein is then mechanically coupled to the spindle along
with any other disks that may normally be coupled to the spindle.
In a particular application, a plurality of disks to be written or
tested is arranged in a stacked formation and is mechanically
coupled to the spindle. In this particular application, the ideal
disk is also mechanically coupled to the spindle to detect movement
of the spindle, and implicitly, of one or more of the stacked
disks. More than one ideal disk may be attached to the spindle to
further improve the accuracy of the movement detection process. In
the present arrangement, the system has predetermined knowledge of
the parameters of the ideal, or reference, disk and uses the ideal
disk to form a reference point for tracking the actual position of
the spindle and media located thereon. Use of additional ideal
disks provides further reference points to track and eliminate
media position irregularities.
[0114] A non-contact radiation detection system interacts with the
ideal disk to detect movement of the ideal disk, and implicitly, of
the spindle mechanically coupled to the ideal disk.
[0115] In one aspect of this non-contact radiation detection
system, the non-contact radiation detection system comprises an
optical system, conceptually illustrated in FIG. 6. The optical
system 601 comprises an optical transmitter 602, such as a laser
diode, and an optical receiver 603, such as an optical detector.
The optical transmitter and receiver may be disposed on the base of
the system, such as at base 201, and may cooperate to detect
movement of the ideal disk with respect to the base 201. Depending
on the structure and properties of the ideal disk, the optical
transmitter and receiver may be disposed on opposite sides of the
ideal disk. For example, the positional guiding information may be
derived from apertures that permit transmission of optical
radiation. Alternately, positional guiding information may be
derived from a same side of the ideal disk. For example, the
positional guiding information and/or the ideal disk may exhibit
reflective properties, and data may be transmitted to the disk
surface and be reflected and interpreted therefrom.
[0116] The optical system 601 detects movement of the ideal disk
with respect to the optical transmitter 602 and receiver 603.
Hardware and/or software logic utilizes the information provided by
the optical system to determine the magnitude and direction of
movement at any point along the spindle or on the disks, both with
respect to the base and with respect to any heads operating on the
disks. In one aspect, the optical system may be affixed or
mechanically interconnected to the base 201, and the optical system
601 knows the position of the base 201, the spindle, and the disks.
The optical system monitors disk position relative to its own
position and transmits any variations to hardware and/or software
logic to correct for perceived deviations based on the pattern
observed from the ideal disk. Once the direction and magnitude of
motion of a particular disk is determined at a point proximate to a
corresponding head reading from, or writing to the disk, the head
moves accordingly to compensate for disk motion. As a result, the
system minimizes or eliminates relative motion of the head with
respect to the media disk.
[0117] In a particular implementation, a voice coil motor (VCM)
that normally engages and operates the head utilizes information
provided by the optical system 601 and/or other logic to move the
head in response to disk movement. In this implementation, the head
is substantially rigidly coupled to an arm that moves under control
of the VCM. A positional difference in the ideal disk perceived by
the optical system 201 is provided to the VCM logic such that the
head and arm are moved to compensate for the perceived positional
shift. In many situations, the positional shift will be a rotation
that is too fast or too slow, meaning the head is either ahead of
or behind its desired position. In such a lead or lag situation,
the rotation of the system may be altered or the head shifted
forward or backward in the rotation.
[0118] In an alternative implementation, the head is mechanically
coupled via a jointed connection to a first end of the arm
controlled by the VCM, and the head may move (rotate or translate)
with respect to the first end of the arm under the control of one
or more actuators.
2. Ideal Magnetic Disk Serving as a Reference for a Head
[0119] Another aspect of the present invention utilizes an ideal
magnetic disk to detect movement of disks mechanically coupled to a
spindle.
[0120] An ideal magnetic disk comprising positional guiding
information, such as a preferred data and/or servo-data track
structure, is produced according to an aspect of the present
invention. The ideal magnetic disk may be produced separate and
apart from the multiple disk configuration of FIGS. 2 through 5,
but this is not specifically required. The ideal magnetic disk
having magnetic positional information located thereon is then
mechanically coupled to the spindle, in addition to any other disks
that may normally be coupled to the spindle. In a particular
application, a plurality of disks to be written or tested is
arranged in a stacked formation and is mechanically coupled to the
spindle, as in FIG. 2. In this particular application, the ideal
magnetic disk is also mechanically coupled to the spindle to detect
movement of the spindle, and implicitly, of one or more of the
stacked disks. More than one ideal magnetic disk may be attached to
the spindle to again improve the accuracy of the movement detection
process.
[0121] Thus the system may reduce relative movement between the
head and the ideal disk by either moving the spindle in combination
with the disk(s), or moving the heads. If moving the spindle, such
movement may be accomplished using an air pulse, a mechanical
centrifugal device such as a screw or actuator, varying the
magnetic field in the spindle electromotor, or varying the external
magnetic field surrounding the spindle. If the system reduces
relative movement by moving the heads, it employs either jointed
head arms having individual actuators located thereon, moving only
the tip of the head arm, or alternately may move the entire head
arm.
[0122] According to one aspect of the invention, the ideal magnetic
disk (not shown) is produced by writing a data or servo track in
multiple revolutions instead of writing the track in a single
revolution. Commonly, a data or servo track may be written in a
single revolution, but the track may exhibit random deviations from
the desirable circular pattern. The random deviations may include
non repeatable run out errors that may occur due to temporary and
nonrecurring factors. An aspect of the current invention is to
provide for writing such a track during multiple revolutions by
partitioning the track into multiple segments and writing different
segments in different revolutions to average out the random
deviations. By writing different segments of the track during
different passes, random errors introduced into the system by
sources that move the disks with respect to the heads are averaged
out, thereby being reduced or eliminated.
[0123] One aspect of the current invention associated with
employing an ideal magnetic disk as a reference is that of writing
servo bursts in multiple revolutions to average the adverse affects
associated with servowriting, such as the problem of non-repetitive
run out. This aspect requires writing servo data in multiple
revolutions. Under previously known servowriting operation, when
the system servowrites a track, the NRRO (non-repetitive run out)
occurring during the servowriting revolution is written into the
track. The NRRO contribution can be minimized by averaging such
writing over all or part of servowritten data. Data writing
averaging may be achieved by writing a servo burst in multiple
revolutions, with different portions of the servo data written in
different revolutions.
[0124] In a particular implementation of the invention, one or more
portions of the servo data may be written multiple times in
substantially the same physical location on the disk during
different tracks. Writing a particular portion of servo data more
than one time may be desirable under various circumstances,
including, for example, to assess characteristics of the disk
and/or heads, or to improve the accuracy of the track by further
averaging out random errors. In a particular embodiment, writing a
particular portion of servo data more than one time may be achieved
by partially or fully overlapping data written to contiguous
portions of the disk.
[0125] In operation, in one embodiment of the invention, the
servowriter writes a long track, such as a four-revolution track,
during four separate revolutions. The segments written every
revolution produce the final servo pattern. In one case, the system
performs dynamic control of the write gate to avoid overwriting
portions written in previous revolutions, i.e. the write gate does
not write when commanded under all conditions as had been done on
previous systems. In another case, the system performs dynamic
control of the write gate but permits partial or total overwriting
of one or more portions written in previous revolutions. The
switching of head current in connection with embodiments disclosed
herein may be performed at a significant rate, typically higher
than that previously done. The rate at which the head current is
switched may be decreased in situations where the system writes
data patterns comprising segments spaced further apart on the
disk.
[0126] According to this aspect of the invention, the system writes
servo data multiple times over the surface of the disk. For
example, servo data for a certain position of the disk may be
written more than once, such as four times, to the same area.
Alternatively, a particular segment of data may be partitioned into
multiple overlapping, contiguous and/or non-contiguous subsegments,
and the subsegments may be written during one or more different
revolutions. In either case, should one of the writing functions
suffer from non-repetitive runout, that writing function may be
averaged with the other writing functions and the system may
selectively read from the areas exceeding or not exceeding an
averaged threshold, or a combined threshold. This averaging
technique may be achieved by writing the servo data multiple times
over a single disk.
[0127] FIGS. 7-10 illustrate further aspects of the system relating
to the concept of the averaging technique of an aspect of the
invention. FIG. 7 shows normal operation of writing bursts to a
track. Track 701 is the target for writing and also subsequently
for reading of information using a series of bursts. First burst
702, or Burst A, is written first, and second burst 703, or Burst
B, is written thereafter. FIG. 7 is an ideal version of the burst
writing arrangement. In reality, tracks may be neither perfectly
straight nor perfectly circular, and burst writing is frequently
inexact, off center, too short or too long, and/or otherwise
imperfect. A more typical illustration is provided in FIG. 8,
wherein burst A spans the track and Burst B is located entirely off
the track. This effect makes reading and writing over the locations
as imprecise and undesirable. A conventional write head writes a
burst in a single revolution, shown in FIG. 9 as Burst A 901. In
reality, this conceptual depiction of Burst A 901 may be
inaccurate, as the head may impart a magnetic signal in the form of
a typical sine wave to the track and disk, such as that shown as
magnetic signal 902.
[0128] Thus, according to the embodiments of FIGS. 7 and 8, writing
of Burst A and Burst B comprises writing a first set of data in a
sine wave as Burst A and a second set of data in a sine wave on the
opposite side of the track as Burst B. The result may be sine waves
disposed in varied orientation on the disk with respect to the
track. In one case, once the head writes Bursts A and B to the
disk, the system positions the read and/or write head on the track
and reads the A and B Bursts. SA and SB represent the energy
perceived by reading Bursts A and B, respectively. In a particular
implementation, the head passes the received energy for the two
bursts to hardware and/or software to compute the following energy
value: E=(S.sub.A-S.sub.B)/(S.sub.A+S.sub.B)
[0129] If the Burst A and Burst B energy levels are equal, this
value goes to zero, indicating that Bursts A and B are located
close to their desirable positions along the intended track. If the
magnitude of energy E exceeds a particular threshold, the system
may decide that the position, shape, or other relevant
characteristics of the track are unsatisfactory, and may choose to
reposition the head and rewrite Bursts A and B. Correction of such
position, shape, or other relevant characteristics of the track may
be achieved and verified by decreasing the magnitude of energy
E.
[0130] Since the value of E may be positive or negative, in one
embodiment the system may utilize two different thresholds,
depending on whether E is positive or negative. The two thresholds
may also be equal in magnitude but opposite in sign. The thresholds
may be predetermined based on characteristics of the disk and/or
system, or may be dynamically computed and/or adjusted along the
tracks based on information that the system obtains while writing
and reading tracks. The sign of E may be used to assess which of
Bursts A or B is deviating more from a desirable position, and this
assessment may be utilized to select an appropriate corrective
action. In one case, the system may select to only rewrite a
particular burst. In other cases, the system may select to rewrite
more than one burst, or a combination of complete and/or partial
bursts. In other embodiments of the invention, other methods may be
employed to determine undesirable deviations in position, shape, or
other relevant characteristics of the track, including more complex
mathematical models and formulas for the energy E.
[0131] In previous systems, an inaccurately-written track would
either go uncorrected or would require reading the written area,
erasing bad tracks, and again writing the data, but this could
again have the data writing errors such as those pictured in FIG. 8
and/or may waste time and system resources.
[0132] According to one aspect of the present invention, the system
writes the A and B bursts in multiple revolutions over the same
disk area. FIG. 10 illustrates writing a first sinusoidal dipulse
1001 for Burst A at the beginning of the desired Burst A location,
followed by a second dipulse 1002 for Burst B at the beginning of
the desired Burst B location. On a second pass, the head writes the
second Burst A dipulse 1003 offset in position from the first Burst
A dipulse 1001, possibly at or near the end of the first dipulse
1001 point. Second Burst B dipulse 1004 is similarly written at a
position offset from first Burst B dipulse, and possibly at or near
the completion point of the first Burst B dipulse 1002. The system
can step through the Burst dipulses and may write more than one
dipulse per pass, illustrated by the ellipsis in FIG. 10. Two
passes may be employed, or more than two passes, within the scope
of the present invention. Alternatively, the system may write
partial dipulses in various passes, or a combination of partial and
full dipulses.
[0133] The result of this partial burst writing technique employed
on multiple passes is to provide an averaged positioning and signal
strength for burst writing such that writing on a single pass with
a single offset becomes unlikely. Should one pass suffer from an
offset during the writing procedure, that offset may be corrected
or decreased in subsequent passes.
[0134] A drive having a substantially-constant offset at all times,
or a bias, may be unacceptable and improperly operating. The system
may elect to correct this bias. Alternatively, such a bias may be
detected and communicated to a disk drive comprising the respective
disk, such that the disk drive may utilize the bias to follow the
track comprising the bias. In one case, such a bias may be
attributed to repeatable run off errors.
[0135] The effect addressed by the present aspect of the system is
random noise or intermittent wandering experienced during writing
under normal operation. Over a number of passes, it is to be
understood that the present aspect of the system tends to reduce
adverse effects due to errant dipulse and burst writing.
[0136] It is to be understood also that part of a dipulse may be
written in one pass, or multiple dipulses, but in most cases the
entire burst area and all dipulses are not written in a single pass
for a particular data burst. Thus it is within the scope of the
present system to write a subset of the pulse or a number of
dipulses which is less than all of the dipulses to the disk in a
first pass, then an additional dipulse or number of dipulses or
portion of the burst or portions of the burst on a subsequent pass
or multiple subsequent passes.
[0137] Once this multiple pass data burst writing technique is
completed, the system may optionally compute the energy calculation
provided above for Bursts A and B. While the energy errors may be
less for the disk written according to the multiple pass technique,
should the value of the energy computation be outside a particular
range the bursts may need to be rewritten. This reading, energy
computation, assessment, and rewriting is optional but may have a
tendency to provide enhanced and improved burst writing
capability.
[0138] With respect to the magnetic disk aspect of the present
system, according to an aspect of the invention, once an ideal
magnetic disk is produced, the ideal magnetic disk is mechanically
coupled to the spindle, possibly in addition to other disks to be
written or tested stacked thereon, such as in the configuration
illustrated in FIG. 1. The ideal magnetic disk spins together with
the other disks. Alternatively, the ideal magnetic disk may not
spin together with the other disks, but may be offset by a
predetermined, predictable or determinable amount with respect to
the other disks. As previously mentioned, more than one ideal
magnetic disk may be utilized.
[0139] In one embodiment, a detector head reads information stored
on the ideal magnetic disk and detects movement of the ideal
magnetic disk with respect to the head. Hardware and/or software
logic utilizes the information provided by the detector head to
determine the magnitude and direction of movement at any point
along the spindle or on the disks, with respect to any heads
operating on the disks. If the disk is ahead or behind the point
where it should be, for example, the differential between the
present position and the desired position is applied to hardware
and/or software logic to either alter the spin of the disk or alter
the head position to move into closer synchronization with the
preferred position. In other words, once the system determines the
direction and magnitude of motion of a particular disk at a point
proximate to a corresponding head reading from or writing to the
disk, the system moves that head to compensate for the motion of
the disk. As a result, the relative motion of the head with respect
to the corresponding disk is reduced or eliminated.
[0140] In one implementation, a voice coil motor (VCM) that
normally engages and operates the head utilizes information
provided by the detector head and/or other logic to move the head
in response to movement of the disk. In this aspect, the head is
substantially-rigidly coupled to an arm that moves under control of
the VCM. In an alternative implementation, the head is mechanically
coupled to a first end of the arm controlled by the VCM via a
jointed connection, and the head may move with respect to the first
end of the arm under the control of one or more actuators.
[0141] The method for averaging out random errors by writing
different segments of a track in multiple revolutions disclosed
herein may be utilized in connection with one or more heads writing
information to a disk. When multiple heads are utilized to write to
a single disk, the heads may be distributed along a single arm
controlled by a single VCM. Each head may be individually
controlled by one or more corresponding actuators mechanically
coupled to the arm. Alternatively, there may be more than one arm,
and each arm may be controlled by the same or different VCMs.
[0142] While the description above has provided an example of how
an aspect of the present invention may be employed to produce an
ideal magnetic disk, the methods and systems disclosed herein may
also be applied to produce regular data disks. More specifically,
the systems and methods taught herein may be utilized by a
commercial system to write data to a disk prior to distribution of
the disk to an end user, or by a disk drive comprised in a system
utilized by an end user. The systems and methods disclosed herein
and discussed in connection with FIGS. 7-10 may be employed to
improve the accuracy with which data tracks are written in a
variety of applications, aside from certification, initialization
and servo writing of disks. For example, but without limitation, a
desktop or a laptop computer system may comprise a disk drive that
utilizes methods and systems taught herein to improve the reading
and/or writing of regular data from and/or to a disk, such as
operating system information, software and word processing files.
As another example, a portable consumer device may employ methods
and systems taught herein to improve storage and/or retrieval of
data to and/or from a disk, including audio, video, and/or
communication data.
[0143] Certain modifications to the methods and systems disclosed
herein may be made while remaining within the scope of the present
aspects of the invention to more appropriately address particular
characteristics of the intended application. For example, in a
mobile consumer device that may be commonly and repeatedly exposed
to physical shocks due to physical impacts or movements, the
expression of the energy E and/or the corresponding thresholds may
be altered to tolerate a wider range of deviations in the position,
shape, or other relevant characteristics of the data tracks,
possibly at the expense of track density.
3. Non-Contact Radiation Detection System that Bounces Radiation
Off a Part of the Spindle
[0144] Yet another aspect of the invention provides a system and
method for detecting movement of a spindle and/or one or more disks
with respect to a common base by detecting radiation reflected by a
part of the spindle. Movement of the spindle and/or one or more
disks with respect to the common base may then be related to
movement with respect to one or more read/write heads.
[0145] As described above, movement of the spindle with respect to
the base may result in relative movement between a disk and a
corresponding head writing to, or reading from the media disk,
thereby possibly interfering with the operation of the head. In one
embodiment, the system detects the magnitude and direction of such
movement between a disk and a corresponding head and compensates
for such movement by moving the head accordingly.
[0146] One implementation of this aspect of the invention utilizes
a source that directs radiation towards an area of the spindle and
a receiver that detects radiation reflected by the area of the
spindle. Hardware and/or software logic functionally connected to
the transmitter and/or receiver detects movement of the spindle
with respect to the base and moves one or more heads reading from,
or writing to the disks accordingly.
[0147] In one aspect, the non-contact radiation detection system
comprises an optical system. The optical system comprises an
optical transmitter, such as a laser diode, and an optical
receiver, such as an optical detector. The optical transmitter and
receiver are disposed or otherwise fixedly mounted to the base of
the equipment and cooperate to detect movement (other than normal
spinning) of the spindle with respect to the base.
[0148] A cylindrical area of the spindle exhibits a certain degree
of reflectivity. In one case, the cylindrical area is manufactured
from a reflective metal, such as steel, and is polished to exhibit
a relatively high degree of reflectivity. Alternatively, the
cylindrical area of the spindle may be covered with a reflective
material. The cylindrical area of the spindle is substantially
perpendicular to the planar surfaces of the disks stacked on the
spindle. The spinning axis of the disks stacked on the spindle is
substantially parallel with the cylindrical area and approximately
coincides with the central axis of the cylindrical area. Both the
cylindrical area and the stacked disks are substantially rigidly
connected to the spindle, such that the cylindrical area and the
stacked disks spin with approximately the same angular speed.
[0149] The optical system detects movement of the spindle with
respect to the base by illuminating the reflective cylindrical area
with a laser beam produced by the optical transmitter and receiving
a reflected portion of the laser beam at the optical detector.
[0150] Cross sections of the cylindrical area may not be perfectly
circular, but may exhibit irregularities, such as an oval,
non-circularly-curved, or "egg" shape. To compensate for any
imperfections in the surface of the cylindrical area, the system in
one aspect analyzes the Fourier frequency spectrum of the light
reflected off the cylindrical area and filters out periodic signals
that may be attributed to imperfections of the cylindrical surface
intercepting the incident laser beam periodically as the spindle
spins at a relatively-high rate.
[0151] Another aspect of this reflective spindle configuration
utilizes two or more laser beams offset with respect to each other.
Each laser beam corresponds to a dedicated laser source and a
dedicated laser detector. Since imperfections of the cylindrical
surface will exhibit similar signatures on each laser beam, as
detected by the various corresponding laser detectors, these
imperfections may be filtered out and the actual movement of the
spindle with respect to the base may be isolated and detected or
estimated.
[0152] One alternate aspect of the invention in addition to those
outlined above is using a series of ridges or non-reflective
material equally spaced around the cylinder such that light energy
transmitted to the cylinder reflects efficiently off reflective
areas but does not reflect efficiently off the ridged or
nonreflective areas. This enables the system to measure relative
position and timing and correct errors by counting the number and
time of reflections provided.
[0153] Hardware and/or software logic may utilize variations in the
intensity, frequency and/or phase of each reflected laser beam
received at the corresponding detector to determine the magnitude
and direction of movement at any point along the spindle or on the
disks, both with respect to the base and with respect to any heads
operating on the disks. The system can determine such parameters
using an interferometer to detect movement of the spindle.
[0154] Once the direction and magnitude of motion of a particular
disk is determined at a point proximate to a corresponding head
reading from, or writing to the disk, the system moves the head to
compensate for the motion of the disk. As a result, the relative
motion of the head with respect to the disk is minimized or
eliminated. In a particular implementation, a voice coil motor
(VCM) that normally engages and operates the head utilizes
information provided by the optical system and/or other logic to
move the head in response to movement of the disk. In this aspect,
the head may be substantially-rigidly coupled to an arm that moves
under control of the VCM. In an alternative implementation, the
head is mechanically coupled to a first end of the arm controlled
by the VCM via a jointed connection, and the head may move with
respect to the first end of the arm under the control of one or
more actuators.
[0155] According to an embodiment of the invention, multiple heads
are utilized to write to a single disk, and the heads may be
distributed along a single arm controlled by a single VCM. Each
head may be individually controlled by one or more corresponding
actuators mechanically coupled to the arm. Alternatively, there may
be more than one arm, and each arm may be controlled by the same or
different VCMs. In each of these implementations, the system may
utilize the information obtained regarding the magnitude and
direction of relative movement between a particular head and a
corresponding disk to reposition the head and/or disk
dynamically.
[0156] An alternative aspect of spindle position measurement
provides alternate differential systems to detect spindle movement
with respect to the base. The differential system for detecting
motion of the spindle may, for example, comprise two or more laser
beams reflecting off different portions of a reflective or
alternating reflectivity/nonreflectivity part of the spindle to
detect the magnitude and direction of spindle movement at different
points in the system.
[0157] As a further feature of the present design, the system
performs various functions designed to minimize repeatable run out
and/or non repeatable runout errors (RRO and NRRO). RRO and NRRO
are measurements of the radial accuracy of written tracks. RRO and
NRRO measurements may be performed after the system has written to
the disk, and can be assessed by assembling the written disks into
drives and testing. Components such as the spindle may also be
tested independently to insure runout error is within predetermined
specifications, but this again typically occurs after the write
operation. Such measurements are generally not made during the
servowriting process. In some cases, a few basic runout performance
values can be made available after writing the servo pattern by
reading the radial positioning error with the same magnetic
read/write head on the servowriter used to write data. The system
then records the standard deviation of the RRO and NRRO for the
just-written tracks.
[0158] The present system monitors runout performance during
servowriting. The runout error signal may be used for a follow up
correction indication so that improperly written data, such as a
servo mark, can be rewritten. Rewriting miswritten data tends to
limit the tail of the runout error statistical distribution,
thereby enabling tighter overall error distribution and therefore
smaller track spacing.
[0159] For simultaneous monitoring of radial track positioning
errors, the system generally cannot use the read/write head during
the writing process. Various supplemental optical or capacitive
sensors monitor the spindle axis position with respect to a base,
reference spindle axis position, or a surface that emulates the
head position with respect to spindle axis position. This relative
measurement may be performed using, for example, a single beam or
differential beam interferometer as discussed herein. Other routine
position monitoring devices such as capacitance probes, inductive
sensors or alternate optical position sensors could also be
employed to monitor spindle position.
[0160] Performance metrics for track writing performance may be
expressed in terms of the standard deviation of radius from a
demanded radius. This standard deviation can be separated into
repeatable and nonrepeatable components for purposes of
measuring/correcting. In addition, numerous monitoring and
performance metrics have not been previously implemented on data
writing devices such as servowriters.
[0161] An aspect of the invention provides a method and system for
determination of a monitoring and performance metric for assessing
track data: the time or RPM dependent servo mark positions, or
optically inferred spindle axis position. Since disks are
mechanically coupled to the spindle, the position of the axis of
the spindle may be reliably correlated with the position of a servo
mark located on any particular disk, and such a correlation is
bi-directional in the sense that knowing either of the two enables
determination of the other one.
[0162] According to various aspects of the present invention,
assessing time or RPM dependent servo mark positions or optically
inferred spindle axis positions can be accomplished in different
ways. In a particular implementation, an optical sensor can be used
to monitor the position r of the spindle chuck or hub surface and
record r(.theta.(t)) as the spindle chuck spins with angular
velocity .omega.. The topographical radius
r.sub.t(.theta.)=r.sub.t(.omega.t) of the surface as a function of
angle .theta. can be determined independently. The difference:
.delta.r(t)=r(.theta.(t))-r.sub.t(.theta.)
[0163] expresses the amount of wobble in the disk axis. This wobble
can be divided into two components: a repeatable part having
harmonics of the basic rotational rate given by the following
Fourier components A.sub.N(.omega.)=(2.pi.).sup.-1.SIGMA..sub.i
exp(iN.omega.t.sub.i).delta.r(t.sub.i);
.delta.r.sub.rro(t.sub.i)=.tau..sub.N
exp(-iN.omega.t.sub.i)A.sub.N(.omega.).
[0164] and a non repeatable part including nonharmonic components
.delta.r.sub.nrro(t.sub.i)=.delta..sub.r(t.sub.i)-.SIGMA..sub.N
exp(-iN.omega.t.sub.i)A.sub.N(.omega.)
[0165] With respect to the repeatable portion, A.sub.N(.omega.) is
the amplitude of the spindle wobble at a frequency of N.omega..
This value may not be constant but may change slowly with time. The
media writer or servo writer has the ability to monitor this
amplitude during writing for process control, grading, media writer
self testing, or for actively controlling the media writer as
disclosed herein using this repeatable portion amplitude. For
example, active control of the media writer may occur by putting a
deflection on the voice coil to place a compensating position on
the writer head.
[0166] Another example of employing processed data in servowriting
performance is using the histogram of the NRRO component
(non-repeatable part of the wobble that includes the nonharmonic
components) of the servo mark positions or optically inferred
spindle axis position. In this arrangement, an optical sensor such
as an interferometer monitors these non repeatable errors during
servowriting. The width and shape of this distribution assesses
data writer performance as well as the quality of the servo
patterns on the disk.
[0167] 4. Radial Positioning Using Interferometer
[0168] Yet another aspect of the invention provides a system and
method for detecting movement of a spindle and/or one or more disks
with respect to one or more read/write heads by detecting radiation
reflected by both a part of the spindle and one or more features
mechanically coupled to one or more of the heads. One embodiment of
the invention employs an interferometer in performing radial
positioning functions. The present design enables in-situ
monitoring of the disks and allows certification by offering
dynamic compensation for spindle movement.
[0169] In an alternative implementation, information regarding
movement of the spindle and/or heads with respect to a common base
obtained as previously described may be employed together with data
obtained according to the embodiment further described in this
section to further improve the accuracy and/or reliability of the
measurements.
[0170] In common implementations, interferometers are devices that
convert the phase difference between two input waves into intensity
variations on one or more output waves that carry information about
the phase difference between the input waves. The interferometer
outputs may represent superpositions of portions of the two input
waves. The amount of each input delivered to each output and the
phase shift imparted during delivery correlates to the optical path
length difference between the two beams.
[0171] One type of interferometer that may be used in the present
system is that described in U.S. patent application Ser. No.
09/______, entitled "Waveguide Based Parallel Multi-Phaseshift
Interferometry for High Speed Metrology, Optical Inspection, and
Non Contact Sensing," inventors David Peale, et al., assigned to
the assignee of the present invention, which is hereby incorporated
by reference into the present application. The interferometer of
this aforementioned application is a multiphase interferometer that
employs waveguided optics and an optical coupler to produce a
tri-phase signal that enables measurement of phase differences
between two emitted beams.
[0172] One aspect of the invention disclosed herein is to measure
the distance of the head to the disk axis, or spindle, as
accurately and directly as possible. Direct measurement comprises
using as actual a distance measure of the head position as
possible, with as little indirect or calculated measurement as may
be performed under the circumstances. One aspect of the present
invention is illustrated in FIG. 11. From FIG. 11, the system
employs an optical interferometer transmitting two laser beams in a
differential mode. Interferometer 1101 comprises a laser light
generating source, and possibly more than one such source, to
generate two separate laser beams. The first laser beam strikes a
first lens 1102 and a second focusing lens 1103 and directs the
resultant beam to the polished chuck 1106. Polished chuck 1106
typically comprises a highly reflective or mirror like surface. The
second beam passes through third lens 1104 and is retro reflected
from a corner cube 1105 or other retro reflecting surface mounted
on the e-block, illustrated in FIG. 4 as element 404. A corner
cube, or cat's eye, operates under the law of reflection, but
operates differently from a typical mirror or reflective surface. A
beam of light entering the corner cube is reflected back in the
same general direction as its angle of entry. This same-direction
reflection occurs for not only one special angle of incidence with
a mirror, but for all angles of incidence with the corner cube. The
second beam in FIG. 11 is typically collimated, or emits energy
waves that are substantially parallel. Mounting the retro element,
such as corner cube 1105, to the e-block, is performed in an
orientation that emulates the head position. In other words, the
retro reflective element is mounted in a position on the positioner
or e-block that emulates the position of the read/write head, and
the stiffness of the positioner arm and connection between the
e-block position and the read/write head offers a substantial
analogy to actual head position. The retro reflector or corner cube
1105 swings in an arc tangent to the second, substantially
collimated, interferometer beam, and reflects back through third
lens 1104 and back to the interferometer, where the time of
reflection or distance from the interferometer 1101 to the emulated
head position is determined. The resultant interferometer signal
substantially measures the distance between the surface of the
chuck or chuck spindle 1103 and the simulated head position at the
retro reflector or corner cube 1105. The difference between the
interferometer and the chuck minus the distance between the
emulated head and the interferometer is .delta.raw, or the raw
measurement of head position relative to the polished chuck
1106.
[0173] The difference signal .delta.raw must be corrected for
topological parameters of the polished chuck 1106. The chuck 1106
can deviate from a perfect and exactly centered cylinder, and under
certain circumstances may move or shift during operation. The
system measures deviation independently as a function of disk
angle, .THETA., and the measurement is dynamically stored in
memory. Deviation of the cylindrical chuck is represented by
.delta.topo(.THETA.). The system then computes the error signal
based on the difference between the raw position of the emulated
head minus the topographical error of the disk cylinder,
.delta.err=.delta.raw-.delta.topo(.THETA.). This error signal is
employed by the system to actuate the voice coil 1107 and micro
actuators on the suspension to reposition the head to more
accurately track the radius of the true axis of the disk. The error
measurement is factored into the desired position of the head to
affect movement of the head to a more exact position over the disk.
In addition, that portion of the error signal at frequencies too
high for the positioning servo to correct for can be used to
inhibit writing of the servo information if this signal is above a
predetermined limit. Writing of the servo information may
recommence once the error signal falls below the limit.
[0174] In an alternate aspect of the present design, an additional
interferometer is employed above the disk to provide a z-axis
measurement and to address issues of tilt. In this embodiment, the
retro reflector or corner cube is located at a different height
than the lateral version to measure differential z position caused
by tilt. The second interferometer also uses lensing to set up a
collimated beam and tracks a reference Z point, which may be disk
position or spindle location, or some other available reference
height point on the arrangement. The measurement at an additional
axial position (z) is fed back to the signal processor and the
voice coil is employed to correct the head position over the disk.
If the system measures the tilt of a rotating spindle, signal
processing requires the raw positional z measurement minus the
topographical shift resulting from tilt. Depending on the parameter
desired to be measured, whether head position, spindle position, or
disk position, the retro reflector must be positioned to offer an
accurate representation of the target parameter. Thus if z position
of the head is the desired parameter to be measured, the retro
reflector positioning must, like the aspect described above,
emulate the head position, such as on the e-block or otherwise
associated as directly as possible with the positioner and/or
read/write head. Alternately, if tilt of the spindle is the desired
measured parameter, one beam may reflect off approximately the top
center point of the spindle, for example, while the second beam
reflects off a point as far to the periphery of the spindle as
possible.
[0175] In another alternate aspect of the present system, a second
lateral interferometer is used with the system illustrated in FIG.
11, with a 90 degree difference between the first interferometer
and the second to measure y axis movement in addition to x axis
movement.
[0176] Unless indicated or implied otherwise, as used herein, x and
y directions are conventionally assumed to indicate directions
substantially in the plane of a particular disk, while the z
direction indicates a direction substantially parallel with the
axis of the spindle. In particular embodiments, more than one
substantially-parallel x-y planes may be considered when more than
one disk is coupled to the spindle. Depending on the context, the
angle theta (.theta.) may be conventionally defined in a particular
x-y plane, or may be a spindle-characteristic value that is common
to all disks coupled to the spindle.
[0177] This aspect of the invention uses an additional retro
reflector or corner cube mounted on the e-block or other available
and practical location to emulate head position and retro reflect
the incoming collimated beam. The interferometer again passes
energy through a lensing arrangement to focus and/or collimate the
beams, and one beam is also directed toward the spindle
arrangement. This x-y dual interferometer arrangement provides
additional accuracy, and similar parameters are fed to the signal
processor and used to command the voice coil to more accurately
position the e-block, positioner, and associated read/write
heads.
[0178] An embodiment of a system employed as taught herein to
attain high accuracy positioning may include a dual beam
interferometer as described in the Peale application, U.S. patent
Ser. No. 09/______. The Peale design uses a tri-coupler where the
reference beam of the tri-coupler is collimated onto a
retro-reflector mounted to the E-Block described previously and the
other beam is focused onto the spindle hub.
[0179] More specifically, the guided wave interferometer is a
system comprises a tri-coupler and has the following aspects. The
tri-coupler consists of three waveguide inputs, three waveguide
outputs, and a region between the inputs and outputs wherein waves
from each of the three inputs are redistributed approximately
equally to each of the three outputs. Assuming that the tri-coupler
is lossless and distributes light from an input waveguide equally
to each of the three output waveguides, then there may be a 120
degree phase shift between each of the three output light waves.
Thus, if light is injected into two of the input waveguides, the
intensity of the light in the three output waveguides will possess
a periodic interferometric modulation as the phase difference
between the input beams advances, and in particular, the phase
relation among the intensities of these three beams will be 120
degrees. It is thus possible to measure the intensities of the
three output beams, and accurately determine the phase difference
between the two input beams. In addition, the total intensity of
the input light can also be calculated.
[0180] Referring to the drawings more particularly by reference
numbers, FIG. 14 is a schematic cross section through one section
of a fused-fiber optical tri-coupler 10 showing the spatial
symmetry of the three fibers 12, 14 and 16, leading to the
characteristic 120 degree phase relation between the light waves
within each of the three waveguides. The tri-coupler 10 couples
light between the first 12, second 14 and third 16 waveguides such
that light input at one end of any waveguide is substantially
equally distributed to each of the three waveguides at the output
end.
[0181] FIG. 15 shows an embodiment of an optical interferometer 50
of the present invention. The interferometer 50 may include a first
waveguide 12, a second waveguide 14 and a third waveguide 16. The
waveguides may be fiber optic cables or integrated waveguides that
transmit light.
[0182] One of the waveguides, namely the second waveguide 14, may
be coupled to a light source 18. By way of example, the light
source 18 may be a laser. The light source 18 may have a return
isolator 19 that prevents back reflections from feeding back into
the source 18. The light emitted from the light source 18 and
isolator 19 may be directed into the tri-coupler 10 via an optical
circulator 22.
[0183] Light entering the tri-coupler 10 along waveguide 14 is
distributed to each of the three output waveguides in roughly equal
intensities. Light exiting the tri-coupler on waveguide 14 is
allowed to escape the waveguide unused, and the waveguide is
terminated in such a way that minimal light is reflected back into
the tri-coupler. The light exiting the first waveguide 12 is
reflected from an object surface 24 back into the waveguide 12. The
interferometer 50 may include a lens assembly 26 and autofocus
system 38 that focuses the light onto surface 24 and back into
waveguide 12. Light within the third waveguide 16 may be reflected
from a reference surface 27 back into the waveguide 16. The object
24 and reference 27 surfaces may be separate locations of the same
test surface. Alternatively, the light from the third waveguide 16
may be reflected from a reference surface (not shown) separate from
the object surface 24.
[0184] The light reflected from the test surface 24 and reference
surface 27 through the first 12 and third 16 waveguides travels
back through the tri-coupler 10. The reflected light within the
first waveguide 12 provides an object beam. The light within the
third waveguide 16 provides a reference beam that interferes with
the object beam within the tri-coupler 10.
[0185] The tri-coupler 10 allows reflected light within the first
waveguide 12 to be coupled into the second 14 and third 16
waveguides, and reflected light from the third waveguide 16 to be
coupled into the first 12 and second 14 waveguides. The output of
the tri-coupler 10 is three light beams with intensities that are
out of phase with each other by approximately 120 degrees. The
light intensity of each light beam detected by photodetectors 28,
30, and 32. The light exiting the tri-coupler along waveguide 14 is
directed to the detector 28 via the circulator 22.
[0186] Photodetectors 28, 30, and 32 provide electrical output
signals to the computer 34. The computer 34 may have one or more
analog to digital converters, processor, memory etc. that can
process the output signals.
[0187] By way of example, the interferometer 50 can be used to
infer the distance between the retro-reflector mounted on the
E-Block and the surface of the spindle hub where the surface of the
spindle hub 24 is at the focus and the retro-reflector 27 returns
the collimated beam.
[0188] The differential distance (modulo .lamda./2) at any point
can be inferred from the following equation.
h=.lamda.*.theta./4.pi. (1) where:
[0189] h is the apparent differential distance;
[0190] .theta. is the interferometric phase angle between the
object and reference beams, and
[0191] .lamda. is the wavelength of the reflected light.
[0192] The interferometric phase angle can be determined by solving
the following three equations.
I1=.alpha.1(E1.sup.2+(.beta.1E2).sup.2+2.beta.1E1E2
cos(.theta.-.PHI.1)) (2)
I2=.alpha.2(E1.sup.2+(.beta.2E2).sup.2+2.beta.2E1E2
cos(.theta.-.PHI.2)) (3)
I3=.alpha.3(E1.sup.2+(.beta.3E2).sup.2+2.beta.3E1E2
cos(.theta.-.PHI.3)) (4) where:
[0193] I1=is the light intensity measured by the photodetector
28;
[0194] I2=is the light intensity measured by the photodetector
30;
[0195] I3=is the light intensity measured by the photodetector
32;
[0196] E1=is the optical field of the light reflected from the test
surface into the first waveguide 12;
[0197] E2=is the optical field of the light reflected from the test
surface into the third waveguide 16;
[0198] .PHI.1=is the phase shift of the detected light within the
first waveguide, this may be approximately -120 degrees;
[0199] .PHI.2=is the phase shift of the detected light within the
second waveguide, this may be defined to be 0 degrees;
[0200] .PHI.3=is the phase shift of the detected light within the
third waveguide, this may be approximately +120 degrees;
[0201] .alpha.1=is a channel scaling factor for the first waveguide
and detector;
[0202] .alpha.2=is a channel scaling factor for the second
waveguide and detector;
[0203] .alpha.3=is a channel scaling factor for the third waveguide
and detector;
[0204] .beta.1=is a coupler nonideality correction term for channel
1;
[0205] .beta.2=is a coupler nonideality correction term for channel
2, and
[0206] .beta.3=is a coupler nonideality correction term for channel
3.
[0207] The interferometer 50 may include a phase shifter 36 that
shifts the phase of the light within the third waveguide 16. The
phase shifter 36 may be an electro-optic device that can change the
phase to obtain a number of calibration data points. The
calibration data can be used to solve for the phase shift values
.PHI.1, and .PHI.3, the channel scaling factors .alpha.1, .alpha.2,
and .alpha.3, and the coupler nonideality factors .beta.1, .beta.2,
and .beta.3. The values are stored by the computer 34 and together
with the measured light intensities I1, I2, and I3 are used to
solve equations 1, 2, 3, and 4 to compute the phase angle, .theta.
and the apparent distance h.
[0208] FIG. 16 shows an alternate embodiment of an optical
interferometer 60 of the present invention. The interferometer 60
uses a 2.times.2 optical coupler 23 in place of the circulator 22
used in interferometer 50. In this case, light from the laser is
split as it passes forward through coupler 23. Light exiting
coupler 23 along waveguide 15 is discarded. Light exiting coupler
23 in waveguide 13 is fed into tri-coupler 10 as in the
interferometer 50 previously discussed. Light returning from
tri-coupler 10 along waveguide 13 is split. Light exiting coupler
23 along waveguide 13 is rejected by isolator 19 and does not
interfere with the laser. Light exiting coupler 23 along waveguide
15 is fed to detector 28. This embodiment of interferometer 60 may
be less expensive to produce than that of interferometer 50 owing
to the fact that coupler 23 may be considerably less expensive than
circulator 22. However, the laser power delivered into the
tri-coupler 10 may be correspondingly reduced and the signal
detected by detector 28 may also be reduced as compared to those
detected in detectors 30 and 32.
[0209] The output signals of the photodetectors 28, 30, and 32,
responding to a steadily advancing phase angle at the inputs, are
shown superimposed in FIG. 17. The phase shifts between different
light beams separates the maxima and minima of the output signals.
With such an arrangement at least one of the signals will be in a
relatively sensitive portion of the waveform between a maximum and
minimum. This illustrates how the present invention provides an
interferometric detector that has a relatively uniform sensitivity
and is therefore desirable for metrological applications.
[0210] Interferometers 50 and 60 of the present invention provide
three out-of-phase signals with a minimal number of parts. The
tri-coupler 10 and fiber optic waveguides 12, 14, and 16 can be
packaged into a relatively small unit, typically measuring only
0.12 inches diameter by two inches in length. This reduces the
size, weight and cost of the interferometers. By way of example,
the tri-coupler 10 and waveguides 12, 14, and 16 could be also
constructed onto a single planar substrate using known
photolithographic and waveguide fabrication techniques. Such a
construction method would have advantageous properties which would
allow tighter integration with other portions of the
interferometric system together with reduced assembly costs.
[0211] As an alternative to those aspects discussed herein using
interferometers, other sensing means or sensors may be employed to
detect head position, using independently positioned detectors.
Such a construct may employ fiber optics where the fibers are in
close proximity to the head and/or spindle. In such a design, the
position of the spindle and heads are generally known to a degree.
Light energy or other energy may be directed toward, for example, a
head, and energy reflected off the head and received by a sensor
located proximate or near the head in the zone of expected energy
reflection. Capacitance sensors or inductive sensors could also be
employed in the design. In general, any three independent position
detectors could be used to detect head position or spindle position
in this design.
[0212] The present aspect of the invention is not limited to the
specific constructions and arrangements shown and described, since
various other modifications may occur to those ordinarily skilled
in the art. For example, although the light reflected from the test
surface 24 is initially directed through the tri-coupler 10, it is
to be understood that the light can be introduced to the test
surface 24 without initially traveling through the coupler 10.
[0213] Adjustment of Spindle Position
[0214] Various aspects of the invention described herein provide
methods and systems for directly on indirectly determining relative
motion between one or more heads and one or more corresponding
disks. In a typical case, one or more heads are operationally
coupled to a disk reading to or writing from the disk, and a system
provided by an embodiment of the present invention attempts to
accurately position the one or more heads on the disk by
identifying and minimizing or eliminating positional error
interferences. In particular embodiments, the system operates
substantially simultaneously on more than one disk. In the
embodiments previously disclosed, correction of positional errors
has been generally achieved by repositioning the heads.
[0215] An aspect of the present invention provides an alternative
method for correcting positional errors between heads and disks,
namely, rather than repositioning a head, the system may reposition
the spindle. Alternatively, the system may reposition both the head
and the spindle. In a general case, according to an embodiment of
the invention, the system may reposition each head in the system
while, substantially-simultaneously, also repositioning the
spindle. In this general case, there may be more than one head
operationally coupled to each disk, and each of these heads may be
individually repositioned.
[0216] Cooperative repositioning of heads and spindle may help
reduce or eliminate positioning errors with respect to each disk on
which the system operates, and therefore may improve reading and
writing of data to each such disk. In a servowriting and/or
certification system, but also in any other commercial or end user
system or application, this may improve system performance, such as
increasing the track density and the throughput, and may reduce
costs.
[0217] In one embodiment, as the system tracks positioning errors
for each disk and head in the system, the system may elect to
solely reposition the spindle without repositioning any of the
heads in the system. This may occur when the system determines that
repositioning of the spindle may satisfactorily reduce all or
sufficiently many of the positional errors associated with
individual heads in the system without repositioning any of the
individual heads. This may be a more efficient and faster solution
to correcting positioning errors during operation of the system as
compared to individually adjusting the position of individual
heads.
[0218] Movement of the spindle may be an effective approach to
resolve repeatable run out errors. One cause for repeatable run out
errors is an imbalance in the mass distribution of the spindle and
disks. An aspect of the invention may reduce positioning errors
attributed to repeatable runout by addressing and attempting to
compensate for imbalances in the spindle and/or disk mass
distribution.
[0219] Various embodiments of the invention provide methods and
systems for repositioning a spindle to address positioning errors
in the system. Once an error is detected, the spindle may be moved
using conventional means while rotating, including but not limited
to using an electromotive force (EMF) to alter spindle position. In
one implementation, the spindle motor that normally drives the
spindle to rotate the disks coupled to the spindle may move the
spindle in any arbitrary direction. For example, the spindle motor
may move the spindle along the spindle axis, in the plane of any
particular disk coupled to the spindle, or in an arbitrary three
dimensional spatial direction. Such an arbitrary three dimensional
direction may include displacement both in a plane that
substantially comprises the spindle axis and in an x-y plane that
substantially comprises the surface of a particular disk coupled to
the spindle.
[0220] In one embodiment, the spindle may be moved by altering the
current through the spindle motor coil. In one embodiment, the
spindle may be moved using one or more electromagnets disposed in
proximity of the spindle to interact with the spindle and move the
spindle via a magnetic field. In one implementation, at least three
external electromagnets are disposed around the spindle, and the
three electromagnets cooperate to produce magnetic fields of
arbitrary orientations and intensities that may move the spindle in
any three dimensional arbitrary direction. In one embodiment,
permanent magnets are mechanically coupled to the spindle to
interact with the external electromagnets. In another embodiment,
one or more spindle electromagnets are mechanically coupled to the
spindle to interact with the external electromagnets.
Electromagnets coupled to the spindle may also interact with
external permanent magnets. Any combination and number of permanent
magnets and electromagnets may be mechanically coupled to the
spindle and/or disposed along the spindle. To reposition the
spindle, the system may vary electric currents through such spindle
or external electromagnets to produce appropriate variations in the
magnetic fields interacting with the spindle, thereby moving the
spindle as desired.
[0221] Various devices may be utilized as electromagnets, including
Helmholtz Coils, magnetic coils with or without cores, and others.
Generally, and device or combination of devices that produce a
magnetic field with an adjustable intensity, gradient, and/or
orientation may be utilized as described herein to move the
spindle. Some of the embodiments disclosed herein insulate
sensitive system components from the magnetic fields produced by
permanent magnets and/or electromagnets to avoid interference. The
system components that may be protected from magnetic fields
include actuators, read and/or write heads, and other components
sensitive to electromagnetic interference.
[0222] According to an aspect of the invention, a spindle may also
be moved mechanically, via physical forces. In one aspect, variable
air pressure through the orifices of the air bearing could be
employed to control and correct spindle positioning.
[0223] An embodiment of the invention utilizes actuators embedded
in the spindle to redistribute the mass of the spindle and disks.
In one case, if the system determines an imbalance in the mass
distribution of the spindle that produces a repeatable run out
error on one or more disks, the system may activate one or more
actuators disposed along the spindle subsystem to rebalance the
mass distribution. This may be achieved by extending and/or
retrieving one or more objects via actuators with respect to the
spindle axis. In a particular implementation, for example, the
system may extend an actuator beyond the circumference of the
rotating spindle, thereby adding mass in a particular radial
direction of the spindle. Adding mass in particular radial
direction of a rotating spindle would increase the local
centrifugal force, thereby producing an additional local force,
which could be utilized to move the spindle. The reverse effect
could be achieved by retrieving an actuator inside the
circumference of a rotating spindle, thereby decreasing the local
centrifugal force.
[0224] One embodiment may include altering spindle position by
interacting with the spindle via particles that exhibit mass. In a
particular implementation, the system may utilize air bursts or
other fluid bursts produced by one or more sources disposed in
proximity of the spindle to move the spindle. Such an arrangement
may employ a nozzle or nozzles, and may require submerging the
spindle and/or media in fluid.
[0225] According to an aspect of the invention, any combination of
the methods and systems disclosed above for moving a spindle may be
utilized to reposition the spindle alone, or in further combination
with repositioning of any group of one or more individual heads.
For example, in one case, mechanical actuators may be employed to
rebalance a spindle system exhibiting a mass-induced repeatable run
out error, while a combination of magnetic devices actively
reposition the spindle and individual heads are repositioned with
respect to particular disks.
[0226] Multiple Sector Servo Writing
[0227] Another aspect of the invention disclosed herein seeks to
improve disk manufacturing yield by writing multiple sets of servo
sectors or data sectors to the disk in a single revolution and then
selecting the set of servo sectors exhibiting the highest data
integrity. This aspect of the present invention applies to various
types of data storage employing circular media, including but not
limited to magnetic disk systems, optical disk systems, and the
like. The use of a single revolution to write data to circular
media and subsequent selection of specific sectors of the media is
applicable to any circular media writing system.
[0228] An aspect of the current invention provides a method for
increasing magnetic disk yield during the manufacturing process.
During the media disk formatting phase, the system writes a set of
servo sectors to the disk to provide a structure that guides
writing and/or reading of data to the disk in subsequent phases.
Generally, the number of servo sectors on a particular disk is the
same as the number of data sectors. According to one embodiment,
each servo sector 1201 corresponds to a data sector and is
comprised within the data sector 1202 as shown in FIG. 12.
Conventionally, the servo sector 1201 is located at the beginning
of the data sector, as perceived in the angular direction of
rotation of the disk. Physically, both the data sector 1202 and the
servo sector 1201 are shaped as partial substantially-circular
sectors, but the servo sector 1201 subtends a significantly lower
angle and occupies a correspondingly lower overall area. The servo
sectors comprised in the set of servo sectors written to the disk
during the formatting stage are disposed at substantially regular
angular offset positions around the disk, a representation of which
is illustrated in FIG. 13. More or fewer servo sectors may be
written to the disk depending on system requirements, but the
important characteristic of this aspect of the invention is that
servo data is disposed around the disk during this single
revolution initial formatting stage.
[0229] According to an aspect of the present invention, once the
system has written the set of servo sectors to the disk, the
servowriter verifies data written in the servo sectors to validate
the disk. If the data written within the servo sectors exhibits
sufficient integrity, the servowriting process is considered
successful, and data sectors corresponding to the servo sectors are
produced and validated. The data sectors may store data
subsequently written to the disk.
[0230] According to an aspect of the present invention, more than
one set of servo sectors is written to the disk in the formatting
phase, preferably during the same revolution. As a result, instead
of a single set of servo sectors disposed at substantially regular
angular positions around the disk as shown in FIG. 13, the method
disclosed herein produces one or more additional sets of servo
sectors, each of these servo sectors being also disposed at
substantially regular angular positions around the disk with
respect to other servo sectors within the same set. Alternatively
stated, this method produces duplicates of the original set of
servo sectors, wherein each servo sector comprised in a duplicate
set is offset by a constant angular amount with respect to a
corresponding servo sector in the original set of servo sectors.
For example, if the original set of servo sectors comprises a total
of 36 servo sectors, the beginning of each servo sector is offset
from the beginning of the preceding servo sector by ten degrees. A
duplicate set of servo sectors would comprise a total of 36
duplicate servo sectors, and each of these duplicate servo sectors
would be offset with respect to the preceding duplicate servo
sector by ten degrees. If, for example, the duplicate set of servo
sectors is disposed on the disk such that a particular duplicate
servo sector is offset from a particular original servo sector by
three degrees, each subsequent duplicate servo sector will also be
offset from a corresponding original servo sector by three degrees.
In an alternative implementation, individual servo sectors may be
offset at arbitrary intervals, but the system may need to store
more information regarding the actual position of such servo
sectors.
[0231] Upon writing one or more duplicate sets of servo sectors to
the disk, the system proceeds to verify the integrity of the data
written to each servo sector. One way of verifying the integrity of
this data is to read the data and compare it against the data
originally written to the disk. The system then selects the set of
servo sectors exhibiting the highest degree of data integrity and
erases or discards all other servo sectors. Depending on the result
of the verification process, the system may elect to retain the
original set of servo sectors, or may retain one of the duplicate
sets of servo sectors. After erasure, the disk may be removed from
the servowriter and located in a hard disk drive, or if in a disk
drive originally, the disk may remain therein and operate normally.
The system comprising the media disk may then utilize the selected
set of servo sectors as a basis for further operations on the disk,
including data storage to the disk.
[0232] Another aspect of the invention utilizes the writing and
reading concepts disclosed above to increase the data storage
capacity of a disk by writing multiple duplicate versions of data
to the disk in different data sectors around the disk, and then
retaining only the data exhibiting a sufficient degree of
integrity. This aspect of the invention applies the method
described above to regular data commonly stored on magnetic disks,
such as computer operating system data or a word processing file
stored on a hard disk, rather than just to servo data. In this
aspect of the invention, similar to the servowriting aspect
outlined above, more than one set of data sectors is written to the
media disk during normal operation, preferably during the same
revolution. As a result, instead of a single set of data sectors
disposed at predetermined positions around the disk based on
available space on the disk, this aspect of the method disclosed
herein produces one or more additional sets of data sectors, each
of these data sectors being also disposed at predetermined and
available positions around the disk with respect to other data
sectors. The system in this aspect of the invention writes data,
here called "associated data," to available areas of the disk using
an associated data header to indicate the beginning of the data
area. As used herein, the term "associated data" indicates data
located on a media disk surface typically associated with other
data on said media disk surface, as differentiated from the term
"data," which indicates data generally, associated or unassociated.
Associated data subsets are located at available positions around
the disk with information correlating such associated data with
similarly associated data. The system writes a second set of data
with a predetermined header indicating the beginning of said data
and writes the remaining data around the disk to available
locations. Data included in this second group may be spaced at
different locations around the disk, but the data is associated
with the second group and second header such that it can be
retrieved appropriately. The result is two identical sets of data
written to the disk, with header information indicating that the
associated data is identical but separate, along with information
specifically associating the separate but identical groupings of
associated data.
[0233] Alternatively stated, this method produces duplicates of the
original set of data sectors, wherein each data sector in a
duplicate set is offset with respect to a corresponding data sector
in the original set of data sectors. The data sectors are not
necessarily equally offset from one another, but rather may be
randomly offset and broken apart in different configurations.
[0234] Upon writing one or more duplicate sets of data sectors to
the disk, in one embodiment, the system proceeds to verify the
integrity of the data written to each data sector. One way of
verifying the integrity of this data is to read the data and
compare it against the data originally written to the disk. The
system then selects the set of data sectors exhibiting the highest
degree of data integrity and erases all redundant data sectors.
Depending on the result of the verification process, the system may
elect to retain the original set of data sectors, or may retain one
of the duplicate sets of data sectors, including the relevant
header information and association data. Once the disk has been
erased, the disk may be operated normally. The system where the
media disk is integrated then utilizes the selected set of data
sectors as a basis for further operations on the disk, including
data storage to the disk.
[0235] Head Stack Failure Detection and Handling
[0236] FIG. 18 illustrates one possible implementation of the
present system. From FIG. 18, the media disks of the present system
are optionally encased by a shrouding arrangement, shown as two
shrouds, and an acoustic sensor 1801 is mounted on a positioner arm
1802 proximate the disks. The acoustic sensor is employed to detect
the noise produced by one or more heads that come in contact with
one or more corresponding disks upon the occurrence of or in
advance of a head crash. When a head crash is imminent, it is
understood that the acoustical emissions by the drive may take on
certain abnormal characteristics, and in the presence of these
abnormal characteristics, it is preferable to remove the head or
heads from the disk. Impending head crashes may produce different
characteristics in different drives and may even vary under
different circumstances within a single drive. Unusual or abnormal
circumstances may include, but are not limited to, high frequency
variations or ripples. With respect to sensing such abnormal
circumstances or the existence of a head crash, it is to be
specifically understood that the acoustic sensor may be located in
an alternate position from that shown in FIG. 18, such as on the
e-block, on a disk cover, or otherwise, and more than one such
sensor may be employed. Location of the acoustic sensor as close to
the head as physically possible and practicable is one possible way
to locate the sensor. Sensor location will depend on a variety of
factors, including but not limited to physical construction of the
servowriter, placement of the heads, and associated acoustical
issues.
[0237] During normal operation, the head reading from or writing to
a disk is displaced in physical proximity of the disk. The head and
the disk are normally not in direct physical contact, but are
operationally coupled. For example, for a magnetic disk, a head
flies relatively close to the surface of the disk reading from, or
writing to the media disk via magnetic fields that propagate across
the physical gap between the head and the disk.
[0238] When a head crashes, possibly as a result of a mechanical or
power failure, the head may contact the corresponding disk
producing a characteristic noise. While a disk failure may create
sound waves having varying characteristics, the noise is typically
characterized by frequencies and amplitudes in particular ranges.
Certain pending head crashes may also exhibit frequency or
amplitude abnormalities. The implementation of the invention
described herein utilizes an acoustic sensor 1801 to detect this
characteristic noise. The noise characteristic to a head crash
exhibits a certain sound intensity and operates within a certain
frequency spectrum. This implementation of the invention
distinguishes the noise characteristic to a head crash from other
noises that may otherwise occur in the system by determining the
noise in the system, detecting amplitude and frequency levels, and
indicating when those amplitude and frequency levels fall outside
an expected range or within an undesirable range. The acoustic
sensor and associated electronics only react to sound whose
intensity exceeds a certain threshold and whose frequency spectrum
matches the frequency spectrum characteristic to a head crash.
[0239] From FIG. 18, media disk 1805 has head 1803 operating above
and in association therewith. Positioner base 1802 has acoustic
sensor 1801 affixed thereto, and positioner base 1802 is adjoined
to head 1803 via positioner arm 1804. Acoustic sensor 1801 is
electronically linked to computing device 1806, which may be any
electronic device capable of discriminating between signals,
dynamically computing values in real time, and transmitting command
values to a voice coil and/or voice coil motor, such as a digital
signal processor. The computing device 1806 determines whether the
sound intensity is within an expected range or within an unexpected
range and commands the VCM (not shown) to lift the head 1803 from
the disk 1805 under failure conditions.
[0240] The sound intensity associated with the noise produced by a
head crash depends on various factors, including the physical
characteristics of the disk and head. The system, via the acoustic
sensor 1801 and the associated electronics, only reacts when the
intensity of the sound detected exceeds a certain threshold or is
within an undesirable threshold range. A value of this threshold
may be determined experimentally for a particular combination of
head and disk, or may be developed analytically. As may be
appreciated, a disk failure due to, among other causes, a broken
disk, produces a high amplitude sound. In other circumstances, such
as a power failure, a failure is indicated by an absence of sound.
Normal operation of disks, particularly in servowriting and
certification, is a constant speed rotational sound, sometimes
called a "whirring" or "whizzing" sound. These tend to be constant
sounds, unlike a traditional hard drive sound that operates in fits
and starts depending upon the function performed by the hard disk
drive. In hard disk drive operation, the disk may not spin for a
period of time and then spin for an extended period of time. The
servowriter/certifier hardware system, by contrast, may be either
on or off for an extended period of time, and thus noises outside
the expected norm may be considered a system failure.
[0241] In one aspect, the acoustic sensor has a relatively low
sensitivity such that it only detects noise above the threshold. In
another case, the acoustic sensor detects a wider range of sound
intensities, but software and/or hardware logic coupled to the
acoustic sensor responds to the system when the sound intensity
detected by the sensor is below a particular threshold. Software
and/or hardware logic coupled to the acoustic sensor may be
configured to respond to a range of sound thresholds.
[0242] The frequency spectrum associated with the noise produced by
a head crash also depends on the physical characteristics of the
disk and head, among other factors. The system only reacts when the
frequency spectrum of the sound detected matches a certain
frequency spectrum signature. This frequency spectrum signature may
be determined experimentally for a particular combination of head
and disk or disks, or may be developed analytically. In one case,
the acoustic sensor has a particular spectral sensitivity such that
it only detects noise whose frequency spectrum matches the
frequency spectrum signature. In another case, the acoustic sensor
detects a wide range of frequencies, but software and/or hardware
logic coupled to the acoustic sensor suppresses response of the
system when the frequency spectrum detected by the sensor does not
match the appropriate frequency spectrum signature. Software and/or
hardware logic coupled to the acoustic sensor, possibly including
frequency filtering logic, may be configured to respond to a range
of spectral frequencies and suppress other frequencies.
[0243] The intensity and frequency spectrum of the sound detected
by the acoustic sensor may also depend on the proximity of the
sensor with respect to the point of contact between the disk and
the head. In a particular implementation, the acoustic sensor is
disposed on the arm supporting the head, in physical proximity to
the head. In another implementation, the acoustic sensor is located
on the e-block, further away from the head.
[0244] In one implementation, multiple acoustic sensors are
employed to detect head crash in a multiple head, multiple disk
environment. In this implementation, multiple heads read and/or
write information to multiple disks substantially simultaneously.
There may be more than one head operationally coupled to each disk.
Further, there may be more than one head coupled to each VCM-driven
arm, possibly coupled via actuators, and there may be more than one
arm operating on each disk. In this implementation, multiple
acoustic sensors may be disposed throughout the system to detect
head crashes that may occur at any point in the system. Each
acoustic sensor and associated logic may correspond to a particular
head and may be configured to ignore head crash noises produced by
any other head. Alternatively, the system may utilize information
produced by a multitude of sensors to identify the head that
crashed (e.g., through triangulation and/or through a spectral and
intensity sound analysis that considers the characteristics of
various disks, heads and system components disposed throughout the
system).
[0245] If possible, in the current system and in many other
systems, the acoustic sensor would be located as close to the head
as possible. Physical drive characteristics limit the proximity of
the acoustic sensor to the disk, but such a sensor may be employed
at or near the positioner, e-block, shroud, or other points in the
representative design illustrated herein.
[0246] In operation, once a head crash or other system failure is
detected using the sensor or sensors disclosed herein, the system
retracts the heads or otherwise moves the head or heads away from
the disk or disks as rapidly as possible. This removal of heads
from disks provides necessary space between disk and head. While
the head may still contact the disk under certain failure
conditions, such as a disk fracture or head failure, removal of the
heads from the disk breaks the typical association between disks
and heads and minimizes the chance of damaging either. Removing
heads from the disk is a normal circumstance of media servowriting,
and thus the system operates in a known manner when removing heads
from the disks. Under one condition, a power failure causes the
system to rectify the voltage available from the spindle and that
voltage is applied to the voice coil, or alternately directly to
the voice coil motor, which moves the head or heads away from the
media disk or disks. In operation, a ramp type structure is moved
by the voice coil motor to contact head holding apparatus and lift
the head.
[0247] In other words, in one implementation, the invention
utilizes the spindle as an electrical power generator to retract
the heads off the disk.
[0248] In this implementation, the system utilizes a relay to
detect a power failure. In one case, the relay detects when the
electrical voltage at a particular point decreases below a certain
threshold. In a particular case, this threshold is eight volts.
[0249] Upon a loss of power, the spindle continues to rotate due to
its angular momentum. The mass of the spindle and other subsystems
mechanically coupled to the spindle is relatively large, such that
the angular momentum of the spindle system is correspondingly
large. Upon loss of power, the spindle continues to spin for a
significant period of time.
[0250] The invention exploits the angular momentum of the spindle
by utilizing the spindle as an induction power generator. Inertial
rotation of the spindle induces electricity in a coil. This coil
may be substantially stationary with respect to the spindle, and
therefore rotate with the spindle, or may be stationary with
respect to the base of the spindle. In one case, the coil is part
of the electrical motor that engages and rotates the spindle under
normal operating conditions.
[0251] The electrical power produced by the spindle is rectified
and is employed to operate servo systems that may retract the heads
off the disk. In one aspect, the electrical power produced by the
spindle is divided into two components: a first component operates
a voice coil motor that retracts the heads off the disk, while a
second component operates a motor that moves a ramp that
mechanically engages the heads in a preferred resting position.
[0252] The present invention may apply to a single head operating
on a corresponding disk, to multiple heads operating on a single
corresponding disk, or to multiple heads operating on multiple
disks.
[0253] As an alternative to the foregoing, the system may determine
that a pending crash is imminent or has occurred if vibrations
occur within the spindle. In such an arrangement, the spindle is
monitored with a vibration sensor to detect spindle movement, and
abnormal readings in frequency, amplitude, or intensity may be
employed to remove the heads from the disk in certain
circumstances.
[0254] This aspect of the invention has been outlined in the
context of a rotating spindle. In an alternative implementation,
the invention may also apply to a medium in linear motion (e.g.,
conveyor belt-type of system). In such a system, failure causes
operation of a ramp that mechanically engages the heads in a
preferred resting position.
[0255] Media Shroud
1. Multiple-Disk Shroud.
[0256] One implementation of the invention disclosed herein
provides a multiple-disk shroud comprising a left baffle shroud and
a right baffle shroud. From FIG. 19, the left baffle 1901 comprises
a plurality of individual left baffle cavities 1902a-n
corresponding to disks arranged in a stacked formation. Each
individual left baffle cavity 1902 comprises an opening or slot
that fits around the media and is adapted to partially receive a
corresponding media disk, thereby partially enclosing the disk. In
a particular embodiment, each individual left baffle cavity 1902
extends substantially to the center of the corresponding disk,
thereby enclosing substantially half of the disk. The distances
between the inner planar surfaces of each left baffle shroud and
the corresponding planar surfaces of the corresponding disk are
preferably small. In a particular case, these distances are
approximately 10 mils, or 10/1000 of one inch. Construction of this
aspect of the current invention therefore comprises a series of
separating walls, wherein the separating walls create the cavities
1902 in the baffle shroud.
[0257] As may be appreciated by those skilled in the art, the
number of left baffle cavities or openings generally corresponds to
the number of media disks in the arrangement or disk stack, such
that the existence of five disks in the stack dictates a baffle
shroud or shrouds with five cavities, while the existence of eleven
media disks in the stack suggests eleven left sets of cavities in
each baffle shroud. The number of left baffle cavities is generally
related to the number of available disks or media that may be
employed, rather than the actual number employed. In the previous
example, if the spindle or disk holding device is capable of
holding five disks but is only fitted with three disks, the number
of cavities will be five. The foregoing is meant by way of example
and not as a limitation.
[0258] The media disks are disposed in substantially parallel
planes and may spin around a common axis that is substantially
normal to the planes of the media disks. The disks are
operationally coupled to corresponding heads that may read and/or
write data to the disks.
[0259] The left baffle 1901 may be translationally coupled to the
frame of the servowriter such that the left baffle 1901 may pivot
into physical proximity of the media disks. In one embodiment, the
left baffle 1901 is not directly coupled to either the media disks
or the read/write heads, and may translate independently of the
disks and heads. Upon translating proximally to the disks, each of
the individual left baffle shrouds 1902a-n partially encloses a
corresponding disk, thereby controlling air flow around the disk as
the disk spins at a relatively high velocity.
[0260] In a further aspect of the present invention, a right baffle
2001 as illustrated in FIG. 20 is analogous to the left baffle 1901
described above and comprises a plurality of individual right
baffle cavities 2002a-n corresponding to the number of media disks
that may be loaded on the spindle. The structure and functionality
of the right baffle are substantially the same as the structure and
functionality of the left baffle, although certain differences
exist. One such difference between the left and the right baffles
1901 and 2001 is that the planar dimensions of the right baffle
shrouds in this aspect of the invention are smaller, such that each
right baffle shroud receives and protects a smaller portion of the
corresponding disk. In a particular embodiment, each right baffle
shroud encloses substantially a quarter of the corresponding disk.
In a related embodiment, each left baffle shroud and the
corresponding right baffle shroud cooperatively enclose a
non-insubstantial portion of the disk, in the aspect illustrated
approximately 3/4 of the corresponding disk. The remaining 1/4 of
each such disk is essentially covered by one or more heads and/or
other related hardware.
[0261] Other specific dimensional characteristics are available for
the left and right baffle, as may be appreciated by one of skill in
the art. The function and purpose of the shrouding arrangement is
to cover as much media disk surface as reasonably practicable while
at the same time allowing reasonably free access by the read and
write heads to the media disks. Alternate designs include, but are
not limited to, use of a single shroud similar to the left shroud
covering approximately half the media surface, and use of a shroud
covering approximately half the surface similar to the left shroud
1901 and a larger or smaller dimension right shroud than that
shown. Dimensions of the shroud or shrouds are dictated by various
factors, including desired rotation speed of the disks, physical
dimensions of the positioner arm or arms, amount of media disk
access required, and disk holding considerations, such as spindle,
chuck, and other holding mechanism dimensions. By way of example
and not limitation, the spacing between the disks and the shroud or
baffle hardware may be as small as on the order of 10 mils and
possibly lower, such as 9 or 8 mils.
[0262] When engaged in an operational position in the configuration
illustrated in FIGS. 19 and 20, the right baffle 2001 may be
disposed substantially opposite to the left baffle 1901 with
respect to the spinning axis of the disks. The translating
directions of the left and right baffles 1901 and 2001 are also
opposite, with the left baffle 1901 approaching the disks from the
left direction and the right baffle 2001 approaching the disks from
the right direction. Further, unlike the left baffle 1901, which
may translate independently of the heads, the right baffle 2001 is
mechanically coupled to the read/write heads and associated
positioner in one aspect, such that the heads and the right baffle
are disposed on the same arm. In this aspect, when the heads are
engaged in a functional position by the voice coil motor (VCM), the
right baffle 2001 is substantially simultaneously disposed in an
operational position. Subsequently, during normal operation, the
heads may move with respect to the disks and the right baffle 2001
while reading and/or writing to the disks, but the individual right
baffle shrouds 2002a-n remain substantially stationary with respect
to the corresponding left baffle shrouds 1902a-n and the spinning
axis of the disks.
[0263] It is to be understood that the foregoing represents a
single specific design of the present invention and is not meant to
be limiting to the design shown. Translating is not necessarily
required, and for example the shrouds may be fixed in position,
disks may be rotated into the shroud using a movable spindle, and
either one, both, or neither shroud may interact directly with the
positioner, VCM, and other system hardware. The design must, at a
minimum, provide a level of coverage or enclosure of the media
disks and decrease the risk of windage disrupting the interaction
between head and disk.
[0264] In one aspect of the current invention, the left baffle 1901
and the right baffle 2001 are constructed from aluminum.
Alternatively, the left baffle 1901 and/or the right baffle 2001
may be constructed from plastic. Other materials may be employed
while within the scope of the present invention, provided the
materials provide adequate strength characteristics and operate to
minimize the risk of turbulent flow in the arrangement selected.
Thus materials such as aluminum and/or plastic may be used, but
these materials are neither required nor exclusive for constructing
the inventive baffle arrangement shown herein.
[0265] In a particular implementation, the left and/or right
baffles 1901 and/or 2001 may comprise one or more vacuum ports or
inlets (not shown in the illustrated aspect but known to those of
skill in the art) that may be utilized to remove debris or
particles located in proximity of the spinning disks. Such debris
is typically found in the form of small particles, and such small
particles may inhibit performance of the disk stack. The inlet
operates in connection with a vacuum pump to intake or vacuum air
and particles from the shroud arrangement. The inlets may be
located at each baffle, or at one baffle, and may span all chambers
of the baffle, a single chamber of the baffle, or any intermediate
number of chambers. The purpose and functionality of the inlet
arrangement is to remove unwanted particles and provides a means to
reduce the quantity of ambient particles contacting disk surfaces
in the multi disk arrangement. The inlets or vacuum ports may be a
single small diameter hole located atop or on the side of the
baffle, or alternately a long sealed opening on the side of the
baffle to afford access to each disk and chamber or cavity. Other
vacuum port or inlet shapes and configurations may be employed
while still within the scope of this aspect of the invention.
[0266] While varying dimensions may be employed, particularly of
the shroud, baffle, baffle
[0267] Alternate views of the baffles are illustrated in FIGS. 22
through 27. FIG. 22 is a top cutaway view of the left baffle. FIG.
23 is a side cutaway view of the left baffle. FIG. 24 is a bottom
view of the left baffle. FIG. 25 is a side view of the right
baffle. FIG. 26 is an alternate perspective view of the right
baffle. FIG. 27 is a bottom view of the right baffle.
2. Clock Head Shroud.
[0268] Another embodiment of the invention provides a shroud that
may protect a media disk while a clock head reads or writes data
from the disk. The shroud of this aspect of the invention is
presented in FIG. 28. The clock shroud 2801 encloses the head at
close proximity to the disk substantially completely, but comprises
a number of apertures, such as first relief cut 2802 and second
relief cut 2803, that permit introduction and withdrawal of the
clock head and/or of other devices. Such relief cuts are beneficial
in certain circumstances but are not required as part of the
present invention; rather, the important aspect of the invention is
to provide a shroud or covering that covers the head and decreases
the amount of windage encountering the head and reduces risk of
disruption of the head-media disk interaction. In the design shown,
additional apertures located in the shroud permit disposition of
certain devices, such as a motor. The use of the clock shroud
enables a more accurate clock and timing arrangement for the
system, minimizes interference between the clock head and the disk,
keeps certain data, such as servo pattern data phase coherent, and
minimizes vibration. The clock head sits in the notch illustrated
in FIG. 28. FIG. 29 is a top view of a clock shroud that may be
employed in association with the current invention.
[0269] Head Mounting Design
[0270] A further aspect of the present design is employed in
connection with the heads writing to and reading from the media in
the configuration presented above. More particularly, the present
design includes a system and method for mounting the heads to
relevant hardware, such as an assembly or holding device,
positioner arms and an E-block, so that the heads can be removed
and replaced in a more efficient manner than previously known.
[0271] FIG. 30 presents one rotary voice coil motor design 3001
that may be employed in a media track writer or servowriter as
shown above, wherein the voice coil motor is used to drive the head
positioner and the heads located thereon. The voice coil motor
design 3001 is a balanced torque design having twin coils 3002 and
3003 placed on opposite sides of a central pivot. The rotating
portion of the voice coil motor is suspended on two high precision
preloaded ball bearings (not shown), and includes the coil housing
3101 of FIG. 31, two coils 3201 shown in FIG. 32, scale holder 3301
and shaft 3302. The shaft on the scale holder 3301 and shaft 3302
assembly, including dowels 3303, 3304, and 3305, are used to guide
and align the scale holder to the FIG. 34 E-block positioner arm
assembly 3401. The shaft 3302 fits into cavity 3402 in E-block
positioner arm assembly 3401, with coarse angular alignment
established by crosswise dowel pin 3303 and final angular alignment
performed by smaller dowel pin 3304. E-Block 3403 is attached to
the remainder of the E-Block positioner arm assembly 3401. This
smaller dowel pin 3304 is inserted between scale holder 3301 and
the E-block positioner arm assembly 3401. A standard wing nut, not
shown, fastens the E-block positioner arm assembly 3401 to the
scale holder 3301 and shaft 3302. This wing-nut attachment of
E-block and head assembly provides for rapid loosening of the wing
nut, releasing the shaft, removing the shaft, and disengaging the
E-Block positioner arm assembly 3401 from the rest of the media
writer. It is desirable to periodically replace the head assembly
to address normal wear and tear during servowriting or damage to
one or more heads resulting from faulty disks while retaining the
assembly for future use.
[0272] With respect to the head assembly, and namely the assembly
exclusive of the head, E-Block, and positioner arms, the way the
device is assembled during operation is as follows. Individual
head-gimbal assemblies (HGAs) are attached to small mounting tabs.
When assembled, the HGA may be attached to mounting tab 3501 as
shown in FIG. 35, which is then affixed to the arms of the E-block
3601, shown in detail in FIG. 36. Each mounting tab 3501 is held in
place on the E-block arms using a small screw, such as a M1.2
screw, which passes through channel 3504. FIG. 36 illustrates a top
view of the E-Block 3601 bifurcated by an imaginary centerline.
Alignment of the mounting tab and E-block 3601 of FIG. 36 occurs
using the two dowel pointed pins 3502 and 3503, which are
ultimately inserted into two slots 3602 and 3603 in E-Block 3601.
From the angle of FIG. 36, only one slot 3603 is visible. Use of
the dowel pointed pins 3502 and 3503 align the tab 3501 to the arm
3606 of the E-block 3601. A tab having one or two heads may be
removed from or assembled to the E-block with the installation or
removal of a single screw.
[0273] The present apparatus obviates the need for the previous
method of "staking." The present design uses a press fit scheme,
whereby the HGA and head mount components are pressed into place
and secured to other assemblies using dowels, pins, screw, wing
nut, and other components. Staking required mounting tab
replacement or head arm or E-block after only two or three head
replacements due to permanent deformation of the boss receiving
bore 3504 of the head mount. The present design employs a smaller
head bore 3504 than the mating boss on the head suspension,
enabling the HGA to be attached to the head mount by applying
pressure, or pressing, the part and forcing the suspension boss
into the head mount bore 3504. This pressing operation allows the
suspension boss to maintain sufficient torque to allow proper head
operation during functions such as ramp load and unload of heads
onto the disks. Compared to staking, a press fit or a pressure
fitting has the ability to impart less distortion to the interface
between the HGA and the mating head mount bore, increasing the
number of reuses of the head mount tab 3501 before replacement is
indicated. Since HGA distortion is generally less than that of the
mating head mount bore, head damage can be minimized by press
fitting rather than staking.
[0274] An alignment and pressing fixture may be employed to
assemble one or two HGAs to a head mount. HGAs may be assembled
using the devices shown in FIG. 37. In practice, the head mount is
located within the center section 3702 while one or two HGAs are
affixed to the head mount depending on the application. HGAs are
sandwiched between the left section 3701 and the head mount fixedly
positioned within center section 3702, and/or the head mount
fixedly positioned within the center section 3702 and the right
section 3703. The heads are then aligned with and affixed to the
head mount tab, which is thereafter assembled on the E-block.
[0275] FIG. 37 illustrates an exploded view of the three sections
and the associated hardware used to prepare the HGA or head
assembly and mount for receiving a read/write head. In FIG. 37, the
head mount tab (not shown) is mounted to the head assembly tool
3704. The center section is used to align and mount the tab to the
HGA using the aforementioned M1.2 screw (not shown in this Figure).
Heads are placed between the press-fit jaws of left and right
assembly tool parts 3701 and 3703, between those assembly tool
parts and the center section 3702, and are aligned using the HGA
support 3705. The right head assembly tool part 3701 may be forced
toward the center section 3702 using a vise or other clamping
device, and the HGA bosses are press fit to the head mount tab
bore. The head mount tab is aligned using the HGA support 3705 and
alignment tool pins 3706 and 3707. The pins may be a straight or
stepped pin to provide necessary support and alignment for the
tasks outlined below.
[0276] Each of the assembly tool parts, left section 3701, center
section 3702, and right section 3703 have slots cut through the
material to provide limited lateral flexibility. The flexibility
enables the tool to be used for a head to be assembled on either
side of the head mount tab, or both sides may be assembled at
once.
[0277] FIGS. 38A, 38B, and 384C show details of the three assembly
tool parts, left section 3701, center section 3702, and right
section 3703. These are representative of one possible
implementation, and other implementations may be employed while
within the scope of the present invention.
[0278] Assembly of the system is shown in FIGS. 39-43. FIG. 39
illustrates a high precision vise 3901, the two alignment tool pins
3706 and 3707, the assembly tool 3902 comprising left section 3702,
center section 3703, and right section 3704, the head assembly
3803, and tools for performing the head assembly. ESD protection
may be employed during handling operation, and the work may be
performed under a clean hood by an operator with gloved hands. The
assembly tool may be constructed from any appropriate material,
including but not limited to stainless steel, such as a cold rolled
type 302 or 304 stainless steel. Other materials may be employed
that provide sufficient holding, wear, and strength
characteristics, among other advantageous aspects.
[0279] Head arm mount 3501 is inserted into the assembly tool 3902.
The head assembly tool 3902 is maintained within the precision vise
3901 grasping the base of the tool 3902, thereby applying a level
of pressure or tension to the assembly tool, but not so much as to
restrict movement of the upper section of the tool sections. The
center, right, and left sections of the assembly tool 3905 may be
spread such that the head arm mount may be inserted in the gap and
the pins of the head arm mount aligned into the center section 3703
of the assembly tool 3902. Spreading may occur by various means,
including using the operator's fingers to separate the left,
center, and right sections of the assembly tool 3902. The M1.2
screw is then tightened, thereby wedging the sides of the head arm
mount 3501 within the center section 3703 of the assembly tool
3905. The operator or a machine may then pick up the head assembly,
spread the outer members of the assembly tool and gently insert the
head assembly between two of the sections, such as the left section
3702 and the head arm mount 3501. The staking boss (not shown) of
the head assembly 3903 may be approximately aligned with the upper
hole of the head arm mount 3501.
[0280] FIG. 40 presents a side view of a sample head assembly 3903,
held with tweezers by an operator. This sample head assembly is
only representative of the types of head assemblies that may be
employed, and the head assembly shown has the ability to maintain
the drive head 4002 at the top end in the orientation shown and has
various openings which enable the assembly and alignment described
below. It is to be particularly noted that other head assembly
designs may be employed while still within the scope of the present
invention.
[0281] In initial operation, the head arm mount 3501 is located
within the assembly tool 3905, namely center section 3702. In an
orientation where the center section spacing gap is positioned
upward, the pins 3502 and 3503 of the head arm mount 3501 are
oriented downward and the head arm mount 3501 is pushed down into
the center section 3702. A screw is inserted through channel 3504,
such as an M1.2 screw, to apply pressure to the sides of the head
arm mount 3501 and fixedly mount the head arm mount 3501 to the
center section 3702. FIG. 41 illustrates a head arm mount 3501
positioned against the head assembly 3903 within the assembly tool
3905. FIG. 41 further illustrates insertion of a pin 3707, such as
a straight 0.8 mm diameter pin, through the upper slots of the
assembly tool 4103 and through a tooling pin hole in the head
assembly 4103.
[0282] In certain circumstances, the head assembly may be
repositioned so that pin 3707 can engage the tooling hole in the
head assembly 3903. FIG. 42 illustrates insertion of pin 3706, such
as a stepped 2.13 mm diameter pin, into a lower hole 4201 in the
assembly tool 3905. The pin 3706 may be inserted carefully such
that it passes through the head assembly 3903. An operator or
machine may at this point inspect alignment of the head assembly
3903 within the head arm mount 3904. Inspection may occur in any
available reasonable manner, including but not limited to a low
power stereo inspection microscope. If alignment is acceptable, the
pins 3706 and 3707 may be removed from the alignment tool. Spring
pressure from the assembly tool 3905 in many circumstances will
keep the head assembly aligned to the head arm mount 3501.
[0283] The upper edge of the alignment tool 3905 may then be
repositioned within the vise 3901 as shown in FIG. 43. A relatively
small section of the alignment tool 3905 may be inserted into the
vise 3901, such as less than 10 mm. A relatively small amount of
pressure is then applied by tightening the vise 3901, thereby press
fitting the head assembly 3903 into the head arm mount 3904. The
screw may then be removed from the head arm mount 3501 and the head
assembly press fitted to the head arm mount 3501 may be removed
from the assembly tool.
[0284] Other implementations of the press fitting method described
above are within the scope of the present invention, and the
foregoing description, as with all descriptions of particular
design aspects herein, is not intended to be restrictive or
limiting.
[0285] Disk Biasing
[0286] An aspect of the present invention provides methods and
systems for controlling disk position on a central hub or chuck
during servo track writing and/or reading. The disk position
control may occur prior to installation into a Hard Disk Drive. The
disk biasing methods and systems disclosed herein may be applied to
single or multiple disks, require minimal or no operator
intervention, and provide a repeatable way to control eccentric
placement of servo information onto the disk.
[0287] One aspect of the MTW that is particularly noteworthy is the
mechanical clearance between the disk inside diameter, and the hub
or chuck outside diameter, namely the disk opening and the hub that
fills the opening. A significant clearance dimension is necessary
to enable fast and reliable disk installation on and off the hub
and to accommodate disk and hub manufacturing tolerances. Excessive
eccentricity, or servo track "runout", can cause servo capture and
performance problems for the HDD, in that the head can be
mislocated above the disk and can run outside a track, or begin in
one track and end in another.
[0288] One way to deal with this excessive eccentricity aspect of a
media track writer is to have a mechanism to "center" the disk on
the hub at disk installation. Centering the disk typically may
require precise and expensive fixturing to achieve reasonable
accuracy. Another, often less expensive, way to address excessive
concentricity is to "bias" the disk ID against the hub OD in a
controlled manner so that this same "bias" can be applied when the
disk is eventually installed into an HDA, thereby controlling the
eccentricity rather than allowing tolerances to vary unpredictably
to significant error levels. A necessary part of this process is
maintaining and/or determining the bias direction and
circumferential point where the bias is applied. Such use of bias
direction and circumferential point may be accomplished by marking
the disks or by handling the disks in a controlled and repeatable
way.
[0289] To consistently bias a disk, an embodiment of the invention
can apply biasing force to the disk OD, usually by using a very
precise fixture or tool. By alternately biasing disks against the
HDA spindle hub in opposite directions using "V" shape devices to
push on the disk OD, rotational unbalance forces can be minimized.
Typically, these "V" shape devices are placed on either side of the
disk and spindle stack, such that half the disks are biased in one
direction and the other half biased 180 degrees in the opposite
direction. This way, for stacks of even numbers of disks, first
order disk unbalances can be minimized. These "V" shape blades may
be made slightly compliant to compensate for disk, spindle hub, and
biasing tool mechanical tolerances, either by using a compliant
material or some mechanical compliance, such as a spring type
mechanism. The vertical axis of the biasing tool used to apply the
"V" shape blades may be precisely aligned to the spindle hub axis
to consistently bias the disks in the appropriate direction at all
locations in the disk stack. Further, biasing of disk spacers may
be employed using OD biasing.
[0290] An embodiment of the invention biases the disks using the
disk ID. In this case, biasing forces are applied in an outward
radial direction to the disk ID at one or more points, such as two
points, to force the disk in a known direction against the spindle
hub. The biasing force can be applied in various ways, including
but not limited to using air pressure to automatically bias disks
in the stack in the required direction. Two, small, piston-like
devices within the spindle hub may be used to apply a radial vector
sum force in a known direction to each disk. By arranging the
piston-like devices in a pattern, forces can be directed in any
direction for each disk. The simplest pattern would be 180 degree
opposite force vectors for each disk, such that the net rotational
unbalance force for an even number of disks, assuming identical
disks, would be zero. Even numbers of disks ensure dynamic as well
as static force balance. For each disk, each group of two
piston-like devices is arranged in a manner to provide a vector sum
force in a known direction.
[0291] According to an embodiment, an arrangement that facilitates
the manufacturing process, comprises two pistons radially oriented
with respect to hub axis and spaced an angle apart. Although many
angles will work, the preferred angle for manufacturing is 90
degrees. This angle provides a vector sum of 1.414 times the force
generated by each piston, in a direction half-way between the
pistons, or in this case, 45 degrees from either piston, directed
radially outward. In addition, lateral forces are generated by each
piston, and these lateral forces tend to force the disk laterally
until a force balance exists on the disk. Friction related forces
may also exist. A friction force has a tendency to oppose the
biasing force, irrespective of the direction of the biasing
force.
[0292] The directional accuracy with which the disk will be biased
depends upon the ratio of the magnitudes of the friction force to
the biasing force. It may be beneficial in certain circumstances to
minimize friction and maximize the biasing forces for each disk.
Friction between disks and disk spacers can be minimized by using
special plating processes on the spacers. For example, hard nickel
plating or nickel plating with embedded Teflon particles have
demonstrated low friction coefficients with most disk surfaces.
Other coatings and/or materials can be used as well.
[0293] One implementation of the present aspect of the design
includes a four disk chuck assembly with integral disk biasing.
Disks are stacked onto a chuck and spaced vertically using a
spacer. Once the stack is assembled and biasing done, the stack is
clamped together using a top cap. Biasing is accomplished by use of
pressurized air or other gas such as nitrogen, prior to clamping.
Disk clamping is performed with a single screw, although alternate
designs may utilize vacuum or other mechanical clamping means. Air
or other gas used for biasing is introduced through the bottom base
of chuck, distributed by a shaft, with biasing forces generated by
a ball and orifice housing assembly. If both air pressure and
vacuum is used (first for biasing then for clamping), internal
check valves within chuck body direct air or vacuum to the
appropriate areas as necessary. The biasing forces generated by the
pair of ball and orifice housing assemblies are self balancing via
use of a series combination fixed and variable orifice within the
assembly.
[0294] The design resembles air-bearing systems where self
balancing forces are generated by use of a fixed orifice in series
with a variable orifice, with the air pressure between the two
orifices used to provide a lifting or noncontact bearing action. In
an air bearing, the variable orifice is nearly always created by
one member of the bearing moving with respect to the other. In this
biasing design, the variable orifice is created between the moving
ball which contacts the disk I.D. and the angled ball seat within
the housing. Pressurized air flows first through the fixed orifice,
which is in the order of 0.010 inches diameter, then through the
variable orifice. The air pressure between the 2 orifices acts on
the ball to create a force directly proportional to that pressure.
As the ball moves outward, the pressure falls, reducing ball force.
As the ball moves inward, thus reducing the area of the variable
orifice, the pressure increases, increasing the ball force. With
two of these ball and orifice housing assemblies arranged so that
radially outward forces are applied to a disk at a fixed angle
between the devices, a vector sum force can be applied such that
the direction is controlled. Use of the fixed/variable orifice set
devices provides a self-balancing action such that the force vector
always applies a force vector to the disk such that the disk is
forced or "biased" against the chuck body in a specific direction
and point on the chuck. That contact point between disk and hub is
approximately 180 degrees opposite the two ball orifice housing
piston devices.
[0295] By alternating the direction, e.g. 180 degrees, in sequence
for each disk, the disks can be forced outward in alternating
directions such that half the disks are biased one way and half are
biased the opposite direction. This alternating of bias direction
compensates for first-order unbalance effects due to the disk
centers being displaced from the chuck rotational center.
[0296] The described disk ID "biasing" method is but one of many
possible detail configurations wherein changes in the design would
not provide a fundamental difference from the basic concept
described herein. Specifically, the number of disks, disk spacing
and angles between the pair of ball and orifice housings can be
easily modified to a near infinite number of combinations without
affecting the fundamental operation of the biasing concept. Also,
the pushing elements can be other than ball shapes, including but
not limited to other piston-like devices. In addition, while a
fixed orifice in combination with variable orifice is believed to
have higher accuracy of final vector direction, it may also be
possible to simplify the design further, by using pistons or balls
alone within a simple radial bore, provided the forces are limited
so that no permanent disk ID surface deformation, "brinneling", or
other damage occur.
[0297] Locking Cap
[0298] A further aspect of the present invention includes a
specific mechanical aspect used to hold one or more of the disks in
place in the media servowriter. An aspect of the present system
includes certain aspects designed to facilitate maintaining disks
at high rotation speeds. FIG. 44 illustrates a general view of one
aspect of the device. FIG. 44 illustrates the disk maintenance
design in a locked down configuration. A closer view of the inner
elements of the design is presented in FIG. 45. The device includes
a top cap 4401, a central chamber 4402, an annular compression
spring 4403 and 4404 designed to pull the cap downward, and a set
of ball bearings 4405, two of which are visible in these views,
abutting the central core 4406 of the cap 4401. To unlock the
device, the cap 4401 must be released, which requires application
of air to the central chamber. Air is applied to the central
chamber through the bottom of the device (hub). Air pushes up the
central cylinder and the ball bearings 4405 buttressing the central
core 4406 of the cap, thereby applying tension to the compression
springs 4403 and 4404. When the ball bearings 4405 and the chambers
in which they are located rise to a level proximate the upward
sloping walls in the interior of the chamber, the ball bearings
4405 slide outward along the upward sloping walls 4407 and out of
the way of the central core 4406 of the cap 4401. With the ball
bearings 4405 out of the way, the cap 4401 can be readily released
and disks 4410 either loaded or unloaded. In lieu of using air to
engage and release the mechanism and cap 4401, a pushrod 4410 may
be employed to push the central core upward and release the
cap.
[0299] FIGS. 46 and 47 illustrate the cap in released position with
the ball bearing and cap core in released position. Application of
the cap 4401, specifically locking the cap down, requires removing
air pressure from the interior of the cap, whereupon the central
chamber slides downward and the ball bearings re-seat in the
sloping holes and lock down the cap. Most of the components
illustrated in these drawings are fashioned of metal, while the cap
may be fashioned of a hardened plastic. Any materials may be
employed that satisfy the engagement and release aspects and
functionality described herein, and the central core and other
exterior components, for example, may be fashioned of steel,
nickel, or any other strong metal.
[0300] FIGS. 46 and 47 illustrate the ball bearings 4405 after
having risen up to meet the chamber inner walls. The second figure
is a close up view of the first figure. FIGS. 46 and 47 represent
an alternative construct having larger compression springs and a
larger interior chamber. The present design uses six ball bearings
with six inner conical-shaped passages in the ball bearing set
4405. More or fewer ball bearings may be used. Alternate sloping of
the channels where the ball bearings sit or the inner chamber walls
which receive the ball bearings may be employed, as long as
depressurization causes a release of the cap and pressurization
holds the cap in place.
[0301] The present aspect of the system may be employed in a hard
disk drive employing multiple disks, such as a servowriter and/or
certification system verifying multiple disks, or in any other
application requiring use of multiple fixed media, such as computer
disks.
[0302] Multiple Finger Clamp
[0303] An additional aspect of the present system provides systems
and methods for holding a hub, specifically a hub of a disk
stacking cylinder employed to hold multiple disks during disk
servowriting and certification. Previously available hub holding
devices used some type of mechanical "jaws" that gripped the
exterior of the hub and/or the notch formed between the hub and the
main cylinder. The jaws were formed of some type of metal and were
metal pieces used to pin the hub down and hold it in position by
applying pressure to the upper side of the hub. These jaw-type
locking devices tend to be imprecise in holding the hub or other
cylindrical piece. At significantly high RPMs, such as in excess of
10,000 to 20,000 RPMs, centrifugal force works to pry these devices
open, and many jaw type devices are pried open or move the piece as
a result of high forces applied thereto. This prying tends to
damage the hub and/or maintaining device and is generally
unacceptable. Thus the previous devices could be characterized as
easily pried open, with poor repeatability, and highly subject to
movement of the piece.
[0304] FIG. 48 illustrates one aspect of the present design. The
lowest piece is the spindle 4801, to which the chuck mounting plate
4802 is bolted. The central piece of the chuck mounting plate 4802
is the spindle 4803. The piece surrounding the chuck mounting plate
4802 and engaging the hub 4804 is the chuck clamp 4805. This design
is air-actuated by passing air upward through the spindle and
around the chuck mounting plate 4802. When air is applied, such as
at a pressure of 60 psi, the chuck clamp 4805 rises and the hub
4804 can be removed from the clamp due to the set of fingers 4806
at the top of the clamp 4805, releasing the grip on the hub 4804.
When air is applied, the Bellville spring 4807 collapses, and the
central chuck clamp 4805 rises upward in the orientation shown, and
releases. The "fingers" 4806 on the exterior flex and permit a
close grip under ambient conditions. In other words, when the
machine fails, it defaults to the gripped position shown in FIG.
48. The circles in the central chuck clamp are O-rings 4808 that
provide air seals when in operation. The application of air
pressure and the upward releasing push with the finger
configuration shown enables sufficient clearance to "grasp" the hub
4804. The design shown has good positional repeatability, and the
fail-safe design offers advantages over existing designs.
[0305] All parts may be fabricated from steel or similar material
providing the functionality described, while the fingers 4806 and
associated chuck clamp 4805 may be formed from high strength
aluminum. This material affords sufficient flexibility of the
fingers in the configuration shown while at the same time providing
sufficient strength to hold the hub 4804. The fingers 4806 and
aluminum chuck clamp 4805 may be coated with a synergistic coating
that provides significant lubrisity. The chuck clamp housing may be
formed from hardened steel. Again, other materials may be used as
long as they provide the functionality and benefits described
herein.
[0306] Further illustrations of the present design are shown in
FIGS. 49 and 50. The angles of the fingers 4806 may be altered from
the current approximate 10 degrees shown in FIG. 45 to 5 degrees or
some other number. Further, the present design uses six fingers,
but any number greater than three fingers could be used with likely
adequate results. The present aspect of the design may be employed
in any spin device where a hub or rounded end piece must be grasped
accurately, such as a lathe or other industrial application. The
implementation illustrated herein is that of clamping a disk hub
for use in servowriting and disk inspection.
[0307] While the invention has been described in connection with
specific embodiments thereof, it will be understood that the
invention is capable of further modifications. This application is
intended to cover any variations, uses or adaptations of the
invention following, in general, the principles of the invention,
and including such departures from the present disclosure as come
within known and customary practice within the art to which the
invention pertains.
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