U.S. patent application number 14/141998 was filed with the patent office on 2014-04-24 for multi-drive printed product processing device with verified feedback control.
The applicant listed for this patent is Goss International Americas, Inc.. Invention is credited to Kevin Lauren Cote, Lothar John Schroeder.
Application Number | 20140109786 14/141998 |
Document ID | / |
Family ID | 43822179 |
Filed Date | 2014-04-24 |
United States Patent
Application |
20140109786 |
Kind Code |
A1 |
Cote; Kevin Lauren ; et
al. |
April 24, 2014 |
MULTI-DRIVE PRINTED PRODUCT PROCESSING DEVICE WITH VERIFIED
FEEDBACK CONTROL
Abstract
A multi-drive printed product processing device is provided that
includes a processing component and a motor driving the processing
component. A motor control controls the motor. An encoder measures
a position of the motor and sends an encoder feedback signal
indicating the position. The motor control receives the encoder
feedback signal. An encoder feedback signal verification circuit
verifies the integrity of the feedback signal. A printing press is
also provided.
Inventors: |
Cote; Kevin Lauren; (Allen,
TX) ; Schroeder; Lothar John; (West Chester,
OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Goss International Americas, Inc. |
Durham |
NH |
US |
|
|
Family ID: |
43822179 |
Appl. No.: |
14/141998 |
Filed: |
December 27, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12587443 |
Oct 7, 2009 |
8640617 |
|
|
14141998 |
|
|
|
|
Current U.S.
Class: |
101/486 |
Current CPC
Class: |
B41F 33/02 20130101;
B41F 13/0045 20130101; G05B 19/231 20130101; B41F 33/0009 20130101;
B41P 2213/734 20130101; G05B 2219/45187 20130101 |
Class at
Publication: |
101/486 |
International
Class: |
B41F 33/00 20060101
B41F033/00 |
Claims
1. A multi-drive printed product processing device comprising: a
processing component; a motor driving the processing component; a
motor control controlling the motor; an encoder for measuring a
position of the motor and sending an encoder feedback signal
indicating the position of the motor, the motor control receiving
the encoder feedback signal; and an encoder feedback signal
verification circuit verifying the feedback signal.
2. The multi-drive printed product processing device recited in
claim 1 wherein the processing component is a printing unit.
3. The multi-drive printed product processing device recited in
claim 1 further comprising a system control sending a command
signal indicating a desired position of the motor to the motor
control.
4. The multi-drive printed product processing device recited in
claim 3 further comprising a summing junction for receiving the
encoder feedback signal and the command signal and determining an
error as a function of the encoder feedback signal and command
signal.
5. The multi-drive printed product processing device recited in
claim 4 wherein the summing junction sends the error and the motor
control receives the error and adjusts the position of the motor
according to the error.
6. The multi-drive printed product processing device as recited in
claim 1 wherein the encoder feedback signal verification circuit
insures the encoder is functioning properly.
7. The multi-drive printed product processing device as recited in
claim 1 further comprising feedback control loop circuitry
independent of the encoder feedback signal verification
circuit.
8. The multi-drive printed product processing device as recited in
claim 7 wherein the feedback control loop circuitry receives a
command signal for positioning the motor and the encoder feedback
signal, the feedback control loop circuitry determining a
difference between the command signal and the encoder feedback
signal and sends a signal indicating the difference between the
command signal and the encoder feedback signal to the motor
control.
9. A printing press comprising: a first printing unit including a
first plate cylinder and a first blanket cylinder; a first motor
driving the first printing unit; a first motor control controlling
the first motor; a first encoder for measuring a first position of
the first motor and sending a first encoder feedback signal
indicating the first position of the first motor; a first encoder
feedback signal verification circuit verifying the integrity of the
first feedback signal; a second printing unit including a second
plate cylinder and a second blanket cylinder; a second motor
driving the second printing unit; a second motor control
controlling the second motor; a second encoder for measuring a
second position of the second motor and sending a second encoder
feedback signal indicating the second position of the second motor;
a second encoder feedback signal verification circuit verifying the
integrity of the second encoder feedback signal; and a system
control for controlling the first and second motor controls.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation of U.S. application Ser. No.
12/587,443 filed on Oct. 7, 2009, the entire disclosure of which is
hereby incorporated by reference herein.
[0002] The present invention relates generally to multi-drive
graphic systems and more specifically the use of encoder feedback
to monitor the positioning of motors.
BACKGROUND OF INVENTION
[0003] U.S. Pat. No. 4,271,379 discloses a web fed press with two
press units, each including a driving means driven by a motor. Each
motor has an encoder that produces pulse trains corresponding to
the positioning of the motor. These pulse trains are compared by a
phase comparator, producing a voltage that passes through a filter
amplifier and is level shifted by a level shifting circuit, which
outputs a signal that represents the speed error between the
motors. The signal then passes through a proportional amplifier, an
integrator amplifier, two summing input resistors and a summing
amplifier, to a regenerative drive circuit. If the relationship
between the speed of the motors is not as desired, the energization
of the second motor is corrected by the regenerative drive circuit
to achieve the proper speed relationship.
[0004] U.S. Pat. No. 5,894,802 discloses a method and apparatus for
providing disturbance-free speed and position reference signals to
drive shafts in a printing press. An isolated position reference
unit receives a signal indicating the desired speed of a printing
web and generates isolated position reference signals. The position
reference signals and are then sent to speed controllers that
control the speed of the drive shafts accordingly. Position
encoders determine the position of the drive shaft. Regulators then
correct the isolated position reference signal based on the
determined drive shaft position.
[0005] U.S. Pat. Pub. 2006/0267529 discloses an apparatus for use
with an encoder feedback device including a comparator, a counter,
and a prediction unit. An encoder includes a scanner and determines
the position of a rotating load by identifying radially displaced
optical markings disposed about the periphery of a disk that is
coupled to and rotates with the load. The encoder then sends
sine/cosine signals indicating the position of the load to the
comparator, which converts the signals into square waves. The
counter then counts the rising and falling edges of the square wave
signals and stores a position value that represents the position of
the load at a certain time. The prediction unit then receives the
position value from the counter at a certain time and predicts the
position of the rotating load at that time as a function of at
least a subset of the position values generated prior to that time
and a misalignment between that time and a predetermined update
interval to generate an aligned position signal.
[0006] U.S. Pat. Pub. 2007/0013334 discloses an electronic line
shaft system with master controller that includes a predictor for
anticipating a position value of an encoder at a fixed future time.
The encoder measures the position of the master line shaft and
sends a position signal to the master controller. The master
controller, after receiving a command signal from a virtual
encoder, then sends a position signal to the predictor, which
anticipates the position value of the encoder at a fixed future
time. This predicted position value is sent to servant motor drives
that hold the predicted position value until a strobe signal sent
by the predictor causes each of the servant motor drives to accept
the predicted position value and to control their motor systems
accordingly. This allows the line shafts driven by the motors to
synchronize their positioning.
BRIEF SUMMARY OF THE INVENTION
[0007] The present invention provides a multi-drive printed product
processing device including a processing component and a motor
driving the processing component. A motor control controls the
motor. An encoder measures a position of the motor and sends an
encoder feedback signal indicating the position. The motor control
receives the encoder feedback signal. An encoder feedback signal
verification circuit verifies the integrity of the feedback
signal.
[0008] The present invention also provides a printing press
including a first printing unit, which includes a first plate
cylinder and a first blanket cylinder. A first motor drives the
first printing unit and a first motor control controls the first
motor. A first encoder measures a first position of the first motor
and sends a first encoder feedback signal indicating the first
position of the first motor. A first encoder feedback signal
verification circuit verifies the integrity of the first feedback
signal. A second printing unit includes a second plate cylinder and
a second blanket cylinder. A second motor drives the second
printing unit and a second motor control controls the second motor.
A second encoder for measures a second position of the second motor
and sends a second encoder feedback signal indicating the second
position of the second motor. A second encoder feedback signal
verification circuit verifies the integrity of the second encoder
feedback signal. A system control controls the first and second
motor controls.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The present invention is described below by reference to the
following drawings, in which:
[0010] FIG. 1 shows a schematic view of an encoder feedback
integrity verification system according to an embodiment of the
present invention;
[0011] FIG. 2a shows a plot of a position command of the motor of
FIG. 1 versus time;
[0012] FIG. 2b shows a plot of a typical sequence of encoder
feedback pulses generated by the encoder of FIG. 1 versus time,
generated to correspond with the time of FIG. 2a;
[0013] FIG. 2c shows a plot of the position feedback signal
generated by the encoder of FIG. 1, or the actual position of the
motor, formed from adding the pulses from FIG. 2b together, versus
time; and
[0014] FIG. 3 shows a schematic view of an encoder integrity
feedback verification system according to an embodiment of the
present invention incorporated into a four color web-offset
lithographic printing press.
DETAILED DESCRIPTION
[0015] Systems using multiple motors to drive processing components
of the system control the timing and the speed of the motors so
that the components of the system interact properly and
effectively. One way to effectuate such interaction is to use
encoders to send feedback signals to the system control center
informing the control center of the actual positioning of the
motors. Systems using encoder feedback for multi-drive applications
are negatively impacted if the integrity of the encoder feedback
signal is not high. Both system performance and the ability to use
drive diagnostic tools may diminish as the integrity of the encoder
feedback signal deteriorates. Absence of reliable diagnostic tools
often results in excessive servicing or replacement of encoders,
cables, and encoder cards.
[0016] FIG. 1 shows a schematic view an encoder feedback integrity
verification system 90 according to an embodiment of the present
invention. An encoder 32 is connected to a motor 31. A system
control 35 controls the positioning of motor 31 by a command signal
34 to a motor control 41, which controls the positioning of motor
31 by sending a position signal 43 to motor 31. Command signal 34
is also measured by a negative feedback summing junction 39. When
motor 1 receives position signal 43 from system control 35, if the
system is working perfectly, motor 31 should rotate to a position
as commanded by system control 35. Encoder 32 then measures the
actual position of motor 31 and sends an encoder feedback signal 33
to a negative feedback summing junction 39. Next, negative feedback
summing junction 39 compares signals 33, 34. The difference between
signals 33, 34 is determined to be a resulting error 40. A signal
indicating resulting error 40 is then sent to motor control 41,
which through position signal 43 causes motor 31 to increase or
decrease speed based on resulting error 40. This section thus
defines a feedback control loop running from motor 31, through
encoder 32, feedback signal 33 and summing junction 39 to motor
control 41.
[0017] The present invention also provides a feedback signal
verification circuit or integrity check loop to insure the encoder
is functioning properly. A summing junction 36, an integrator 42,
and a system control 35 make up a feedback signal verification
circuit to check encoder integrity. Encoder feedback signal 33 and
command signal 34 can thus also be measured for diagnostic purposes
to verify the integrity of encoder feedback signal 33. The actual
position of the motor, as indicated by encoder feedback signal 33,
is subtracted from the command position, as indicated by command
signal 34, in summing junction 36. A resulting error 37, the
difference between signals 33, 34, is then transmitted to
integrator 42, where error 37 is summed over time. Integrated value
38 is sent back to system control 35, where integrated value 38 can
be compared to an expected value. Error 37 alternatively may be
taken directly from error 40.
[0018] The expected value may be a function of speed and can be
determined experimentally or empirically, as will be described
herein. Once integrated value 38 and the expected value are
compared, an appropriate action message related to the encoder
feedback integrity can be generated. An example of a group of error
messages are as follows. When there is only a small error between
the expected value and integrated value 38, a message can be
generated stating "Check feedback components at next scheduled
service," when there is a medium error the message can be
"Performance may be compromised, check product quality, stop and
correct problem if critical components are altered," and when the
error is large the message can be "Instability is possible, stop
and correct problem."
[0019] FIGS. 2a, 2b, 2c illustrate a missed encoder pulse during
steady state running in the system shown in FIG. 1. FIG. 2a shows a
plot of a position command of the motor 31 from FIG. 1 versus time.
FIG. 2b shows a plot of a typical sequence of encoder feedback
pulses generated by the encoder 32 of FIG. 1 versus time, generated
to correspond with the time of FIG. 2a. FIG. 2c shows a plot of the
position feedback signal 34 generated by the encoder 32 of FIG. 1,
or the actual position of the motor 31, formed from adding the
pulses from FIG. 2b together, versus time. Comparing FIG. 2a to
FIG. 2c illustrates the difference between the motor position
command, sent as command signal 34 (FIG. 1), and the actual
position, as indicated by encoder feedback signal 33 (FIG. 1). At
time T1 position command 20 and position feedback 25 are equal, so
no additional error 40 is integrated in the diagnostics. The same
is true for time T2, where position command 19 equals position
feedback 24. At time T3 encoder pulse 15 was missing and therefore
position feedback value 24 did not increase as desired by system
control 35. However, the position command 18 at time T3 did
increase, leaving an error 40 (FIG. 1) between the position command
and the actual position.
[0020] As shown in FIG. 1, error 40 causes motor control 41 to send
position signal 43 to increase speed of motor 31 temporarily until
error 40 is driven to zero. Just as a missing pulse may generate an
error, an inadvertent extra pulse may generate an error. If this
occurs, motor control 41 may command motor 31 to slow down until
the error has been driven to zero. However, if motor 31 is in the
actual position commanded by system control 35 and encoder 32
erroneously sends a signal indicating the incorrect position, motor
controller 41 alters the position of motor 31 so the position of
motor 31 does not accurately correspond to the position desired by
system control 35.
[0021] To identify an erroneous encoder feedback signal 33, the
difference between command signal 34 and encoder feedback signal
33, error 37, is integrated in the diagnostic integrator 42 to
verify the integrity of encoder feedback signal 33, while motor
control 41 is correcting the position of motor 31. It may be
expected that value 38, corresponding to motor speed, is a constant
non-zero value during operation. However, if encoder 32 is working
properly and the integrity of encoder feedback signal 33 is
adequate, value 38 should remain constant at a steady state speed.
Also, value 38 should be near or equal to the expected value for a
certain speed. Any deviations in value 38 should signify a problem
with encoder 32 and can be reported to the user in a manner
corresponding to the amount of deviation. Depending on the size of
the deviation, the size of the error can be estimated. The expected
value can also be, for example, a function of time during start up
or non-steady state running and can be determined empirically, for
example, by testing.
[0022] The system of the present invention may be particularly
useful when used in an offset lithographic printing press. In an
offset lithographic printing press a plurality of motors may drive
cylinders of printing units. Some type of control system may direct
the operation of the motors and therefore the rotation of the
cylinders. In an offset lithographic printing press it is important
that the rotation of the cylinders in relation to one another is
timed so that the cylinders interact properly and effectively. This
permits, for example, proper color registration for a four color
printing press. The present invention would ensure proper timing of
the cylinders and would allow problems to be diagnosed and
corrected, thereby ensuring a quality printed product.
[0023] An example of a multi-drive system is a printing press,
wherein the processing components are printing units. FIG. 3 shows
a schematic view of an encoder integrity feedback verification
system according to an embodiment of the present invention
incorporated into a four color web-offset lithographic printing
press 70. Printing press 70 includes four printing units 72, 74,
76, 78, each printing unit 72, 74, 76, 78 having the same
configuration, but printing a different color on a passing web 60
to form images on the web 60. A first common drive 80 rotates first
plate cylinders 62, 68 and first blanket cylinders 64, 66 of a
first print unit 76, and a second common drive 180 rotates second
plate cylinders 162, 168 and second blanket cylinders 64, 66. A
first motor 31 drives first common drive 80 as directed by a first
motor control 41, and a second motor 131 drives second common drive
180 as directed by a second motor control 141.
[0024] Each motor control 41, 141 receive position commands from a
system control 35 via a first command signal 34 and second command
signal 134, respectively. A first encoder 32 and a second encoder
132 include encoder disks 52, 152, an encoder sensors 50, 150,
respectively. Encoder disks 52, 152 are mounted on common drives
80, 180 and rotate in relation to the position of motors 31, 131,
respectively. First encoder sensor 50 measures a first position of
first encoder disk 52 and converts the first position into a first
encoder feedback signal 33, and second encoder sensor 150 measures
a second position of second encoder disk 152 and converts the
second position into a second encoder feedback signal 133. Encoder
feedback signals 33, 133 are sent to a first negative feedback
summing junction 39 and a second negative feedback summing junction
139, respectively. Command signals 34, 134 are sent to respective
motor controls 41, 141 and also to respective negative feedback
summing junctions 39, 139. Summing junction 39 compares signals 33,
34, while summing junction 139 compares signals 133, 134.
[0025] The difference between the values of signals 33, 34, as
determined by first summing junction 39, is a first error 40. The
difference between the values of signals 133, 134, as determined by
second summing junction 39, is a second error 140. A signal
indicating first error 40 is then sent to first motor control 41,
which causes first motor 31 to increase or decrease speed based on
first error 40, to be in the position as commanded by system
control 35, via position signal 43. A signal indicating second
error 140 is then sent to second motor control 141, which causes
second motor 131 to increase or decrease speed based on second
error 140, to be in the position as commanded by system control 35,
via position signal 143. This system ensures that blanket cylinders
64, 66 of first printing unit 76 and blanket cylinders 164, 166 of
second printing unit 176 print on web 60 at the proper time and
position in relation to one another. Because the four printing
units 72, 74, 76, 78 are timed in relation with one another to
produce a desired final image, any positioning errors by the motor
may affect the quality of the final printed products produced by
printing press 70. Positioning errors may lead to blurring or other
deficiencies in the final products, thereby preventing the products
from being of sufficient quality to be used for their intended
purpose.
[0026] To further ensure proper timing and position of print
cylinders 62, 64, 66, 68 of printing unit 76, and of print
cylinders 162, 164, 166, 168 of printing unit 74, two encoder
feedback integrity verification circuits monitor the signals 33,
133 transmitted by encoder sensors 50, 150, respectively, to
confirm that encoder sensors 50, 150 are working properly. A first
integrity verification circuit of first printing unit 76 includes
first summing junction 39, a first integrator 42, and system
control 35. A second integrity verification circuit of second
printing unit 74 includes summing junction 139, a second integrator
142, and system control 35. Errors 40, 140, determined by
respective summing junction 39, 139, are transmitted to respective
integrators 42, 142, where errors 40, 140 are integrated over time.
Finally, integrated values 38, 138, corresponding to the respective
speeds of motors 31, 131, are sent back to system control 35, where
integrated values 38, 138 can be compared to respective expected
values.
[0027] Depending on the difference between integrated value 38 and
the corresponding expected value, system 90 may generate a message
to inform an operator whether encoder disk 52 and encoder sensor 50
need to be repaired or replaced. The same procedure occurs in
regards to integrated value 138, and a message is produced related
to encoder disk 152 and encoder sensor 150. A defective encoder
disk or encoder sensor may disrupt the speed and positioning of
cylinders of printing units 74, 76 and may result in substandard
printed products.
[0028] Although FIG. 3 only shows two printing units 74, 76
equipped with an encoder feedback integrity verification system 90,
proper coordination of printing units 72, 74, 76, 78 with one
another may require that at least three or all of the printing
units 72, 74, 76, 78 be equipped with an encoder feedback integrity
verification system 90. System control 35 may control multiple
motors and check the integrity of multiple encoders, or
alternatively, an individual system control may be provided for
each motor and may communicate with the other system controls to
correctly align their corresponding print cylinders for proper
operation and check the integrity of their corresponding encoders.
Printing units may also have different drive arrangements, with
each cylinder being driven by different motor or with two motors,
each motor driving a plate and blanket cylinder pair. In such an
arrangement an encoder feedback integrity verification circuit may
be provided for each motor. In addition to printing presses, the
present invention could be used with post-press equipment such as
inserters or saddle stitchers, or other multi-drive printing
equipment.
[0029] Should system control 35 also provide speed signals, the
encoder feedback signal verification circuit could also be sent to
verify these signals, for example by identifying unaccounted for
accelerations.
[0030] In the preceding specification, the invention has been
described with reference to specific exemplary embodiments and
examples thereof. It will, however, be evident that various
modifications and changes may be made thereto without departing
from the broader spirit and scope of invention as set forth in the
claims that follow. The specification and drawings are accordingly
to be regarded in an illustrative manner rather than a restrictive
sense.
* * * * *