U.S. patent application number 10/863427 was filed with the patent office on 2004-12-09 for ultra sensitive magnetic field sensors.
This patent application is currently assigned to TPL, Inc.. Invention is credited to Jarratt, Raymond L. JR., Summers, Stephen D., Tiernan, Timothy C..
Application Number | 20040244625 10/863427 |
Document ID | / |
Family ID | 26972589 |
Filed Date | 2004-12-09 |
United States Patent
Application |
20040244625 |
Kind Code |
A1 |
Tiernan, Timothy C. ; et
al. |
December 9, 2004 |
Ultra sensitive magnetic field sensors
Abstract
A magnetic sensor and magnetic field sensing method for
ordnance, comprising locating a giant magnetoresistance detector
within the ordnance and detecting magnetic fields with the
detector. Also other sensing method and sensors employing such
detectors.
Inventors: |
Tiernan, Timothy C.;
(Newton, MA) ; Jarratt, Raymond L. JR.; (Los
Lunas, NM) ; Summers, Stephen D.; (Albuquerque,
NM) |
Correspondence
Address: |
PEACOCK MYERS AND ADAMS P C
P O BOX 26927
ALBUQUERQUE
NM
871256927
|
Assignee: |
TPL, Inc.
Albuquerque
NM
|
Family ID: |
26972589 |
Appl. No.: |
10/863427 |
Filed: |
June 7, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10863427 |
Jun 7, 2004 |
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09969946 |
Oct 2, 2001 |
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10863427 |
Jun 7, 2004 |
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09265991 |
Mar 9, 1999 |
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6295931 |
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60301786 |
Jun 29, 2001 |
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60077525 |
Mar 11, 1998 |
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60092717 |
Jul 14, 1998 |
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Current U.S.
Class: |
102/221 |
Current CPC
Class: |
F42C 15/40 20130101;
G01R 33/09 20130101; G01V 3/081 20130101; B82Y 25/00 20130101; F42C
13/08 20130101; G01R 33/093 20130101 |
Class at
Publication: |
102/221 |
International
Class: |
F42C 015/00 |
Goverment Interests
[0002] The U.S. Government has a paid-up license in this invention
and the right in limited circumstances to require the patent owner
to license others on reasonable terms as provided for by the terms
of Contract No. SOL DAAE30-01-BAA-0500 and Contract No.
DAAE30-99-C-1068 awarded by the U.S. Army TACOM-ARDEC, by the terms
of Contract Nos. DMI-0060397 and DMI-9704080 awarded by the
National Science Foundation, and a contract with the U.S. Navy.
Claims
What is claimed is:
1. A magnetic field sensor for ordnance, said sensor comprising a
magnetoresistance detector and said sensor being located within the
ordnance.
2. The sensor of claim 1 additionally comprising means for counting
turns of spinning ordnance.
3. The sensor of claim 2 additionally comprising autonulling
means.
4. The sensor of claim 3 wherein said autonulling means injects a
charge into a circuit comprising said magnetoresistance
detector.
5. The sensor of claim 4 wherein said injecting means is triggered
when a rate of spin of the ordnance exceeds a predetermined
rate.
6. The sensor of claim 1 additionally comprising means for arming
ordnance a pre-determined time after exit of the ordnance from a
weapon firing the ordnance.
7. The sensor of claim 6 wherein said arming means comprises means
selected from the group consisting of means for determining exit of
the ordnance from a weapon firing the ordnance, means for
determining exit velocity, means for determining proximity to
metallic targets, and means for determining direction to metallic
targets.
8. The sensor of claim 7 wherein said exit determining means
detects concentrated earth's magnetic field lines at an opening of
a weapon firing the ordnance.
9. The sensor of claim 1 wherein said detector is fabricated on a
device selected from the group consisting of printed circuit
boards, hybrid circuits, and integrated circuits.
10. The sensor of claim 1 wherein said sensor detects incoming
munitions.
11. The sensor of claim 10 wherein said sensor additionally
comprises a biasing magnet.
12. The sensor of claim 10 additionally comprising means for
providing an oscillation frequency.
13. The sensor of claim 10 wherein said providing means comprises a
coil proximate a nose of the ordnance.
14. The sensor of claim 10 comprising multiple detectors and
triangulation means.
15. The sensor of claim 10 comprising an array of detectors.
16. The sensor of claim 1 additionally comprising means selected
from the group consisting of means for outputting a signal
characteristic of impact of the ordnance, means for employing a map
of local magnetic fields to determining position and direction of
an object, means for detecting flying objects by looking for
response to an emitted magnetic field, and means for determining
eddy currents output by flying object traversing earth's magnetic
field.
17. A magnetic field sensing method for ordnance, the method
comprising the steps of locating a magnetoresistance detector
within the ordnance and detecting magnetic fields with the
detector.
18. The method of claim 17 additionally comprising the step of
counting turns of spinning ordnance.
19. The method of claim 18 additionally comprising the step of
employing autonulling means.
20. The method of claim 19 wherein the employing step comprises
injecting a charge into a circuit comprising the magnetoresistance
detector.
21. The method of claim 20 wherein the injecting step is triggered
when a rate of spin of the ordnance exceeds a predetermined
rate.
22. The method of claim 17 additionally comprising the step of
arming ordnance a pre-determined time after exit of the ordnance
from a weapon firing the ordnance.
23. The method of claim 22 wherein the arming step comprises a step
selected from the group consisting of determining exit of the
ordnance from a weapon firing the ordnance, determining exit
velocity, determining proximity to metallic targets, and
determining direction to metallic targets.
24. The method of claim 23 wherein the exit determining step
comprises detecting concentrated earth's magnetic field lines at an
opening of a weapon firing the ordnance.
25. The method of claim 17 additionally comprising the step of
fabricating the detector on a device selected from the group
consisting of printed circuit boards, hybrid circuits, and
integrated circuits.
26. The method of claim 17 additionally comprising the step of
detecting incoming munitions.
27. The method of claim 26 wherein the detecting step comprises
employing a biasing magnet.
28. The method of claim 26 wherein the detecting step comprises
providing an oscillation frequency.
29. The method of claim 26 wherein the detecting step comprises
employing a coil proximate a nose of the ordnance.
30. The method of claim 26 wherein the locating step comprises
locating multiple detectors and triangulation means.
31. The method of claim 26 wherein the locating step comprises
locating an array of detectors.
39. The method of claim 24 additionally comprising a step selected
from the group consisting of outputting a signal characteristic of
impact of the ordnance, employing a map of local magnetic fields to
determining position and direction of an object, detecting flying
objects by looking for response to an emitted magnetic field, and
determining eddy currents output by flying object traversing
earth's magnetic field.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 09/969,946, entitled ULTRA SENSITIVE MAGNETIC
FIELD SENSORS, filed on Oct. 2, 2001, which claims the benefit of
the filing of U.S. Provisional Patent Application Ser. No.
60/301,786, entitled ULTRA SENSITIVE MAGNETIC FIELD SENSORS, filed
on Jun. 29, 2001, and which is a continuation-in-part application
of U.S. patent application Ser. No. 09/265,991, entitled INTEGRATED
MAGNETIC FIELD SENSORS FOR FUZES, to David W. Cutler, et al., filed
on Mar. 9, 1999, issued on Oct. 2, 2001, as U.S. Pat. No.
6,295,931, which claimed the benefit of the filing of U.S.
Provisional Patent Application Ser. No. 60/077,525, entitled
SENSITIVE INTEGRATED MAGNETIC FIELD SENSORS FOR FUZES, filed on
Mar. 11, 1998; and of U.S. Provisional Patent Application Ser. No.
60/092,717, entitled SENSITIVE INTEGRATED MAGNETIC FIELD SENSORS
FOR FUZES, filed on Jul. 14, 1998. The specifications and claims of
all these references are incorporated herein by reference.
BACKGROUND OF THE INVENTION
Field of the Invention (Technical Field)
[0003] The present invention relates to sensors made of giant
magnetoresistance materials (GMR) or colossal magnetoresistive
materials. The term GMR, as used throughout the specification, is
intended to include both giant and colossal magnetoresistance or
magnetoresistive materials.
SUMMARY OF THE INVENTION (DISCLOSURE OF THE INVENTION)
[0004] The present invention is of a magnetic sensor and magnetic
field sensing method for ordnance, comprising locating a giant
magnetoresistance detector within the ordnance and detecting
magnetic fields with the detector. In one embodiment, turns of
spinning ordnance are counted, with autonulling being employed,
such as injecting a charge into a circuit comprising the giant
magnetoresistance detector, the injecting being triggered when a
rate of spin of the ordnance exceeds a predetermined rate. In
another embodiment, ordnance is armed a pre-determined time after
exit of the ordnance from a weapon firing the ordnance, which can
involve one or more of the following: determining exit of the
ordnance from a weapon firing the ordnance (preferably by detecting
concentrated earth's magnetic field lines at an opening of a weapon
firing the ordnance), determining exit velocity, determining
proximity to metallic targets, and determining direction to
metallic targets. In another embodiment, incoming munitions are
detected, such as by employing a biasing magnet, employing an
oscillation frequency, employing a coil proximate the nose of the
ordnance, employing multiple detectors and triangulation means,
and/or employing an array of detectors. The detector is preferably
fabricated on a printed circuit board, hybrid circuit, or
integrated circuit. The sensor can also perform one or more of the
following functions: outputting a signal characteristic of impact
of the ordnance, employing a map of local magnetic fields to
determining position and direction of an object, detecting flying
objects by looking for response to an emitted magnetic field, and
determining eddy currents output by flying object traversing
earth's magnetic field.
[0005] The present invention is also of a magnetic field sensor and
sensing method for locating defects in objects in two or three
dimensions, comprising providing to a sensor a giant
magnetoresistance detector and traversing the sensor over an
object. In the preferred embodiment, one or more of the following
functions are performed: determining type of defect, determining
volume lost to defect, determining depth of defect, imaging the
defect, determining dimensions of defect, and producing Lissajous
plots of amplitude versus phase for magnetic fields.
[0006] The present invention is further of a magnetic field sensor
and sensing method for medical imaging, comprising providing to a
sensor a giant magnetoresistance detector and traversing the sensor
over a patient. In the preferred embodiment, one or more of the
following functions are performed: measuring electromagnetic
activity in the patient's heart, measuring electromagnetic activity
in the patient's brain, performing biomagnetics analysis,
performing nuclear resonance imaging, and imaging skin defects.
[0007] The invention is additionally of a magnetometer and
magnetometry method comprising providing a giant magnetoresistance
detector and operating the detector. In the preferred embodiment,
one or more of the following functions are performed: detecting
conductive materials on a surface, detecting conductive materials
beneath a surface, detecting conductive materials in a body of
liquid, locating naval vessels, detecting electrical currents
flowing through printed circuit board traces, detecting electrical
currents flowing through integrated circuit components, measuring
amplitudes of electrical currents, and detecting breaks in
electrical conductors. Operation may be in DC detection mode or
employing oscillating magnetic fields.
[0008] Objects, advantages and novel features, and further scope of
applicability of the present invention will be set forth in part in
the detailed description to follow, taken in conjunction with the
accompanying drawings, and in part will become apparent to those
skilled in the art upon examination of the following, or may be
learned by practice of the invention. The objects and advantages of
the invention may be realized and attained by means of the
instrumentalities and combinations particularly pointed out in the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The accompanying drawings, which are incorporated into and
form a part of the specification, illustrate one or more
embodiments of the present invention and, together with the
description, serve to explain the principles of the invention. The
drawings are only for the purpose of illustrating one or more
preferred embodiments of the invention and are not to be construed
as limiting the invention. In the drawings:
[0010] FIG. 1 is an electrical schematic of the preferred spinning
round sensor of the invention;
[0011] FIG. 2 is a diagram of a circuit board incorporating the
sensor of the invention;
[0012] FIG. 3 is a graph showing signal pulse upon exit from a
mortar tube of a munition incorporating the sensor;
[0013] FIG. 4 illustrates the sine wave detected by the sensor as
generated by the rotation of a munition, with each cycle being
equivalent to one rotation of the munition;
[0014] FIG. 5 is an electrical schematic of the barrel exit
detection embodiment of the invention, useful with mortars and
non-rotating rounds;
[0015] FIG. 6 is a perspective view of a data logger PCB
incorporatable into a 40 mm round for testing purposes;
[0016] FIG. 7 is a front perspective view of a round incorporating
data logger and sensor PCBs just before final assembly;
[0017] FIG. 8 is a block diagram of a system useful in arming a
device according to the invention and collecting data from an
on-board data acquisition system;
[0018] FIG. 9 illustrates a conditioned signal output by the data
logger PCB, each square wave transition corresponding to one
revolution of the 40 mm round;
[0019] FIG. 10 illustrates use of the sensor of the invention
within a counter munition;
[0020] FIG. 11 is a perspective view of a handheld NDE unit
including graphical modes that can resolve defects to a depth of
more than 0.4" in 6061T6;
[0021] FIG. 12 is a top view of a 196-element tunnel junction
imaging array;
[0022] FIG. 13 is an 11 kHz C-scan of first and second layer rivet
heads in an aluminum sheet metal section simulating an aircraft
wing;
[0023] FIG. 14 shows 100 micron wide cuts in an aluminum sheet
metal sample;
[0024] FIG. 15 is an APET image of a 10% mass loss corroded region
measured through 60 mils of aluminum, made from the side opposite
the corrosion;
[0025] FIG. 16 illustrates use of the sensor of the invention for
guidance of a munition according to the invention to an under-sea
mine;
[0026] FIG. 17 is a top view of a 14.times.14 element array of GMR
sensors produced on a single substrate, each element being
approximately 10.times.10 microns;
[0027] FIG. 18 is output from a two-dimensional GMR sensor array
according to the invention showing variations in magnetic field
strength over an area of metal; and
[0028] FIG. 19 is a block diagram of a system according to the
invention used for non-destructive evaluation of a sample.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
BEST MODES FOR CARRYING OUT THE INVENTION
[0029] Magnetic Field Sensors for Munitions
[0030] The present invention is directed to an advanced, giant
magnetoresistive (GMR) based sensor platform for detection of spin
rate and muzzle exit, muzzle exit velocity, range, proximity,
attitude, and/or guidance of munitions from within the fuze
assembly of an advanced munition. The sensor can operate with both
rotating rounds such as a 40 mm rotating round or with non-rotating
rounds such as a 60 mm mortar. The invention can also operate with
finned munitions.
[0031] Extensive shock and thermal testing was employed to verify
the robustness of the sensor. The sensor and support electronics
were transferred to a production board package in order to provide
single board sensors for turns counting or barrel exit sensing.
Live-fire tests were successfully completed for a 40 mm rotating
round. The tests were successful and showed that it is possible to
monitor barrel exit, rotations, velocity, and range all with a
single sensor. The results showed that the sensor was able to
provide data that can monitor munition flight distance with an
error of less than 1% (0.84%). Evaluations of barrel exit
detection, tolerance of mechanical shock, and environmental
durability of the sensors were also positive using an 60 mm mortar
tube. Laboratory simulated live-fire tests for the mortar barrel
exit sensor were performed.
[0032] The preferred spinning round circuit design is as follows,
including an autonulling capability (see FIG. 1). As soon as the
sensor begins to spin at a rate above a few Hz, the circuit injects
a small charge into the sensor to compensate for any polling (due
to large magnetic field exposure) that has taken place during
storage of the sensor or munition. The rate of rotation for
activation is high enough that it will not null the sensor if the
munition is dropped or rolled during handling. When fired, the
rotation due to rifling of the gun barrel makes the sensor spin at
a sufficient rate, while the sensor is still in the barrel of the
gun, to activate the autonulling. This ensures that the sensor is
biased properly to detect barrel exit when it is fired, and begin
counting turns when the munition exits the barrel.
[0033] The circuit automatically nulls the GMR sensor during
power-up. This compensates for any residual magnetization that may
have occurred due to close proximity of the sensor to large
magnetic fields.
[0034] The circuits are preferably built on printed circuit boards
(PCB), which offer low power operation in a small enough package to
meet the demands of both 40 mm rounds and 60 mm mortars. Circuits
built this way are much less expensive to design layout, build and
test, than are circuits made with hybrid techniques. However,
hybrid circuits may be used where a smaller package is needed.
[0035] Shock testing was performed prior to firing the 40 mm test
rounds. The sensor and electronics system were unaffected by
exposure to shock equivalent to live firing of the round. During
live fire tests with 40 mm rounds the sensor and electronics
withstood the shock with no failures or any signs of damaging
effects.
[0036] The present invention can also measure barrel exit time and
barrel exit velocity for mortars. Using techniques and sensors made
from giant magnetoresistance materials (GMR), highly durable, low
power sensors detect barrel exit in both 60 mm mortars, and 40 mm
spinning rounds (FIGS. 2 and 5). Larger diameter mortars (e.g., 80
mm and 120 mm) require that the sensor have the ability to
dependably detect the edge of the mortar tube using a passive
approach such as measuring the earth's magnetic field concentration
at the edge (exit) of the mortar, or using an active mode, for
example, a small permanent magnet mounted on the end of the mortar
tube at a large distance between the sensor and the edge of the
mortar tube. Laboratory tests with larger diameter mortars indicate
that the invention can measure both exit time and exit velocity in
these munitions.
[0037] The present invention also provides an advanced magnetic
safing and arming (S&A) sensor technology based on giant
magnetoresistive sensors. Extensive tests, including live fire
tests with 40 mm munitions were performed with both turns-counting
and barrel-exit sensing configurations for rotating rounds. The
present invention includes non-rotating rounds, specifically 60 mm
mortars. The sensors survived repeated mechanical shock tests in
excess of 100,000 gs and environmental cycling ranging from 150 C.
to -180 C.
[0038] Tunnel-junction or spin valve GMR sensors with a resistance
change of 7-15% in a 2 Oe magnetic field applied perpendicular to
the easy axis of the device have been used. In general, high
sensitivity to magnetic field is desirable The sensor sizes used
range from 0.4 mm.times.1 mm to 10 .mu.m.times.10 .mu.m. The device
impedance used ranged from 100 .OMEGA. to 10 k.OMEGA. but other
device impedances can be used depending on the application. In
general high impedance (ohms per square) helps reduce the size of
the sensor, and this saves power and reduces the size of the
sensor. The bandwidth of the sensor used was >1 Ghz, making it
capable of detecting extremely rapid changes in magnetic fields.
Power consumption of the sensor and support electronics is has been
shown to be no more than approximately 1 milliamp at 3 volts for
the spinning round sensor. Power requirement will vary depending on
the sensors and circuitry needed for each application. The size of
the sensor and its support electronics, mounted on a standard
printed circuit board, is not an impediment since the entire
assembly easily fits inside a 40 mm round or a 60 mm mortar without
the need for modifications to the munition. If a smaller sensor
system is needed the sensor and circuit can be fabricated as a
hybrid integrated circuit, greatly reducing the physical size of
the sensor device.
[0039] In one embodiment, the sensor operates by detecting the
magnetic field of the earth. In the case of a mortar round, the
local field gradient is concentrated by the metal mortar tube.
Inside the tube there is little or no magnetic field. At the
opening of the mortar tube, the earth's magnetic field lines are
concentrated by the edges of the mortar tube, resulting in a
relatively strong field. When the mortar is fired, the sensor does
not respond until it passes the end of the mortar tube where it
detects the concentrated magnetic field. The sensor outputs an
electrical pulse that can be used as a trigger to mark barrel exit,
and arm the mortar (FIG. 3).
[0040] In the case of a rotating round, the sensor is mounted such
that it spins along with the munition. As it spins, its sensitive
axis cycles from alignment with the earth's magnetic filed, to
nonalignment. This results in the sensor outputting a variable
amplitude sine wave corresponding to one revolution of the munition
(FIG. 4). Since the rifling dimensions for the gun from which the
sensor is fired are known, it is possible to detect barrel exit,
speed and range of the munition.
[0041] The sensor of the present invention has a wide range of uses
including barrel exit and velocity for mortars. It can also be used
for trajectory measurements and proximity to metallic targets for
non-rotating rounds. The sensor system has highly desirable
characteristics including: extremely small size, low power
operation, high shock resistance, wide temperature range, and
extremely fast response time. Its operation is based on the earth's
magnetic field making it highly reliable and independent of other
system such as GPS. The sensor system benefits munitions programs
by offering a high performance low cost alternative for arming and
safing applications for both non-rotating and rotating
munitions.
[0042] Design of the Barrel Exit Sensor and Circuitry for a 120 mm
Mortar
[0043] Accurate barrel exit detection is related to the ambient
noise level, signal state separation, and sensor bandwidth. The
sensor output when in the mortar tube compared to sensor output
during barrel exit is sufficient reliable barrel exit detection. If
the sensor bandwidth is much smaller than the event bandwidth both
event detection and timing accuracy are degraded. Bandwidth, and
signal output while inside the mortar tube do not pose problems.
The sensor can detect the threshold of the mortar tube where the
earth's magnetic field is concentrated by the metal mortar
tube.
[0044] Several techniques can be used to increase detection
capability and reliability:
[0045] Using the same sensors described above for a 60 mm mortar,
determine if there is sufficient sensitivity to detect barrel exit.
If not, refine the gain and frequency response of the circuitry to
improve performance as needed.
[0046] Use a more sensitive sensor and/or sensor arrays with
extremely high sensitivity.
[0047] Use a number of offset sensors each oriented in a different
direction to determine if any one of them or any combination of
them detect the concentrated field at the mouth of the mortar tube.
This array of sensor can be read in a logical mode (e.g., AND, OR)
to increase the detection capabilities and reliability of the
sensor configuration.
[0048] Use permanent magnet in conjunction with the sensor. For
example, a permanent magnet may be placed at the end of the mortar
tube where the field would be detected by the sensor(s) as the
munition exits the mortar tube.
[0049] The preferred barrel exit circuitry (see FIG. 5) is
preferably similar to the electronics developed and tested for
mortar exit and spinning rounds. In its simplest form, the circuit
has a self-nulling capability so that when it is activated by
powering the sensor, the bias point of the sensor is set to the
center of its full range output. The circuit will then continuously
compare the real-time output of the sensor to a preset voltage that
corresponds to the output of the sensor under low magnetic field
conditions.
[0050] When the sensor (and mortar) exit the mortar tube, the
sensor detects the earth's magnetic field concentrated at the mouth
of the launch tube (barrel). When the sensor detects the magnetic
field concentration, its output causes the on-board detection
circuitry to cross a preset comparison voltage. To accomplish the
same goal, the sensor may also detect permanent magnets mounted at
the end of the launch tube. This results in a high-speed digital
pulse that is used to trigger the fuzing system. If two sensors are
used with a known distance between the sensors, then the speed of
the munition can be determined at barrel exit. This information can
be used for range analysis and compensation due to weather, wind,
or other conditions. Additional filtering circuitry may be used so
that the sensor amplifier responds only to high frequency pulse
characteristic of high-speed barrel exit. This helps eliminate
noise and other spurious signals due to set back, permanent
magnetic fields in the mortar tube, and accidental dropping of the
mortar round.
[0051] The barrel exit sensors of the invention preferably use
standard printed circuit board (PCB) techniques utilizing SIOC
packaged ICs, and chip capacitors and resistors.
[0052] The barrel exit sensors of the invention were evaluated
using both a drop tower and a simulation station. The drop tower
consists of a metal tube made of materials and dimensions similar
to a 120 mm mortar tube. Alternatively, a modified 120 mortar tube
may be used. The test apparatus allowed for mechanical acceleration
to achieve high velocities for meaningful testing of the barrel
exit sensor.
[0053] The simulation test station was based on using an arbitrary
waveform generator, coupled to a discharge-capacitor driven current
source to simulate the transient of a much faster barrel exit than
that achievable using a drop tower configuration. In principle this
simulation station accurately reproduce the magnetic field
perturbation of a gun barrel exit at speeds in excess of 5,000 m/s,
a velocity actually achieved by some munitions such as the kinetic
energy rod. This velocity is well within the bandwidth limitations
of the sensor of the present invention.
[0054] 60, 80, and 120 mm mortar tubes were tested. Barrel exit
detectability was enhanced for the larger mortar tubes by improving
the sensor and circuitry specifically for the larger mortar by
using flux guides, optimized geometry and signal processing
techniques. The sensor was able to detect the edge of the larger
mortar tubes during barrel exit under simulated conditions.
[0055] Programs were performed related to GMR sensors for
applications in both safing and fuzing, and in the use of GMR
sensors and sensor arrays for nondestructive evaluation. In the
area of safing and fuzing it was shown that the sensor can be used
to detect revolutions in a 40 mm round during live fire testing.
The sensor provided information that enabled an on-munition system
to determine barrel exit, munition velocity, and range.
[0056] Tests with mortars were conducted. A sensor was made that
was able to detect barrel exit in a 60 mm mortar. Live fire tests
confirmed the utility of the sensor. In addition to sensor and
circuit design, mechanical shock testing, and environmental testing
were performed with good results.
[0057] Signal conditioning and readout electronics were also
developed. This resulted in tunnel junction GMR sensor arrays for
NDE. The sensor elements developed were only 10 microns on a side,
yet delivered 7% (R in a 2 Oe field with nominal resistance near 10
k). Signal conditioning and readout electronics for the sensors
were also developed.
[0058] Sensors for Fuze Applications
[0059] As described previously, the present invention provides
technology to measure barrel exit, spin velocity, and range using
GMR sensors detecting the earth's magnetic field. Sensor systems
were fabricated for live-fire testing. Tests with the 40 mm
spinning round were done. Three (3) data recorder/spin sensor
assemblies were fabricated, tested and potted into 40 mm back
shells. Each final potted test unit was numbered 1, 2 and 3. Once
the operation of the data recorder and spin sensor were
individually functionally verified, the two PCBs were
interconnected and tested (assembly shown in FIGS. 6 and 7).
[0060] Prior to triggering and recording, the data recorder was
powered and armed. This was accomplished through a 7.5 v battery or
power supply source, laptop computer and an RS-232 interface. This
setup is shown in FIG. 8. The computer communicates to the data
recorder through the RS-232 interface and cable. The data recorder
microprocessor firmware program is a self-contained program that
performs BIT functions, arming, data upload, sampling rate and
record time selection. The computer used the Windows program
"Hyperterminal" to communicate with the data recorder. This program
provides communication with the data recorder for operator
parameter entry as well as data upload "receive text file" mode to
upload the data from the data recorder to a file on the hard disk.
This text was then imported to "Excel" to plot the data to a graph
(see FIG. 9).
[0061] Flight Distance Calculations During Field Testing
Predicted Flight Distance==Muzzle Velocity*Flight
Time=831*0.25=207.75 ft
Turns Calculated Flight Distance=# of Turns*4 ft/Turn=51.5*4=206.0
ft
% Error=((Predicted Flight Distance-Turns Calculated Flight
Distance)/Predicted Flight
Distance)*100=((207.75-206)/207.75)*100%=0.84%
[0062] Safing and Arming Sensor--Counter Munitions
[0063] The present invention also relates to advanced magnetic
safing and arming (S&A) sensor technology based on giant
magnetoresistive (GMR) sensors (see FIG. 10). The counter munition
would initially be guided by radar which would also sense the
munition. Once the counter munition neared its target the GMR
sensor(s) would pinpoint its location and set the needed time delay
on the fuze for maximum destructive power to the target. The
present invention provides a sensor that can detect incoming
munitions such as the KE rod or TOW missile. The sensor provides
proximity information that is used by ISP to destroy the incoming
munition before it reaches its target (e.g., a tank).
[0064] The sensor is mounted in the nose of the counter munition.
It senses the local field strength. When nearing an incoming
munition, it detects a change in the magnetic field strength due to
permanent magnetic fields generated by ferromagnetic metal in the
munition. It also detects the change in the Earth's magnetic field
due to the variations in the field lines caused by metal in the
munition. Changes in field strength detected by the sensor provides
the proximity information needed to detonate the counter munition
at the most advantageous time
[0065] One approach to increase sensitivity is to place a permanent
magnet near the sensor as a biasing magnet. As the sensor
approaches the metallic munition, the bias point changes due to the
ferromagnetic metal in the munition.
[0066] An active sensor with an oscillation frequency selected for
the type of munition can be used. The sensor is inductively
programmed at the time of counter munition launch for the type of
incoming munition, based on radar information from the ISP system.
A coil wrapped around the nose of the counter munition emanates an
electromagnetic frequency selected for the type of munition. The
magnetic field properties generated by the coil change as the
counter munition nears its target, thus providing the information
needed for optimum detonation of the counter munition.
[0067] In all of these cases, multiple sensors can be used for
triangulation. This increases angular sensitivity, and provide more
detailed information about the incoming munition which can be used
to enhance the performance of the counter munition.
[0068] The sensor preferably has the following properties:
[0069] Reponse time: 1 ns
[0070] Bandwidth: >1 GHz
[0071] Signal to noise ratio: depending on application cane be
>1000
[0072] Power consumption: -3 V at 2 mA for passive sensor
[0073] Field of view: 3600
[0074] Environmental ruggedness: The sensor and circuit on a PCB
have been tested to 100,000 g in live fire tests of rotating
rounds; temperature tolerance of sensor has been demonstrated at
-1800 C. to +1500 C.
[0075] Size and weight: Current fuze circuit and sensor fit on
round PCB 25 mm diameter that weighs 1.8 grams. Could be smaller as
a hybrid circuit. Actual sensor is approximately 100.times.100
microns.
[0076] The sensor technology has a wide range of uses including
barrel exit and velocity for mortars, and range for spinning
rounds. It also can be used for trajectory measurements and
proximity to metallic targets. The sensor system has highly
desirable characteristics including: extremely small size, low
power operation, high shock resistance, wide temperature range, and
extremely fast response time. Its operation is based on the local
magnetic fields, making it highly reliable and independent of other
system such as GPS. The sensor system benefits munitions programs
by offering a high-performance, low-cost alternative for arming and
safing applications for both non-rotating and rotating
munitions.
[0077] Targeting Sensor
[0078] The present invention also provides a targeting sensor. It
uses a single sensor or an array of sensors (see FIG. 17). The
sensors provide information regarding the location and/or proximity
of the munition to its target. Relative signal strengths and
frequency responses are used to identify types of targets for
positive identification or IFF (identification friend or foe).
[0079] Medical Imaging Sensor
[0080] This type of sensor or sensor array can also be used in the
medical field. For example, it can be used to measure
electromagnetic activity in the heart or brain. It can be used as a
sensor in the field of biomagnetics. It can also be used in nuclear
magnetic resonance imaging. The ability of the sensor to detect
magnetic fields in a single plane or line makes it suitable for use
in imaging skin defects. It can also be used for imaging low volume
point defects. The small signals from small volume defects can be
extremely difficult to detect using standard NMR imaging because
the signals from the small volume area are overshadowed by those
from larger volume areas which contain more hydrogen, and therefore
produce larger signals.
[0081] GMR Sensors and Sensor Arrays for Nondestructive Evaluation
(NDE)
[0082] The GMR sensors and arrays of the present invention can also
be employed for NDE of metallic components (see FIG. 19, sample
results in FIG. 18). The GMR detectors were used to detect, scan,
and image eddy currents in defective metallic components, such as
sheet metal parts or pipe welds. Tunnel junction GMR sensor arrays
for NDE were developed. The sensor elements developed were only 10
microns on a side, yet delivered 7% (R in a 2 Oe field with nominal
resistance near 10 k). Signal conditioning and readout electronics
for the sensors may also be employed. Other types of GMR and CMR
sensors can also be used rather than the preferred tunnel junction
type of GMR device.
[0083] U.S. Pat. No. 6,150,809, entitled "Giant Magnetorestive
Sensors and Sensor Arrays for Detection and Imaging of Anomalies in
Conductive Materials" relates to magnetic and electromagnetic
nondestructive evaluation. This technology is based on a
synergistic combination of a traditional eddy-current coil or
permanent magnet and a unique magnetic sensor based on a class of
materials known as giant magnetoresistors. The result is a sensor
exhibiting substantially higher field sensitivity and spatial
resolution when compared with traditional methods. Since these
sensors directly sense the magnetic field, rather than changes in
the field as is the case for coils, they can be operated with high
sensitivity at very low frequencies and even with DC generated
fields.
[0084] A handheld NDE instrument was developed. This system was
able to detect third layer (0.065" 2024T3 per layer) cracks without
the need for bench-top instrumentation. The present invention is a
handheld NDE unit along with a variety of sensors as shown in FIG.
11. This unit provides four different graphical data display modes
and is capable of resolving defects to a depth of approximately
0.2" using the smaller diameter probes and to a depth of
approximately 0.4" using the larger probe.
[0085] Current GMR detectors include several configurations. Most
are fabricated using molded urethane. The process begins with a
sensor, coil and flux focusing (if applicable) alignment on a
metrology station. The aligned assembly, along with the electronics
subsystem, sapphire wear surface and electrical connector, is then
encased in color-coded urethane. This process provides a rugged and
compact package for the sensor and eliminates costly machining.
[0086] The sensors are typically driven with a constant-current AC
drive between 50 Hz and 25 kHz. At 1 kHz the 3/8" diameter sensors
can easily resolve EDM cuts less than 0.25" in length through
0.195" of 2024T3. A larger, 3/4" version of this sensor has be used
to image anomalies to over 0.4" in 6061T6.
[0087] Two-dimensional imaging arrays of GMR elements have been
designed and units have been fabricated. Functional arrays
consisting of 196 tunnel-junction sensors (14.times.14). The
individual sensors are only a few square microns in area and are
positioned on a grid with a sensor-to-sensor spacing of
approximately 210 microns. The active area of the entire
14.times.14 element array is less than 3 mm on a side (9 mm.sup.2).
FIG. 12 shows a photo of one of the imaging array prototypes. In
this photo the magnetic field generation has been removed. Large
(4".times.4") arrays provide for real-time imaging of deeply
imbedded defects and corrosion.
[0088] High resolution images were obtained by performing raster,
"C-Scans" of various test samples using the APET-CR(tm) sensor
configuration. FIG. 13 shows an 11 kHz C-scan of first and second
layer rivet heads in an aluminum sheet metal section simulating an
aircraft wing. FIG. 14 shows 100 micron wide cuts in an aluminum
sheet metal sample. This data demonstrates the extremely high
signal-to noise ratio obtainable with the GMR sensor technology of
the present invention.
[0089] FIG. 15 shows an image of a corrosion test sample provided
by the Federal Aviation Administration, Nondestructive Inspection
Validation Center (FAA/AANC). The sample is a 0.06" thick, 2024T3
plate with a nominal 10% uniform mass loss corrosion region on one
side. The image corresponds to a scan performed on the side
opposite the corroded region. The boundary of the corroded region,
as well as the pitting within the corroded region is sharply
defined in the image and the signal-to-noise ratio in excess of 100
for these features.
[0090] Detection of Conductive Materials
[0091] The present invention also provides a magnetometer (see FIG.
16) for detecting conductive materials either on the surface or
underneath other materials such as earth or water (e.g., mines).
This sensor is handheld or operated from a vehicle or aircraft. It
operates in a DC detection mode or with oscillating magnetic
fields. Permanent magnets or flux concentrators are used to enhance
the signal detected by the sensor.
[0092] This type of sensor may be used to locate ships, submarines,
and other vessels. It can also be used to detect electrical
currents flowing through PCB traces or IC components. It can be
used to measure the amplitude of electrical currents. It can also
be used to detect breaks in electrical conductors which would
result in low or non-existent current flow. As such, it can be used
for inspection of many types of circuitry and wiring.
[0093] Impact Sensing
[0094] GMR sensors are magnetorestrictive. During impact such
sensors are compressed and will output a signal characteristic of
impact.
[0095] Magnetic Field Tracking for Guidance
[0096] GMR sensors according to the invention may also be used for
more sophisticated means of guidance of ordnance. A sensor can use
a map of local magnetic fields to determine position and direction
of a munition or any moving object such as an aircraft or truck.
Flying objects may be detected by looking for response to an
emitted magnetic field (active sensing) or looking for eddy
currents output by aircraft as they traverse the earth's magnetic
field (passive sensing).
[0097] Although the invention has been described in detail with
particular reference to these preferred embodiments, other
embodiments can achieve the same results. Variations and
modifications of the present invention will be obvious to those
skilled in the art and it is intended to cover in the appended
claims all such modifications and equivalents. The entire
disclosures of all references, applications, patents, and
publications cited above are hereby incorporated by reference.
* * * * *