U.S. patent application number 13/441194 was filed with the patent office on 2012-10-18 for mine detection.
This patent application is currently assigned to L-3 COMMUNICATIONS CYTERRA CORPORATION. Invention is credited to Elizabeth Bartosz, Paul Crabb, Herbert Duvoisin, III, David H. Fine, Kevin L. Johnson, Geoffrey Solomon, William Steinway, Gregory W. Stilwell.
Application Number | 20120262325 13/441194 |
Document ID | / |
Family ID | 42075380 |
Filed Date | 2012-10-18 |
United States Patent
Application |
20120262325 |
Kind Code |
A1 |
Steinway; William ; et
al. |
October 18, 2012 |
MINE DETECTION
Abstract
An integrated mine detection system includes a ground
penetrating metal detector and a ground penetrating radar detector.
The integrated mine detection system includes an integrated search
device housing a radio-wave transmitter of the radar detector and a
coil of the metal detector. The radio-wave transmitter includes an
antenna. The integrated search device includes a radio-wave
receiver in the form of a pair of receiving antennas.
Inventors: |
Steinway; William; (New
Smyrna Beach, FL) ; Stilwell; Gregory W.;
(Windermere, FL) ; Fine; David H.; (Cocoa Beach,
FL) ; Crabb; Paul; (Orlando, FL) ; Johnson;
Kevin L.; (Ocoee, FL) ; Duvoisin, III; Herbert;
(Orlando, FL) ; Solomon; Geoffrey; (Maitland,
FL) ; Bartosz; Elizabeth; (Cape Canaveral,
FL) |
Assignee: |
L-3 COMMUNICATIONS CYTERRA
CORPORATION
Orlando
FL
|
Family ID: |
42075380 |
Appl. No.: |
13/441194 |
Filed: |
April 6, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12495699 |
Jun 30, 2009 |
8174429 |
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13441194 |
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10918736 |
Aug 16, 2004 |
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12495699 |
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60495871 |
Aug 19, 2003 |
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60495084 |
Aug 15, 2003 |
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Current U.S.
Class: |
342/22 |
Current CPC
Class: |
G01V 3/15 20130101; G01S
13/888 20130101; G01S 13/885 20130101 |
Class at
Publication: |
342/22 |
International
Class: |
G01S 13/86 20060101
G01S013/86 |
Claims
1. An integrated mine detection system comprising: a ground
penetrating metal detector; and a ground penetrating radar
detector.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/495,699, filed Jun. 30, 2009, and titled
MINE DETECTION, now allowed, which is a continuation of U.S. patent
application Ser. No. 10/918,736, filed Aug. 16, 2004, and titled
MINE DETECTION, now abandoned, which claims the benefit of U.S.
Provisional Application No. 60/495,871, filed Aug. 19, 2003 and
U.S. Provisional Application No. 60/495,084, filed Aug. 15, 2003.
The prior applications are incorporated herein by reference in
their entirety.
TECHNICAL FIELD
[0002] This application relates to a mine detection system.
BACKGROUND
[0003] A large percentage of land mines contain some amount of
metal. Many versions of mines use metal for firing pins, shrapnel,
and portions of the casing. If a mine has a sufficient quantity of
a detectable metal, that mine can be found using a metal
detector.
SUMMARY
[0004] In one general aspect, an integrated mine detection system
includes a ground penetrating metal detector and a ground
penetrating radar detector.
[0005] Implementations may include one or more of the following
features. For example, the ground penetrating metal detector may
include a transmitter, a coil coupled to the transmitter to produce
a magnetic field, and a signal processor coupled to the coil and
configured to detect a secondary magnetic field.
[0006] The ground penetrating radar detector may include a radio
frequency generator, and a radio frequency transmitter coupled to
the radio frequency generator to transmit radio-wave signals toward
the ground. The radio frequency transmitter may include an antenna.
The ground penetrating radio detector may include a radio frequency
receiver that receives radio-wave signals from the ground, and a
signal processor coupled to the radio frequency receiver to detect
the radio-wave signals. The radio frequency receiver may include an
antenna.
[0007] The metal detector may include a coil that produces a
magnetic field and the radar detector may include a transmitting
antenna that transmits radio-wave signals toward the ground and a
receiving antenna that receives radio-wave signals reflected from
objects within the ground. The antennas may be surrounded by the
coil. The antennas may be shielded from external electromagnetic
radiation.
[0008] The system may include an output device that outputs a
signal indicating a presence of a mine in the ground if either the
ground penetrating metal detector, the ground penetrating radar
detector, or both detect the presence of an object within the
ground.
[0009] The ground penetrating radar detector and the ground
penetrating metal detector may be housed in a single housing.
Operation of the metal detector may not interfere with operation of
the radar detector.
[0010] In another general aspect, a mine detection system includes
an integrated search device housing a radio-wave transmitter and a
metal detector coil.
[0011] Implementations may include one or more of the following
features. For example, the system may also include a first set of
electronic components coupled to the radio transmitter, and a
second set of electronic components coupled to the metal detector
coil.
[0012] The system may include a radio-wave receiver. The radio-wave
transmitter and the receiver may be shielded from external
electro-magnetic radiation.
[0013] In another general aspect, a method of detecting mines
includes producing a primary magnetic field, detecting a presence
of a secondary magnetic field, transmitting radio-wave frequency
energy into a surrounding region, and detecting radio-wave
frequency energy reflected by an object in the surrounding
region.
[0014] In another general aspect, a method of detecting mines
includes providing a mine-detection system for collecting and
analyzing data taken from a surrounding region, and training the
mine-detection system only with background clutter data to develop
detection models for the mine-detection system.
[0015] Implementations may include one or more of the following
features. For example, the training may include using a principal
components analysis of the background clutter data.
[0016] The method may include automatically adapting the
mine-detection system to the surrounding region to determine
whether a mine is present in the surrounding region. The adapting
may include using a principal components analysis of the data taken
from the surrounding region.
[0017] The method may also include analyzing data taken from the
surrounding region using a metal detector, analyzing data taken
from the surrounding region using a radar detector based on the
training, and analyzing a depth of an object detected by the radar
detector using the data. Analyzing the depth of the object may
include transforming data from the radar detector from the
frequency domain to the time domain. Analyzing the depth may
include receiving data from two or more antennas of the radar
detector. Analyzing data taken from the surrounding region using
the radar detector may include using a principal component analysis
of the data.
[0018] Aspects of the techniques and systems can include one or
more of the following advantages. The mine detection system uses
both a radar detector and a metal detector to improve detection for
mines and reduce the false alarm rate. Metal debris can mask the
detection of mines. Because of this, a metal detector alone might
not detect the presence of a mine among metal debris. Additionally,
a metal detector alone might falsely issue an alarm over metal
debris even in the absence of a mine because the metal detector
cannot always distinguish metal debris from mines. Accordingly, the
mine detection system, which uses a radar detector in addition to a
metal detector, is able to reject metallic battlefield debris that
otherwise creates a significant signal.
[0019] Because clutter data (data from features other than mines)
is the only data used to train the model of radar detector response
to current ground conditions, the training and adaptation of the
radar detector model is easier to perform than the training an
adaptation of those models requiring both clutter and mine data for
training. Adaptation of the model to new environments is done
automatically and on the fly, which reduces human resources and
costs of training associated with operation of the mine detection
system. Collection of clutter data is easier to implement than
collection of mine data, which requires collection of mine data for
every site before use of the system.
[0020] Other features and advantages will be apparent from the
description, the drawings, and the claims.
DESCRIPTION OF DRAWINGS
[0021] FIG. 1 is a perspective view of a mine detection system.
[0022] FIG. 2 is a block diagram of the mine detection system of
FIG. 1.
[0023] FIG. 3 is a side view of the mine detection system of FIG. 1
partially opened from storage.
[0024] FIG. 4 is a side view of the mine detection system of FIG. 1
ready for storage.
[0025] FIGS. 5 and 6 are, respectively, front and side perspective
views of an interface controller of the mine detection system of
FIG. 1.
[0026] FIG. 7 is a perspective view of a battery pack of the mine
detection system of FIG. 1.
[0027] FIG. 8 is an exploded perspective view of the battery pack
of FIG. 7.
[0028] FIG. 9 is a perspective view of an earpiece of the mine
detection system of FIG. 1.
[0029] FIG. 10 shows back and front perspective views of an
electronics unit of the mine detection system of FIG. 1.
[0030] FIG. 11 is an exploded perspective view of a search device
of the mine detection system of FIG. 1.
[0031] FIG. 12 is a perspective view of the search device of the
mine detection system of FIG. 1 without its lid to show internal
components.
[0032] FIG. 13 is a block diagram of the metal detector of the mine
detection system of FIG. 1.
[0033] FIG. 14 is a block diagram of the radar detector of the mine
detection system of FIG. 1.
[0034] FIG. 15 is a perspective view of a kit for storing and
transporting the mine detection system of FIG. 1.
[0035] FIG. 16 is a flow chart of a procedure performed by a user
for unpacking, preparing, and operating the mine detection system
of FIG. 1.
[0036] FIG. 17 is a flow chart of a procedure performed by a user
for preparing the mine detection system of FIG. 1 for
operation.
[0037] FIG. 18 is a procedure performed by the metal detector of
the mine detection system of FIG. 1 for detecting a presence of a
mine.
[0038] FIG. 19 is a flow chart of a procedure performed by the
radar detector of the mine detection system of FIG. 1 for detecting
a presence of a mine.
[0039] FIGS. 20 and 21 are side views of the search device of the
mine detection system of FIG. 1.
[0040] FIG. 22 is a flow chart of a procedure performed by a user
of the mine detection system of FIG. 1 after receiving an alert
signal.
[0041] FIG. 23A shows an overhead view of a sweep pattern performed
by a user of the metal detector of the mine detection system of
FIG. 1.
[0042] FIG. 23B is a flow chart of a procedure performed by the
user during the sweep pattern of FIG. 23A.
[0043] FIGS. 24A and 24C show overhead views of sweep patterns
performed by a user of the radar detector of the mine detection
system of FIG. 1.
[0044] FIG. 24B is a flow chart of a procedure performed by the
user during the sweep pattern of FIGS. 24A and C.
[0045] FIGS. 25A and 25B show another implementation of the mine
detection system of FIG. 1.
[0046] FIGS. 26-28 are flow charts of procedures performed by a
processor of the radar detector within the mine detection system of
FIG. 1.
[0047] FIG. 29 is a graph of sample results produced by the
processer using the procedures of FIGS. 26-28.
[0048] Like reference symbols in the various drawings indicate like
elements.
DETAILED DESCRIPTION
[0049] Referring to FIGS. 1, 2, 13, and 14, an integrated mine
detection system 100 incorporates a metal detector 1350 (FIG. 13)
and a radar detector 1450 (FIG. 14) into a single integrated system
for detecting mines, including those mines that would otherwise not
be detected solely with the use of a metal detector. The mine
detection system 100 includes a search device 105, an interface
controller 110, and an electronics unit 115. The search device 105
connects to the electronics unit 115 through a bundled set of wires
106 and the interface controller 110 connects to the electronics
unit 115 through a bundled set of wires 111. To ensure that
internal electronics are kept dry and secure, the bundled sets 106
and 111 enter the search device 105 and the electronics unit 115
through weatherproof seals 116. In general, the metal detector 1350
and the radar detector 1450 each include a set of electronics
within the unit 115 and transmitting and receiving components
within the search device 105, as further described below.
[0050] The mine detection system 100 includes an elongated shaft
120 coupled to the search device 105, and an armrest 125 coupled to
the shaft 120 with a cradle 127. The interface controller 110 is
attached to the shaft 120 to enable a user to access the interface
controller 110 with a first arm while resting her second arm in the
armrest 125.
[0051] The mine detection system 100 also includes one or more
audio output devices, such as an earpiece 135 that is coupled to
the electronics unit 115 and a speaker 137 (shown in FIG. 2) within
the electronics unit 115. A power source such as a battery pack 140
is coupled to the electronics unit 115 to provide power to the unit
115.
[0052] FIGS. 3 and 4 show the mine detection system 100 without the
battery pack 140 and the earpiece 135. The shaft 120 is telescoping
and is made of segments 200 that slide into each other to adjust
the length of the shaft 120 to accommodate the particular height of
the user and to accommodate compact storage (as detailed below).
Each of the segments 200 is secured in place relative to the
adjacent segments 200 with a set of clamps 205 positioned between
each pair of adjacent segments 200. Upon loosening a clamp, the
smaller segment 200 can be slid into the adjacent larger segment
200, as shown in FIG. 3.
[0053] The shaft 120 is able to be folded relative to the cradle
127 at a joint 210. The shaft 120 includes a latching yoke 212 that
secures the shaft 120 to the cradle 127 with a friction fit when
the shaft 120 is folded relative to the cradle 127. The shaft 120
is secured in the open (unfolded) position relative to the cradle
127 by use of a latch 215 at the joint 210.
[0054] Referring also to FIGS. 5 and 6, the interface controller
110 includes a control section 400, a pair of clamps 405, and a
handle 410 extending from the control section 400. The clamps 405
are sized to receive the cradle 127 with a friction fit to secure
the controller 110 to the cradle 127. The interface controller 110
includes a housing 112 that houses all of its internal components
and provides the control section 400, the clamps 405, and the
handle 410. The housing 112 of the controller 110 can be made of
any suitably durable material, such as, for example, molded
plastic.
[0055] The control section 400 includes a set of switches that
enable a user to control operation of the mine detection system
100. The set of switches includes a power switch 415, a metal
detection control switch 420, a radar sensitivity switch 425, an
audio control switch 430, and a trigger switch 435. The control
section 400 also includes a set of indicators that provide feedback
to a user of the mine detection system 100. The set of indicators
includes a ready indicator 440 and a power and function indicator
445.
[0056] Referring also to FIGS. 7 and 8, the battery pack 140 is
connected to the electronics unit 115 with a cable 600 and a
connector 605 (such as a circular twist lock connector) that mates
with a connector 900 (shown in FIGS. 2 and 10) on the electronics
unit 115. The battery pack 140 includes a pair of clips 610 that
can be used to attach the battery pack 140 to a belt on a user. The
battery pack 140 houses a battery 615 within a case 620 having
latches 625 and a lid 630 having a lip 635. The case 620 and the
lid 630 mate with each other and are secured to each other when the
latches 625 lock to the lip 635. The case 620 and the lid 630 can
be made of any non-metallic durable material, such as, for example,
molded plastic. The battery 615 includes a connector 640 that mates
with a connector 645 of the case 620 when the battery 615 is housed
within the case 620.
[0057] Referring also to FIG. 9, the earpiece 135 includes a cable
800 and a connector 805 (such as a circular twist lock connector)
that mates with a connector 910 (shown in FIGS. 2 and 10) on the
electronics unit 115.
[0058] Referring again to FIG. 2 and also to FIG. 10, the
electronics unit 115 includes a housing 136, a speaker 137 (FIG. 2)
within the housing 136, a set of switches external to the housing
136 that enable a user to control the unit 115, and a set of
connectors 900 and 910 on the surface of the housing 136 that
couple, respectively, to the connector 605 of the battery pack and
the connector 805 of the earpiece 135. The set of switches includes
a volume control switch 915. The internal speaker 137 is positioned
adjacent one or more openings 920 on a housing 136 to permit audio
waves to emanate from the unit 115. The housing 136 can be made of
any suitable material, such as, for example, molded plastic.
[0059] The housing 136 houses a processor card 220, an interface
card 225, electronics 230 of the metal detector, electronics 235 of
the radar detector, and a power supply 240.
[0060] The power supply 240 is connected to the battery pack 140
through connectors 900 and 605, to the earpiece 135 through
connectors 910 and 805, to the interface card 225, and to the radar
detector electronics 235. The power supply 240 also connects to the
interface controller 110 to enable a user to turn the mine
detection system 100 using the power switch 415. The processor card
220 is connected to the interface card 225 and the metal detector
electronics 230. The metal detector electronics 230 and the radar
detector electronics 235 are controlled by software that is run by
their respective processors and that is stored within memory. The
memory can be either internal to the unit 115 or external to the
unit 115, such as, for example, through a portable storage device
245 that can be accessed by the electronics 230 and 235 of the unit
115. Both the metal detector electronics 230 and the radar detector
electronics 235 are connected to the search device 105, as
discussed further below.
[0061] Referring again to FIG. 2 and also to FIGS. 11 and 12, the
search device 105 includes a lid 250 that mates with and connects
to a base 255 to form a hollow enclosure. The lid 250 includes an
extension piece 260 to which the last segment 200 of the shaft 120
connects. The lid 250 and the base 255 may be formed of any
non-magnetic material, such as, for example, molded plastic.
[0062] The hollow enclosure of the search device 105 houses the
transmitting and receiving components of the metal detector and the
radar detector. Thus, the hollow enclosure houses a magnetic field
producing device such as a coil 265 that acts as a
transmitting/receiving component for the metal detector.
Additionally, the hollow enclosure houses a radio wave transmitter
such as a transmitting antenna 270, and a radio wave receiver such
as a set of receiving antennas 275 and 280. The antenna 270 acts as
a transmitting component for the radar detector and the antennas
275 and 280 act as receiving components for the radar detector.
[0063] The components of the metal detector and the radar detector
within the search device 105 are placed and designed so that
operation of one detector does not interfere with the results of
the other detector. For example, each of the antennas 270, 275, and
280 can be shielded from external electro-magnetic radiation and
such that they radiate radio-waves into a narrow path and receive
only that electro-magnetic radiation from a downward direction that
is approximately perpendicular to a bottom surface of the search
device 105.
[0064] Referring to FIG. 13, the metal detector electronics 230
includes a processor 231 that is connected to the coil 265, a pulse
generator 232 coupled to the processor 231, and a transmitter 233
that receives electric signals from the pulse generator 232 and
transmits the electric signals in the form of an electric current
to the coil 265. The processor 231 is also coupled to one or more
audio output devices 135, 137 through the interface card 225 (FIG.
2). Referring to FIG. 14, the radar detector electronics 235
includes a processor 236 coupled to the receiving antennas 275 and
280 and a radio frequency generator 237 coupled to the processor
236 and to the transmitting antenna 270. The processor 236 is also
coupled to audio output devices 135 and 137 through the interface
card 225 or directly (FIG. 2).
[0065] Referring also to FIG. 15, the integrated mine detection
system 100 is typically stored and transported in the form of a kit
1500 that includes the system 100, the battery pack 140, and the
earpiece 135. The kit 1500 also includes a set of spare batteries
1505, a test piece 1510 that mimics a mine and is used to test the
system 100, and a set of training materials that are stored on an
external memory device such as a floppy disk 1515 (as shown), a USB
memory key, or a CD-ROM. The kit 1500 may include a support sling
1517 that attaches to the interface controller 110 and to clothing
worn by a user, such as, for example, a load-bearing vest, to
relieve some of the weight of the system 100 during operation.
[0066] The kit 1500 includes a storage and transport container
1520, an additional support handle 1525 for carrying the container
1520, and a backpack 1530. The container 1520 is sized to receive
the backpack 1530 and includes a lid 1522 and a base 1524. The
container 1520 may be lined with cushioning such as foam 1535 to
protect the system 100 during storage and transport. Additionally,
the container 1520 may be vacuum or air sealed to prevent moisture
from entering the system 100 during storage. The seal of the
container 1520 is broken by use of an air pressure release valve
1540 on a front of the container 1520.
[0067] The backpack 1530 is sized to receive the system 100 in a
folded state (shown in FIG. 4), the batteries 1505, the test piece
1510, the floppy disk 1515, and the support sling 1517 (if
provided). Thus, during storage in the container 1520, all of the
equipment is stored within the backpack 1530, which is then stored
in the container 1520. Such a configuration reduces size
requirements for storage and transport.
[0068] Referring to FIG. 16, a procedure 1600 is performed to use
the system 100. Initially, the user unpacks the system 100 from the
container 1520 (step 1605) and assembles the system 100 prior to
use (step 1610). Initially, during unpacking (step 1605), the user
opens the valve 1540 and unlatches the container lid 1522 from the
base 1524. Then, the user removes the backpack 1530 from the
container 1520 and opens the backpack 1530. The user then removes
the system 100 and any other needed equipment from the backpack
1530.
[0069] Referring also to FIG. 4, during assembly (step 1610), the
user unlatches the yoke 212 from the cradle 127 and unfolds the
shaft 120 away from the cradle 127. The user secures the shaft 120
with the latch 215 and unfolds the electronics unit from the cradle
127, as shown in FIG. 3. The user rotates the search device 105
relative to the shaft 120 and the interface controller 110 relative
to the cradle 127, as shown in FIG. 1. The user also opens the
clamps 205 and expands the segments 200 out to a comfortable
position. When the comfortable position is reached, the user closes
the clamps 205 to secure the segments 200 and the shaft 120 for
use.
[0070] Referring also to FIG. 8, the user opens the latches 625,
removes the battery pack lid 630 from the case 620, and inserts the
battery 615 into the case 620 making sure the battery connector 640
is properly connected to the case connector 645. The user replaces
the lid 630 and closes the latches 625. Then, the user connects the
battery connector 605 to the electronics unit connector 900, as
shown in FIG. 10. If the earpiece 135 is to be used along with the
speaker 137, then the user connects the earpiece connector 805 to
the electronics unit connector 910, as shown in FIG. 10. Next, the
user inserts her arm through the armrest 125 and grabs the handle
410 of the interface controller 110 (FIGS. 1, 5, and 6). The user
can adjust the position of the handle 410 by rotating the handle
410 and by sliding the handle and the controller 110 along the
cradle 127. The user can also adjust the tightness of the armrest
125 to her personal comfort.
[0071] Once the system is unpacked and assembled (steps 1605 and
1610), the user makes initial adjustments to the system 100 (step
1615). If only the earpiece 135 is to be used during operation
(that is, the speaker 137 is not active), then the user should
connect the earpiece 135 to the unit 115 during these initial
adjustments (step 1615) and prior to startup. If only the speaker
137 is to be used during operation (that is, the earpiece 135 is
not active), then the user should not connect the earpiece 135 to
the unit 115 during these initial adjustments (step 1615) and prior
to startup. If both the earpiece 135 and the speaker 137 are to be
used, the user should connect the earpiece 135 after the system 100
is turned on (as discussed below).
[0072] After the initial adjustments are made (step 1615), the user
starts the system 100 (step 1620). Initially, referring also to
FIG. 5, the user sets the radar sensitivity switch 425 to a center
position and pushes the power switch 415 momentarily to the on
position (for example, to the right). The user then lets the system
100 warm up for a predetermined time such as five minutes. Next,
the user pushes the power switch 415 momentarily to the off
position (for example, to the left) to shut down the system 100.
Then, the user pushes the power switch 415 momentarily to the on
position once again while the search device 105 is resting on the
ground. The user then waits until the processor 231 or the
processor 236 sends a signal to the audio device 135 or 137
indicating that the system 100 is ready to be trained. The power
and function indicator 445 emits a signal (such as a flashing
light) after the system 100 has completed startup (step 1620).
[0073] After startup (step 1620), the user prepares the system 100
(step 1625) by calibrating the system 100 to the local ground and
electromagnetic interference (EMI) conditions and training the
system 100, as discussed in detail below with respect to FIG. 17.
Once the system 100 is prepared (step 1625), the user can then
operate the system (step 1630), as discussed in detail below. When
the user is finished operating the system 100 (step 1630), the user
shuts down the system 100 by pushing the power switch 415 to the
off position (step 1635). After the system 100 is shut down (step
1635), the user disassembles the system 100 (step 1640) and repacks
the system 100 (step 1645) in the backpack 1530 and the container
1520 in a reverse order from which the system is assembled and
unpacked.
[0074] Referring to FIG. 17, the user performs a procedure 1625 to
prepare the system 100. Initially, the user performs a procedure
for canceling the effects of EMI conditions on operation of the
metal detector (step 1700). During this procedure, the user holds
the search device 105 on the ground but not above metal for a
predetermined duration (such as 55 seconds). During this duration,
the user pushes the metal detection control switch 420 to the left
momentarily, and the processor 231 causes the audio device 135 or
137 to continually emit an audio signal such as "noise cancel"
indicating to the user that the system 100 is being calibrated to
the effects of the EMI conditions. At the end of the duration, the
processor 231 causes the audio device 135 or 137 to emit an audio
signal such as "noise cancel complete" indicating to the user that
the system 100 has been calibrated to the effects of the EMI
conditions.
[0075] Next, the user performs a procedure for canceling the
effects of minerals in the soil on operation of the metal detector
(step 1705). Before beginning this procedure, the user ensures that
the area is free of all metallic targets. The user then holds the
search device 105 a predetermined height (for example, 6-10 inches)
above the surface of the ground and pushes and holds the metal
detection control switch 420 to the right (FIG. 5). At this time,
the processor 231 causes the audio device 135 or 137 to emit a
message such as "cal mode" to indicate to the user that the system
100 is being calibrated to the effects of minerals in the soil. The
user then maneuvers the search device 105 in an appropriate manner
while this calibration is taking place. For example, the user
lowers the search device 105 slowly to the ground surface and then
returns it to the predetermined height in a smooth, continuous
motion for about four seconds. Or, the user moves the search device
105 up and down relative to the ground surface for a predetermined
time period. When the user finishes maneuvering the search device
105, the user releases the metal detection control switch 420 and
listens for an audio signal emitted from the device 135 or 137
indicating that calibration is complete. For example, the processor
231 may send a "cal mode complete" signal to the audio device 135
or 137 after the user releases the control switch 420.
[0076] Moreover, the user may perform this procedure (step 1705) at
any time if the user determines that background audio levels have
increased or decreased during normal operation as long as there is
no mineralized soil or metal in the region.
[0077] Next, the user trains the radar detector electronics 235
(step 1710) over ground that is similar to the area to be searched.
Training sets a baseline for the mine detection system 100 to
compare future readings. Furthermore, the system 100 is retrained
when the ground to be swept is drastically different from the
ground on which the system 100 was trained. In this case, the
system 100 is first shut down completely (step 1635) and then
restarted (step 1620). To train, the user pushes and holds the
trigger switch 435 (FIG. 6) on the interface controller 110. Then,
the user performs a normal sweep pattern over the ground in front
of the user, advancing about 1/3 of the diameter of the search
device 105 after each swing while keeping the search device 105
below a predetermined height (for example, 2 inches) from the
ground. The user can then cover about 3-6 feet of ground in a
forward direction during the normal sweep pattern. The user
performs the normal sweep pattern while the processor 236 sends a
signal to the audio device 135 or 137 to emit a "training" sound.
The user releases the trigger switch 435 when the user hears the
sound "training complete" from the audio device 135 or 137. The
training takes about 45 seconds and at the end of the training, the
processor 236 sends a signal to the audio device 135 or 137 to emit
a sound (for example, "localize") indicating that the user can
begin normal operation of the system 100.
[0078] Generally, during start up (step 1620), the user can set the
radar sensitivity switch 425 to an up position. The user can adjust
the radar sensitivity by moving the switch 425 to accommodate for
the user's sweeping technique or a particular terrain.
[0079] After training (step 1710), the user then verifies that the
system 100 is ready to be operated (step 1715). During
verification, the user releases the trigger switch 435, places the
test piece 1510 on the ground, passes the search device 105 over
the test piece 1510, and verifies proper operation of the metal
detector and the radar detector by listening for audio signals from
the devices 135 or 137. If either or both of the audio signals are
not heard, then the user must shut down the system 100 (step 1635)
and repeat startup (step 1620) and preparation (step 1625).
[0080] After the system has been prepared (step 1625), the user can
operate the system 100 during normal operation (step 1630). During
normal operation, the user pushes the trigger switch 435 (FIG. 6)
on the interface controller 110 and performs a sweep technique,
which is detailed below. During this time, the metal detector (made
up of the electronics 230 and the coil 265) and the radar detector
(made up of the electronics 235 and the antennas 270, 275, and 280)
operate independently and simultaneously to detect mines in the
vicinity of the sweep. Both detectors transmit and receive data and
automatically and continuously update the audio signal sent to the
device 135 or 137 to notify the user of any changes in detection
that might indicate the presence of a mine. As discussed above, the
two detectors are operationally compatible with each other such
that they do not interfere with each other during simultaneous
operation.
[0081] Referring to FIG. 18 and again to FIGS. 2 and 13, the metal
detector electronics 230 perform a procedure 1800 during a sweeping
operation (either during preparation at step 1625 or during normal
operation at step 1630). Initially, the pulse generator 232 sends
pulses to the transmitter 233 (step 1805), which transmits electric
current to the coil 265 (step 1810). The electric current through
the coil 265 induces a magnetic field 1300 that emanates from the
coil 265 and into the ground 1305. When the magnetic field strikes
a metal object 1310, it induces a secondary magnetic field in the
metal object 1310. The secondary magnetic field of the metal object
1310 induces a secondary current in the coil 265. The processor 231
monitors the current from the coil 265 and detects the secondary
current by detecting a change in the electric current through the
coil 265 from the transmitter 233 (step 1815). If the processor 231
determines that the secondary current is greater than a
predetermined threshold (step 1820), then the processor sends an
audio signal to the device 135 or 137 to indicate to the user that
metal is present under the ground 1305 (step 1825).
[0082] Referring to FIG. 19 and again to FIG. 14, the radar
detector electronics 235 perform a procedure 1900 during a sweeping
operation (either during preparation at step 1625 or during normal
operation at step 1630). The radio frequency generator 237
continuously sends a radio frequency (RF) signal of sufficient
strength or power for the radar sensitivity desired (as determined
by the configuration of the radar sensitivity switch 425) to the
transmitting antenna 270 (step 1905). The transmitting antenna 270
emits the RF signal 1400 into the ground 1405 (step 1910). Either
or both of the receiving antennas 275 and 280 collect any RF
signals 1410 that have been reflected by an underground feature
1415 and that reach the antenna 275 or 280 (step 1915). During this
process, the generator 237 steps the RF signal between a start
frequency and a stop frequency in equal increments. For each
frequency step, the RF signals reflected from the underground
feature 1415 are received by the antenna 275 or 280, which
transmits the RF signals to the processor 236 (step 1920), which
then digitizes and stores the signals (step 1925). The processor
236 collects the data for all steps between the start and stop
frequencies and the data collection is referred to as a "frequency
packet." The processor 236 analyzes the frequency packet (step
1930) to determine if a mine is underground (step 1940). If the
processor 236 determines that a mine is underground, the processor
236 sends a signal to the audio device 135 or 137 indicating the
presence of the mine (step 1945). If the processor 236 determines
that a mine is not underground (step 1940), then the processor 236
simply awaits the next transmission from the antenna 275 or 280
(step 1920).
[0083] As mentioned above, the user "sweeps" the mine detection
system 100 to detect mines, with the quality of the mine detection
results being directly related to the quality of the user's sweep
technique. The important components to a proper sweep technique are
the user's stance, the position of the search device 105, the speed
at which the user sweeps the search device 105, and the coverage of
the sweep (called a lane).
[0084] First, the user stands in a comfortable and balanced
position that permits the user to cover a full lane width without
having to change position.
[0085] Second, referring to FIG. 20, the search device 105 is
positioned parallel to and as close to the ground 2000 as possible
but not more than a predetermined height 2005 above the ground. In
one implementation, the predetermined height 2005 is 2 inches.
Moreover, before beginning a sweep, the user adjusts the relative
angle between the search device 105 and the shaft 120 to ensure
that the search device 105 is parallel to the ground during a
sweep.
[0086] Third, the user sweeps the search device 105 across the
ground within a predetermined sweep speed. In one implementation,
the sweep speed is between about 1 to 3.6 feet/second across a
five-foot lane.
[0087] Fourth, the user moves the search device 105 across a lane
in as straight a line as possible, while trying not to pull the
search device 105 back toward the user's body or rock the device
105 near the edge of the lane. Referring also to FIG. 21, the
actual search width 2100 of the radar detector does not extend to
the edges of the search device 105. In practice, the search width
for the radar detector extends to the locations of the antennas
270, 275, and 280 and is indicated on a top of the search device
105 by a different colored marking, called a sweet spot 282 (FIGS.
1 and 11). The search width 2105 of the metal detector is
approximately equal to the diameter of the coil 265. Because the
search width 2100 for the radar detector is about 1/3 of the
diameter of the search device 105, the search device 105 should be
moved forward no more than about 1/3 of the diameter of the search
device 105 between sweeps.
[0088] If the user passes the search device 105 over a suspected
buried mine or debris, the processor 231 of the metal detector
sends a tone to the audio device 135 or 137 or the processor 236 of
the radar detector sends a beep to the audio device 135 or 137. In
this way, the user can distinguish between the results from the
radar detector and the results from the metal detector. After the
user hears the tone or the beep, the user then investigates the
suspected mine further according to a procedure 2200 as shown in
FIG. 22. To investigate the suspected mine, the user typically
first tries to repeat the alert signal (that is, the beep or the
tone) (step 2205). To do this, the user repeats the sweep several
times at different angles over the same area while adjusting
sensitivity higher or lower if necessary. If the new sweep does not
repeat the alert signal then the user can continue sweeping the
lane. Next, once the alert signal has been repeated, the user can
then proceed to determine the object's size and position (step
2210). Meanwhile, the user also investigates surrounding clues
(step 2215) to make an overall determination of the location of a
mine.
[0089] Referring also to FIGS. 23A and 23B, in determining the
object's size and position at step 2210, the user performs a
procedure 2210 if using the metal detector to investigate. First,
the user releases the trigger switch 435 and waits for an audio
ready signal such as "localize" (step 2300). If needed, the user
then moves the audio control switch 430 to the right to activate
the metal detector only (step 2305). Next, the user moves the
search device 105 back from the suspected mine area 2350 until the
audio sound for the metal detector diminishes (step 2310) and then
moves the search device 105 toward the center 2355 of the suspected
mine area 2350 until the audio sound for the metal detector is
heard or increases (step 2315). The user moves the search device
105 back and forth and in and out such that the search device 105
spirals around the target area (step 2320), thus forming a spiral
pattern 2360.
[0090] Referring also to FIGS. 24A and 24B, in determining the
object's size and position at step 2210, the user performs a
procedure 2211 if using the radar detector to investigate. First,
the user releases the trigger switch 435 and waits for an audio
ready signal such as "localize" (step 2400). Then, the user
establishes the suspected mine pattern using the procedure 2210
detailed in FIG. 23B (step 2405). If needed, the user then moves
the audio control switch 430 to the left to activate the radar
detector only (step 2415). Next, the user moves the search device
105 back from the suspected mine area 2450 until the audio sound
for the radar detector stops (step 2420). Then, the user moves the
search device 105 in short sweeps within the suspected mine area
2450 and around the approximate center of the mine 2355 until the
audio sound for the radar detector is heard (step 2425). The user
continues the short forward sweeps through the suspected mine area
2450 while the radar detector alerts are activating, thus forming a
zigzag pattern 2460. The user then repeats the zigzag pattern from
several different approach angles (one alternate zigzag pattern
2465 is shown in FIG. 24C) to verify the results of the suspected
mine location (step 2430).
[0091] The user can also use characteristics of known mines to
evaluate the results of the investigation. For example, an
anti-tank, metallic mine (AT-M) shows a metal detector footprint of
a semi-circular halo of about 20-26 inches from the mine center
when buried at a depth of 5 inches and a radar detector footprint
of an outside edge of about 13 inches in diameter.
[0092] Other implementations are within the scope of the following
claims. For example, the audio signals sent to the audio device 135
or 137 may be sounds other than beeps or tones.
[0093] Referring also to FIGS. 25A and 25B, in another
implementation, instead of the telescoping shaft 120, the shaft
2520 is articulated at joints 2500 to form segments 2505. Thus,
each segment 2505 can be folded over to reduce the length for
storage and transportation (as shown in FIG. 25B).
[0094] The mine detection system 100 may include infrared detection
integrated with the radar and the metal detection. The radar
detector may include more than one transmitting antenna and more
than two receiving antennas.
[0095] In the procedure discussed above, the metal detector (made
up of the electronics 230 and the coil 265) and the radar detector
(made up of the electronics 235 and the antennas 270, 275, and 280)
operate independently and simultaneously to detect mines in the
vicinity of the sweep. Thus, each detector includes its own
processor. However, in another implementation, a single processor
can be used to control both the metal detector and the radar
detector. The processor can run a single algorithm for analyzing
the results and notifying the user of any changes in detection that
might indicate the presence of a mine.
[0096] In one implementation, the processor 236 analyzes the data
(that are in the form of packets) from the transmitting and
receiving components of both the radar detector and the metal
detector to determine if a mine is underground at step 1940.
Referring to FIG. 26, in this implementation, the processor 236
uses a procedure 2600 that begins by receiving the data packet from
the radar detector receiving component (for example, the antennas
275 and 280) (step 2605) and receiving the data packet from the
metal detector that came from its receiving component, that is, the
coil 265 (step 2610).
[0097] The processor 236 analyzes a model of radar detector
response to current ground conditions using a principal component
analysis to describe clutter features, as detailed below (step
2615). The processor 236 also transforms the radar data from the
frequency domain to the time domain in order to analyze the depth
of the anomaly (step 2620). The processor 236 receives results from
the analysis of the metal detector (step 2625) and uses these
results later to eliminate clutter noise and localize alarms from
the radar detector.
[0098] Next, the processor 236 compares the results of the model
analysis from step 2615, the depth analysis from step 2620, and the
metal detector analysis from step 2625 (step 2630) to make a
determination of whether an alert signal should be sent to the
audio device 135 or 137 (step 2635) based on a signal threshold
2640 that depends, at least in part, on the sensitivity setting
2645 from the radar sensitivity switch 425.
[0099] Additionally, at various stages (for example, steps 2650,
2655, and 2660) during the procedure 2600, the processor 236
adjusts the signal threshold 2640 to maintain a constant false
alarm rate (CFAR). Often, the alarm rate can rapidly rise or drop
with abrupt changes in background statistics due to changing ground
conditions. Thus, the processor 236 dampens the effects of the
changing ground conditions by recognizing a rapid change in
background statistics and adjusting the signal threshold 2640 on
the fly to accommodate for such changes.
[0100] Referring also to FIG. 27, the model of radar detector
response is trained prior to use of the mine detection system 100
using a procedure 2700. Initially, data is collected from a trial
run in a mine-free region such that the only features present
during the trial run are clutter features. Typically, clutter and
noise data remain relatively constant from scan to scan and often
contain less energy than data obtained from scans of mines.
Ultimately, common features among the clutter scans are captured
and new scans that display significantly distinct features are
considered to contain mines.
[0101] Although the scans for data can be applied to many different
types of clutter features, the scans for data are based on
principal components analysis (PCA), which describes features
through principal components, thus permitting automation and
enabling adaptation to clutter features in local environments. The
number of variables involved in the modelling is reduced and the
structure of the relationships between variables can be detected
using PCA.
[0102] Basically, PCA involves a mathematical procedure that
transforms a number of possibly correlated variables into a smaller
number of uncorrelated variables that are called principal
components. The first principal component accounts for as much of
the variability in the data as possible, and each succeeding
component accounts for as much of the remaining variability as
possible. PCA determines a direction with the most variance and
rotates the space such that this direction is now the first
dimension. Then, PCA finds the direction with the next largest
variance and rotates the space such that this direction is the
second dimension. This process continues until all dimensions are
accounted for. The result is a new feature space with the same
number of dimensions as the original space but with the variance
concentrated in the lower order dimensions.
[0103] In general, the mathematical technique used in PCA is eigen
analysis in which the eigenvalues and the eigenvectors of a square
symmetric matrix are solved with sums of squares and cross
products. The eigenvector associated with the largest eigenvalue
has the same direction as the first principal component. The
eigenvector associated with the second largest eigenvalue
determines the direction of the second principal component. The sum
of the eigenvalues equals the trace of the square matrix and the
maximum number of eigenvectors equals the number of rows (or
columns) of this matrix.
[0104] Referring to FIG. 27, to begin the PCA process, the
processor 236 receives the collected data from the trial run in the
form of frequency packets (step 2705). Typically, several hundred
clutter-only frequency packets are received. Next, the data is
prepared (step 2710) and the covariance matrix is determined (step
2715). Then, using single value decomposition, the eigenvalues and
eigenvectors are obtained (step 2720).
[0105] Referring again to FIG. 26, once the model is trained using
the procedure 2700, the processor 236 can update the model using a
procedure 2615. Initially, the data received in the form of
frequency packets (step 2605) are prepared (step 2665). Then, the
processor 236 processes the prepared data using PCA (step 2670), a
procedure further discussed below. Based on the PCA, the processor
236 outputs a preliminary result of whether a mine is present (step
2675).
[0106] Referring also to FIG. 28, the processor 236 processes the
prepared data using a PCA procedure 2670. Initially, the processor
236 projects the prepared data into eigenspace by multiplying the
data vector by the eigenvalue matrix (step 2800). Then, the results
are provided in the form of a function of the projection of the
data and the weight matrix (step 2805).
[0107] Because PCA can safely discard some of the higher order
dimensions, noisy sources of variability are removed and the
dimensionality of the input is reduced, thus making modelling
simpler. Referring to FIG. 29, sample results for PCA in the form
of a graph 2900 are shown for various mine locations 2905. Raw data
2910 is input into PCA and PCA outputs a signal 2915 that has a
strength measured in the upper graph 2920. As shown, PCA enhances
the target-to-clutter signal ratio.
[0108] Referring again to FIG. 26, the processor 236 transforms the
radar data from the frequency domain to the time domain at step
2620. As discussed above, during operation of the system 100, the
radar data is stepped through frequencies. Typically, the range
through which the radar is stepped is about one and a half
gigahertz. The processor 236 uses Fourier transformation to
transform the radar data from the frequency domain to the time
domain. Because the data is transformed into the time domain,
information about depth (if using two or more antennas) or distance
to the mine may be obtained.
[0109] The system 100 employs two receiving antennas 275 and 280 to
determine the depth of a mine. For example, with a single receiving
antenna, an object located five inches directly below the antenna
might appear to be in the same time domain location as an object
located three inches deep but four inches laterally from the
antenna (where the distance from the antenna to the object is still
five inches). By using a second receiving antenna, data from the
two receiving antennas may be correlated to permit a higher degree
of accuracy and to permit a determination of depth.
[0110] Referring again to FIG. 26, the processor 236 compares the
results of the model analysis, the depth analysis, and the metal
detector analysis (step 2630) to make a determination of whether an
alert signal should be sent to the audio device 135 or 137 (step
2635). The comparison may determine that the alert signal should be
sent even if model analysis provides a weak mine signal if the
metal detector analysis signal is strong.
* * * * *