Automotive vehicle classification and identification by inductive signature

• US 6,611,210 B2
• Filed: 02/18/2002
• Issued: 08/26/2003
• Est. Priority Date: 12/03/1996
• Status: Expired due to Fees

• Current Assignee: Inductive Signature Technologies Incorporated
• Original Assignee: Inductive Signature Technologies Incorporated
• Inventors: Hilliard, Steven R., Hilliard, Geoffrey W.
• Primary Examiner(s): POPE, DARYL C
• Application Number:
  US10/079,297
• Publication Number:
  US 20020154032A1
• Time in Patent Office: 554 Days
• Field of Search: 340/902, 340/903, 340/904, 340/905, 340/907, 340/933, 340/939, 340/991, 340/992, 340/993, 340/996, 340/10.1, 340/825.71, 340/941, 340/917, 455/41, 455/54, 455/55, 455/99, 701/23, 701/117
• US Class Current: 340/941
• CPC Class Codes: G08G 1/015 with provision for distinguishing between two or more types of vehicles, e.g. between motor-cars and cycles
• CPC Class Codes: G08G 1/042 using inductive or magnetic detectors

Abstract

A wire-loop vehicle detector is configured with a vertically oriented blade aligned at an angle to the direction of traffic-flow with each end of the blade extending laterally beyond the normal limits of vehicle presence over the blade. The extended blade configuration of the wire-loop constrains over-passing vehicles to present repeatable inductive signatures while electromagnetic noise and thermal-drift are selectively canceled using a secondary coil to increase the signal-to-noise ratio of inductance measurements. Inductive signatures of vehicles are recorded using a high-speed and high-precision method of making multiple successive measurements of the inductance of a wire-loop as vehicles pass over. Inductive signatures of automotive vehicles are useful for parking-lot revenue control, car-bomb detection, passive security of isolated communities, and other traffic-flow monitoring and control applications.

Claims

1. An inductive vehicle detector, for a traffic-lane having width, comprising:

at least one inductive sensor situated in the traffic-lane; and

wherein said inductive sensor comprises;

a wire-loop having width which is at least as great as the width of the traffic-lane; and

a means for measuring the inductance of the wire-loop.

2. The detector of claim 1 wherein the wire-loop is situated at an angle to the flow of traffic.

3. The detector of claim 2 wherein the wire loop has a common terminal and a charging terminal and intrinsic resistance, and wherein said means for measuring the inductance of the wire-loop comprises:

a capacitor having two terminals, wherein each terminal of the capacitor is connected to a corresponding terminal of the wire-loop, forming an LCR circuit which generates an output signal;

a means for generating a first and a second control signal;

a current source having a common terminal which is connected to the common terminal of the wire-loop, and a power terminal;

a first switching means for connecting and disconnecting the power terminal of said current source to the charging terminal of said LCR circuit in response to said first control signal;

a reference-signal generating means which generates a reference-signal;

an instrumentation amplifier means having first and second input terminals and an output terminal, wherein the output signal from said LCR circuit is connected to the first input terminal of the instrumentation amplifier, and said reference-signal is connected to the second input terminal of the instrumentation amplifier; and

a sample-and-hold amplifier means having an analog input terminal, an analog output terminal, and a logic input terminal wherein said output terminal of said instrumentation amplifier means is connected to the analog input terminal, said second control signal is connected to said logic input terminal.

4. The detector of claim 3 wherein said reference-signal generating means comprises:

a second LCR circuit which generates said reference-signal.

5. The detector of claim 4 wherein said means for measuring the inductance of the wire-loop further comprises:

a band-pass filter which is interposed between the output terminal of said instrumentation amplifier means and the analog input terminal of said sample-and-hold amplifier means.

6. The detector of claim 5 wherein said means for measuring the inductance of the wire-loop further comprises:

an analog-to-digital converter means having an analog input terminal and a plurality of digital output terminals, and wherein the analog input terminal is connected to the analog output terminal of said sample-and-hold amplifier means; and

a digital-signal-processing means having a plurality of digital input terminals which are connected to the respective digital output terminals of said analog-to-digital converter means.

7. An inductive vehicle detector, for a traffic-lane, comprising:

at least one inductive sensor situated in the traffic-lane; and

wherein said inductive sensor comprises;

a vertically-oriented wire-loop; and

a means for measuring the inductance of the wire loop.

8. The detector of claim 7 wherein the wire-loop is attached to a flexible forming body prior to situation into the traffic-lane and does not enclose pavement material.

9. The detector of claim 8 wherein the wire loop has a common terminal and a charging terminal and intrinsic resistance, and wherein said means for measuring the inductance of the wire-loop comprises:

a capacitor having two terminals, wherein each terminal of the capacitor is connected to a corresponding terminal of the wire-loop, forming an LCR circuit which generates an output signal;

a means for generating a first and a second control signal;

a current source having a common terminal which is connected to the common terminal of the wire-loop, and a power terminal;

a first switching means for connecting and disconnecting the power terminal of said current source to the charging terminal of said LCR circuit in response to said first control signal;

a reference-signal generating means which generates a reference-signal;

an instrumentation amplifier means having first and second input terminals and an output terminal, wherein the output signal from said LCR circuit is connected to the first input terminal of the instrumentation amplifier, and said reference-signal is connected to the second input terminal of the instrumentation amplifier; and

a sample-and-hold amplifier means having an analog input terminal, an analog output terminal, and a logic input terminal wherein said output terminal of said instrumentation amplifier means is connected to the analog input terminal, said second control signal is connected to said logic input terminal.

10. The detector of claim 9 wherein said reference-signal generating means comprises:

a second LCR circuit which generates said reference-signal.

11. The detector of claim 10 wherein said means for measuring the inductance of the wire-loop further comprises:

a band-pass filter which is interposed between the output terminal of said instrumentation amplifier means and the analog input terminal of said sample-and-hold amplifier means.

12. The detector of claim 11 wherein said means for measuring the inductance of the wire-loop further comprises:

an analog-to-digital converter means having an analog input terminal and a plurality of digital output terminals, and wherein the analog input terminal is connected to the analog output terminal of said sample-and-hold amplifier means; and

a digital-signal-processing means having a plurality of digital input terminals which are connected to the respective digital output terminals of said analog-to-digital converter means.

13. An inductive vehicle detector, for a traffic-lane, comprising:

at least one inductive sensor situated in the traffic-lane; and

wherein said inductive sensor comprises;

a primary wire-loop with fixed spatial dimensions and orientation;

a secondary wire-loop having substantially similar spatial dimensions and orientation as the primary wire-loop, but wherein at least one spatial dimension of the secondary wire-loop is significantly offset with respect to the primary wire-loop; and

a means for measuring the inductance of the two wire-loops wherein the electromagnetic noise associated with both wire-loops combine and reduces the total electromagnetic noise associated with the two wire-loops.

14. The detector of claim 13 wherein the primary wire-loop and the secondary wire-loop are formed together on the same substrate which conducts heat between the two wire-loops whereby the thermal drift of the secondary wire-loop partially cancels the thermal-drift of the primary wire-loop.

15. The detector of claim 14 wherein the secondary wire-loop is positioned below the primary wire-loop and lies in substantially the same plane as the primary wire-loop.

16. The detector of claim 15 wherein the each wire-loop has an upper-horizontal leg and a lower-horizontal leg, and wherein the upper-horizontal leg of the secondary wire-loop abuts the lower-horizontal leg of the primary wire-loop.

17. The detector of claim 16 wherein the upper-horizontal leg of the secondary wire-loop and the lower-horizontal leg of the primary wire-loop are twisted together.

18. The detector of claim 17 wherein the primary wire-loop and the secondary wire-loop are charged by separate excitation circuits operated by common timing signals.

19. The detector of claim 18 wherein each wire-loop has a common terminal and a charging terminal and intrinsic resistance, and wherein said means for measuring the inductance of the wire-loop comprises:

a first and a second capacitor, each capacitor having two terminals, wherein each terminal of each capacitor is connected to a corresponding terminal of each respective wire-loop, forming a first and a second LCR circuit which generate a first and a second output signal respectively;

a means for generating a first and a second control signal;

a current source having a common terminal which is connected to the common terminals of each wire-loop, and a power terminal;

a first and a second switching means for connecting and disconnecting the power terminal of said current source to the charging terminals of each of said LCR circuits respectively in response to said first control signal;

an instrumentation amplifier means having first and second input terminals and an output terminal, wherein said first output signal from said first LCR circuit is connected to the first input terminal of the instrumentation amplifier, and said second output signal from said second LCR circuit is connected to the second input terminal of the instrumentation amplifier; and

a sample-and-hold amplifier means having an analog input terminal, an analog output terminal, and a logic input terminal wherein said output terminal of said instrumentation amplifier means is connected to the analog input terminal, said second control signal is connected to said logic input terminal.

20. The detector of claim 19 wherein said means for measuring the inductance of the wire-loop further comprises:

a band-pass filter which is interposed between the output terminal of said instrumentation amplifier means and the analog input terminal of said sample-and-hold amplifier means.

21. The detector of claim 20 wherein said means for measuring the inductance of the wire-loop further comprises:

an analog-to-digital converter means having an analog input terminal and a plurality of digital output terminals, and wherein the analog input terminal is connected to the analog output terminal of said sample-and-hold amplifier means; and

a digital-signal-processing means having a plurality of digital input terminals which are connected to the respective digital output terminals of said analog-to-digital converter means.