Automotive vehicle classification and identification by inductive signature

• US 6,417,784 B1
• Filed: 12/02/1997
• Issued: 07/09/2002
• Est. Priority Date: 12/03/1996
• Status: Expired due to Fees

• Current Assignee: Inductive Signature Technologies Incorporated
• Original Assignee: Inductive Signature
• Inventors: Hilliard, Steven R., Hilliard, Geoffrey W.
• Primary Examiner(s): POPE, DARYL C
• Application Number:
  US08/982,743
• Time in Patent Office: 1,680 Days
• Field of Search: 340/902, 340/903, 340/904, 340/939, 340/905, 340/933, 340/991, 340/907, 340/992, 340/993, 340/996, 340/989, 340/825.54, 340/825.71, 340/941, 340/917, 455/41, 455/54, 455/55, 455/99
• 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. A system for inductive vehicle detection comprising:

at least one inductive sensor situated in a traffic-lane having a width, said inductive sensor being a wire-loop dimensioned to substantially extend across the width of the traffic-lane and situated at an angle to the flow of traffic, said wire-loop having a common terminal, a charging terminal, and an intrinsic resistance; and

an inductance measuring device in electrical communication with said wire-loop, said inductance measuring device including

a capacitor having two terminals, each said terminal of said capacitor in electrical communication with a corresponding said terminal of said wire-loop thereby forming an LCR circuit which generates an output signal;

a first control signal generator for generating a first control signal;

a second control signal generator for generating a second control signal;

a current source having a common terminal and a power terminal, said current source common terminal in electrical communication with said wire-loop common terminal;

a first switch in electrical communication with said first control signal, said first switch for electrically connecting and disconnecting said current source power terminal to said wire-loop charging terminal in response to said first control signal;

a reference-signal generator for generating a reference-signal;

an instrumentation amplifier having a first input terminal, a second input terminal, and an output terminal, said LCR circuit output signal being delivered to said instrumentation amplifier first input terminal and said reference-signal generator in electrical communication with said instrumentation amplifier second input terminal; and

a sample-and-hold amplifier having an analog input terminal, an analog output terminal, and a logic input terminal, said instrumentation amplifier output terminal in electrical communication with said analog input terminal and said second control signal generator in electrical communication with said logic input terminal.

2. The system of claim 1 wherein said reference-signal generator includes a second LCR circuit which generates said reference-signal.

3. The system of claim 2 wherein said inductance measuring device includes a band-pass filter which is interposed between said output terminal of said instrumentation amplifier and said analog input terminal of said sample-and-hold amplifier.

4. The system of claim 3 wherein said inductance measuring device includes

an analog-to-digital converter having an analog input terminal and a plurality of digital output terminals, said analog input terminal being in electrical communication with said analog output terminal of said sample-and-hold amplifier; and

a digital-signal processor having a plurality of digital input terminals in electrical communication with the respective digital output terminals of said analog-to-digital converter.

5. A system for inductive vehicle detection comprising:

at least one inductive sensor situated in a traffic-lane having a width, said inductive sensor being a wire-loop dimensioned to substantially extend across the width of the traffic-lane; and

an inductance measuring device in electrical communication with said wire-loop.

6. The system of claim 5 wherein said wire-loop is situated at an angle to the flow of traffic.

7. A system for inductive vehicle detection comprising:

a loop forming member;

at least one inductive sensor situated in a traffic-lane having a surface, said inductive sensor being a substantially vertically oriented wire-loop formed on said loop forming member; and

an inductance measuring device in electrical communication with said wire-loop.

8. The system of claim 7 wherein the roadway defines at least one slot, said loop forming member being flexible such that said wire-loop conforms to the at least one slot.

9. A system for inductive vehicle detection comprising:

at least one inductive sensor situated in a traffic-lane having a surface, said inductive sensor being a vertically oriented wire-loop attached to a flexible forming body prior to situation into the traffic-lane and not enclosing pavement material, said wire-loop having a common terminal, a charging terminal, and an intrinsic resistance;

an inductance measuring device in electrical communication with said wire-loop, said inductance measuring device including a capacitor having two terminals, each said terminal of said capacitor in electrical communication with a corresponding said terminal of said wire-loop thereby forming an LCR circuit which generates an output signal;

a first control signal generator for generating a first control signal;

a second control signal generator for generating a second control signal;

a current source having a common terminal and a power terminal, said current source common terminal in electrical communication with said common terminal of said wire-loop;

a first switch in electrical communication with said first control signal generator, said first switch for electrically connecting and disconnecting said power terminal of said current source to said charging terminal of said LCR circuit in response to said first control signal;

a reference-signal generator for generating a reference-signal;

an instrumentation amplifier having first input terminal, a second input terminal, and an output terminal, said LCR circuit output signal being delivered to said instrumentation amplifier first input terminal and said reference-signal generator in electrical communication with said instrumentation amplifier second input terminal; and

a sample-and-hold amplifier having an analog input terminal, an analog output terminal, and a logic input terminal, said instrumentation amplifier output terminal in electrical communication with said analog input terminal and said second control signal generator in electrical communication with said logic input terminal.

10. The system of claim 9 wherein said reference-signal generator includes a second LCR circuit which generates said reference-signal.

11. The system of claim 10 wherein said inductance measuring device includes a band-pass filter which is interposed between said output terminal of said instrumentation amplifier and said analog input terminal of said sample-and-hold amplifier.

12. The system of claim 11 wherein said inductance measuring device includes

an analog-to-digital converter having an analog input terminal and a plurality of digital output terminals, said analog input terminal being in electrical communication with said analog output terminal of said sample-and-hold amplifier; and

a digital-signal processor having a plurality of digital input terminals in electrical communication with to the respective digital output terminals of said analog-to-digital converter.

13. A system for inductive vehicle detection comprising:

at least one inductive sensor situated in a traffic-lane, said inductive sensor including a primary wire-loop with fixed spatial dimensions and orientation and a secondary wire-loop having substantially similar spatial dimensions and orientation as said primary wire-loop, said primary wire-loop and said secondary wire-loop having independent current paths; and

an inductance measuring device in electrical communication with each of said primary and secondary wire-loops, said inductance measuring device combining the electromagnetic noise associated with both said primary and secondary wire-loops thereby reducing the total electromagnetic noise associated with said primary and secondary wire loops.

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

15. The system of claim 14 wherein said secondary wire-loop is positioned below said primary wire-loop.

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

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

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

19. A system for inductive vehicle detection comprising:

at least one inductive sensor situated in a traffic-lane, said inductive sensor including a primary wire-loop with fixed spatial dimensions and orientation and a secondary wire-loop, substantially coplanar with said primary wire-loop and having substantially similar spatial dimensions and orientation as said primary wire-loop, said primary and secondary wire-loops being formed together on a single thermally-conductive substrate, said secondary wire-loop being positioned below said primary wire-loop, each of said primary and secondary wire-loops having an upper-horizontal leg and a lower-horizontal leg, said secondary wire-loop upper-horizontal leg abutting said primary wire-loop lower-horizontal leg, said secondary wire-loop upper-horizontal leg and said primary wire-loop lower-horizontal leg being twisted together, each of said primary and secondary wire-loops being charged by separate excitation circuits operated by common timing signals, each of said primary and said secondary wire-loops having a common terminal, a charging terminal, and an intrinsic resistance; and

an inductance measuring device in electrical communication with each of said primary and secondary wire-loops wherein the electromagnetic noise associated with both of said primary and secondary wire-loops is combined and reduces the total electromagnetic noise associated with said primary and secondary wire-loops, said inductance measuring device including

a first capacitor and a second capacitor, each of said first and second capacitors having two terminals, each said terminal of each of said first and second capacitors in electrical communication with a corresponding said 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 first control signal generator for generating a first control signal;

a second control signal generator for generating a second control signal;

a current source having a common terminal and a power terminal, said current source common terminal in electrical communication with said common terminals of each of said primary and secondary wire-loops;

a first switch in electrical communication with said second control signal generator, said first switch for electrically connecting and disconnecting said current source power terminal to said first wire-loop charging terminal in response to said first control signal;

a second switch in electrical communication with said second control signal generator, said second switch for electrically connecting and disconnecting said current source power terminal to said second wire-loop charging terminal in response to said second control signal;

an instrumentation amplifier having a first input terminal, a second input terminal, and an output terminal, said first LCR circuit output signal being delivered to said instrumentation amplifier first input terminal and said second LCR circuit output signal being delivered to said instrumentation amplifier second input terminal; and

a sample-and-hold amplifier having an analog input terminal, an analog output terminal, and a logic input terminal, said instrumentation amplifier output terminal in electrical communication with said analog input terminal and said second control signal generator in electrical communication with said logic input terminal.

20. The system of claim 19 wherein said inductance measuring device includes a band-pass filter which is interposed between said output terminal of said instrumentation amplifier and said analog input terminal of said sample-and-hold amplifier.

21. The system of claim 20 wherein said inductance measuring device includes

an analog-to-digital converter having an analog input terminal and a plurality of digital output terminals, said analog input terminal being in electrical communication with said analog output terminal of said sample-and-hold amplifier; and

a digital-signal processor having a plurality of digital input terminals in electrical communication with to the respective digital output terminals of said analog-to-digital converter.