Monitoring process and system

• US 7,522,044 B2
• Filed: 06/04/2002
• Issued: 04/21/2009
• Est. Priority Date: 06/04/2001
• Status: Expired due to Fees

• Current Assignee: CEOS Industrial Pty Limited
• Original Assignee: CEOS Industrial Pty Limited
• Inventors: Dickson, Adam Matthew, Phillips, Austin, Spring, Jonathan, Murtonen, Casper, Robb, Terrance
• Primary Examiner(s): Pope; Daryl C
• Application Number:
  US10/479,464
• Publication Number:
  US 20040149939A1
• Time in Patent Office: 2,513 Days
• Field of Search: 340/555, 340/541, 340/552, 340/556, 340/557, 340/565, 340/567
• US Class Current: 340/555
• CPC Class Codes: G01P 3/68 using optical means, i.e. using infrared, visible, or ultraviolet light G01P3/80 takes precedence ; by reflection of waves G01S17/58
• CPC Class Codes: G08G 1/04 using optical or ultrasonic detectors

Abstract

A monitoring system includes a transmitter (102) with two transmit modules (208, 210) and a receiver (104) with two receive modules (212, 214). Each of the transmit modules (208, 210) generates an optical signal modulated at a unique frequency. The optical signals are transmitted across a roadway (112) and are detected by the receive modules (212, 214). When a vehicle (110) moves between the transmitter (102) and receiver (104), the optical signals are blocked. The receiver (104) generates timestamped make and break events corresponding to the blocking and unblocking of the signals, and these are used to determine parameters for the vehicle (110) such as velocity and vehicle classification. Because each signal is modulated at a different frequency, each receive module (212, 214) can distinguish the signals received from each of the transmit modules (208, 210), allowing the lane position of the vehicle (110) in a multi-lane roadway (112) to be determined.

Claims

1. A process for monitoring at least one moving object, including the steps of:

generating first and second optical signals at respective first and second locations mutually spaced along a moving direction of said object, said optical signals being modulated at respective modulation frequencies;

transmitting said optical signals across a path of said moving object;

detecting, at one or more detecting locations, at least one of making and breaking of each of said first and second optical signals due to movement of said object by monitoring substantially at one or more of said modulation frequencies to determine at least one of blocking and unblocking of paths between each detecting location and said first location and between each detecting location and said second location, wherein two of the detected signals correspond to respective receiving directions for a diverging signal transmitted from one of said first and second locations; and

determining at least one parameter of said object on the basis of said detecting.

2. A process as claimed in claim 1, wherein including detecting changes in a modulation spectrum of each received signal due to movement of said object.

3. A process as claimed in claim 1, including determining a position of said object in a direction substantially transverse to said moving direction on the basis of at least one of said blocking and said unblocking of said paths.

4. A process as claimed in claim 1, including associating a time value with at least one make or break event for each of the detected signals due to the passage of said object between a transmitter and a receiver of each of said detected signals, at least one of the detected signals being substantially inclined with respect to another of the detected signals, and determining the position of said object in a direction substantially transverse to said moving direction by comparing said time values.

5. A process as claimed in claim 1, including associating respective time values with four make or break events for respective detected signals comprising first and second substantially parallel signals substantially transverse to said moving direction and transmitted from respective first and second transmitters mutually spaced in said moving direction and received at respective first and second receivers, and third and fourth signals respectively transmitted from said first transmitter and received at said second receiver, and transmitted from said second transmitter and received at said first receiver.

6. A process as claimed in claim 1, including receiving said optical signals, converting said optical signals to respective electrical signals, digitizing said electrical signals, and downconverting said digitized signals to provide data representative of at least one of making and breaking of said optical signals due to said movement.

7. A process as claimed in claim 6, wherein said downconverting is digital quadrature amplitude modulation direct downconversion.

8. A process as claimed in claim 1, wherein said at least one parameter includes the passage of said object.

9. A process as claimed in claim 1, wherein said at least one parameter includes a moving direction of said object.

10. A process as claimed in claim 1, wherein said at least one parameter includes a speed or velocity of said object.

11. A process as claimed in claim 1, wherein said at least one parameter includes a dimension of said object.

12. A process as claimed in claim 11, wherein said dimension is used to classify said object.

13. A process as claimed in claim 1, wherein said at least one parameter includes a classification of said object.

14. A process as claimed in claim 13, wherein said object includes a vehicle, and said classification is into one of a number of vehicle types.

15. A monitoring system having components for executing the steps of claim 1.

16. A computer readable storage medium, having stored thereon program code for executing the steps of claim 1.

17. A system for monitoring at least one moving object, the system including transmitters for transmitting optical signals modulated at respective different modulation frequencies, receivers for receiving said optical signals, each of said receivers being adapted to detect one or more of the received optical signals on the basis of said modulation frequencies, and means for detecting at least one of making and breaking of the one or more detected signals due to movement of said object to determine at least one parameter of said object, and means for detecting changes in a modulation spectrum of each detected signal due to said movements, wherein each of said receivers includes a sensor, an input circuit for converting one or more received optical signals to an electrical signal, and an analog-to-digital (ADC) converter for digitizing said electrical signal, and the system includes a digital signal processor (DSP) for demodulating the digitized signal from each of said receivers to provide output data representative of said at least one of making and breaking of the one or more detected optical signals, said output data including at least one of I and Q modulation data, the system including means to lock respective frequencies of one or more oscillators to said modulation frequencies on the basis of said modulation data.

18. A system as claimed in claim 17, wherein said at least one parameter includes the passage of said object.

19. A system as claimed in claim 17, wherein said at least one parameter includes a moving direction of said object.

20. A system as claimed in claim 17, wherein said at least one parameter includes a speed or velocity of said object.

21. A system as claimed in claim 17, wherein said at least one parameter includes a dimension of said object.

22. A system as claimed in claim 21, wherein said dimension is used to classify said object.

23. A system as claimed in claim 17, wherein said at least one parameter includes a classification of said object.

24. A system as claimed in claim 23, wherein said object includes a vehicle, and said classification is into one of a number of vehicle types.

25. A system for monitoring at least one moving object, the system including transmitters for transmitting optical signals modulated at respective different modulation frequencies, receivers for receiving said optical signals, each of said receivers being adapted to detect one or more of the received optical signals on the basis of said modulation frequencies, and means for detecting at least one of making and breaking of the one or more detected signals due to movement of said object to determine at least one parameter of said object, and means for detecting changes in a modulation spectrum of each detected signal due to said movement, wherein each of said receivers includes a sensor, an input circuit for converting one or more received optical signals to an electrical signal, and an analog-to-digital (ADC) converter for digitizing said electrical signal, and the system includes a digital signal processor (DSP) for demodulating the digitized signal from each of said receivers to provide output data representative of said at least one of making and breaking of the one or more detected optical signals, wherein each input circuit includes at least one variable resonant circuit, and circuitry for matching the resonant frequency of said resonant circuit to a selected modulation frequency to minimize referred input noise, maximize overall gain, and minimize input impedance at the selected modulation frequency.

26. A system as claimed in claim 25, wherein said at least one variable resonant circuit includes a varactor and an inductor in parallel.

27. A system as claimed in claim 26, wherein one of said variable resonant circuits includes an inductor used for biasing said sensor.

28. A system as claimed in claim 26, wherein said input circuit includes an input electrode, at least one guard electrode, and a bootstrap circuit for matching the potential of said at least one guard electrode to the potential of said input electrode.

29. A system as claimed in claim 28, wherein said bootstrap circuit can be selectively disabled by grounding input to said circuit.

30. A system as claimed in claim 28, wherein said bootstrap circuit includes an amplifier and a variable resonant circuit for reducing noise coupled into said input electrode from said amplifier.

31. A system as claimed in claim 30, wherein said variable resonant circuit of said bootstrap circuit includes a varactor and an inductor in parallel.

32. A system as claimed in claim 31, wherein said bootstrap circuit has substantially unity gain and substantially zero phase shift at said modulation frequency.

33. A system as claimed in claim 31, wherein said input circuit includes a signal amplifier with variable feedback.

34. A system as claimed in claim 33, wherein said variable feedback and said at least one variable resonant circuit are varied under control of a microprocessor of the receiver to maintain stability of said input circuit.

35. A process for tuning the bias varactor of the bias circuit and the bootstrap varactor of the bootstrap circuit claimed in claim 34, including the steps of:

(i) setting the bootstrap varactor to a nominal value;

(ii) enabling the bootstrap circuit;

(iii) maximising loop gain of a signal amplifier of said bootstrap circuit at said modulation frequency by tuning the bias varactor;

(iv) disabling said bootstrap circuit;

(v) maximising the loop gain of said signal amplifier at said modulation frequency by tuning the bootstrap varactor; and

(vi) repeating steps (ii) to (v) until the tuning voltages applied to each varactor converge.

36. A system for monitoring at least one moving object, the system including transmitters for transmitting optical signals modulated at respective different modulation frequencies, receivers for receiving said optical signals, each of said receivers being adapted to detect one or more of the received optical signals on the basis of said modulation frequencies, and means for detecting at least one of making and breaking of the one or more detected signals due to movement of said object to determine at least one parameter of said obiect, and means for detecting changes in a modulation spectrum of each detected signal due to said movement, wherein each of said receivers includes a sensor, an input circuit for converting one or more received optical signals to an electrical signal, and an analog-to-digital (ADC) converter tbr digitizing said electrical signal, and the system includes a digital signal processor (DSP) for demodulating the digitized signal from each of said receivers to provide output data representative of said at least one of making and breaking of the one or more detected optical signals, the system including at least one switch-mode power supply synchronised to half of the ADC sampling frequency, and wherein said DSP is configured to reduce digital signal artifacts from said power supply.