Vehicle presence, speed and length detecting system and roadway installed detector therefor

• US 6,208,268 B1
• Filed: 04/30/1993
• Issued: 03/27/2001
• Est. Priority Date: 04/30/1993
• Status: Expired due to Term

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: Feaga, Adam C., Lenko, Daniel S., Scarzello, John F
• Primary Examiner(s): TONG, NINA C
• Application Number:
  US08/054,166
• Time in Patent Office: 2,888 Days
• Field of Search: 340/941, 340/933, 340/906, 340/938, 340/936, 340/939, 340/940, 324/247, 324/207.14, 324/207.23, 324/207.24, 324/207.26, 324/173, 324/174, 324/175, 324/179, 364/565, 364/438, 364/436, 361/156, 361/180, 180/282
• US Class Current: 340/941
• CPC Class Codes: G08G 1/042 using inductive or magnetic detectors
• CPC Class Codes: G08G 1/052 with provision for determining speed or overspeed speed measuring in general G01P

Abstract

An improved detector is provided for installation in a roadway surface. The detector finds utility in a highway vehicle detection system for determining vehicle presence, vehicle speed and vehicle length. First and second matched induction coil magnetic sensors are maintained at or near the roadway surface. Each of the sensors has a longitudinal axis aligned normal to the roadway surface. The first and second sensors are separated from one another by a known distance in a direction substantially aligned with a direction of traffic flow. Each of the sensors generate a differential magnetic field signature with respect to time to indicate a passing vehicle'"'"'s leading and trailing edge magnetic signatures. Vehicle speed is determined by a time-distance relationship using the leading and trailing edge magnetic signatures and the known distance. Vehicle length is determined by a time-speed relationship using the leading and trailing edge magnetic signatures and the determined vehicle speed. A triaxial magnetometer maintained at a location in close proximity to the first and second sensors measures a DC magnetic field. The DC magnetic field has vertical and horizontal magnetic field components with the horizontal components including a component substantially aligned with the direction of traffic flow and a component substantially perpendicular to the direction of traffic flow. The vertical and horizontal components caused by the passing vehicle are used to determine vehicle presence. An ELF communications system may be incorporated with the detector to link roadside and vehicle transmitted/received information.

Claims

1. A highway vehicle sensing system comprising:

vehicle speed and length detection means including first and second matched induction coil magnetic sensors maintained at or near a roadway surface, each of said sensors having a longitudinal axis aligned normal to the roadway surface, said sensors being separated from one an oher by a known distance in a direction substantially aligned with a direction of traffic flow, each of said sensors generating a differential magnetic field signature with respect to time to indicate a passing vehicle'"'"'s leading and trailing edge magnetic signatures, wherein said leading and trailing edge magnetic signatures are used in conjunction with said known distance to determine vehicle speed and vehicle length; and

vehicle presence detection means, including a triaxial magnetometer maintained at a location in close proximity to said first and second sensors, for measuring a DC magnetic field at said location to determine vehicle presence, said DC magnetic field having vertical and horizontal magnetic field components with said horizontal components including a component substantially aligned with the direction of traffic flow and a component substantially perpendicular to the direction of traffic flow, wherein said vertical and horizontal components caused by the passing vehicle are used to determine vehicle presence.

2. A system as in claim 1 wherein said vehicle speed and length detection means further includes timing means for determining a first, second and third time interval, said first time interval occurring between the passing vehicle'"'"'s leading edge magnetic signatures detected by said first and second sensors, said second time interval occurring between the passing vehicle'"'"'s trailing edge magnetic signatures detected by said first and second sensors, and said third time interval occurring between the passing vehicle'"'"'s leading and trailing edge magnetic signatures detected by one of said first and second sensors, wherein said vehicle speed is determined by a time-distance relationship using at least one of said first and second time intervals and said known distance, and wherein said vehicle length is determined by a time-speed relationship using said third time interval and said determined vehicle speed.

3. A system as in claim 1 wherein said vehicle presence detection means further includes means for nulling out the earth'"'"'s ambient magnetic field along each of said vertical and horizontal components.

4. A system as in claim 1 wherein said known distance is a fraction of the passing vehicle'"'"'s length.

5. A system as in claim 1 wherein said known distance is six inches or less.

6. A system as in claim 1 wherein said location in close proximity to said first and second sensors is within six inches of said first and second sensors.

7. A system as in claim 2 further including first and second identical bandpass filters for receiving and passing to said timing means that portion of each sensor'"'"'s generated differential magnetic field signature containing the passing vehicle'"'"'s leading and trailing edge magnetic signatures.

8. A system as in claim 1 wherein said triaxial magnetometer is ring-core fluxgate magnetometer.

9. A highway vehicle sensing and communication system comprising:

a transceiver for transmitting extremely low frequency (ELF) signals to a remote location and receiving ELF signals from the remote location, said transceiver including first and second matched induction coil magnetic sensors maintained at or near a roadway surface, each of said sensors having a longitudinal axis aligned normal to the roadway surface, said sensors being separated from one another by a known distance in a direction substantially aligned with a direction of traffic flow, each of said sensors further generating a differential magnetic field signature with respect to time to indicate the passing vehicle'"'"'s leading and trailing edge magnetic signatures;

a triaxial magnetometer maintained at a location in close proximity to said first and second sensors, for measuring a DC magnetic field at said location, said DC magnetic field having vertical and horizontal magnetic field components with said horizontal components including a component substantially aligned with the direction of traffic flow and a component substantially perpendicular to the direction of traffic flow; and

processing means for determining a first, second and third time interval, said first time interval occurring between the passing vehicle'"'"'s leading edge magnetic signatures detected by said first and second sensors, said second time interval occurring between the passing vehicle'"'"'s trailing edge magnetic signatures detected by said first and second sensors, and said third time interval occurring between the passing vehicle'"'"'s leading and trailing edge magnetic signatures detected by one of said first and second sensors, wherein vehicle speed is determined by a time-distance relationship using one at least of said first and second time intervals and said known distance, vehicle length is determined by a time-speed relationship using said third time interval and said determined vehicle speed, and vehicle presence is determined by said vertical and horizontal components caused by the passing vehicle.

10. A system as in claim 9 further including means for nulling out the earth'"'"'s ambient magnetic field along each of said vertical and horizontal components.

11. A system as in claim 9 wherein said known distance is a fraction of the passing vehicle'"'"'s length.

12. A system as in claim 9 wherein said known distance is six inches or less.

13. A system as in claim 9 wherein said location in close proximity to said first and second sensors is within six inches of said first and second sensors.

14. A system as in claim 9 further including first and second identical bandpass filters for receiving and passing to said processing means that portion of each sensor'"'"'s generated differential magnetic field signature containing the passing vehicle'"'"'s leading and trailing edge magnetic signatures.

15. A system as in claim 9 wherein said triaxial magnetometer is ring-core fluxgate magnetometer.

16. A highway vehicle sensing and communication system comprising:

first and second matched induction coil magnetic sensors maintained at or near a roadway surface, each of said first and second sensors having a longitudinal axis aligned normal to the roadway surface, said first and second sensors being separated from one another by a known distance in a direction substantially aligned with a direction of traffic flow, each of said first and second sensors further generating a differential magnetic field signature with respect to time to indicate the passing vehicle'"'"'s leading and trailing edge magnetic signatures;

third and fourth matched induction coil magnetic sensors maintained at or near the roadway surface in close proximity to said first and second sensors, each of said third and fourth sensors lying in a unique horizontal plane and having a longitudinal axis aligned substantially parallel to the roadway surface, said third and fourth sensors forming an orthogonal crossing pattern when viewed with respect to a direction normal to the roadway surface, said orthogonal crossing pattern arranged so that each of said third and fourth sensor'"'"'s longitudinal axis bisects the direction of traffic flow by an angle of approximately 45°

, wherein said third and fourth sensors transmit extremely low frequency (ELF) signals to the passing vehicle and receive ELF signals from the passing vehicle;

a triaxial magnetometer, maintained at or near the roadway surface in close proximity to said first through fourth sensors, for measuring a DC magnetic field thereat, said DC magnetic field having vertical and horizontal magnetic field components with said horizontal components including a component substantially aligned with the direction of traffic flow and a component substantially perpendicular to the direction of traffic flow; and

processing means for determining a first, second and third time interval, said first time interval occurring between the passing vehicle'"'"'s leading edge magnetic signatures detected by said first and second sensors, said second time interval occurring between the passing vehicle'"'"'s trailing edge magnetic signatures detected by said first and second sensors, and said third time interval occurring between the passing vehicle'"'"'s leading and trailing edge magnetic signatures detected by one of said first and second sensors, wherein vehicle speed is determined by a time-distance relationship using at least one of said first and second time intervals and said known distance, vehicle length is determined by a time-speed relationship using said third time interval and said determined vehicle speed, and vehicle presence is determined by said vertical and horizontal components caused by the passing vehicle.

17. A system as in claim 16 further including means for nulling out the earth'"'"'s ambient magnetic field along each of said vertical and horizontal components.

18. A system as in claim 16 wherein said known distance is a fraction of the passing vehicle'"'"'s length.

19. A system as in claim 16 wherein said known distance is six inches or less.

20. A system as in claim 16 wherein said triaxial magnetometer is within six inches of said first through fourth sensors.

21. A system as in claim 16 further including first and second identical bandpass filters for receiving and passing to said processing means that portion of said first and second sensors generated differential magnetic field signature containing the passing vehicle'"'"'s leading and trailing edge magnetic signatures.

22. A system as in claim 16 wherein said triaxial magnetometer is ring-core fluxgate magnetometer.

23. In a highway vehicle detection system for determining vehicle presence, vehicle speed and vehicle length, an improved detector for installation in a roadway surface comprising:

first and second matched induction coil magnetic sensors maintained at or near the roadway surface, each of said sensors having a longitudinal axis aligned normal to the roadway surface, said first and second sensors being separated from one another by a known distance in a direction substantially aligned with a direction of traffic flow, each of said first and second sensors generating a differential magnetic field signature with respect to time to indicate a passing vehicle'"'"'s leading and trailing edge magnetic signatures, wherein first, second and third time intervals associated with said leading and trailing edge magnetic signatures are used in conjunction with said known distance to determine vehicle speed and vehicle length, said first time interval occurring between the passing vehicle'"'"'s leading edge magnetic signatures detected by said first and second sensors, said second time interval occurring between the passing vehicle'"'"'s trailing edge magnetic signatures detected by said first and second sensors, and said third time interval occurring between the passing vehicle'"'"'s leading and trailing edge magnetic signatures detected by one of said first and second sensors, wherein said vehicle speed is determined by a time-distance relationship using at least one of said first and second time intervals and said known distance, and wherein said vehicle length is determined by a time-speed relationship using said third time interval and said determined vehicle speed; and

a triaxial magnetometer maintained at a location in close proximity to said first and second sensors, for measuring a DC magnetic field at said location to determine vehicle presence, said DC magnetic field having vertical and horizontal magnetic field components with said horizontal components including a component substantially aligned with the direction of traffic flow and a component substantially perpendicular to the direction of traffic flow, wherein said vertical and horizontal components caused by the passing vehicle are used to determine vehicle presence.

24. An improved detector as in claim 23 wherein said known distance is a fraction of the passing vehicle'"'"'s length.

25. An improved detector as in claim 23 wherein said known distance is six inches or less.

26. An improved detector as in claim 23 wherein said location in close proximity to said first and second sensors is within six inches of said first and second sensors.

27. An improved detector as in claim 23 wherein said triaxial magnetometer is ring-core fluxgate magnetometer.

28. An improved detector as in claim 23 further comprising third and fourth matched induction coil magnetic sensors maintained at or near the roadway surface in close proximity to said first and second sensors, each of said third and fourth sensors lying in a unique horizontal plane and having a longitudinal axis aligned substantially parallel to the roadway surface, said third and fourth sensors forming an orthogonal crossing pattern when viewed with respect to a direction normal to the roadway surface, said orthogonal crossing pattern arranged so that each of said third and fourth sensor'"'"'s longitudinal axis bisects the direction of traffic flow by an angle of approximately 45°

, wherein said third and fourth sensors transmit extremely low frequency (ELF) signals to the passing vehicle and receive ELF signals from the passing vehicle.

29. An improved detector as in claim 28 wherein said third and fourth sensors lie between said first and second sensors.

30. An improved detector as in claim 28 wherein said first through fourth sensors and said triaxial magnetometer span a distance along the direction of traffic flow that is a fraction of the passing vehicle'"'"'s length.

31. An improved detector as in claim 30 wherein said distance span is six inches or less.