Vehicle traveling position detecting system

• US 20020022926A1
• Filed: 08/20/2001
• Published: 02/21/2002
• Est. Priority Date: 08/21/2000
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Suzuki, Jun
• Granted Patent: US 6,512,978 B2
• Time in Patent Office: Days
• US Class Current: 701/207
• CPC Class Codes: G01C 21/26 specially adapted for navigation in a road network
• CPC Class Codes: G05D 1/0261 using magnetic plots
• CPC Class Codes: G05D 2201/0213 Road vehicle, e.g. car or truck

Abstract

A vehicle travelling position detecting system includes a plurality of magnetic sensors arranged on a vehicle for detecting magnetic fields generated by magnetic markers arranged on the road in the travelling direction of the vehicle to output detected magnetic field signal. A difference signal between the detected magnetic field signal and delayed magnetic field signal generated from the detected magnetic field signal allows reduction of the noise. The difference signal is used for calculating displacement of the vehicle with respect to the magnetic markers.

Claims

1. A vehicle travelling position detecting system comprising a magnetic sensor mounted on a vehicle for detecting a magnetic field generated by one of magnetic markers arranged in a travelling direction of the vehicle to output a detected magnetic field signal, a speed sensor for detecting a travelling speed of the vehicle, a delay unit for delaying the detected magnetic field signal by a delay time calculated based on the detected travelling speed to output a delayed magnetic field signal, a subtracter for calculating a difference between the detected magnetic field signal and the delayed magnetic field signal to output a difference signal, a displacement calculating unit for calculating based on the difference signal a displacement with respect to the one of the magnetic markers in a lateral direction normal to the travelling direction.

2. The vehicle travelling position detecting system as defined in claim 1, wherein the delay time D is calculated by:

D=L/(2×

V),

given L and V being a detectable distance of the one of the magnetic markers and the detected travelling speed, respectively.

3. The vehicle travelling position detecting system as defined in claim 1, wherein said magnetic sensor is selected from a magnetic array, among which said magnetic sensor outputs a highest amplitude of the detected magnetic field signal.

4. The vehicle travelling position detecting system as defined in claim 1, wherein said subtracter comprises an inverter for inverting the detected magnetic field signal to output an inverted magnetic field signal, and an adder for adding the inverted magnetic field signal and the detected magnetic field signal.

5. A vehicle travelling position detecting system comprising a magnetic sensor mounted on a vehicle for detecting a magnetic field generated by one of magnetic markers arranged in a travelling direction of the vehicle to output a detected magnetic field signal, a speed sensor for detecting a travelling speed of the vehicle, a sample/hold circuit for sampling the detected magnetic field signal at a specified sampling period to output a series of sampled magnetic field signals, a first memory section for storing the series of sampled magnetic field signals, a subtracter for calculating a difference between each two of the series of sampled magnetic field signals sampled at a specified interval to output a series of difference signals, a second memory section for storing the series of difference signals, and a displacement calculating unit for calculating based on the series of difference signals a displacement with respect to the one of the magnetic markers in a lateral direction normal to the travelling direction.

6. The vehicle travelling position detecting system as defined in claim 5, wherein the delay time D is calculated by:

D=L/(2×

V),

given L and V being a detectable distance of the one of the magnetic markers and the detected travelling speed, respectively.

7. The vehicle travelling position detecting system as defined in claim 5, wherein said magnetic sensor is selected from a magnetic array, among which said magnetic sensor outputs a highest amplitude of the detected magnetic field signal.

8. The vehicle travelling position detecting system as defined in claim 5, wherein said subtracter comprises an inverter for inverting one of the each two of the sampled magnetic field signals to output an inverted magnetic field signal, and an adder for adding the inverted magnetic field signal and the other of the each two of sampled magnetic field signals.