Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
2000-04-18
2001-04-17
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C701S024000, C342S042000, C342S046000, C342S051000
Reexamination Certificate
active
06219613
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed towards a vehicle position determination system and method for determining the position of a moving vehicle having a transponder.
In electronic toll systems which monitor adjacent lanes of traffic flow, Automatic Vehicle Identification (“AVI”) Radio Frequency (“RF”) coverage is often used to provide coverage zones that extend from side-to-side of each lane. RF transponders mounted on the vehicles using the toll system are interrogated by AVI RF antennas that are connected to a roadside AVI reader. In toll systems, the roadside AVI reader is typically connected to a lane controller which is also connected to a vehicle detector and an imaging system which works in association with the AVI RF system to permit the vehicles to be detected, classified, and photographed, and the license plate numbers analyzed in order to permit the operator of the toll system to apply appropriate charges to the owner of the vehicle. In electronic toll systems, it is often necessary to determine in which lateral position a vehicle is traveling. For example, it is often necessary to separate vehicles equipped with transponders from vehicles without transponders and associate video images with vehicles that are not equipped. In order to do so, the electronic toll system must clearly identify where the subject vehicle is located within the multiple zones of coverage.
In previous systems, the location of the transponder and vehicle is subject to uncertainty because the RF capture zones may overlap. In open road applications, the overlap provided is usually extensive by design in order to provide shoulder-to-shoulder coverage of the entire roadway. In such systems, the roadside AVI reader establishes communications with the transponder in any one of several overlapping zones, and accordingly the system cannot ascertain in which lane the subject vehicle is located by using communications as the only location method. One attempt to solve this problem uses separate coverage zones to cover each of the adjacent lanes, with a further trailing coverage zone to cover vehicles that might drive along the center of the road. In such previous systems, the trailing center capture zone could not be placed co-linear with the capture zones for the adjacent lanes as it was necessary to differentiate the transponder data available from the center zone from the other capture zones in order to allow the roadside equipment to differentiate between vehicles correctly positioned within their respective lanes, and vehicles straddling the center line between two lanes. Such a configuration can result in time ambiguity as the data from the trailing coverage zone is received later than the data from the other coverage zones, during which time the co-ordination with the vehicle detector and lane controller is made ambiguous and the vehicle may have changed positions.
Overlapping coverage zones can also be problematic in conventional toll plaza or toll gate systems. In such systems, the lanes are typically separated by physical barriers, and accordingly the overlap between adjacent coverage zones is generally small. Nonetheless, the small amount of overlap that does exist can result in a transponder equipped vehicle being processed in the wrong lane. When a transponder is processed in the wrong lane, the normal high speed processing of AVI transactions is severely disrupted because the patron who is charged incorrectly will not receive an indication to proceed through the lane.
It is therefore desirable to provide a vehicle position determination system and method having improved accuracy for determining the position of a moving vehicle having a transponder in an electronic toll system. It is also desirable to provide such a system in which all the RF coverage zones can be aligned co-linearly across a roadway in order to minimize time ambiguity between the zones.
SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided a vehicle position determination system for determining the position of a moving vehicle having a transponder, comprising a first antenna positioned to receive periodic radio frequency data signals from the transponder when the transponder is moving through a first predetermined coverage zone having a width that is orthogonal to the travel path of the moving vehicle and a length that is parallel to the travel path of the moving vehicle, the length of the first coverage zone varying in a predetermined manner across the width thereof. The system also includes a second antenna positioned to receive periodic radio frequency data signals from the transponder when the transponder is moving through a second predetermined coverage zone that partially overlaps the first coverage zone and has a width that is orthogonal to the travel path of the moving vehicle and a length that is parallel to the travel path of the moving vehicle, the length of the second coverage zone varying in a predetermined manner across the width thereof Processing means responsive to the antennas counts the number of periodic data signals received by each of the antennas from the transponder during a time period and determines based on the count a probable location of the vehicle. Preferably, the processing means causes the first and second antennas to each transmit periodic interrogation signals to the first and second coverage zones, respectively, to cause the transponder to transmit the data signals when the transponder is located in at least one of the coverage zones.
According to a further aspect of the invention, there is provided a vehicle position determination system for determining the position of a moving vehicle having a transponder that transmits data signals in response to interrogation signals, comprising a plurality of antennas positioned to transmit periodic radio frequency interrogation signals to a plurality of coverage zones and receive data signals transmitted by the transponder in response to the interrogation signals when the transponder is located in one or more of the coverage zones, the coverage zones (a) being substantially aligned along an axis that extends orthogonal to the travel path of the moving vehicle with adjacent coverage zones partially overlapping each other, and (b) each having a generally known shape and size and each having a width that is orthogonal to the travel path of the moving vehicle and a length that is parallel to the travel path of the moving vehicle and which varies across the width of the coverage zone. The system also includes processing means operatively connected to the antennas to cause the antennas to transmit the interrogation signals and to count the number of data signals received by the antennas in respect of each of the coverage zones during a time period and determine based on the count a probable location of the vehicle.
According to another aspect of the invention, there is provided a method of determining the position of a moving vehicle having a transponder, comprising the steps of (a) transmitting periodic data signals from the transponder when the transponder is located within one or more of a plurality of coverage zones that are aligned along an axis that extends orthogonal to the travel path of the moving vehicle with adjacent coverage zones partially overlapping each other, the coverage zones each having a known shape and size and each having a width that is orthogonal to the travel path of the moving vehicle and a length that is parallel to the travel path of the moving vehicle and which varies across the width of the coverage zone; (b) counting, for a time period that commences when the transponder first enters one of the coverage zones, the data signals transmitted by the transponder in each of the coverage zones; and (c)determining, based on the counted data signals for each of the coverage zones a probable location of the vehicle.
REFERENCES:
patent: 5485520 (1996-01-01), Chaum et al.
patent: 5675342 (1997-10-01), Sharpe
patent: 5710556 (1998-01-01), Nishimura et al.
patent: 5790052 (1998-
Terrier Daniel L.
Tiernay Robert Walter
Beaulieu Yonel
Cuchlinski Jr. William A.
Cummings & Lockwood
Mark IV Industries Limited
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