Traffic control system and method of operation
First Claim
1. A traffic control system, comprising:
- A vehicle sensor comprising a flux gate magnetometer including vertical and horizontal sensing coils, a microprocessor controlled detector for evaluating vertical and horizontal perturbations sensed by said flux gate magnetometer, said microprocessor controlled detector configured to evaluate only vertical perturbations when considering a possible vehicle arrival and requiring both vertical and horizontal perturbations to be below predetermined levels to determine a departure and provide output signals reflecting its evaluation of vehicle arrival and departure, means for encoding said output signals as NRZ data packets, and an FM transmitter for transmitting said NRZ data packets; and
a traffic control receiver comprising an FM receiver tuned to said FM transmitter, a microprocessor controlled decoder for said NRZ data packets transmitted by said FM transmitter and received by said FM receiver and output means for supplying to said traffic control signal means vehicle arrival and departure data decoded from said NRZ data packets by said microprocessor controlled decoder.
1 Assignment
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Accused Products
Abstract
A vehicle detector comprising a flux gate magnetometer with vertical and horizontal sensing coils is positioned within a roadway. The ambient levels of the earth'"'"'s magnetic field as sensed by the magnetometer are used to establish reference levels and deviations therefrom are evaluated by a microprocessor which produces a vehicle arrived signal when the vertical component of sensed perturbations exceed a threshold and in an alternate mode when either vertical or horizontal levels exceed threshold values. Both vertical and horizontal levels must fall below threshold levels to determine a departure in either mode. Vehicle arrival and departure events are encoded as NRZ data packets which are transmitted by an edge-fired antenna as FM modulated signals. A remote multi-channel receiver capable of responding to a plurality of magnetometer modulated FM transmitters processes the received data and provides signals that are used by traffic signal controlling computers.
50 Citations
20 Claims
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1. A traffic control system, comprising:
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A vehicle sensor comprising a flux gate magnetometer including vertical and horizontal sensing coils, a microprocessor controlled detector for evaluating vertical and horizontal perturbations sensed by said flux gate magnetometer, said microprocessor controlled detector configured to evaluate only vertical perturbations when considering a possible vehicle arrival and requiring both vertical and horizontal perturbations to be below predetermined levels to determine a departure and provide output signals reflecting its evaluation of vehicle arrival and departure, means for encoding said output signals as NRZ data packets, and an FM transmitter for transmitting said NRZ data packets; and a traffic control receiver comprising an FM receiver tuned to said FM transmitter, a microprocessor controlled decoder for said NRZ data packets transmitted by said FM transmitter and received by said FM receiver and output means for supplying to said traffic control signal means vehicle arrival and departure data decoded from said NRZ data packets by said microprocessor controlled decoder. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for controlling vehicular traffic, including the steps of:
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measuring the vertical magnetic field relative to a roadway with a magnetometer; transmitting an arrival signal indicative of a vehicle arrival when said measured vertical magnetic field exceeds a predetermined threshold; measuring the vertical and horizontal magnetic fields relative to a roadway with a magnetometer after said step of transmitting an arrival signal; and transmitting a departure signal indicative of a vehicle departure when said measured vertical and horizontal magnetic fields both are less than respective predetermined thresholds after said step of transmitting an arrival signal. - View Dependent Claims (11)
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12. A traffic control system, comprising:
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a vehicle sensor comprising a flux gate magnetometer including vertical and horizontal sensing coils, means for independently comparing perturbations of said vertical and horizontal sensing coils to predetermined respective arrival and departure threshold levels, means for providing a vehicle arrival signal when either of said vertical or horizontal perturbations exceed their respective predetermined arrival threshold level, means for producing a departure signal when said perturbations of said vertical and horizontal sensing coils are simultaneously below their respective predetermined departure threshold levels, and means for transmitting said arrival and departure signals; a traffic control receiver tuned to said transmitter; and
means for controlling traffic signalling means in response to said arrival and departure signals received by said receiver. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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Specification