Normalization of inductive vehicle detector outputs
First Claim
1. A method for normalizing signatures obtained from a plurality of inductive vehicle detectors, said method comprising the steps of:
- a) driving a first vehicle over a first wire loop sensor connected to a first detector;
b) producing a first inductive vehicle signature from said first detector;
c) driving said first vehicle over a second wire loop sensor connected to a second detector;
d) producing a second inductive vehicle signature from said second detector;
e) comparing said first inductive vehicle signature to said second inductive vehicle signature; and
f) determining at least one normalization coefficient from a comparison of said first inductive vehicle signature to said second inductive vehicle signature.
1 Assignment
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Accused Products
Abstract
Methods and apparatus for such that a measurement made for a given vehicle by a given detector is substantially repeatable using either the same detector from one time to another, or using a different detector. In one embodiment, normalization coefficients are determined by measuring one or more common probe vehicles and standardizing the outputs of the detector(s) to give a consistent output. In another embodiment, normalization coefficients are determined by measuring one or more operating or circuit parameters of the detector circuit(s), and compensating the outputs of the detector(s) for variations in these measured parameters.
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Citations
32 Claims
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1. A method for normalizing signatures obtained from a plurality of inductive vehicle detectors, said method comprising the steps of:
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a) driving a first vehicle over a first wire loop sensor connected to a first detector;
b) producing a first inductive vehicle signature from said first detector;
c) driving said first vehicle over a second wire loop sensor connected to a second detector;
d) producing a second inductive vehicle signature from said second detector;
e) comparing said first inductive vehicle signature to said second inductive vehicle signature; and
f) determining at least one normalization coefficient from a comparison of said first inductive vehicle signature to said second inductive vehicle signature. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method for normalizing signatures obtained from a plurality of inductive vehicle detectors, said method comprising the steps of:
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a) measuring a first parameter of a first inductive vehicle detector;
b) measuring a second parameter of a second inductive vehicle detector;
c) comparing said first parameter to said second parameter;
d) determining at least one normalization coefficient from a comparison of said first parameter to said second parameter. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15)
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16. An apparatus for normalizing an inductive vehicle signature, said apparatus including:
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a wire loop sensor;
an inductive vehicle detector connected to said wire loop sensor;
a differential amplifier connected to said inductive vehicle detector, said differential amplifier having a gain equal to a first order normalization coefficient;
whereby said differential amplifier multiplies the inductive vehicle signature by said first order normalization coefficient. - View Dependent Claims (17)
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18. An apparatus for normalizing an inductive vehicle signature, said apparatus including:
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a wire loop sensor;
an inductive vehicle detector connected to said wire loop sensor, said inductive vehicle detector producing the inductive vehicle signature;
an analog to digital converter connected to an output of said inductive vehicle detector; and
a processor connected to said analog to digital converter, said processor applying at least one normalization coefficient to the inductive vehicle signature. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25)
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26. A method for normalizing lane occupancy, said method comprising the steps of:
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a) measure a speed of a vehicle with an inductive vehicle detector;
b) measure an on-time for said vehicle crossing a wire loop sensor of said inductive vehicle detector c) determine an inductive length of said vehicle from said measured speed; and
d) compute a normalized on-time by subtracting a longitudinal length of said wire loop sensor from said inductive length and dividing the difference by said measured speed. - View Dependent Claims (27, 28)
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29. A method for monitoring signal quality for a vehicle detection system, said method comprising the steps of:
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a) measuring a baseline noise level of a series of inductive vehicle signatures on a first detector;
b) avoiding a second detector having a frequency that is identical to an operating frequency of said first detector by selecting said operating frequency having a relatively low baseline noise level;
c) automatically setting a detection threshold to an optimal level to minimize false detections and maximize real detections;
d) measuring a vehicle detector signal level;
e) measuring a quality of a recent history of vehicle detection events; and
f) when the quality of said recent history of vehicle detection events falls below a pre-determined threshold, re-evaluating a plurality of operating conditions of said detector and re-configuring for a more favorable signal-to-noise ratio. - View Dependent Claims (30, 31)
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32. A method for determining a normalized lane occupancy for a vehicle detection system, said method comprising the steps of:
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a) measuring a speed and an inductive length of a vehicle as a function of vehicle speed, and a loop detector on-time whereby said inductive length equals said speed multiplied by said loop detector on-time;
b) subtracting a longitudinal dimension of a wire loop from said inductive length;
c) computing a normalized on-time wherein said normalized on-time equals said inductive length minus said longitudinal dimension of said inductive loop, all divided by said speed; and
d) measuring a total time corresponding to a measurement period;
whereby said normalized lane occupancy is reported as a percentage of said normalized on-time divided by said total time.
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Specification