Shadow zone fault detection
First Claim
Patent Images
1. A method for monitoring an active wheel speed sensor comprising the steps of:
- (a) providing an active wheel speed sensor that generates alternating high and low output signals;
(b) sampling the high and low output signals of the wheel speed sensor within a sampling range that is dithered;
(c) constructing high and low histograms corresponding to the high and low output signal samples obtained in step (b);
(d) comparing the histogram values within each of the histograms to one another to determine whether a single histogram value for each of the histograms is dominate over the other values contained in that histogram;
(e) comparing a voltage corresponding to the single dominant value of the high histogram to a threshold voltage value that is determined by the following formula;
VTH=K*VL, whereVTH is the voltage threshold,VL is the voltage value associated with the dominate value of the low histogram, andK is a constant associated with the wheel speed sensor; and
(f) setting an error flag upon the voltage corresponding to the single dominant value of the high histogram being less than the threshold voltage value.
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Abstract
The output of a wheel speed sensor is sampled at dithered time intervals and the samples used to construct a pair of histograms representing high and low sample values. A minimum voltage threshold is determined as a function of the output voltage associated with the dominate histogram value for the low sample values. The output voltage associated with the dominant histogram value for the high sample values is compared to the minimum voltage threshold to determine whether a potential sensor wiring problem is developing.
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Citations
15 Claims
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1. A method for monitoring an active wheel speed sensor comprising the steps of:
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(a) providing an active wheel speed sensor that generates alternating high and low output signals; (b) sampling the high and low output signals of the wheel speed sensor within a sampling range that is dithered; (c) constructing high and low histograms corresponding to the high and low output signal samples obtained in step (b); (d) comparing the histogram values within each of the histograms to one another to determine whether a single histogram value for each of the histograms is dominate over the other values contained in that histogram; (e) comparing a voltage corresponding to the single dominant value of the high histogram to a threshold voltage value that is determined by the following formula;
VTH=K*VL, whereVTH is the voltage threshold, VL is the voltage value associated with the dominate value of the low histogram, and K is a constant associated with the wheel speed sensor; and (f) setting an error flag upon the voltage corresponding to the single dominant value of the high histogram being less than the threshold voltage value. - View Dependent Claims (2, 3, 4, 5)
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6. A method for monitoring an active wheel speed sensor comprising the steps of:
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(a) providing an active wheel speed sensor that generates alternating high and low output signals; (b) sampling the high and low output signals of the wheel speed sensor within a sampling range that is dithered; (c) constructing high and low histograms corresponding to the high and low output signal samples obtained in step (b); (d) comparing the histogram values within each of the histograms to one another to determine whether a single histogram value for each of the histograms is dominate over the other values contained in that histogram; (e) comparing a voltage corresponding to the single dominant value of the high histogram to a threshold voltage value that is determined by the following formula;
VTH=K*VL, whereVTH is the voltage threshold, VL is the voltage value associated with the dominate value of the low histogram, and K is a minimum ratio between high and low current output signals for the wheel speed sensor; and (f) setting an error flag upon the voltage corresponding to the single dominant value of the high histogram being less than the threshold voltage value. - View Dependent Claims (7, 8, 9, 10)
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11. A method for monitoring an active wheel speed sensor comprising the steps of:
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(a) providing an active wheel speed sensor that generates alternating high and low output signals; (b) sampling the high and low output signals of the wheel speed sensor within a sampling range that is dithered; (c) constructing high and low histograms corresponding to the high and low output signal samples obtained in step (b); (d) comparing the histogram values within each of the histograms to one another to determine whether a single histogram value for each of the histograms is dominate over the other values contained in that histogram; (e) comparing a voltage corresponding to the single dominant value of the high histogram to a threshold voltage value that is a non-linear function of the voltage value associated with the dominate value of the low histogram; and (f) setting an error flag upon the voltage corresponding to the single dominant value of the high histogram being less than the threshold voltage value. - View Dependent Claims (12, 13, 14, 15)
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Specification