Vehicle acceleration sensor
First Claim
1. A method of determining the acceleration of a vehicle from an acceleration signal α
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r generated by an accelerometer carried by the vehicle, the acceleration signal being contaminated by a noise signal, the method comprising the steps of;
determining a magnitude n.sub.α
of the noise signal;
filtering the acceleration signal α
r by a filter having a time constant C to generate a filtered acceleration signal α
f having a magnitude that comprises the determination of the vehicle acceleration;
comparing the magnitude of a difference between the acceleration signal α
r and the filtered acceleration signal α
f with a magnitude of a predetermined function of the noise signal;
setting the value of the time constant C equal to a value C1 when the magnitude of the difference between the acceleration signal α
r and the filtered acceleration signal α
f is less than the magnitude of the predetermined function of the noise signal, the value C1 establishing a predetermined low cutoff frequency of the filter to remove the noise signal from the acceleration signal α
r ; and
setting the value of the time constant C equal to a value Ch when the magnitude of the difference between the acceleration signal α
r and the filtered acceleration signal α
f is greater than the magnitude of the predetermined function of the noise signal, the value Ch establishing a predetermined cutoff frequency of the filter higher than the predetermined low cutoff frequency so that the determination of vehicle acceleration represented by the filtered acceleration signal α
f more rapidly responds to rapid changes int he actual vehicle acceleration.
1 Assignment
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Accused Products
Abstract
A vehicle accelerometer measures vehicle acceleration and provides acceleration data subject to contamination by noise signals. The acceleration data is filtered by a filter. A predetermined function of the noise level in the acceleration data is compared with the filter error which is the difference between raw acceleration data and the filtered value of acceleration. When the filter error is less than the noise level, the filter time constant is set to establish a low cutoff frequency so that the filter rejects the noise like a conventional low pass filter. When the filter error becomes greater than the predetermined function of the noise level, the filter time constant is set to establish a higher cutoff frequency so that the filtered value of acceleration converges to the ideal value faster than would occur with the filter having the lower cutoff frequency.
18 Citations
5 Claims
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1. A method of determining the acceleration of a vehicle from an acceleration signal α
-
r generated by an accelerometer carried by the vehicle, the acceleration signal being contaminated by a noise signal, the method comprising the steps of;
determining a magnitude n.sub.α
of the noise signal;filtering the acceleration signal α
r by a filter having a time constant C to generate a filtered acceleration signal α
f having a magnitude that comprises the determination of the vehicle acceleration;comparing the magnitude of a difference between the acceleration signal α
r and the filtered acceleration signal α
f with a magnitude of a predetermined function of the noise signal;setting the value of the time constant C equal to a value C1 when the magnitude of the difference between the acceleration signal α
r and the filtered acceleration signal α
f is less than the magnitude of the predetermined function of the noise signal, the value C1 establishing a predetermined low cutoff frequency of the filter to remove the noise signal from the acceleration signal α
r ; andsetting the value of the time constant C equal to a value Ch when the magnitude of the difference between the acceleration signal α
r and the filtered acceleration signal α
f is greater than the magnitude of the predetermined function of the noise signal, the value Ch establishing a predetermined cutoff frequency of the filter higher than the predetermined low cutoff frequency so that the determination of vehicle acceleration represented by the filtered acceleration signal α
f more rapidly responds to rapid changes int he actual vehicle acceleration. - View Dependent Claims (2, 3, 4)
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r generated by an accelerometer carried by the vehicle, the acceleration signal being contaminated by a noise signal, the method comprising the steps of;
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5. A system for determining the acceleration of a vehicle, the system comprising:
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an accelerometer responsive to vehicle acceleration for generating an acceleration signal α
r, the acceleration signal being subject to contamination by a noise signal;means for determining a magnitude n60 of the noise signal; a signal filter for filtering the acceleration signal α
r to generate a filtered acceleration signal α
f by repeatedly determining the value of α
f in accord with the expression
space="preserve" listing-type="equation">α
.sub.f =(1-C)*α
.sub.f (LAST)+Cα
.sub.r,where c is a filter time constant and α
f (LAST) is the last determined value of α
f, the magnitude of α
f comprising a determination of the vehicle acceleration;means for comparing the magnitude of a difference between the acceleration signal α
r and the filtered acceleration signal α
f with a magnitude of a predetermined function of the noise signal;means for setting the value of the time constant C equal to a value C1 when the magnitude of the difference between the acceleration signal α
r and the filtered acceleration signal α
f is less than the magnitude of the predetermined function of the noise signal, the value C1 establishing a predetermined low cutoff frequency of the signal filter to remove the noise signal from the acceleration signal α
r ; andmeans for setting the value of the time constant C equal to a value Ch when the magnitude of the difference between the acceleration signal α
r and the filtered acceleration signal α
f is greater than the magnitude of the predetermined function of the noise signal, the value Ch establishing a predetermined cutoff frequency of the signal filter higher than the predetermined low cutoff frequency so that the determination of vehicle acceleration represented by the filtered acceleration signal α
f more rapidly responds to rapid changes in the actual vehicle acceleration.
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Specification