Digital wheel speed circuit arranged to compensate for dimensional irregularities of sensor rotor member
First Claim
1. A circuit for providing a digital speed signal according to the angular velocity of a vehicle wheel comprising:
- a. a wheel speed sensor device including a toothed rotor rotatable with the wheel, said sensor device generating a sinusoidal voltage having a fundamental frequency proportional to the rotational speed of the toothed rotor;
b. means for converting said sinusoidal voltage into a square wave signal; and
c. means for measuring the time duration between two positive polarity transitions of said square wave signal occurring at full cycle intervals and between two negative polarity transitions of said square wave signal occurring at full cycle intervals to provide said digital speed signal for each said full cycle interval thereof, said full cycle intervals defined by said positive and said negative polarity transitions having an overlapping relationship therebetween.
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Accused Products
Abstract
A wheel speed measuring apparatus is provided for use in an anti-skid brake control system such that a digital speed signal is obtained having good accuracy without resorting to expensive manufacturing methods to assure exact conformity of the teeth and teeth spaces of the rotor member of the wheel sensor device used in the anti-skid control system. The speed measuring apparatus consists of at least two corresponding portions, each consisting of a control unit, a counter and a data register. The control unit of one portion responds to a positive polarity transition of the square wave signal generated by the wheel sensor, while the control unit of the other portion responds to negative polarity transitions, to initiate operation of the respective counters. The count output of each counter therefore provides a digital speed signal corresponding to a full cycle duration of the square wave signal, with one cycle overlapping the other to compensate for any deviations in the half-cycle durations due to size differences in the teeth and spaces of the rotor member of the sensor that generates the square wave signal.
22 Citations
7 Claims
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1. A circuit for providing a digital speed signal according to the angular velocity of a vehicle wheel comprising:
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a. a wheel speed sensor device including a toothed rotor rotatable with the wheel, said sensor device generating a sinusoidal voltage having a fundamental frequency proportional to the rotational speed of the toothed rotor; b. means for converting said sinusoidal voltage into a square wave signal; and c. means for measuring the time duration between two positive polarity transitions of said square wave signal occurring at full cycle intervals and between two negative polarity transitions of said square wave signal occurring at full cycle intervals to provide said digital speed signal for each said full cycle interval thereof, said full cycle intervals defined by said positive and said negative polarity transitions having an overlapping relationship therebetween. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification