| 摘要 |
PURPOSE:To obtain an appropriate vehicle speed value from a vehicle speed signal input having disturbance, in an arrangement in which a pulse train from a vehicle speed sensor which varies its frequency in accordance with the vehicle speed is processed, by providing a vehicle speed filter having a sufficient cut-off performance with no frequency modulating characteristic. CONSTITUTION:A vehicle speed sensor SEN in an automobile constant speed running device is composed, in combination, of a reed switch and a magnetized rotor to which the rotation of a propeller shaft is transmitted through an wire and which therefore rotates to turn on and off the reed switch. Further, A vehicle speed signal processing circuit processes a pulse train from the vehicle speed sensor SEN. In this arrangement, times among a predetermined number of successive pulses are measured in synchronization with the pulses in the pulse train, and the thus obtained values are introduced through an integration filter. Then the value obtained by the result is converted into reverse numbers for every predetermined time to obtain a vehicle speed value. Further, thus obtained value is introduced through the integration filter to deliver a vehicle speed at each time point.
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