| 摘要 |
A closed-loop system for precisely regulating the speed of an electrically driven rotating body. A tachometer rotor, mechanically linked to the rotating body, is provided with p "teeth " around its periphery. A sensor produces a pulse signal upon passage of each of these teeth, to generate a cyclical tachometer signal having a frequency p times the frequency of rotation. A tachometer counter counts this signal and produces a single output pulse after every nxp pulses from the sensor, such that the same one of the p teeth is responsible for triggering each of the successive output pulses, and variations in spacing between teeth do not cause variations in the period of the counter output. A high frequency clock is counted by a second counter, which transfers its count to a storage register and resets upon each pulse from the tachometer counter, such that the count held by the storage register is a continuously updated, highly accurate digital representation of the period of the rotating body. A period comparator derives a speed control signal which is proportional to the inverse of the difference between the count and a digital speed command signal representative of the rotational period of the desired rotational speed.
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