초록 ▼

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

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 n×p 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.

대표청구항 ▼

Apparatus for controlling the speed of a rotating body, comprising: tachometer means mechanically coupled to said rotating body to sense cyclic passage of a specific angular index of rotation relative to a position of a reference thereby to eliminate pulse-to-pulse jitter for generating a periodic e

Apparatus for controlling the speed of a rotating body, comprising: tachometer means mechanically coupled to said rotating body to sense cyclic passage of a specific angular index of rotation relative to a position of a reference thereby to eliminate pulse-to-pulse jitter for generating a periodic electrical pulse signal, said periodic electrical pulse signal having a period which is an integral multiple of the period of rotation of said angular index, which period is inversely proportional to the rotational frequency of said body; free-running counter means operative at a fixed clock frequency substantially greater than said rotational frequency and connected to receive said periodic pulse signal of said tachometer means for continuously counting at said fixed frequency and accumulating a count value throughout each said period of said periodic pulse signal, said counter means being operative to respond to each said periodic pulse signal by resetting said count value to zero and being operative to continuously produce a digital electrical signal which is a numerical representation of said count value at the end of the most recent period of said periodic pulse signal and which is precisely indicative of time length of said periodic pulse signal period; means for producing a command digital reference signal representative of a desired time length of said periodic pulse signal period; period comparator means for comparing said digital electrical signal with said command digital reference signal, and for generating in response to a measured difference therebetween a speed control signal having a magnitude representative of said difference; and speed control means connected to said period comparator means to vary the rotational speed of said rotating body in response to said speed control signal in a sense to continuously minimize said difference between said digital electrical signal and said digital reference signal.