Apparatus and method for controlling the rotational speed of a motor

Abstract

An apparatus for controlling the rotational speed of a motor. The apparatus comprises a subtracter for subtrating a speed error signal corresponding to a frequency signal generated from a frequency generator from a period deviation signal between the frequency signal and a predetermined reference frequency signal to produce a primarily compensated speed error signal; a first adder for adding the primarily compensated signal and the period deviation signal to produce an added signal; a delay circuit for delaying the output signal of the first adder, wherein the delay circuit comprises a first to an Nth delay cells, wherein each of the delay cells latches the output signal of the first adder entering the first delay cell and serially shifts the latched signal in each of the delay cells toward the Nth delay cell by one signal at a time whenever the output of the first adder is supplied to the delay circuit and wherein the output of the delay circuit is supplied to the subtracter and to the first adder; a summation circuit for summing up all of the signals being shifted from the respective delay cells to produce a sum period deviation signal; an averaging circuit for averaging the sum period deviation signal to produce an averaged deviation signal; and second adder for adding the primarily compensated signal and the averaged deviation signal to produce the motor speed control signal with a compensated period deviation. A method is also provided for controlling the speed of the motor.