Patent ID: 6031966
Filing Date: 2000-02-29
Classification: G01P,H02P

Abstract:
A motor speed control device comprising:a rotation speed detecting circuit for obtaining N FG pulse signals, N.gtoreq.1 where N is an integer, in one rotation of a motor; anda first controlling circuit for controlling a rotation speed of the motor in accordance with respective period information of (1) a rising edge-falling edge period and (2) a falling edge-rising edge period of the FG pulse signal;wherein said first controlling circuit includes a first FG nonuniformity correcting circuit for correcting, in accordance with the respective period information of the rising edge-falling edge period and the falling edge-rising edge period of the FG pulse signal, periodic nonuniformity of each said period, said first FG nonuniformity correcting circuit further including:a first period ratio calculating circuit for calculating respective period ratio information of the rising edge-falling edge period and the falling edge-rising edge period; anda first target correcting circuit for correcting a control target in accordance with a correction value that varies depending on the period ratio information,wherein said first period ratio calculating circuit calculates period ratio information from information which is an average of respective period information of the rising edge-falling edge period and the falling edge-rising edge period during i rotations of a motor, i.gtoreq.where i is an integer.