Motor control method and a motor control unit

PROBLEM TO BE SOLVED: To enable a motor to return to a target speed immediately even if the motor is caused to decelerate suddenly by motor load fluctuation and the like and consequently no pulse signal is outputted from an encoder continues for a long period of time, when the feedback control over the motor is carried out based on the pulse signal from the encoder. SOLUTION: Measurement results (edge period) by a period counter 61 are stored in a memory 62 every time a period pulse is inputted. On the other hand, every time an operation sampling pulse is inputted, a switch 65 outputs either one of an edge period α stored in the memory 62 and the measured value β of the period counter 61 as a detection period for operation, based on comparison result of a comparator 64. Namely, when the operation sampling pulse is inputted, the edge period α in the memory 62 is outputted as the detection period for operation if the measured value β of the period counter 61 at that time, is equal to or lower than a target period, while the measured value β is outputted if the measured value β of the period counter 61 exceeds the target period. COPYRIGHT: (C)2008,JPO&INPIT