PURPOSE: To allow a motor to be controlled stably and precisely, by letting a speed estimate value be a feedback signal when no output of a position detector varies for the time longer than a sampling period.
CONSTITUTION: A current command value Ir is calculated using a speed command value Nr and a speed feedback value Nf by a speed control operation 2 of a microcomputer 1. A pulse Ep generated by an encoder 9 is converted into a rotating speed detection value Nd and a rotating position detection value Pd by a positional speed detection circuit 10, a speed detection operation 3 and a position detection operation 5. A speed estimate operation 4 determines a speed estimate value Nd' in accordance with a current command value Ir, a speed detection value Nd and a position detection value Pd. A speed feedback signal Nf is changed over to a speed estimate value Nd' in a low speed when no output pulse of the encoder 9 will come to change in a sampling period of speed control.
KUBO KENJI
OMAE TSUTOMU
