| 摘要 |
A motor speed controlling device controls the rotational speed of a motor by feeding back an actual rotational speed, for example detected by a photocoupler. An encoder disk formed with equi-pitch slits in the periphery thereof is attached to the drive shaft of the motor, and the photocoupler is provided in association with the encoder disk. A CPU computes (S100) ON duration Ton and OFF duration Toff of pulse trains produced from the photocoupler when the motor is rotating at a constant speed. If the ON duration Ton and OFF duration Toff are unequal, ON correction and OFF correction factors alpha , beta are computed (S120) based on the measured ON and OFF durations, whereas if the ON duration and the OFF duration are equal to each other, the ON and OFF correction factors are set to one (S130). The CPU corrects the ON and OFF durations Ton and Toff based on the ON and OFF correction factors. The pulse trains nominally have a 50:50 duty ratio but this may vary due to, for example, aging of the photocoupler. The device may be used in an electronic typewriter. <IMAGE> |
