| 摘要 |
PROBLEM TO BE SOLVED: To reduce rotational speed change and to realize an accurate rotational speed by detecting a frequency difference between a detection pulse train and a reference pulse train, detecting a phase difference between a detection pulse and a reference pulse, and increasing or decreasing a rotational speed of a rotary drive source, based on the detected frequency difference and phase difference. SOLUTION: A frequency difference detector 4 detects a frequency difference between a detection pulse output from a sensor S and a reference pulse train, and a phase difference detector 3 detects a phase difference between the detected pulse and a reference pulse. The rotational speed of a DC electric motor 9 is increased or decreased by a charge pump circuit 5 of a rotational speed increasing or decreasing means, low-pass filter 6 and a PWM circuit 7, based on its frequency difference and its phase difference. Thus, a rotational speed change can be reduced, without depending upon a flywheel. Even in the case of using a traction reduction gear having unfixed reduction gear ratio, the rotational speed of a rotor is used as a feedback signal, and hence accurate rotational speed can be realized. |
