| 摘要 |
PROBLEM TO BE SOLVED: To positively prevent a speed detector from detecting malfunction erroneously, for higher operating efficiency by stopping a torque command when such a condition that rotational speed is zero continues for over a fixed period, and determining that a speed detecting means is normal when detected that the rotational speed is not zero at the time of stopping the torque. SOLUTION: The rotational speed of a motor 4 is converted into a pulse by a speed detector 5 and is sent to a pulse count unit 7d, where the number of pulses are counted and a counted value is sent to a CPU 7A. When the rotational speed is zero for a preset period with door stopping caused at a prescribed point, the CPU 7A involves a torque stop means which sets a speed command value sent to a pulse width modulation unit 7F and a torque command value to zero. After the prescribed period passes, rotational speed in the opposite direction is generated by the reaction where the driving force to the motor 4 is lost. It is determined as no failure in the speed detector 5 if the CPU 7A determines that the speed detector 5 detects the rotational speed in the opposite direction at another preset time.
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