| 摘要 |
PURPOSE:To drive an ultrasonic motor even at the time of high temperature or a high load by providing frequency monitoring means for monitoring whether the frequency of a high frequency voltage reaches a predetermined frequency or not, and reference value altering means for lowering a reference value if the monitoring means detects that the frequency reaches a predetermined frequency. CONSTITUTION:When a start switch is closed at the time of a high temperature, even if a driving frequency is lowered, since the vibrating amount of a stator 1 is lowered, the vibrating amount of the stator 1 does not reach a reference vibrating amount. Thus, the driving frequency becomes a lower limit, and the rotation of an ultrasonic motor is stopped. Then, a microcomputer 4 reduces a reference vibration amount, and sets the driving frequency to an upper limit frequency. The vibrating amount of the stator 1 soon reaches the reference amount, and the motor is driven by the optimum driving frequency. Even if a high load is connected to a moving element, the vibrating amount of the stator 1 is lowered, but it is operated as above. Thus, the motor can be driven at the optimum driving frequency even in the case of high temperature or a high load. |
