Patent ID: 9148076
Filing Date: 2015-09-29
Classification: B25J,H02N,Y10T

Abstract:
1. A method for driving an ultrasonic motor that is driven by applying an alternating-current driving voltage, the method comprising: setting, in a memory, an upper limit rotation speed that is lower than a rotation speed at a resonance frequency at a lowest temperature of a predetermined operating temperature range and a lower limit frequency that is more than or equal to a resonance frequency at a highest temperature of the operating temperature range; wherein when the ultrasonic motor drives, a rotation speed of the ultrasonic motor detected by a rotation detection device becomes lower than the upper limit rotation speed and a frequency control circuit outputs a driving frequency which is higher than the lower limit frequency, and wherein the upper limit rotation speed is set to a speed between the rotation speed at the resonance frequency at the lowest temperature of the operating temperature range and a maximum value of a target rotation speed given when the ultrasonic motor is driven.