Driving and Controlling of a Watch Device Ultrasonic Motor by Two Phase Pulse Signals

A drive and control system of a light-load ultrasonic motor for a watch device is described. The ultrasonic motor is driven with two phase pulse signals having π/2 phase differences and 50% duty cycles. An angular displacement is detected by a rotary encoder and a rotor moves a 6 deg. step per second. The experimental results using the system have proved that the light-load ultrasonic motor can be used as a stable stepping motor for a watch device.