An Encoder-Less Ultrasonic Stepping Motor Using Open-Loop Control System

Abstract

The construction of a light-load ultrasonic stepping motor for a watch device, and its angular displacement control by the open-loop control are described. In this control system, a rotary encoder as an angular displacement sensor is not used. A function of an angular displacement self-correction is added to an ultrasonic motor itself, applying a new type rotor and a new drive method. As a result, the correct setting of an angular displacement has been achieved with no use of the rotary encoder.