Abstract
A hybrid transducer-type ultrasonic motor serves a high controllability, since the driving force can be controlled independently of the friction controlling component. The torsional vibration velocity has a direct effect on the speed, while the longitudinal vibration controls the traction transmission through friction. We can change the speed smoothly, if we vary the torsional vibration velocity, with the longitudinal vibration being maintained at the optimum value.
This paper presents an experimental study of a speed control system for a hybrid transducer-type ultrasonic motor. First, we utilize an optical rotary encoder to measure the speed of the rotor, and it is feedbacked to the excitation magnitude of the torsional vibration. Stability and transient responses of the speed are improved. Second, we point out that the speed has a linear relation to the current of the torsional port. Then, by monitoring the current, a feedback system can be built without any auxiliary encoders.
