Microstepping control of ultrasonic stepping motors

The ultrasonic stepping motor (USSM) using spatially shifted standing vibrations shows the advantages of high torque, good controllability, and open-loop operation. Due to the segmentation problem of piezoelectric materials, the corresponding step size is practically limited. The purpose of this paper is to propose and implement microstepping control of this USSM. Different from the available half-step operation, the proposed control simultaneously varies both the combination of phase excitations and the magnitude of applied voltages in such a way that the desired step size can be attained. Digital implementation and experimental verification are given to validate the proposed microstepping control.