Towards an Omni-directional Orientation Manipulation of Spherical Piezoelectric Motor: A Torque Vector Composition Method

This paper presents the application of a torque vector composition method realizing omni-directional rotor orientations for a novel standing wave spherical piezoelectric motor (SPM). The developed SPM system comprises four stators where each stator can provide three fundamental orientations or torque vectors implemented with the technique of electrode configuration. The concept of vector composition applied to the SPM system is illustrated with two stator actuation configurations: symmetrical and adjacent actuation stator pairs. The proposed method has the advantage of easy generation of new rotor orientations by adjusting the magnitude ratio of the excitation signals given to the stators. Composited vector analysis shows that the use of all stator pairs is able to offer omni-directional rotor orientations in the xy, yz, and xz planes. The estimated orientations in the experiments demonstrate the feasibility of the proposed torque vector composition method and the potentials of expanding omni-directional orientations to the whole 3D space with more than two actuating units.