Torsional inchworm ultrasonic piezomotor combining continuous rotation with precise control over angular positions and high torque output

The paper describes a piezoelectric motor that combines the merits of piezoelectric materials, such as high power density generated at electromechanical resonance, and a precise control of displacement. The motor utilizes a direct coupling mechanism between the stator, which is based on the shear piezoelectric response, and rotor, where a clutch drives the rotor via locking it. The direct coupling makes it possible to transmit the whole power generated in the piezoelectric element to the rotor, and thus achieve the high efficiency of the motor. It also allows combining two regimes of operation: continuous rotation and a stepwise motion within a 360° interval with a high resolution of angular displacement.