Traveling Wave Ultrasonic Motors Based on the Piezoelectric Shear Effect

This dissertation discusses piezoelectric ultrasonic traveling wave motors (USM) based on the piezoelectric dIS shear effect. USM produce a rotation by utilizing the high-frequency vibrations of astator which are transferred to the steady motion of a rotor in frictional contact with the stator. Over the last decades, USM have gained interest in research and application due to their advantageous properties of small dimensions, positioning accuracy and silent operation. Conventionally, piezoelectric USM are based on the d 31 or d 33 piezoelectric effect. AIthough the electromechanical coupling of the dIS piezoelectric shear effect is large for some important piezoceramic materials and is established in sensor applications, it is hardly used in ultrasonic actuators. This dissertation aims at assessing the applicability of the piezoelectric shear effect in such motors, devising appropriate models for the optimization of the same, and demonstrates the feasibility by studying a prototype of a new motor design. In this thesis, appropriate structural models are derived for different actuator geometries. These inc1ude beam and plate theories according to TIMOSHENKO and MINDLIN augmented to inc1ude the electric potential. These models serve for the ca1culation of free and excited bending vibrations due to the induced transverse shear. The inplane-shear vibrations of a plate are solved by an approximation.