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A U-shape linear piezoelectric motor with double driving feet is proposed and tested. It adopts bonded-type structure to realize the miniaturization. Six pieces of PZT ceramic plates are bonded on a U-shape duralumin alloy base to form the motor. This structure makes it has simple fabrication and assemblage processes. The proposed motor produces elliptical movements on the two driving feet by the superimposing of longitudinal vibrations. The resonance frequencies of the two vibration modes are tuned to be close at about 54 kHz. Transient analysis is developed to illustrate the movements of the driving feet. The vibration characteristics of a prototype are measured by a scanning laser Doppler vibrometer. The no-load speed and the maximum output thrust force of the prototype are tested to be 765 mm/s and 7.3 N, respectively. The weight of the miniaturized U-shape piezoelectric motor is about 0.026 kg; its power density is about 6.4 times that of the previous one with bolt-clamped structure.

This study intends to present and verify a new idea for constructing rotary piezoelectric motor that utilize multi-bending vibrators to achieve high output power. The vibrator in the proposed motor contains two exponential shape horns located on the two leading ends; two groups of PZT elements are clamped between the two horns by a flange with double head bolt. Two second-order bending vibrations, which are orthogonal in space, are excited by the two groups of PZT elements respectively and then superimpose in the vibrator to produce elliptical movements at the two driving tips. Six vibrators are fabricated and tested using a scanning laser Doppler vibrometer; four of them with closer resonance frequencies are selected to construct the rotary motor. The output abilities of motor with single vibrator, two vibrators and four vibrators are measured respectively; a maximum no-load speed of 298 r/min and a maximum torque of 9.3 N m are achieved under four vibrators driving. It is easy for the proposed motor to change its mechanical output characteristics by changing the number of the vibrators and the diameters of the rotors, which states its practicability.

This paper presents and verifies a new idea for constructing rotary ultrasonic motor that may effectively make use of the longitudinal vibrations of the bolt-clamped transducers. Based on the idea of generating elliptical motion on the driving tip by superimposing longitudinal vibrations, a square-type rotary ultrasonic motor with four driving feet is proposed. This new motor consists of four longitudinal vibration transducers, which are located in square-type and form an enclosed construction. The longitudinal vibrations of the four transducers are superimposed to produce the same circular movements on the four feet, which can push the rotor into motion when a preload is applied. By using FEM method, the proposed motor is designed and analyzed, and circular trajectories on the driving feet are gained. The vibration and input impedance characteristics of the motor are measured after the fabricating of a prototype, and the test results are in good agreement with the FEM analysis results. Typical output of the prototype is no-load speed of 71 r/min and maximum torque of 12.3 Nm at an exciting voltage of 200 V rms .