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To increase the mechanical output ability of a rectangle-shape linear piezoelectric motor with four feet, an improved motor is designed in this study. The improved motor inherits the basic structure of the previous one, but the structure dimensions are adjusted by widening the horizontal beam, shortening the length of the vertical beam׳s uniform part, increasing the length of the vertical horn, and changing the widths of the horns׳ tips. Modal analysis and transient analysis are developed to gain the vibration modes of the motor and the motion trajectories of the driving feet, respectively. After the fabrication of a prototype, its vibration characteristics and mechanical output ability are measured. Experiment results show that a maximum no-load speed of 621 mm/s, a maximum thrust force of 11 N, and a maximum power of 1.9 W are achieved by the prototype. Comparison between the improved motor and the previous one verifies that this study accomplish the design intention of mechanical output ability improvement perfectly.

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 proposes and studies a new rotary ultrasonic motor, which consists of one square-type metal frame and eight pieces of PZT ceramics. Four metal beams with exponential shape horns are located in square-type to form the enclosed frame. The PZT ceramics are bonded on the upper and lower surfaces of the four beams respectively. By applying sine and cosine signals on the PZT ceramics, the longitudinal vibrations of the piezoelectric-metal composite beams can be generated alternately, which can produce circular movements on the four feet located at the corners of the square-type metal frame. The structure, working principle, design, and analysis of the proposed ultrasonic motor are introduced. Vibration characteristics and mechanical output performance of a prototype are measured to verify the feasibility of the proposed design. Maximum speed and torque of 106 rpm and 0.29 N · m are achieved by the prototype.

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 .

In a previous study, the authors have proposed, designed and fabricated a cylindrical traveling wave piezoelectric motor excited by a longitudinal and bending hybrid composite transducer. This study focuses the research on the vibration coupling problems of the proposed stator. After the introduction of the working principle of the motor, harmonic analysis is developed to gain the input impedance characteristics of the longitudinal and bending vibration modes of single transducer; the electromechanical coupling factors are calculated to evaluate the energy transfer efficiency. Then, the input impedance characteristics of the two vibration modes of the stator are analyzed to gain the corresponding electromechanical coupling factors. At last, the resonance frequencies of the transducer and cylinder are adjusted to obtain their effects on the electromechanical coupling factors. The study results can guide the design of traveling wave motors that utilized sandwich transducers as actuators.