Working Principle And Optimization Of Bi-directional Composite Ultrasonic Linear Motor

Ultrasonic motors (USM) are developed as novel effective actuator in the field of miniature applications, which are composed of the stator and the rotor and converting ultrasonic vibration to driving force through friction. The piezoelectric wafer is bonded with an elastic body to constitute the stator. The ultrasonic motor is quite different from the electromagnetic motor; its driving torque isn't got by electromagnetic interaction. The fundamental operation mechanism of ultrasonic motors is based on microscopic material deformations and macroscopic friction drive.Compared to the conventional electromagnetic motors, these motors have unique characteristics such as insensitive to the magnetic fields, simple construction, high torque density at low speed, high power, precise positioning, fast response characteristic. Such unique characteristics make ultrasonic motors promisingly have the best prospect.Though differences exist in the styles and functions of the ultrasonic motors that have been developed, the key component—the elastic vibration body is usually made of isotropic material. In order to produce the so-called"Elliptical Movement"that cause the motor to act, the combination of vibration patterns or the spatial distribution of exciting vibration points must be used. This would result in the complexity of the motor and the difficulty in the design and debug of the whole system. This thesis developed a sample linear ultrasonic motor whose vibration body was made of anisotropic composite, and its Actuating Mechanism, Material Characteristic, Finite Element Modal,harmonic and transient Analysis were studied theoretically and experimentally to design and optimization its structure.Based on the analytical solution of the CFRP's vibration model, The Finite Element Method was employed to perform the analysis and the model of the piezoelectric wafer and composite material CFRP (Carbon Fiber Reinforced Plastic) was established. The finite modal analysis's conclusions had a vital theoretical guidance for the designing of the motor's vibration body and driving. Several phenomena were summarized as follows: the converse piezoelectric effect of the piezoelectric and the have its displacement excited by the external electric field , the proper thickness of the piezoelectric wafer was selected; the simplest vibrating model at B(1,1) , two degeneration resonant frequencies at B(1,1) vibration modals, and reverse equivalent stress distribution during the actions at the two degeneration resonant frequencies were proved by the modal analysis; Further analysis as the response amplitudes and ranges were calculated by harmonic analysis; the motor worked at the B(1,1) vibration mode will have the best velocity of the two reverse moving directions and wider frequency range. Through comparing the dynamic simulation of the CFRP with different carbon fiber angles, it was indicated that the carbon fiber angles of CFRP should be close-by 45-degree in order to gain a biggish adjustable range of the bidirectional rate. According to the fact that the two-resonant-frequency corresponded the CFRP's two-vibration direction; the prototype motor was made and tested, and it is effective to design and simulate the structure and characteristics of the motor by using the FEM.