Researches On Modeling And Validation Of Ultrasonic Motor

In contrast to traditional electromagnetic motors, ultrasonic motors provide co- mpact design, larger torque to volume ratio, high precision, high holding torque in the absence of applied power, silent operation and faster response. However, the de- velopment of ultrasonic motors has been limited in precision mechanical and servo systems, primarily due to the particularities of construction and movement principle. And ultrasonic motors exhibit strong nonlinear response during operation. To be ap- plied in precision electromechanical servo system, the present dissertation proposes a comprehensive equivalent circuit model for the purpose of prediction the motor per- formance, including governing characteristic and mechanism characteristic. And to test the model experiments were designed. The model is very usefull for controller and driver development.Firstly, the energy transfer process between electric energy and mechanical energy are discussed in detail in this paper. And the piezoelectric effect in ultrasonic motors, the principle of traveling wave and the fundamental of elliptical motion are analyzed. There are three speed regulation methods which include voltage amplitude, frequency and phase. The theoretical derivation and analysis of each method are discussed.Secondly, based on the energy transfer process, combined with Mason's model, the equivalent circuit of a free stator is set up. Considered the preloaded force and the friction force synthetically, the equivalent circuit of ultrasonic motors is built. The inputs of the model are the two driving voltage signals; the output is the current signal which is reflected to the speed of the motor. The model includes three parts, as follows the model of the stator, the model of the contact area and the model of the rotor. The equivalent circuit can be used in the qualitative analysis of the governing characteristic and mechanism characteristic.Thirdly, based on the equivalent circuit of ultrasonic motors, the simulation analysis is carried out. And the test platform is put up. By contrast with the simulation results and the test results, the correctness of the model is verified.