The Theoretical Analysis And Experimental Research Of Energy Harvesting Type Ultrasonic Motor

Ultrasonic motor (USM) has an excellent electromechanical coupling performance with simple structure and big mass/torque ratio. It has widely applied in many areas, such as aerospace, medical equipment, micro robot, deep-sea exploration and so on. Especially in some special circumstances, ultrasonic motor has replaced the electromagnetic type motor.Because the USM is driven by the friction force of the contact surface between the stator and the rotor, there has more energy lost during the operating period, which leads to a serious heating phenomenon and a decrement of motor performance. In order to improve the performance of USM and to reduce the energy loss, this paper proposes a new type of USM with the ability of vibration energy harvesting. The new type USM is called energy harvesting type USM (EH-USM), it integrates with the functions of precision driving and energy harvesting. Establishing the whole electromechanical coupling model of the EH-USM is very important to analyze the output performances, as well as to optimize the structure of the EH-USM.The main research contents of this paper include:Part Ⅰ, the general reviews of USM and the basic theory knowledge that this research subject covered, such as piezoelectric theory and beam’s bending vibration theory and so on, are described.Part Ⅱ, This part includes three aspects of the research. Firstly, the composition structure and working principle of EH-USM is described, the electromechanical coupling model and dynamics equation is established based on the stator’s lumped parameters of EF-USM. In addition, the key parameters of the model is defined by finite element method and curve fitting, Some simulations and analysis of output features of the stator (such as the feature of vibration displacement) are studied by using MATLAB/Simulink. Secondly, the stator and rotor’s contact principle of EH-USM is described, and then the force transferring model of the contact area of between the stator and rotor are derived according to the sticky elastic friction theory. At last, the whole electromechanical coupling model of EH-USM is built; several simulations are carried out to study the effects of the pre-presses, exciting voltage and frequency on the mechanic performances.Part Ⅲ, The energy harvesting model of the EH-UEM is derived based on the direct piezoelectric effect of PZT and the bending vibration theory of beam. Furthermore, the harvesting performance is simulated in MATLAB/Simulink. Ultimately, the effects of the vibration frequency and exciting voltage on the harvesting output voltage, current and output power are analyzed in detail.Part Ⅳ, The equivalent circuit model of EH-USM stator is studied. The parameters are identified based on the motor stator impedance characteristics and admittance circle. And then, the impedance characteristic experiment system of the EH-USM is established. Finally, a comparative analysis of the model parameters obtained from the experimental results and theoretical simulation is conducted to testify the validity of the theoretical model.