Finite Element Analyses On Ultrasonic Motor Driving Fluid Directly

Compared with the contact type ultrasonic motor, the non-contact type one resolves the problems caused by friction, such as shorter life expectancy and continuous running time. Therefore, it becomes a new research direction in the field of ultrasonic motor. The motor introduced in this paper is a non-contact type ultrasonic motor with fluid medium. The rotor swimming in fluid isn't in contact with the stator directly. The energy produced by the piezoelectric vibration is transferred from the stator to the rotor through the fluid medium, which rotates the rotor.Several subjects in relation to the structure and the operating principle, vibration of the stator, acoustic streaming field and saturated flow velocity are covered. At first, the development and application of ultrasonic motor are briefly reviewed. The background as well as the status of the research on the non-contact type ultrasonic motor is highlighted. Then, the motor structure and the operating principle are proposed. The unique structure of the motor is analyzed in detail. The production of the vibration, the formation of the standing wave, the combination of the traveling wave and the process of energy transmission in the fluid are discussed. Next, finite element method (FEM) is adopted to analyze the vibration of the stator. Starting from the characteristics of the structure and operating mechanism, numerical simulation of the vibration is conducted. After that, a new finite element method based on the nonlinear wave equation derived by Kuznetsov is applied to simulate the acoustic streaming field. At last, saturation of the acoustic streaming is highlighted. It is revealed that acoustic nonlinearity is the main cause of saturation of the acoustic streaming velocity, which is analyzed from the nonlinear acoustics later. Based on the numerical analysis, the saturated flow velocity is discussed further.