Study On The Longitudinal-Torsional Ultrasonic Motor

Ultrasonic Motor (USM) as a new type of motor that has beingdeveloped quickly in recent years at home and abroad. It's a driving device that is drove by ultrasonic vibration. USM is often composed with stator and rotor. The stator produces ultrasonic vibration that is then delivered by rotor through the friction between stator and rotor. This kind of vibration can be changed into continuous revolution or linear move; it's the way USM works. One unique character of USM IS that no electromagnetic coils are used in them, instead the interference of coils, the PZT's effect is used as the energy to produce ultrasonic vibration, which is amplified and changed into rotor's moving. So you can see stator (by made of P2T) replaces the millions of electromagnetic coils. It has many advantages comparing with the traditional electromagnetic motor, such as high torque and low speed, high-energy volume ratio, short response time, no interference of electromagnetism, etc. It has prospect in the field of aviation, precise instrument and robot, etc. Moreover USM itself don't produce magnetic field, but high torque and low speed, high-energy volume ratio. It cost less and has been used in the camera. It can work at the speed of several rpm to several hundred rpm, no need of the gears to change its speed. For this, many problems resulted from gears such as big noise and low efficiency can be avoided. Now we regard USM as a novel intention, which not only makes a breakthrough of the traditional mechanical motor, but also supplements and enriches our transfer tools.Longitudinal-Torsional ultrasonic motor has great advantages in good control, high power output, high torque and low speed, high-energy volume ratio, etc. And has been attach importance in this field. In this paper, the driving mechanism, frictional contact, mathematical model, and vibrate frequency annexing is studied systematically and theoretically.(1) The driving mechanism of the standing wave motor is analyzed in detail, the optimal driving status in various pressures is obtained, and its diving character is given qualitatively.(2) A new frictional pattern has been taken up, and its newly mathematical model is introduced according to this pattern. Base on this model, the motors characteristics are simulated, the conclusions show the small contact angle is benefit to improve the output character and efficiency.(3) A theoretical matrix four-terminal-network method has been presented, and been used to design the longitudinal-torsional ultrasonic motor. The degeneration of the longitudinal and torsional response frequency is achieved. The calculated results have been compared where network method and Finite-Element-Method have been used. And the optimum parameters have been given.