Theoretical Research And Design Of Ultrasonic Motor

An ultrasonic motor is a kind of driving machine which obtains dynamic in virtue of use friction to transfer elastic ultrasonic vibration. It is a kind of motor with a completely new driving principle to obtain turning force. The motor converts a piezoelectrically excited resonant vibration of the stator into a rotational movement of the rotor by frictional forces. As compared with conventional electromagnetic motor, the ultrasonic motor possesses the following features: compactness in size, high-torque at a low-speed range, fast response, insensitive to magnetic fields, high holding torque when power is off and so on. So it is fit for fully utilized for substitutional purposes, mainly in the areas such as actuators of devices for robots, precise positioning devices, miniaturized machines, aerostat and spacecrafts. Since the ultrasonic motor has the excellences that differ from those of the electromagnetic motors and has the wide application foreground, more and more scientists and scholars are enchanted. And it is becoming a new and advanced theme in the world.This paper mainly studied a piezoelectric ultrasonic motor of rotary type, and an ultrasonic motor with multiple reeds was bettered. The following is the basic content.The development of the piezoelectric ultrasonic motor in foreign countries and in China is systematically reviewed. The features and class are summarized. Its scientific purport and application foreground are introduced also.The core of the piezoelectric ultrasonic motor, piezoelectric ceramic is systematically researched. Based on the piezoelectric effect, the piezoelectric equations are derived. From the piezoelectric equations, the important parameter of the piezoelectric ceramic's physical performance and the system equations of the vibrator are derived.The movement mechanisms of the ultrasonic motor are deeply investigated. The movement inbeing of the ultrasonic motors, two type form method of elliptical movement are deeply investigated. Its driving mechanism is studied also by geometric method. The ordinal progressing condition of a forced traveling wave in the elastic plate is investigated.The model from the input to the output of the piezoelectric traveling wave ultrasonic motor is established by synthetically using Lagrange-Maxwell equation, Hertz elastic contact theory and Coulomb friction theory, along with considering electromechanical coupling, influence of the interface force between the stator and rotor of the motor on the amplitude of the traveling wave inside the stator and dynamic contact friction friction force.Based on the theory above, a rotary piezoelectric ultrasonic motor was successfully designed. A new analysis model of the contact between the stator and rotor was first put forword as well, which enriched the theory of ultrasonic motor.An ultrasonic motor with multiple reeds is studied and manufactured, its characters are superior to the motor of the same type which is formerly manufactured.