Research On The Fundamental Technology Of Multi Degree-Of-Freedom Traveling-Wave Type Ultrasonic Motor

Recently, motors with multi degree-of-freedom have been of significant research interests. There are many progress in such research towards basic principle, structure, working mechanism and control etc, especially for ultrasonic motor with multi degree-of-freedom. Ultrasonic motors have many advantages in according with traditional induced spherical motor such as high torque in low speed, high precision and direct driving, which is suitable for the joints of robots, two degree of freedom CCD driving systems etc. In this paper the mathematical model, the construction, driving and control principles and realization of multi degree-of-freedom ultrasonic motor are introduced.In the fisrt chapter, the history and the present situation of multi degree-of-freedom ultrasonic motor are introduced. Then the structure, the working mechanism, the property and the application prospect and control methods of spherical ultrasonic motor are also discussed. Four kinds of motors are discussed in different points of view. Multi degree-of-freedom ultrasonic motors have many advantages in compared with other ones. Then the scientific and engineering problems of ultrasonic motor with multi degree-of-freedom and research object and content are presented in this paper.In the second chapter, the mathematical model of three degree-of-freedom spherical traveling type ultrasonic motor is introduced. In order to get its motion rule, statics analysis of motor should be discussed. The driving mechanism and basic structure of this kind of ultrasonic motor are introduced. The coordinate transformation model and the position relations of rotor and stators of spherical ultrasonic motor are also set up. Then the stress of the rotor and the contact force of the rotor and the stators on the contact circle are also analyzed. In according with the force balance equations of its stator and rotor, the relation of micro displacement of the center of rotor and axial compaction and preload force of stators are presented. On the basis of that, the distribution of the force on the contact area can be got when the rotor rotates. The frictional driving torques are analyzed. The velocity is decomposed at the tangential and the normal direction , the driving torque and the frictional torque of the stator are calculated. By solving the balance equations of rotation the frictional and driving torque are calculated. The model is analyzed by simulation and the results are used for setting up designing theory of three degree-of-freedom spherical traveling type ultrasonic motor.In the third chapter, the dynamic characteristic measurement sytem of ultrasonic motor are introduced. It can be used for quick dynamic process of ultrasonic motor. The system can be used for dynamic characteristic measurement for multi-degree-of-freedom ultrasonic motor. Some basic problems of measurement sytem are solved in this chapter. Then a novel control system which is based on neuron adaptive PID and combined with phase difference and frequency control is introduced, since the ultrasonic motor is a system of severe non-linearity and parameter variations. The parameters of neuron PID controller can be changed its online when the operation conditions change. The control characteristic can be changed automatically to realize the speed and position control. The experiment results show that ultrasonic motor can do rapid response speed and precise position control while using neuron PID controller.In the fourth chapter, two degree-of-freedom spherical traveling wave type ultrasonic motor was designed. The mathematical model for three degree-of-freedom spherical ultrasonic motor can be used for the two degree-of-freedom spherical traveling wave type ultrasonic motor. Then the model is verifird by simulation results of the two degree-of-freedom spherical traveling wave type ultrasonic motor ultrasonic motor. The working principle of the two degree-of-freedom spherical traveling wave type ultrasonic motor is presented. Some basic problems of motor are to be presented. Then the optimal structure of stator and the tuning devices are explained. This paper presents centering adjustment device and stator with big rake angle on outer edge and small rake angle on inner edge and tuning method of adjusting rake angle on outer edge of stator. The diameter of prototype motor is 45mm in rotor and 30mm in stator, the maximum output torque is 120mNm, the maximum speed is 12r/min. From the above discussion and the practical experiments availability of devices is to be verified.In the fifth chapter, the driving and the position control system of the two degree-of-freedom spherical traveling wave type ultrasonic motor are introduced. Firstly, phase-difference driving system is also set up and can be applied for multi degree-of-freedom spherical traveling type ultrasonic motor. Secondly, a motion attitude control system is set up for the two degree-of-freedom spherical traveling wave type ultrasonic motor, through experiments the driving and position control system is to be verified feasibly and can be got high position accuracy less than 3%.This thesis is useful for optimization designing theory and performance improvement of multi degree-of-freedom spherical traveling type ultrasonic motor.