Research On The Several Key Problems Of The Traveling-Wave Type Ultrasonic Motor

The traveling-wave type ultrasonic motor (TWUSM) has been put into application in the fields of robot, instrumentation, industrial control, precision positioning and aerospace for its high torque, low speed and smooth operation. From the research and development of the TWUSM, the trend of the TWUSM is to acquire high-torque, high precision, high stability and high reliability. In order to improve the performances and accelerate the practical process of the TWUSM, several key technologies, such as the driving model, the friction and the noise mechanism, the structure design, the manufacture craft, etc, should be studied deeply and systematically in this thesis. The research work and the creative achievements of the thesis are as following:The analytical model of the TWUSM was put forward based on the energy equivalent principle. The simplified equivalent composite beam model of the stator was obtained at first;the frequency-equation and the equation describing the amplitude of transverse vibration were established by Timoshinko beam theory. And then by using the Coulomb friction law, the force transfer model of the contact surface between the stator and the rotor was derived;the inter-relationship between contact angles, the frictional material characteristic, the preload and the vibration amplitude were analyzed. According to the energy equivalent principle, the friction loss between the contact surface and the outputting power of the rotor regarded as one of the parts of the equivalent damp loss of the stator vibration were applied to achieve the efficiency of the TWUSM. Finally, all the factors, such as preload, driving frequency and friction layer, influencing the mechanical characteristics were analyzed, and the accuracy of the analytical model was verified by comparison with the experimental results.The noise mechanism of the TWUSM during its operation was studied. The relationship among the noise frequency, the stator's natural frequency and the driving frequency was analyzed by the finite-element method and experiments, and the friction self-exciting vibration model of the motor noise was proposed by nonlinear vibration theory. The influence of the preload, the fractional material characteristics, the driving frequency and the matched induction to the noise was analyzed, and some measures have been put forward to depressing the noise intensity. All the research findings support the theory and the experiment for improving the structure of the TWUSM.The creative research work on the temperature characteristics of the TWUSM was done. At first, the surface temperature rising expression of the TWUSM is derived based on the heat transfer principle and the mathematical model created in chapter 2. Several factors that influence the surface temperature rising of the TWUSM, such as the driving voltage, the driving frequency, the frictional material characteristics and the preload, were discussed. Then the temperature-frequency characteristic and the temperature-speed characteristic were studied. Finally, the effects of temperature to the rotary speed, the resonant frequency and the mechanical performance of the TWUSM were creatively studied with experiments, and the methods of reducing the heat of theTWUSM were presented according to the experimental results.The structure design method of the TWUSM was proposed based on FEM and the scale effect of the performance of the TWUSM;a new type structure TWUSM that was composed of an oblique-spline stator and a flexible rotor was designed. In order to increase the outputting torque of the TWUSM, double stators and double rotators were proposed.The creative research work on the TWUSM friction material was done based on the modified-nanometer technology. And a new compound method of the friction material, Viscosity-Coating method, was put forward to improving the strength of the friction material and decreasing the output heat of the TWUSM. Focusing on the bonding of the piezoelectric ceramic of the TWUSM, the effects of the material characteristics and the thickness of the adhesive layer on the vibrating performances of the stator were studied based on the electromechanical coupling finite element model of the stator. And the resisting-shear and vibrating performances of the adhesive layer at different exciting conditions were deeply analyzed. The methods of improving the bonding quality of the piezoelectric ceramic were presented.Series of TWUSM prototypes in dimension of 80mm, 60mm, 45mm, and 30mm are developed successfully based on the theories and experiments. All the researching results can improve the performances and propel the practical process of the TWUSM in our country.