Design And Experimental Research On A Spherical Stator Multi-DOF Ultrasonic Motor

This project is based on the design of the compact structure of the driving system,high power density,and the convenience of serialized design of the system.A structure with a spherical shell as the stator of the multi-DOF ultrasonic motor and high symmetry and miniaturization has been designed.Firstly,the research status of multi-DOF ultrasonic motor at home and abroad is analyzed.A spherical stator multi-DOF ultrasonic motor is designed.The scheme of the stator structure and the rotor structure is proposed,and the working mode is determined to be the non-axisymmetric vibration mode.The cooperative drive of the eight driving feet is proved by the method of mathmatics.The stator structure adopts a piezoelectric ceramic ball shell pasted with eight driving feet.The piezoelectric ceramic ball shell is polarized along the thickness direction of the ball and divided into six electrode regions and one non-electrode region.The six electrode regions are excited from three mutually orthogonal directions.Three non-axisymmetric vibration modes are orthogonal to each other and they are the same modes,which avoids the problem of the superposition of the different vibration modes.The rotor structure adopts two hemispherical shell structures,and the spring is connected to the rotor to apply and adjust the pre-tightening force.The two hemispherical shells are positioned by the positioning pins,and the load is applied to the motor through the load block.Furthermore,the multi-DOF ultrasonic motor with spherical stator is simulated by finite element method.The modal analysis is used to complete the selection of the vibration modes of the motor and find the available modes to realize the drive of the motor.The impedance characteristic curve of the motor is obtained through the harmonic response analysis.The electromechanical coupling efficiency and mechanical quality factor of the motor are analyzed,and the motor 's performance is estimated through these two parameters.Through the transient analysis,the end-to-end vibration trajectory of the eight driving foots is extracted.At the same time,the feasibility of cooperative drive and the principle scheme of the motor is verified.Finally,according to the special structure of the spherical stator,the corresponding structure of the motor and the supporting structure of the motor are designed in this paper.The prototype of a multi-DOF ultrasonic motor with a spherical stator is also fabricated.To test the mechanical output characteristics of the multi-DOF ultrasonic motor with a spherical stator,this paper design ed a mechanical output characteristic test platform for the multi-DOF ultrasonic motor with a spherical stator.When the amplitude of the excitation voltage is 100 V,the frequency is 31.7k Hz and the pre-tightening force is 8N,the maximum no load speed of the motor is 200r/min,198r/min and 250 r/min respectively and the maximum load torque is 10.8 m N·m,11.0 m N·m and 12.3 m N·m respectively in the x-axis direction,y-axis direction and z-axis direction.