Research On A New Type Of Modulated Rotating Piezoelectric Motor

Because of the large sliding friction and short service life of contact piezoelectric motors,two kinds of new modulated rotary piezoelectric motors are proposed in this paper,a noncontact piezoelectric motor modulated by electromagnetic force and a rotary motor modulated by piezoelectric stack.The sliding friction between the stator and rotor of the motor is reduced,and the rotary motor modulated by piezoelectric stack can significantly improve the output torque per unit volume while reducing the sliding friction.Therefore,it has a good development prospect.This paper introduces the structure and working principle of two kinds of new modulated rotary piezoelectric motors.The electromechanical coupling statics equation of the piezoelectric motor system is derived from statics,the output torque and output speed of two kinds of new piezoelectric motors are studied,and the influences of system parameters on output torque and output speed are analyzed.The transfer function of the output torque of two kinds of new piezoelectric motor systems are established,and the influence of mechanical parameters and electrical parameters on the transfer function is analyzed.The step responses of the motor system are analyzed,and the dynamic response characteristics of the output torque are studied.PI controller and voltage compensation are used,so that the motor system obtains ideal dynamic response characteristics.Based on the continuous system vibration theory and multi-degree-of-freedom system vibration theory,the electromechanical coupling dynamic equation of two kinds of new piezoelectric motor systems are established,and the natural frequencies and vibration modes of the system are obtained.The main vibration modes at different natural frequencies and the changes of the first two natural frequencies with structural parameters are analyzed.Considering the nonlinear piezoelectric effect in the piezoelectric stack and the geometric nonlinearity in the multi-degree-of-freedom system,the nonlinear coupling dynamic equations of two kinds of new piezoelectric motor systems are established,and the nonlinear free vibration,forced vibration and chaotic vibration of the motor system are analyzed.The nonlinear natural frequency,amplitude-frequency characteristic curve,dynamic response curve,bifurcation diagram and maximum Lyapunov exponent diagram of the system are obtained.Two prototypes of new piezoelectric motors are designed and manufactured.The working principle of the motors is verified by experiments,and the motors output characteristics are tested.The experimental results are compared with theoretical calculations.The results show that the maximum output torque of the noncontact piezoelectric motor modulated by electromagnetic force is 3.72 N·mm.The maximum output torque of the rotary motor modulated by piezoelectric stack is 21N·mm.The output torque per unit volume of the rotary motor modulated by piezoelectric stack is about 34 times that of the noncontact piezoelectric motor modulated by electromagnetic force,and about 4.69～18.59 times that of some newly reposted contact piezoelectric rotary motors,which reduces sliding friction and obtains a larger output torque per unit volume than the existing contact piezoelectric motors.The error between the experimental results and the theoretical results is small,which verifies the correctness of the theoretical analysis and the proposed driving principle.