Design And Analysis Of Electromagnetic-Piezoelectric Hybrid Driven Multi-DOF Motor

Traditional motor generally realizes single-degree-of-freedom motion,and its motion principle and control method are becoming more and more mature.With the continuous development of science and technology,the traditional single-degree-of-freedom motor can not meet the needs of further development of electromechanical system.As a kind of special motor with high integration,small volume and high positioning control accuracy,multi-degree-of-freedom motor is suitable for bionic joints,medical devices and multi-degree-of-freedom motion platform,which has become a new research hotspot.At the same time,the complexity and intelligence of industrial production tasks promote the transformation from single-degree-of-freedom system to multi-degree-of-freedom system.The piezoelectric driven multi-degree-of-freedom motor has the advantages of low noise,no electromagnetic pollution,small and light weight,high mechanical integration,good output characteristics and various forms of motion,and is especially suitable for working in low speed and large torque occasions.However,the linear displacement driven by piezoelectric actuator has small actuating stroke and high driving voltage,so it is not suitable for continuous motion occasions.The control principle of multi-degree-of-freedom motor driven by electromagnetic actuator is mature,with wide output range and long service life.However,electromagnetic driven multi-degree-of-freedom motor has the characteristics of low integration,large volume,meanwhile,accurate control of magnetic field and positioning is always a difficulty.In view of the disadvantages of the above two driving methods,an electromagnetic-piezoelectric hybrid driven multi-degree-of-freedom motor is proposed by combining electromagnetic drive and piezoelectric drive.By coordinating the two driving modes,the control accuracy and the reliability of the motor can be improved.Finally,the advantages of the two driving modes can be integrated.It not only has the high speed,high thrust,high reliability and long life of electromagnetic driven,but also has the high dynamic response(millisecond level),high control accuracy and passive self-locking of piezoelectric driven.In this paper,a novel electromagnetic-piezoelectric hybrid driven multi-degree-of-freedom motor structure is studied,which can be used in astronomical telescope,image stabilization control and satellite imaging.The structure and working principle of the motor are introduced,and the finite element simulation model of the motor is established by using the finite element multi physical field coupling software.Modal analysis,harmonic response analysis,transient analysis and magnetic field analysis are carried out for the stator and rotor.The structure parameters with high driving performance correlation,such as the tooth height of the piezoelectric traveling wave stator,the thickness of the elastomer,the thickness of the rotor spherical shell and so on,are analyzed parametrically.The magnetic field finite element model of the permanent magnet is established,and the magnetic field distribution of the permanent magnet under different magnetization methods and the air gap flux density distribution of the permanent magnet with different thickness are analyzed.The optimization design of the motor structure is realized.Different from the electromagnetic driven,the piezoelectric driven part is capacitive.Aiming at the impedance mismatch between the piezoelectric driven mechanism and the drive power supply,a semi-analytical method combining theoretical derivation with finite element method is proposed.Based on the equivalent circuit method,the admittance circle and impedance circle models of the piezoelectric stator are established,The impedance circle can more directly reflect the relationship between resonance frequency and impedance characteristics.The impedance circle value is obtained by finite element simulation,and the electrical parameters in the equivalent circuit are calculated quantitatively.Then,the impedance matching is realized.The correctness of the method is verified by experiments,which provides the basis for the prediction of motor performance and lays the foundation for the design of matching circuit.The friction driven model between the piezoelectric stators and the rotor,and the electromagnetic driven model between the electromagnetic stator and the permanent magnet of the rotor are established respectively by using the analytical method.According to the structural characteristics of the motor,the hybrid driven model is established.Finally,the prototype is manufactured and the mechanical output characteristics of the prototype are tested.