Design Of Low Torque Ripple Permanent Magnet Synchronous Motor For Electro-Hydrostatic Actuator

Electro-hydrostatic actuator is a high-precision position servo system,which is mainly composed of rudder controller,rudder servo motor,etc.As the power source of the whole system,the servo motor is required to possess low vibration,high power density and high reliability.Due to the high reliability,high efficiency and other advantages,permanent magnet synchronous motor is widely used in the field of the electro-hydrostatic actuator motor.However,it has the disadvantages of cogging torque and torque ripple,which objectively limits the promotion and application in actuator field.In order to obtain smaller cogging torque and torque ripple,this paper selects the main size parameters and pole/slot matching from the perspective of motor design.The magnet structure is optimized for low torque ripple.By combining finite element method and analytical method,the each field harmonics on cogging torque components is analyzed.Based on the finite element numerical calculation method,the thermal analysis model and vibration noise prediction model of permanent magnet synchronous motor are constructed.The temperature field and vibration noise of permanent magnet synchronous motor are simulated and calculated.It is verified that the motor design scheme can reduce torque ripple and electromagnetic vibration.Meanwhile,a prototype was designed and manufactured.The experiment verifies the rationality of the motor design scheme and the correctness of the electromagnetic vibration and noise analysis.The main work of this dissertation was:1.According to the technical requirements of the motor for the electro-hydrostatic actuator,the main size parameters of the motor are determined by the power size equation.Aiming at the design requirements of low vibration and noise,pole/slot combination,air gap length and permanent magnet structure are selected.The preliminary design scheme of the prototype is determined.2.The influence of bread-loaf shaped magnet poles under parallel magnetization on the cogging torque is studied for surface-mounted permanent magnet synchronous motor.By combining finite element method and analytical method,the contribution of each field harmonics on cogging torque components with eccentric and sine harmonic compensation magnet poles is analyzed,respectively.At the same time,the effects of permanent magnet structures on the cogging torque are compared from perspective of integer and fractional slot motors.The finite element is conducted to simulate and analyze the electromagnetic performance of the prototype,and the rationality of the design scheme is proved.3.The temperature distribution of the motor is analyzed,and the heat transfer principle between the various parts of the motor is explained.The Motor-CAD software is used to simulate the steady-state temperature field of the motor,verifying that the temperature distribution in the motor is within a reasonable range.The electromagnetic vibration noise is simulated and analyzed by ANSYS workbench,and the effectiveness of rotor eccentric pole design for low vibration noise is verified.4.According to the design scheme,an experimental prototype of 36-slot/12-pole surface-mounted permanent magnet synchronous motor with eccentric magnet pole is manufactured.The experimental platform is built and the drag method is used to test no-load back-EMF.The back-EMF variation with rotating speed under no-load state is analyzed.The experimental results show that the vibration acceleration amplitude of the prototype is small,and the design plan meets the requirements.