Research On Torque Ripple Reduction And Position Loop Bandwidth Improvement Of Slotless Permanent Magnet Synchronous Motor

The slotless permanent magnet motor has gradually become one of the research hotspots in the field of motor design and drive control due to its advantages of no cogging torque,fast dynamic response,high power density and high efficiency.It is widely used in aerospace,high-speed centrifuges,high-speed machine tools and other occasions.In this paper,the slotless permanent magnet motor is taken as the research object,and the analytical model of the slotless motor is introduced.The vector control of the slotless motor is taken as the starting point,and the torque ripple in the speed-current double closed loop control is suppressed,and the position is also targeted.The speed-current three closed-loop control improves the follow-up effect on the high-frequency high-gain sinusoidal position signal.Firstly,the motor structure of the slotless permanent magnet motor is introduced.The magnetic field distribution model of the slotless motor is established according to the electromagnetic theory.According to the magnetization intensity distribution function and the air gap magnetic field boundary condition,the mathematical analysis of the induced electromotive force of the slotless motor is given.The model is compared with the results of two-dimensional finite element simulation to verify the correctness of the analytical model.Aiming at the problem that the back electromotive force is not ideal due to the processing technology,the analytical model is appropriately modified,fitted with the actual prototype,and the corrected slotless motor voltage equation is given.The mathematical model of the inverter nonlinearity is also analyzed.Aiming at the problem of torque ripple caused by non-ideal back EMF and inverter dead zone effect in the double-closed control of slotless motor,a torque ripple suppression strategy based on harmonic injection is proposed.And the calculation method of the harmonic current reference value is given.Aiming at the inherent defects caused by the traditional harmonic injection algorithm using low-pass filter to extract harmonic current,an improved harmonic injection algorithm based on fast harmonic extraction is proposed.The algorithm can effectively improve the harmonic current extraction effect and further reduce the torque ripple.Aiming at the problem that the high frequency and high gain sinusoidal position signal has poor follow-up effect in the position-speed-current three closed-loop control of the slotless permanent magnet motor,the traditional pure proportional position loop controller and the position loop control after the position feedforward is introduced.Device.Based on this,an open-loop closed-loop iterative learning algorithm is proposed.By modifying the reference input signal,the algorithm gradually makes the actual position signal of the slotless motor position servo system gradually approach the desired position signal,and improves the position following effect of the slotless motor.Finally,an experimental platform for the slotless permanent magnet motor drive system with DSP control chip TMS320F28335 as the control core was built.By writing software algorithms,the torque ripple suppression algorithm proposed in this paper and the iterative learning algorithm for modifying the reference input are verified on the hardware experiment platform.The experimental results obtained by the experiment prove that the proposed drive control algorithm can effectively improve the performance of the slotless motor drive system.