Research On Driving System Of A New Self-decelerating Permanent Magnet In-wheel Motor

With the development of economy and society,the concept of sustainable development,environmental awareness and health awareness are gradually popular.However,due to the non-renewable oil resources and increasingly serious environmental problems,it has become a trend to accelerate the adjustment of energy structure and develop the new energy vehicles.Electric vehicles(EVs)have been paid much more attention in recent years for its zero pollution,low noise,high efficiency and oil saving.Motor and its driving system are the core of EVs.Permanent-magnet(PM)in-wheel motor driving system integrates the power,transmission and braking unit together,simplifying the structure and increasing the available space of vehicles,which is one of the main trends of electric vehicle driving mode in the future.This paper studies the self-decelerating permanent magnet in-wheel(SDPMW)motor.SDPMW motor is based on the principle of magnetic field modulation of magnetic gear,which compromises the merits of outer-rotor motor with direct driving and inner-rotor motor with compact structure,so that efficiency and torque density are greatly improved.The driving system has an important influence on the safety,performance,efficiency and comfort of EVs.However,at present,the research of this kind of motor is mainly focused on the design of body,and the control algorithm is less.As the back electromotive force of the SDPMW motor and permanent magnet synchronous motor(PMSM)are similar,thus,this paper uses the control algorithm of PMSM and designs a driving system for the SDPMW motor.This paper first introduces the research status of the hub motor based on the magnetic gear,the control method of the PMSM and the modern control algorithm.Then,the structure,principle and characteristics of the SDPMW motor are studied and analyzed,and the mathematical model of the SDPMW motor is established in the three-phase static coordinate system.This paper focuses on the control strategy of the SDPMW motor driving system.Due to the characteristics of simple and easy to implement of PI controller,the vector control system of PMSM used in EVs currently uses PI control.Firstly,the space vector pulse width modulation(SVPWM)algorithm based on PI controller is applied to the driving system of the SDPMW motor.The results show that the algorithm is simple and fast,which can meet the control performance to a certain extent,but the algorithm parameters are not easy to adjust and the disturbance rejection performance of speed is obviously insufficient.Besides,robustness of the algorithm is poor and algorithm parameters need to be re-tuned in different operating environments.Aiming at the problem of poor robustness and control parameters in different operating environments needed to be re-tuned of the traditional SVPWM based on PI controller,and taking into account the changing operating environment of EVs,the variable system parameters and external load disturbance,to meet the requirements of multi variables,strong coupling and nonlinear system of electric vehicle driving system,sliding mode control(SMC)is proposed to improve the robustness of the system based on the traditional SVPWM system,which is important to improve the dynamic and steady performance,safety and comfort of the electric vehicle driving system,especially to improve the robustness of the control system.Next,in order to further improve the steady performance and reduce the torque ripple of the system,current harmonic suppression methods are investigated in this paper,and a harmonic suppression method based on SMC and adaptive notch filter(ANF)is proposed,which can decrease the fifth and seventh current harmonics.Finally,simulation model of the driving system is established based on Matlab/Simulink,and the experimental platform of driving system is built based on the TMS320F28335 controller.Simulation and experiment based on the SDPMW motor have been carried out and the results of both simulation and experiment have verified the feasibility and effectiveness of the proposed algorithm,which is foundation for further research and practical application of the SDPMW motor driving system.