Research On In-wheel SRM Drive System For Electric Vehicles

With the deterioration of the earth's ecological environment and the depletion of fossil fuel resources,mankind's understanding of the protection of the environment and social sustainable development is more and more clear.As an environmentally friendly means of transportation,electric vehicles have been strongly supported by local governments.The hub-type switched reluctance motor combines the advantages of a hub-type motor with flexible drive,high transmission efficiency,simple and robust structure of the switched reluctance motor,low cost and wide speed range,and is an ideal driving mode for the electric vehicle.However,due to the structure of the double salient pole of the SR motor,its torque ripple and noise during operation are too large,which greatly limits its application and development.Based on the basic structure and principle of hub-type SR motor,this article analyzes the electromagnetic characteristics of SR motor and uses FEMM software to build a three-phase 24/16-pole hub with rated power of 25 kW,rated speed of 1500r/min,and rated voltage of 600 V.The SR motor model,and through the simulation to obtain the motor flux,torque,current and rotor position angle data table.Using MATLAB/Simulink built the drive system model and simulation.Compared with the traditional Torque Sharing Function control strategy,a variablevalued exponential function improvement factor was added to optimize the original function for the problem of vibration caused by excessive current change rate in different operating modes of electric vehicles.Simulations verify the effectiveness of the optimized function in suppressing torque ripple at low speeds in a motor.Combining with the needs of the project,based on the actual operation of the electric vehicle,a feasible control strategy was designed in the aspects of high-precision position detection,startup and operation control,brake control,and system protection control of the motor rotor.Based on the STM32 series ARM main control chip,the design of the hub-type SRM drive system for electric vehicles was completed and divided into software and hardware.Functional modules include: current and voltage detection module,position detection module,communication module,power processing module,main power circuit module,error protection module,and so on.For the optimized Torque Sharing Function strategy proposed in the previous section,the optimal opening and closing angles are set in each rotation speed zone,and this strategy is added to the double closed-loop PI control loop formed by the system current and rotation speed for adjustment.According to the relevant control strategies and experimental conditions designed in this paper,an SR motor with a rated power of 6 kW was selected as the object.Experiments were carried out to obtain the correlation curves of the current waveform and the rotational speed response of the motor from start-up to operation,and the addition of optimized rotation.The current comparison chart obtained by the moment allocation function control strategy verifies the feasibility of the designed system and the effectiveness of the TSF control strategy in reducing motor torque ripple.