Stability Coordination And Torque Distribution Of In-wheel Motor Drive Electric Vehicles Based On FOSMC

Battery electric vehicles have the advantages of energy saving,environmental protection,and safety,which are beneficial to solve future energy and environmental problems and have good development prospects.As a brand-new type of battery electric vehicles,in-wheel motor drive electric vehicles directly driven by the in-wheel motors mounted on the wheels,which greatly simplifies the chassis transmission structure,the power response is more rapid,and the energy transmission is more efficient.The main advantage of the in-wheel motor drive is its excellent dynamic control.The four in-wheel motors can be independently controlled,and the torque distribution is flexible and variable,which greatly improves the controllable freedom of the vehicle,so it is very conducive to achieving the vehicle’s driving stability control,however,considering the coordination of multiple motors in electric vehicles and stability control of the entire vehicle under complex operating conditions is the core issue.This paper takes the inwheel motor drive electric vehicle as the research object.Based on the self-adaptive demand for multi-state driving stability of the vehicle,the vehicle yaw stability and torque distribution method are researched.Firstly,based on the CarSim platform,a in-wheel motor drive electric vehicle model is built,especially the design of the car body model.The drive wheel torque input interface is modified after the drive type is changed,and the drive torque of the wheel motor is output to the drive wheel.A permanent magnet brushless DC motor is used as a in-wheel motor for a vehicle,an equivalent motor Simulink model is built,and a PID driver model is proposed to form a CarSim/Simulink joint simulation platform of a driver-in-wheel motor-tire driving force-dynamics model.The conditions of straight-line acceleration before braking and steering wheel step input are designed respectively to verify the basic performance of vehicle dynamics,which provides guarantee for the simulation verification of the control strategy described later.Secondly,the stability control of electric vehicles driven by in-wheel motors is discussed.Two key parameters that affect vehicle handling stability are analyzed,yaw rate and side slip angle,and a layered control based on direct yaw moment control is designed.The upper layer is the yaw control layer,and the lower layer is the drive distribution layer.The additional yaw moment calculated by the yaw control layer is used to obtain four wheel forces output to the model according to the torque distribution strategy to achieve vehicle stability control.Thirdly,a fractional order calculus controller was designed in Simulink based on the approximation method of Oustaloup recursive filter.The 2-DOF reference model of vehicle is established,the vehicle yaw rate and the side slip angle are taken as the state variables,the sliding mode surface is designed by fractional order calculus operator,the additional yaw moment is obtained by solving the problem according to the exponential approach rate,and the stability of the fractional order sliding mode controller is analyzed.The simulation under the double shifting line found that under the conditions of low speed and low adhesion and high speed and high adhesion,the fractional order sliding mode control(FOSMC)is closer to the side slip angle than the traditional sliding mode control(SMC).At an ideal value,the control error of the yaw rate is reduced by 11.8% and 24%,and the control input is reduced by 35.5% and 23.5%,respectively,and the system chattering is effectively suppressed.Then,according to the characteristics of flexible torque distribution of the in-wheel motor drive electric vehicle,a proportional torque distribution strategy is designed,and a torque optimization distribution method based on the dynamic weight of the vehicle’s side slip angle is proposed.Optimize the objective function and design the weight coefficients of the front and rear axles based on the vehicle’s side slip angle to achieve optimal torque distribution.Through the simulation comparison of the steering wheel sinusoidal input conditions,it is concluded that the optimal distribution can accurately distribute the torque according to the vehicle adhesion,the square sum of the tire utilization rate is reduced by 15.4%,and the lateral margin and driving stability of the vehicle are improved.Finally,a HiL simulation test system is established,and a stability control strategy module and a torque optimization distribution module for hardware-in-the-loop are built based on the D2 P rapid control prototype.The test results show that under fractional order sliding mode control,the tracking of stability parameters is improved,and the situation of peak torque fluctuation under optimized distribution is improved,which verifies the effectiveness and realtime of the control strategy.