Sideslip Angle Estimation And Torque Allocation Strategy Of Distributed Drive Electric Vehicle

Distributed drive electric vehicles have simple structure,high transmission efficiency and independent control of four-wheel torque.Compared with fuel vehicles or centrally driven electric vehicles,its unique structural characteristics and advantages bring more possibilities for the development of vehicle stability control.Among them,the vehicle sideslip angle is an important index to represent the stability of the vehicle,which plays a vital role in the stability control of the vehicle.At the same time,the torque distribution control strategy is the core part of the control stability of distributed driven electric vehicles,and the reasonable torque distribution between driving wheels is very important.This paper takes distributed drive electric vehicles as the research object and carries out the following research work:The vehicle dynamics analysis of distributed drive electric vehicles is carried out and the vehicle dynamics model of seven degrees of freedom(7-DOF)is built.In order to facilitate the follow-up research,the model is further simplified into linear 2-DOF model and nonlinear 3-DOF model.Carsim software was used to build the vehicle model,and the driver model and four hub motor models were built in MATLAB/Simulink to complete the construction of the Carsim-MATLAB/Simulink joint simulation platform.The model is compared with the traditional vehicle model in Carsim software to verify the effectiveness of the model.Aiming at the distributed drive electric vehicle,a method of sideslip angle estimation based on strong tracking Kalman filter and unscented Kalman filter fusion estimation is proposed.Since the vehicle dynamic characteristics change linearly when the lateral acceleration is small,the strong tracking Kalman filter can be used to quickly estimate the vehicle dynamic characteristics.When the lateral acceleration is large,the vehicle dynamic characteristics tend to be nonlinear,and the accurate estimate can be obtained by unscented Kalman filter.Finally,the data obtained by the two estimation methods are fused to realize the estimation of vehicle sideslip angle under different vehicle speeds and working conditions,and the proposed method is verified by the Carsim-MATLAB/Simulink co-simulation platform.The cause of vehicle instability is analyzed and the multi-objective torque optimal distribution strategy is designed.Among them,the torque optimal distribution strategy includes the upper torque decision layer and the lower moment distribution layer.The upper torque decision-making layer decides the total driving torque required to follow the current speed based on the PID control and the additional yaw torque required to maintain the lateral stability of the vehicle based on the sliding mode variable structure control.Lower torque distribution to the upper layer of additional yawing moment to optimize allocation,put forward to improve the tire adhesion margin,improve energy efficiency and improve the vehicle riding comfort as the goal of the multi-objective functions,and the sparrow search algorithm to solve the multi-objective optimization problem.The proposed optimal torque distribution strategy is compared with the dynamic torque distribution method based on tire axial load distribution on the established co-simulation platform,and the results show that the proposed optimal torque distribution strategy makes the vehicle have better stability,economy and ride performance.The hardware in the loop simulation experiment is carried out on the distributed drive electric vehicle platform based on d SPACE,and the proposed torque optimal allocation strategy is verified in the angle step condition,which verifies the feasibility of the proposed torque optimal allocation strategy.