Research On Steering Stability Control For Four-wheel-independent-drive Electric Vehicle

Global energy is becoming scarcer,which has driven the automotive industry’s new demands in the development of new energy vehicles.Four-Wheel Independent Drive Electric vehicles have become the focus of the new energy vehicle industry due to their low pollution,low energy consumption and individually controllable wheel torque in the structure.However,there are many safety problems such as tail or rollover in practical applications,especially in the case of steering driving condition.Therefore,this paper studies the steering stability control of FWID-EV based on the dynamic model and a joint simulation model,combined with modern intelligent control algorithm and classical control,a steering stability control algorithm and an optimal torque distribution algorithm for steering conditions are proposed to improve the steering stability performance of four-wheel independent drive electric vehicles.Firstly,a dynamics model for FWID-EV that contains vehicle dynamics model,tire model,wheel kinematics model and steering system model is established,a closed-loop speed driver model was designed,a motor model was analyzed.Based on the theoretical of the dynamic model,the vehicle control model is build by utilizing Carsim and Simulink joint simulation software.Secondly,the steering stability controller is designed by analyzing the main influencing factors of vehicle instability during steering,which consists of a yaw moment controller and a slip ratio controller.In order to make the yaw moment controller always meet the steering requirements,this paper presents an algorithm of neural network PID algorithm based on particle swarm optimization aiming,which not only avoids the problem of severe vibration of the sliding mode algorithm,but also helps to figure out the problem of slow convergence and easy tendency to fall into local optimal solution,and a yaw moment controller based on sliding mode algorithm is designed as a comparison to prove the efficiency of this algorithm.Then,a fuzzy controller is used to adjust the slip ratio to ensure that the slip ratio of the four wheels does not exceed the slip extreme value based on slip ratios characteristics.Thirdly,a torque distribution strategy for steering conditions is proposed.It is a steering optimal torque distribution strategy that uses the fuzzy control algorithm to correct the driving torque,uses the optimal torque algorithm to find the required torque for each wheel.The optimal torque distribution algorithm is designed to distribute the adjusted driving torque obtained by speed closed-loop model and fuzzy control,yaw torque and slip rate torqueobtained by steering stability controller,constructing a quadratic programming problem get the best calculated distribution torque.The most commonly used rule assignment in steering research is designed as a comparison proof algorithm to improve the stability under steering conditions.Finally,simulation studies are conducted to evaluate the steering stability controller using a co-simulation of Carsim and Simulink.The effectiveness of the steering stability algorithm is proved by comparing with the sliding mode controller.The proportional allocation is chosen as a comparison algorithm to verify the proposed torque distribution for steering conditions method.Simulation results show that the control strategy designed in this paper can improve the steering stability of the vehicle while maintaining good vehicle dynamics.