Stability Analysis And Control Of Wheel Motor Driven Electric Vehicle Steering Under Compound Brake Condition

With the worldwide over-exploitation and utilization of non-renewable resources such as oil,energy reserves have become increasingly scarce and environmental pollution problems have become more serious.This has led the automotive industry to look to the electric vehicle industry.Distributed-drive electric vehicles have their unique advantages.They can independently control the driving and braking of each wheel,so the stability of the vehicle can be improved by rationally distributing the torque.At present,although scholars at home and abroad have conducted some research on the stability control of distributed-driving electric vehicles,most of the research objects are for single-motor front-end electric vehicles.The rare research object is distributed braking with composite braking.Because the vehicle has different dynamic response characteristics when the hydraulic pressure and the motor are braked,it is necessary to coordinately distribute the motor braking and the torque of the hydraulic braking when the wheels are braked,thereby increasing the difficulty of controlling the stability of the vehicle.In order to solve the above problems,firstly,based on MATLAB/Simulink,a seven-degree-of-freedom vehicle dynamics model for distributed-driving electric vehicles is constructed,and a criterion for stability determination based on phase plane analysis method is proposed to provide a vehicle stability determination.Then,a composite brake stratified control strategy was proposed.In the upper strata control strategy,the vehicle brake lateral stability was taken as the goal,and based on the sliding mode control theory,the target yaw moment and longitudinal brake force of the output vehicle were achieved.The lower control strategy is based on the braking force distribution of the direct yaw moment,and is based on the weighted least squares control method.The effective set algorithm is used to solve the objective function and the rational distribution of the braking torque of each wheel is realized.Finally,in order to verify the control effect of the control strategy in this paper,through the numerical simulation,this paper contrasts the control strategy and the existing classical control strategy,and the vehicle stability under the ordinary braking conditions and under the special conditions of the off-road conditions.The difference of energy recovery efficiency,the simulation results show that the control strategy proposed in this paper can be more stable under different conditions and the energy recovery rate is higher,which verifies the effectiveness and rationality of the proposed composite brake control strategy.