Integrated Handling And Stability Control Of AFS And DYC For Electric Vehicles Via Dual Sliding Mode Control

With the continuous development of social economy,the number of vehicles in the world continues to increase.The environmental pollution and energy crisis caused by traditional fuel vehicles powered by internal combustion engine can not be ignored,and electric vehicles have entered a high-speed development period.The distributed drive electric vehicle can control the torque of each wheel independently by the wheel hub motor in each wheel,which is the ideal driving form of electric vehicle.In the field of vehicle active safety control,direct yaw moment control system(DYC)and active front wheel steering system(AFS)are important research directions.The active front wheel steering system can provide additional front wheel angle according to the driving condition of the vehicle,so as to improve the handling stability of the vehicle,but the control effect of the system on the low adhesion road is limited.The direct yaw moment control system can correct the driver's oversteer or understeer by adjusting the tire's longitudinal force to produce additional yaw moment.However,the direct yaw moment control has great interference on the vehicle's longitudinal speed.In order to give full play to the advantages of AFS and DYC system,this paper presents a hierarchical controller integrated with AFS and DYC for distributed driving electric vehicle.Firstly,the nonlinear 7-DOF vehicle model and magic tire mathematical model are built,and the simulation model is built in Matlab / Simulink,and the model is verified in the CarSim vehicle dynamics simulation software.Secondly,considering that it is difficult to measure the sideslip angle of the vehicle directly,this paper uses the unscented Kalman filter algorithm to establish the observer of the sideslip angle of the vehicle,estimates the sideslip angle of the vehicle,and verifies the accuracy of the observer under the two conditions of simulation.Then,the frame of AFS and DYC integrated controller is proposed,and the basic concept of sliding mode and the theory of sliding mode variable structure control are introduced.Based on the theory of sliding mode variable structure control,the upper controller is designed,which includes the centroid sideslip angle controller and the yaw rate controller.The centroid sideslip angle controller is used to obtain the desired additional front wheel angle,and the yaw rate controller is used to obtain the desired additional front wheel angle In the lower controller,with driver driving force input and additional yaw moment asconstraints,Lagrange multiplier method is used to optimize the longitudinal force distribution of tire,so as to achieve the purpose of optimizing driving energy efficiency.Finally,in order to verify the effectiveness of the proposed integrated controller,it is compared with a single DYC control strategy and no control strategy under different working conditions to verify the effectiveness of the proposed integrated layered controller.The simulation results of MATLAB / Simulink show that compared with a single DYC control strategy and no control strategy,the proposed AFS and DYC integrated control strategy based on layered architecture can have It can effectively track the ideal yaw rate and the sideslip angle of the center of mass,so as to improve the handling stability of the vehicle.