Pwa Based Yaw Stability Control For In-wheel-motor Electric Vehicle On Low Adhesion Coefficient Road

Electric vehicles have become important new energy vehicles due to their advantages of energy saving,environmental protection,and high driving efficiency.As a new type of electric vehicle,the in-wheel-motor electric vehicle has the characteristics of simple chassis structure and high transmission efficiency and the wheel torque is driven independently.So it has received a lot of research and attention.With the characteristics of independent driving of wheel torque,the anti-slip and yaw stability control functions of the in-wheel-motor electric vehicle can be realized,and the longitudinal and lateral motion performance of the vehicle can be improved.In this paper,the yaw stability control problem of the vehicle under low adhesion coefficient conditions is studied.The motivation is that the low adhesion coefficient road surface driving conditions can fully reflect the problems that the yaw stability control is facing the nonlinearity of the wheel force,the yaw rate overshoot,and the excessive side slip angle may cause instability.A piecewise affine lateral dynamics modeling method for characterizing nonlinear lateral forces is presented in this paper.A method for designing a piecewise affine yaw stability robust controller is proposed to effectively improve the yaw response of the vehicle.To reduce the large amount of work caused by dynamic modeling and controller design for roads with different adhesion coefficients,and the problem of control quantity jump caused by controller switching under variable adhesion coefficient road conditions.This paper proposes a LPV robust controller design method with the pavement adhesion coefficient as a parameter can effectively reduce the controller design workload and avoid the jump of the control quantity.Aiming at the nonlinear characteristics of the tire force of the in-wheel-motor electric vehicle,this paper presents the piecewise affine expression of the lateral slip angle-tire lateral force.And based on this,establishes the lateral slip angle and the yaw rate as the state quantities.The front and rear axle tire forces are in different zones during the driving of the vehicle.Combining the front and rear axle wheel force zones will result in excessive dynamic model partitioning.For this reason,the effective zoning of front and rear axle wheel forces in different steering conditions is analyzed,and the expression of the lateral dynamic model partition that can characterize the steering process is given.Considering that the la teral motion of the vehicle is affected by the vertical motion,the characteristics of the suspension motion are introduced,and the lateral dynamic segmented affine model with uncertain disturbance is established to reflect the K&C characteristics.In view of the yaw stability control problem of the in-wheel-motor electric vehicle under low adhesion coefficient road conditions,this paper analyzes the dynamic characteristics of the system,and gives the yaw torque versus the rise time and the overshoot range of yaw rate.Based on the established subsection imitation,in the injection model,a piecewise affine yaw stability robust controller wit h guaranteed stability and Hinf disturbance rejection performance is designed.The simulation results show that the yaw stability control method proposed in this paper is effective for improving the tracking performance of vehicle side-slip angle and yaw rate.When the road adhesion coefficient changes,the model parameters and piecewise must be redesigned.This will lead to a large amount of design work and controller switching will bring about the problem of control quantity jump.This paper explores the application of the model determined by the road adhesion coefficient.Parameters and partitions are used to express the model under different road adhesion coefficients.A parameter-dependent piecewise affine lateral dynamics model is established to characterize the variation of the parameters of different road adhesion coefficient models.Based on this,a parameter-dependent piecewise robust control is designed.The simulation results in different road adhesion factors show that the proposed piecewise robust controller,which depends on the road adhesion coefficient,has a good effect on solving controller jumps.