The Control Strategy Research Of Yaw Stability Control System Of The Distributed Electric Vehicles Based On Observer

With the support of national policies for electric vehicle,the electric vehicle will become one of the main means of transportation in the future.Since the yaw stability control of vehicle has become an important indicator to evaluate the performance of the vehicle,and the distributed electric vehicle cancels the differential mechanism,it is important to study the yaw stability control of vehicle to realize the differential control and directional stability control of the vehicle.This paper is supported by the following projects: The key technology about the merge of core equipment of electric vehicle detection line and data fusion(2019ZDLGY15-01),Shaanxi major industry innovation Chain(group)project(2018ZDCXL-GY-05-03-01),project name: Research on key technologies of distributed drive pure electric passenger vehicles,and China postdoctoral fund specially funded project(2018T111006),project name: Coordinated control of electric vehicle composite brake based on braking intention and state estimation.The following work was carried out:(1)A double-layer yaw stability control system model of electric vehicle is designed.The upper layer adopts the sliding mode algorithm to control the desired additional yaw moment;the lower layer adopts the minimum sum of tire utilization ratio as the optimization target,and adopts it to complete the distribution of the desired additional yaw moment to the rear axle drive wheels,which realize yaw stability control of vehicle.The intention of double-layer model is for the better subsequent research and the model is verified by experiments.(2)The accuracy of the cornering stiffness has an important influence on the accuracy of the yaw stability control system model,but the cornering stiffness is dynamically changing during driving and is not easy to measure.In order to study the influence of dynamic cornering stiffness on yaw stability control system of vehicle,the parameter observer is designed based Kalman filter,and its accuracy is verified by experiments,which establishes foundation for solving the dynamic cornering stiffness.(3)Considering the influence of dynamic cornering stiffness on yaw stability system control of vehicle,a three-layer yaw stability control system is designed based on the double yaw stability control system.The effect of dynamic cornering stiffness on vehicle yaw stability is verified by simulation experiments.The test results show that the double-layer control system with sliding-mode algorithm is more inclined to understeer,the yaw rate is reduced and the control stability is better than that without sliding-mode algorithm under both low speed and high speed.At the same time,the maximum error of the sliding mode control system of the three-layer structure is significantly reduced compared with the control system of the two-layer structure,and the reduction is 50%.Therefore,the dynamic cornering stiffness can improve the stability of the yaw stability and the handling stability of the vehicle.