Research On Yaw Stability Control System For Steer-by-Wire Vehicle Based On Sliding Mode Control Theory

With the development of modern automobile industry,people have strict requirements for the stability and safety of automobile.In order to improve the steering stability of the vehicle under specific conditions,this thesis presents a practical control strategy of steer-by-wire yaw stability,taking the steer-by-wire vehicle as the controlled object and based on the non-linear disturbance observation theory and sliding mode control theory.In this paper,the steer-by-wire vehicle is modeled and the lateral dynamics is analyzed.Then the effects of the yaw rate and the sideslip angle on the yaw stability of the vehicle are considered,while the desired yaw rate and the sideslip angle are obtained by using the desired vehicle model at the same time.Finally,the control strategy of yaw stability of the steer-by-wire vehicle is determined.The control strategy is composed of a sideslip angle observer,an upper controller-yaw rate controller and a lower controller-frontwheel steering angle controller:1)Based on the linear two-degree-of-freedom vehicle model,the sliding mode state observer is constructed by using the modern observation theory to obtain the estimation value of the vehicle sideslip angle;2)Yaw rate controller is designed based on the integral terminal sliding mode control theory,which gurantees the desired yaw rate of vehicle can be tracked in finite time.The actual value of the sideslip angle is also close to 0,and the correction angle_{?8? is also outputted.3}Based on the robust adaptive sliding mode control algorithm,the lower controller is designed to ensure the actual frontwheel steering angle to track the desired frontwheel steering angle.The vehicle dynamics model is established by CarSim,the yaw stability control system is built by Simulink,and the CarSim and Simulink are co-simulated to construct the hardware-in-the-loop experiment platform.This thesis introduces the situation with/without lateral wind interference,and two kinds of steering wheel angle input signals,ramp input and single line change input,are used to construct four groups of experimental schemes on roads with low friction coefficient to simulate and test the closed loop of the vehicle.The simulation results show that the proposed integral terminal sliding mode and robust adaptive sliding mode control strategy not only can ensure the yaw stability of vehicle and eliminate the chattering problem existing in the traditional sliding mode controller,but also achieve stronger robustness and accuracy.