Research On Optimum Design Of Handling Stability Of Four-wheel Steering Vehicles

Good handling stability can make the vehicle have better active safety performance,ensure the safety of life and property,and improve the vehicle handling stability has always been the research hotspot of the scientific and technological workers.This article takes fourwheel steering vehicles as the research object,and optimizes the system control strategy by designing a four-wheel steering vehicle stability controller based on model predictive control and a four-wheel steering vehicle stability controller based on fuzzy PID control theory.Through the optimized design of the four-wheel steering vehicle path tracking stability controller,the driving stability problem is guaranteed to improve the handling stability of the vehicle.The specific research contents of this article are as follows:(1)On the basis of fully analyzing the domestic and foreign research status of the fourwheel steering vehicle handling stability control,firstly,a linear two degrees of freedom vehicle dynamics model for four-wheel steering vehicles is established,and the state space equations are derived to prepare the theoretical basis for subsequent research.Then the whole vehicle dynamics model is established based on the vehicle dynamics software of CarSim,and the joint simulation platform of MATLAB / Simulink and CarSim is built to prepare for the subsequent simulation verification.Then,based on the two degrees of freedom vehicle dynamics model of the four-wheel steering vehicle,three kinds of angle transmission ratio of four-wheel steering vehicles are designed.The simulation results show that the four-wheel steering vehicle has better low-speed maneuverability and high-speed stability.(2)Considering the relevant system constraints and optimization problems,a fourwheel steering vehicle stability controller based on the model predictive control is designed.The relevant variables such as input and output are reasonably constrained in the control algorithm,the optimization function based on the control objective is designed,and the rear wheel angle which can achieve the control objective is obtained by solving the optimization problem.At the same time,considering the uncertain factors of the system,a four-wheel steering vehicle stability controller based on the fuzzy PID control theory is designed.The deviation between the actual value of the control target and the reference value and the deviation change rate are taken as the input,and the rear wheel angle is taken as the output to control the vehicle.The performance of the two controllers is verified by the joint simulation platform.At the same time,according to the central idea of comparison and optimization,the optimal stability controller of four-wheel steering vehicles is selected by analyzing the simulation results.(3)Based on model predictive control theory,a four-wheel steering vehicle path tracking stability controller is designed.The controller can control the front and rear wheel angles at the same time.The vehicle stability control target is considered in the path tracking algorithm,and the front and rear wheel angles that can achieve path tracking and improve stability at the same time can be obtained by solving the optimization problem.Through the joint simulation platform,the reference path tracking performance simulation test is carried out on the high and low adhesion road.The results show that the designed controller can effectively track the reference path,and its driving stability in the path tracking process is significantly higher than that of the front wheel steering vehicle.