Research On Active Steering And Braking Force Distribution For Vehicle Lateral Stability Control

As the vehicle active safety is paid more and more attention, many scholars on the vehicle active safety technology were studied, the major automobile manufacturers have launched on automotive active safety technology experiment and application, four wheel steering is a good way to improve vehicle stability,more and more people begin to pay attention to four wheel steering technology. Compared to front-wheel steering vehicle, the wheel steering the car better turning performance vehicles in low-speed steering and more stable at high speed turning. Therefore, four wheel steering has become the development trend, this article launch the research for four wheel steering vehicle stability.Firstly, this paper introduces the principle of four wheel steering and four wheel steering history.Then the paper established front wheel steering two degree of freedom model and four-wheel steering two degrees of freedom model,and then the state space of steering model.through the comparison and analysis of two steering model,four wheel steering model has great advantages in reducing the side slip angle of vehicle body. But the yaw rate is not satisfying,so this paper introduce variable steering ratio design to overcome the shortage of proportional control4WS in yaw rate and achieve a satisfactory result.Secondly, through the Carsim and Simulink joint simulation, making the car model of Carsim software track the proportional4WS model with angle step and sine wave input, we can draw the conclusion that the stability of four wheel steering vehicle has been greatly improved.Finally, when the vehicle appears appropriate understeer or oversteer, four wheel steering additional yaw moment can be adjusted for improving vehicle stability, but when the vehicle encounter severe understeer or oversteer, the vehicle need tire longitudinal force to provide additional yaw moment to improve vehicle stability, through the combined work of differential braking and four wheel steering control. After comparison of the simulation analysis,the results show the validity of differential braking and four wheel steering combined work.