Research On Rollover Stability And Anti-Roll Control For Driver-Vehicle Closed-loop System

The driver is one of the important factors of vehicle rollover accidents, but most researches of rollover stability ignored the dynamic influence of the driver in the driver-vehicle closed-loop system.Obviously, there are many deficiencies in these approaches. In fact, when a rollover happens, the driver needs responding, making decision and performing related operations. Driver's response will affect the active anti rollover system operation of the vehicle, so take the drivers' factors into consideration in the research of rollover stability and anti-roll control will be more closely to the real car rollover, and practical laws and policies can be got easily.Firstly, a driver-vehicle closed-loop system model is established, including the vehicle model, the driver mode of road tracking, and the driver's reaction model of rollover. Based on the theory of vehicle dynamics, a 3 degree of freedom vehicle model is set up, and the Carsim software is used to verify its correctness. After that, a driver model of anti-rollover is established on the base of the analysis of the driver's physiological characteristics and the driver's response to the rollover; then the driver model and the 3 degree of freedom open-loop vehicle model are combined into the driver-vehicle closed-loop system model. Some simulations have been done in typical operating conditions to validate the correctness and rationality of the model.Secondly, the influence of structure parameters of automobile, automobile running parameters and driver behavior characteristics to vehicle rollover stability are analyzed. The Lateral-Load Transfer Ratio and the Dynamic Stability Factor are selected as vehicle rollover index, the influence of the structure parameters(the height of the center of gravity of the car, wheel track and vehicle roll stiffness, etc.) to vehicle rollover stability is analyzed; the influence of the car moving parameters(the vehicle velocity, vehicle steering angle, etc.) to vehicle rollover stability is analyzed, too; the influence of driver's important parameters to the driver-vehicle closed-loop system rollover stability is analyzed,including driver's rollover response gain, driver's thinking time, and driver's rollover response threshold value. This work provides a theoretical basis for improving the effect of the vehicle rollover prevention.Finally, in the conditions which the driver can hardly prevent vehicle rollover, an active control strategy of anti-rollover is designed. Take the driver-vehicle closed-loop system as the object, a PID controller and a fuzzy adaptive PID controller are designed based on vehicle active steering and differential braking system respectively. The slewing road and the double lane change road areselected for simulation experiment, get the results and compare them with each other. Shows that fuzzy PID control strategy based on differential braking can improve vehicle rollover prevention ability effectively, and has strong condition self-adaptability.