Controller Design for Vehicle Stability Improvement Using Optimal Distribution of Tire Forces

In order to improve the lateral stability of the vehicles at a high speed, a Vehicle Dynamics Control system is developed for tracking desired vehicle behavior. The sliding mode controller is exploited for yaw moment controller and the fuzzy logic controller is applied for wheel slip control. Then an optimization problem is solved to find the optimum set of tire forces for generating desired yaw moment. To find out the weighting coefficients of optimization cost function, a fuzzy adaptation mechanism which based on the concept of brake intervention is used by utilizing maximum capacity of all tires. Simulation results on 8-DOF nonlinear vehicle model have shown that if the weighting coefficients of the front wheels are adopted to be greater than corresponding values of the rear wheels, the vehicle will be more responsiveness. On the other hand, if the weighting coefficients of the rear wheels are tuned to be greater than the value of front wheels, the dynamics of the vehicle becomes more stable and to achieve both of them and to use the maximum capacity of the tires an intermediate mode with fuzzy adaptation mechanism is the best case