Vehicle stability enhancement - an adaptive optimal approach to the distribution of tyre forces

In this paper, vehicle stability enhancement, based on the integrated vehicle control notion, is presented. A new method for adaptive optimal distribution of braking and lateral tyre forces is employed. The control inputs considered are the individual wheel steering and braking for each wheel. Since a unique set of tyre forces satisfying control objectives cannot be easily determined, an adaptive optimization problem subjected to two equality and four inequality constraints has been solved to achieve an optimal solution. A proper adaptation mechanism is suggested to minimize the negative effects of direct yaw moment control, such as the undesirable decrease in the total speed of the vehicle. The effectiveness of the proposed vehicle stability enhancement system, especially online balancing of tyre forces in an optimal form with and without an adaptation mechanism, is demonstrated through digital simulations. A comprehensive non-linear vehicle dynamics model is utilized for simulation purposes. The results indicate that the proposed control system can effectively utilize the tyres' frictional forces and significantly improve the vehicle stability and handling performances.