Aiming at the coordination problem of active front steering (AFS) and direct yaw moment control (DYC) in vehicle handling and stability control, an optimal phase plane method for stable region partition was proposed. In order to realize the integrated control of handling and stability on lateral and longitudinal dynamic system, a coordination criterion considering tire force characteristics was established based on the proposed method . Firstly, the side slip angle of front and rear tires and the difference between them were used as the characterization of vehicle lateral stability. Combined with the lateral force characteristics of the tires, the lateral state of the vehicle was divided into stable, critically stable and unstable regions. Thereby the coordination criterion between AFS and DYC was established. Secondly, considering the problem of obtaining the state variables when the control algorithm was oriented to practical applications, a state observer based on the super-twisting algorithm was established to estimate the vehicle front and rear wheel slip angle. Finally, the AFS and DYC higher-order sliding mode controller based on the adaptive super-twisting algorithm was designed to eliminate the chattering phenomenon and avoided frequent switching of the controllers during the process of stability control. Experimental results showed that the proposed coordination criteria and control method had positive effect on the coordination of AFS and DYC and obtained great effect on the control of handling and stability.

Keywords： phase plane method ; intervention criterion ; higher-order sliding mode control ; integrated control ; active front wheel steering (AFS) ; direct yaw moment control (DYC)