Optimal 4WIS-4WID Vehicle Motion Control in Trajectory Deviation Occasions over Handling Limits

Trajectory deviation occasions over handling limits are very dangerous because the vehicle is prone to stability loss or secondary collision owing to the large deviation. This article developed an optimal vehicle motion control algorithm in trajectory deviation occasions over handling limits for 4WIS-4WID vehicles. A double track 7DOF vehicle model and Magic Formula tire models are utilized to describe the vehicle dynamics. A quasi-projectile motion model is established considering Pontryagin minimum principle, based on which the trajectory deviation occasions recognition strategy and optimal control strategy are developed. The effectiveness of the controller is verified through Matlab/Simulink. Simulation results show that the developed optimal control strategy can effectively decrease the maximum lateral error, in the meanwhile the computational complexity is much lower than the numerical nonlinear optimization. The control performance of the controller in 4WIS-4WID vehicles is better than 4WD and 2WS vehicles, proving the superiority of 4WIS-4WID vehicles.

I. Introduction

Nowadays active safety systems such as ABS (Anti-lock Braking System) and ESP (Electronic Stability Program) [1] [2] are widely utilized in vehicles, which exert a significant influence on vehicle safety. With the development of autonomous driving technology, trajectory following algorithms are exploited by many labs and companies, such as lane-departure warning (LDW) [3] and lane-keeping aid (LKA) [4]. However, trajectory deviation occasions over handling limits are rarely discussed. Trajectory deviation occasions over handling limits refer to the conditions when vehicles cannot avoid deviating from the desired trajectory, for instance, the centripetal force required by the vehicle to track the trajectory exceeds the total tire adhesion forces, as Fig. 1 shows, or the vehicles is subjected to large external disturbances such as side collisions. Figure 1.

Trajectory deviation owing to insufficient centripetal force