Abstract: Yaw stability control is an important part of vehicle active safety technology. On the four-wheel independently actuated electric ground vehicles, wheel driving/braking torques can be modulated independently and accurately, this can be used to enhance the performance of vehicle yaw control. In this article, a hierarchical yaw stability control algorithm based on direct slip ratio distribution is presented. Sliding mode control is adopted to yield the desired yaw moment in the high-layer of the algorithm due to the possible modeling inaccuracies and parametric uncertainties. The conditional integrator approach is employed to overcome the chattering issue, and its asymptotic stability property is demonstrated through the Lyapunov method. In the low-layer of the presented method, the magic formula tire model is used to establish the relationship between yaw moment and wheel slip ratio, then yaw moment was allocated to wheels’ target slip ratio directly. Compared with Carsim/ESC by co-simulation based on Matlab and Carsim, sliding mode control with conditional integrator can reduce the yaw rate tracking error, and the presented algorithm can improve vehicle tracking ability, enlarge the safety margin by reducing tire side slip angle.

Key words: direct slip ratio distribution, distributed drive electric vehicle, sliding mode control and conditional integrator, yaw stability control