Sliding-mode controllers implementation for direct yaw moment control in four-wheel steered ground vehicles

In this paper different classes of sliding mode controllers are applied for direct yaw moment control. Theoretical and practical advantages of four principal sliding mode controllers are obtained from their implementation in four-wheel steering, which has gained popularity for ground vehicles due to its potential to enhance handling and stability. While most commercial solutions rely on event-triggered, velocity-dependent strategies, robust controllers such as sliding mode controllers are required to significantly improve vehicle dynamic performance. Although robust control schemes are found in the literature for direct yaw moment control, such as the super-twisting algorithm and barrier function adaptation of relay sliding mode control, the saturation of the actuators or sample-and-hold issues are not considered, as they degrade their performance. Therefore, a modified barrier function adaptation is proposed, which guarantees the predefined performance of the state without the knowledge of the upper bound of the perturbations, in the case of actuator saturation and sample-and-hold implementations. Simulations of a relay sliding-mode controller, a super-twisting algorithm, a barrier function adaptation of relay sliding mode, and the proposal are conducted using an experimentally validated high-fidelity mathematical model. The results show that the proposed barrier function adaptation methodology was the only one that could track the yaw rate reference without oscillations. After that, the modified barrier function adaptation is applied within hardware-in-the-loop. The results are benchmarked against an event-triggered control method performing both open-loop and closed-loop manoeuvres to demonstrate the robustness of the proposed approach.