Robust fractional-order sliding mode direct yaw moment control for lateral stabilization of FWID-EVs with time-delay and uncertainty

This paper presents a direct yaw moment control (DYC) strategy based on the fractional-order (FO) sliding mode control (SMC) algorithm to enhance the lateral stability of four-wheel independent drive electric vehicles (FWID-EVs) with uncertainty and time-delay. First, a two degrees of freedom (2-DOF) vehicle model with uncertainty and time-delay is developed. Based on the nonlinear vehicle model, a peaking-free disturbance observer is designed to mitigate the effect of unknown disturbance on the control system. Then, a robust adaptive nonsingular fast terminal FO sliding mode strategy for DYC is proposed. This strategy has the advantage of considering the key factors of SMC, not only ensuring the global convergence rate but also reducing the chattering problem. Moreover, this research thoroughly analyzes the benefits of introducing fractional operators in sliding mode surfaces or reaching laws. Finally, the proposed schemes are validated by a closed-loop simulation and a hardware-in-the-loop (HIL) test.