An adaptive second‐order sliding mode control based on sliding mode filter for active front steering system

In order to promote the driving stability of in‐wheel electric vehicles, this paper proposes an adaptive second‐order sliding mode (ASOSM) for an active front wheel steering (AFS) system, where the new adaptive strategy is able to automatically seek the minimum control gain to mitigate chattering issue in sliding mode control and enhance the stability and safety of in‐wheel electric vehicles. Firstly, a two‐degree‐of‐freedom (2‐DOF) vehicle model is established via vehicle dynamics analysis to obtain the desired yaw rate. Secondly, an adaptive law is developed via the equivalent control on the grounds of the second‐order sliding mode (SOSM) dynamics, where the average value of sign function is obtained from Arie Levant's differentiator. Thirdly, to avoid overestimating gain, a SOSM combined with the designed adaptive law is applied to the AFS system. Finally, the outcomes of co‐simulation involving CarSim and Matlab/Simulink indicate that the ASOSM controller proposed in this paper can precisely track the ideal yaw rate to improve vehicle stability.