Abstract: A hierarchical controller of differential steering was proposed to improve the steering redundancy and maneuverability. The desired wheel-speeds were determined by the proportion integration differentiation (PID) control and the look-up table model. The required torque for differential steering were calculated by the adaptive discrete sliding mode control. The boundary condition of differential steering was defined by simulation experiments. The influence of vehicle velocity and adhesion coefficient on the boundary condition was analyzed, and the steering performance of vehicles was compared under differential assisted steering control and pure steering wheel control. The results show that the proposed differential steering control strategy can be integrated with the traditional steering system to assist steering, which can effectively reduce the turning radius and improve the steering performance at medium and low vehicle velocity, and the effectiveness and real-time of the differential steering control strategy is also verified. 

Key words: distributed electric vehicle, differential steering, proportion integration differentiation (PID), adaptive discrete sliding mode control, stability boundary