Abstract: Four-wheel independent steering distributed drive electric vehicle has unmatched mobility, traffic ability and handling stability of conventional vehicles, but its complex structural characteristics and high redundancy of actuators increase the risk of steering motors failure. Aiming at the driving stability problem under the failure of single wheel steering, by analyzing the influence of active steering of rear wheels on body stability and using the monorail model with additional rear wheel steering as the steady-state reference model, a hierarchical control method based on tire force distributable reconstruction is proposed. At first, the steering control method of each wheel is determined according to the side deviation state of the tires，considering the steering failure shock and the accumulation of yaw angle error, a recursive non-singular terminal sliding mode controller as the upper level controller is designed based on parameter adaptation. Then, using he minimum tire load rate as the optimization goal, the intervention and withdrawal of the actuator are dynamically adjusted according to the vehicle state, and the wheel steering angles and driving or braking torques are redistributed to design the lower-level controller. Finally, the proposed control method is verified by off-line simulation and controller-in-the-loop simulation. The results show that the designed controller can reduce the maximum lateral position error by 85.2% and 88.1% respectively compared with the common sliding mode controller under the condition of single wheel steering failure, the maximum yaw angle error is reduced by 81.8% and 81.5% respectively, which can keep good driving stability of four-wheel independent steering distributed drive electric vehicle.

Key words: dlectric vehicle, four-wheel independent steering, four-wheel independent drive, steering failure, assignable reconfiguration, driving stability