The passive fault-tolerant performance of the integrated vehicle controller (IVC) applied on 4WID/4WIS Electric Vehicles has been investigated in this study. The 4WID/4WIS EV is driven independently by four in-wheel motors and steered independently by four steering motors. Thanks to increased control flexibility of the over-actuated architecture, Control Allocation (CA) can be applied to control the 4WID/4WIS EVs so as to improve the handling and stability. Another benefit of the over-actuated architecture is that the 4WID/4WIS Electric Vehicle has sufficient redundant actuators to fight against the safety critical situation when one or more actuators fail.
The integrated vehicle control (IVC) approach is composed of two parts, i.e. a motion controller which is based on the Model Predictive Control (MPC) to determine the generalized forces/moments in order to track the desired vehicle motion; a control allocator which adopts Control Allocation (CA) method and distributes the generalized forces/moments among four wheels aiming at maximizing the vehicle-road grip margin.
The MPC-based integrated vehicle controller is robust to parameter uncertainties and external disturbances. The actuator failure can be considered as a sort of disturbances. The integrated vehicle controller can handle the actuatorfailure situation maintaining the desired vehicle motion while the controller configuration is not necessary to be reconfigured. The proposed IVC controller has the passive fault-tolerant performance which does not need the fault detection and diagnosis mechanism so that the control system is simple and has no diagnosis time delay.
The passive fault-tolerant performance of the proposed IVC controller has been confirmed through simulations. Simulations have shown that once the actuator fails, the IVC controller can still maintain the desired vehicle motion. The IVC controller ensures the desired vehicle dynamics after driving motor failures which verify the passive fault-tolerant performance of the proposed IVC controller. In this way, the proposed passive fault-tolerant controller improves the post-fault safety, stability and maneuverability of the 4WID/4WIS EVs.