Torque Fault-Tolerant Hierarchical Control of 4WID Electric Vehicles Based on Improved MPC and SMC

The 4-wheel independent drive (4WID) electric vehicle has better safety and stability. However, the multi-motor drive system would lead to an increased fault probability in the vehicle. In particular, the uncertainty of fault motors and parameter disturbances could lead to uncertainties in control. This study presents a fault-tolerant hierarchical control approach that utilizes an improved Model Predictive Control (MPC) to address the problem. The proposed method employs Sliding Mode Control (SMC) in the upper layer to generate the vehicle's yaw moment, which could inhibit system parameter disturbance and improve the system's robustness. Incorporating the fault matrix induced by motor malfunctions, the state-space equation of the vehicle is modified to establish a vehicle dynamics model under motor faults. In the lower layer, the torque reconstruction allocation strategy is designed to coordinate the four motors under the motor fault condition by the MPC rolling optimization online, which could reduce the impact of the motor fault uncertainty for fault-tolerant control. The multi-constraint conditions of MPC are set up according to the vehicle state parameters. To address the additional yaw moment caused by the MPC torque reconfiguration allocation control strategy, the torque transfer method is used as the input allocation for MPC. Finally, the proposed control strategy is verified by online simulation. The simulation outcomes demonstrate the effectiveness of the proposed hierarchical fault-tolerant control approach in achieving fault-tolerant control of the 4WID electric vehicle, with the improved MPC outperforming the conventional MPC in terms of performance.