Fault-tolerant trajectory tracking control via differential steering considering actuator delay

Distributed-drive chassis systems can provide redundant lateral-control authority through differential steering after complete steering actuator failure, but the reconstructed steering channel introduces pure delay and first-order inertial lag. This mismatch can reduce trajectory tracking accuracy when path curvature changes rapidly. This paper proposes a delaycompensated, fault-tolerant trajectory tracking controller based on MPC (Model Predictive Control) for differential steering. The equivalent actuator is identified as a cascade of pure delay and first-order lag, with τd = 0.150s and Tδ = 1.696s. The actual equivalent front-wheel angle is augmented into the tracking-error model to represent actuator lag, and the system state is propagated over the identified delay horizon before MPC optimization. Thus, the optimized equivalent steering command and additional yaw moment are computed from the predicted vehicle state at the actual actuation instant. The method is evaluated in 36km/h double lane-change and serpentine co-simulations and an 18km/h single lane-change fullscale vehicle test. Compared with a controller without delay compensation, the proposed controller reduces the maximum lateral error by 60.0%, 21.3%, and 21.2% in the three scenarios, respectively, while improving yaw-rate tracking performance. The results demonstrate that actuator-dynamics-embedded prediction and delay compensation improve trajectory tracking accuracy and yaw stability under complete steering actuator failure.