Novel Predefined-Time Sliding Mode Fault-Tolerant Control for Hypersonic Vehicle Attitude Tracking

This article proposes a novel predefined-time sliding mode fault-tolerant control method for the attitude tracking of hypersonic vehicles subject to actuator failures and external disturbance. A novel sufficient condition of the Lyapunov function ensuring predefined-time stability and practical predefined-time stability is established, which serves as the theoretical basis for the controller design. In contrast to existing Lyapunov conditions, this formulation provides greater design flexibility. Based on this theoretical foundation and an extended state observer, a predefined-time sliding mode controller is developed. The controller ensures system robustness while enabling an accurate estimate of the settling time upper bound, which is independent of initial conditions. Furthermore, the actual settling time can be tuned via the preset parameters. Finally, the proposed controller is evaluated on a hypersonic vehicle model subject to actuator bias, loss of effectiveness faults, and external disturbance. Numerical simulations demonstrate that the proposed method exhibits superior performance, including faster convergence, lower tracking errors, and enhanced robustness and fault tolerance, compared to an existing predefined-time sliding mode control approach.