A robust estimation and compensation-based fault-tolerant control for large-scale interconnected systems with actuator saturation

This paper provides a robust approach for controlling large-scale interconnected nonlinear systems under actuator fault and saturation. Preserving closed-loop robustness despite the simultaneous effects of subsystem interactions, faults, and perturbations is the main challenge in such systems. Additionally, tackling the actuator saturation constraint increases the robustness challenge that must be accounted for when designing a controller for the mentioned system. Thus, the main contribution of this paper is the development of a fault-tolerant control for nonlinear interconnected systems under actuator saturation. In this framework, the proposal employs sliding mode control, control allocation, and fault estimation/compensation methodologies to ensure robust closed-loop performance. An augmented unknown input observer is utilized to simultaneously attain a robust estimation for the fault and state signals. Subsequently, the control allocation technique is used to re-locate the control signals across the residual actuators when a failure or fault occurs. The Lyapunov analysis and the linear matrix inequality were used to formulate the design. Finally, the three-degrees of freedom helicopter model are applied to satisfy the effectiveness of the proposed strategy.