Output Feedback Fault Tolerant Control for Linear Parameter Varying Plants Considering Imperfect Fault Information

This study focuses on the design of an integral sliding mode-based fault-tolerant control allocation (ISM-FTCA) scheme for the class of uncertain linear parameter varying (LPV) systems. The objective is to tackle the fault occurring in the actuator channel by exploiting available redundancy through a control allocation (CA) scheme in an output feedback framework. In this work, the assumption on the estimation of actuator effectiveness level, which was previously considered (in the existing literature) to be perfect coming from fault diagnosis and identification (FDI) scheme, is relaxed due to its bit conservatism nature. The uncertain system dynamics, originating due to faults, failures, and imperfect fault information, are catered to by designing a virtual control law using the LPV output ISM control strategy. An unknown input LPV observer is designed to provide the estimate of unmeasured plant states to the virtual control law. This work thoroughly investigates the closed-loop dynamics of the uncertain LPV system, utilizing the small gain theorem to develop criteria for stability. These conditions provide crucial insights into the performance and robustness of the suggested strategy. Finally, the efficiency of the proposed control scheme is verified in the simulation environment by using a nonlinear 6-degree-of-freedom dynamic model of the octarotor unmanned aerial vehicle (UAV) system. Numerical simulations under different faults and failures conditions and in the presence of imprecise estimation validate the closed-loop performance close to nominal scenarios.