Multicontroller-Based Fault-Tolerant Control for Uncertain High-Order Sub-Fully Actuated Systems

This article proposes a novel multicontroller-based fault tolerance method to cope with a class of high-order sub-fully actuated systems (sub-FASs) with nonlinear uncertainties and actuator faults. As a promising control-oriented theory, the FAS approach is a convenient and powerful tool for nonlinear control. However, the stabilization of sub-FASs, whose input matrix function is not globally invertible, is more sophisticated and challenging due to the issue of control singularity. To address the global fault-tolerant stabilization of uncertain sub-FASs, a high-order nonlinear system model with both multiplicative and additive actuator faults is considered. By introducing the concepts of linear singular set and singularity function, the entire state space is analytically divided into several regions. Then, according to the initial states of system, three different control strategies are developed to overcome singularity and achieve global stabilization, including a FAS-based stabilizing control law, a singularity-avoid tracking control strategy, as well as a singularity-free switching control strategy. The closed-loop response of the faulty system is proven to be ultimately uniformly bounded in all cases, and the effectiveness of proposed method is illustrated through a numerical example.