$H_{\infty}$ Mixed Stable Fault Detection Observer for Nonlinear Parameter-Varying Systems

This paper proposes a fault detection observer (FDO) for nonlinear time-varying (NTV) systems under actuator faults and external disturbances, leveraging the nonlinear parameter-varying (NPV) framework. The designed FDO incorporates $H_{\infty}$ mixed-stable performance to enhance robustness, enabling precise fault estimation and improved disturbance rejection compared to conventional FDOs. Simulation on heading control of unmanned surface vehicles (USVs) demonstrates the approach's effectiveness in real-world scenarios, showcasing superior transient and steady-state performance in fault detection and mitigation.