A Virtual-Structure-Based Type-3 Fuzzy System for Predictive Sensor and Actuator Fault Detection, Compensation, and Control in Nonlinear Systems

This paper presents an active fault-tolerant control strategy for a class of nonlinear systems subject to both actuator and sensor faults. The system dynamics are assumed to be completely unknown, and only the measured outputs and the applied control inputs are used for system identification. Accordingly, the system is treated as a black-box model. The proposed control framework consists of three integrated subsystems. The first subsystem incorporates a Type-3 fuzzy logic system to model the unknown nonlinear dynamics, in conjunction with a model predictive controller and an adaptive stabilizing unit. The second subsystem is dedicated to sensor fault diagnosis and compensation, employing two Type-3 fuzzy estimators and a supervisory module that generates a corrective signal proportional to the magnitude of the actual sensor fault. The third subsystem constitutes a virtual dynamic structure composed of a virtual sensor, a virtual actuator, a Type-3 fuzzy identifier, a virtual predictive controller, a virtual fault detection unit, an internal adaptive compensator, and a supervisory mechanism.In the virtual structure, a virtual sensor fault is introduced at the initial stages, and a virtual actuator generates an estimated signal corresponding to the actual actuator's behavior. The main T3FLS model is then dynamically adapted to eliminate the effect of actuator faults, considering the information from the virtual system. A Lyapunov-based stability analysis is applied to demonstrate that the system remains asymptotically stable under the proposed control and fault compensation scheme.