Active Fuzzy-Based Fault-Tolerant Control for Uncertain Electro-Hydraulic Actuators Subject to Simultaneous Actuator and Sensor Faults

Abstract

This paper introduces an active fault-tolerant control (FTC) for servo-valve-driven electro-hydraulic actuators (EHAs) subject to unstructured dynamics, uncertainties, and actuator and sensor faults. The proposed methodology is established based on the backstepping control scheme integrated with observers and a fuzzy logic engine. The fuzzy logic-based approximation is utilized to compensate for the unstructured dynamics, while the observer is hybridized to suppress the effects of disturbance and lumped uncertainties. Moreover, under the adverse impact of the sensor malfunction, a disturbance-state observer (DSO) is developed to decouple the unknown residual signal. Notably, unlike other techniques using a bank-of-observers (BOb) to detect and isolate faults with a linear matrix inequality (LMI) tool to determine observer gains, the proposed observer views the residual as an extended state to identify it directly. Subsequently, the backstepping-based active FTC is developed to fulfill specific control requirements. The stability of the closed-loop system is theoretically achieved through the Lyapunov theorem, while the effectiveness of the proposed methodology is validated through comparative simulations under different faulty scenarios. Note to Practitioners-The main focus of this paper is to clarify the unsolved difficulties in addressing different faults, unknown uncertainties and unstructured dynamics in uncertain electro-hydraulic actuators simultaneously. The feasibility of the proposed methodology is verified through different scenarios of faults for intuitive evaluations. As the challenge in detecting, isolating, and estimating sensor faults for the FTC reconstruction, this paper brings a new methodology that can help instantly estimate and decouple residual signal from a measured one to ease the control development and is potentially expanded to other industrial applications.