DEVELOPMENT OF FAULT DIAGNOSIS AND FAULT-TOLERANT TRACKING CONTROL FOR AN ELECTROHYDRAULIC ACTUATOR WITH SENSOR AND ACTUATOR FAULT

Abstract

In recent decades, electro-hydraulic actuator (EHA) is widely used in the model industry (i.e., aerospace systems, construction machines, robotic manipulators, and ships) due to their high-power weight ratio, low cost, efficient handling of heavy loads, and reliability. However, some negative factors affect the performance system such as nonlinear features, modeling uncertainties, and especially faults. In the EHA, the possible faults have normally happened relating to the mechanism, electronic amplifiers, servo valves, hydraulic cylinders, sensor components, or power supply with different features, which are divided into: sensor fault, component fault, and actuator fault. Therefore, this thesis develops a robust fault diagnosis and fault-tolerant tracking control scheme to not only overcome the influences of lumped disturbances/uncertainties and faults but also warrant stability, safety, and reliability.|In this thesis, various adaptive fault-tolerant controllers are proposed for a typical EHA in the presence of lumped disturbances, actuator fault (i.e., internal leakage fault and partial loss of effectiveness fault), and sensor fault. To construct the suggested controller, an observer-based (i.e., nonlinear unknown input observer, time delay estimation, extended state observer, nonlinear observer) is developed to effectively identify the sensor/actuator fault. Furthermore, various control strategies such as, conventional control, intelligent control, and modern control are applied to tackle the effect of the sensor/actuator fault. The integration of the above-mentioned techniques (i.e., observer-based, advanced control algorithm) is investigated to obtain acceptable tracking performance, robustness as well as fast convergence. The stability of the closed-loop system is proven by Lyapunov theory. Finally, the capability and effectiveness of the proposed approach are validated via the simulation and experiment results under different faulty scenarios.