Study On Observer-Based Fault Diagnosis And Optimal Fault-Tolerant Control Approaches

With the great development of science and technology, control systems become more and more complicated, thus it becomes more and more important to ensure the reliability and security of modern complex systems. Fault diagnosis and fault-tolerant control technology provides a new way for improving the reliability and security of complex systems.Fault diagnosis and fault-tolerant control problems are studied for linear systems and time-delay systems by using the observer-based approach, to the common faults with known type, i.e., a class of faults whose dynamic characteristics are known and the initial conditions are unknown, the main research work on it is done as follows:(1) The fault diagnosis approach is studied based on reduced-order state observer for the linear systems. Sufficient conditions of fault diagnosability are given and proved for linear systems with this class of continuous faults whose dynamic characteristics are known and the initial conditions are unknown. A new design approach of optimal fault diagnoser based on reduced-order state observer is proposed by optimal control theory and duality principle, which realizes the on-line fault diagnosis and makes the designed fault diagnoser optimal.(2) The fault-tolerant control problem is studied for linear systems with non-complete failure fault. Two approaches of dynamic fault-tolerant control are proposed. Firstly, a dynamic optimal fault-tolerant control approach based on state feedback is proposed, and the physically unrealizable problem of optimal fault-tolerant control is considered and solved. The dynamic fault-tolerant control of system is realized and the quadratic performance index is satisfied by the proposed approach. Then an approach of the variable structure optimal fault-tolerant control based on the internal model principle is proposed. In this method, a fault compensator is designed to compensate the influence of faults on the outputs of systems by utilizing internal model principle and the results of fault diagnosis, and the design steps of the dynamic optimal fault-tolerant control are given which can regulate by the variable structure according to the occurrence of faults. The simulation results have demonstrated the validity of the two proposed fault-tolerant control approaches. (3) The fault diagnosis and fault-tolerant control problems are studied for linear systems with control time-delay. The ideas of fault diagnosis and fault-tolerant control for linear systems are generalized, so a fault diagnosis approach and two fault-tolerant control approaches are proposed for systems with control time-delay. The design approach of fault diagnoser is proposed based on reduced-order state observer for linear time-delay systems by delay-free transformation of the control time-delay, the on-line fault diagnosis and the observation of system states are realized. The design approach of dynamic optimal fault-tolerant control law is proposed for time-delay systems, and the physically unrealizable problem of optimal fault-tolerant control is considered. The approach of variable structure optimal fault-tolerant control based on internal model principle is proposed for time-delay systems. The simulation results have demonstrated the validity of the proposed fault diagnosis approach and the two fault-tolerant control approaches.(4) The fault diagnosis and optimal fault-tolerant control problems are studied for linear systems with control time-delay and state time-delay. Firstly, the design approach of optimal fault-tolerant control law is proposed for faulty systems based on the linear transformation of time-delay systems, and the existence and uniqueness of the optimal fault-tolerant control law is proved. Furthermore, the fault diagnoser is designed for time-delay systems, which diagnoses the faults while observing system states. The physically unrealizable problem of the optimal fault-tolerant control is solved by the results of fault diagnosis.