Research On Fault Diagnosis And Optimal Fault-Tolerant Control Approaches For Time-Delay Systems

Fault diagnosis and fault-tolerant control have received extensive attention due to the increasing demands for high safety and reliability of dynamic systems. On the other hand, time-delay exists in many practical systems. Time-delay usually makes the fault diagnosis and fault-tolerant control more complex and difficult, even may result in the fault diagnoser's unstability or poor performances. Therefore, the research on fault diagnosis and fault-tolerant control approaches for time-delay systems is very important.In the face of a class of usual actuator and/or sensor faults in practice, by using the observer-based approach and combining with optimal control theory, duality principle and other some technology, fault diagnosis and fault-tolerant control approaches are researched for systems with different time-delays. The major contents of this dissertation are as follows.(1) The approaches to fault diagnosis and fault-tolerant control are researched for linear continuous systems with state delays. The sufficient conditions of fault diagnosability are proved for systems with the faults whose dynamic characteristics are known but the initial instant and initial conditions are unknown in this paper. A reduced-order state observer is constructed according to meeting the observability of error equation. Then, a new design approach to fault diagnoser is further proposed based on the reduced-order observer which needn't residual to diagnose faults. By utilizing the feedforward-feedback idea and the results of fault diagnosis, a dynamic self-restore fault-tolerant control law and an output measurement compensation law are designed.(2) The fault diagnosis and fault-tolerant control problems are researched for linear continuous systems with delayed measurements and states. A fault diagnoser is designed by proposing the delay-free transformation approach for the delayed measurements. Then a dynamic optimal fault-tolerant control approach is researched based on state feedback, and the physically unrealizable problem of the optimal fault-tolerant control is solved. The proposed fault-tolerant approach can not only realize the dynamic fault-tolerant control but also make the system meet the quadratic performance index. (3) The fault diagnosis and fault-tolerant control problems are researched for discrete control systems. A fault diagnosis approach, which bases on the error equation obserbability but doesn't need the residual to embody faults, is researched for linear time-invariant discrete systems by using the idea of fault diagnosis for linear continuous systems. And a fault-tolerant control law and a compensation law of output measurement which can automatically switch according to the different cases of the faults are designed for discrete control systems.(4) The optimal fault diagnosis problem is researched for discrete control systems with delayed measurements. An observability criterion is proved by researching the delay-free transformation approach to the delayed measurements for discrete control systems. Based on this, an observer-based optimal fault diagnosis approach is proposed which meets the quadratic performance index.