| Designing and implementing a fault-tolerant control (FTC) system for large-scale systems pose a great challenge due to the high dimensionality, multiple inputs and outputs, and processor limitations. In this study, the problem of designing and implementing a decentralized FTC system is considered for large-scale systems. The decentralized FTC system consists of three schemes: decentralized nominal controller, decentralized fault detection and isolation, and decentralized supervision scheme. The proposed approach overcomes the design and implementation complexities by dividing the total task of the FTC system into a number of small tasks. These small tasks can be easily implemented by running a number of commercial processors in parallel. The proposed design is applied to a typical large-scale system: a segmented telescope test bed, which consists of 6 segments giving an overall high order system. The decentralized FTC system consists of 6 local units, each one responsible for controlling one segment, detecting and isolating faults, and reconfiguring the controller for fault accommodation. The algorithm of the 6 local units is implemented by running 3 processors in parallel. Real-time results demonstrate the capability of the proposed decentralized FTC system to tolerate sensor failure in large-scale systems such as in the segmented telescope test bed. In addition, since designing an FTC system to recover the original system performance is impractical in many situations, due to the new physical constraints caused by the fault, designing an FTC system with the ability to comply with the new physical constraints is considered for a class of nonlinear systems subject to actuator saturation fault. The approach is based on the conceptual tools of linear matrix inequalities and on-line fault model estimation. The FTC system consists of nominal control, fault diagnostic, and fault accommodation schemes. These schemes are designed to: (1) achieve stability and tracking requirements; (2) detect, isolate, and estimate a fault; and (3) reduce the fault effect on the system. A nonlinear model of an F16 aircraft longitudinal motion is used to demonstrate the effectiveness of the proposed FTC system. |
