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In this paper fault detection is addressed for networked control systems subject to random packet dropout in both sensor-to-controller link and controller-to-actuator link. First a new model of NCS is proposed, which directly eliminates influence of packet dropout in the sensor-to-controller link. Then adaptive threshold is given to ensure robustness to packet dropout in the controller-to-actuator link. False alarm rate analysis is also given, which is not addressed in most of the literature on fault detection of networked control systems. The fault detection scheme can ensure both robustness to packet dropout as well as disturbance and sensitivity to fault, which is superior to the existing approaches. Moreover, the residual generation can be achieved by using linear matrix inequality based convex optimization technique. Comparison with existing approaches illustrates advantages of our method.

The Parity Space Approach (PSA) in time domain and the H² approach in frequency domain are two important approaches to design robust Fault Detection (FD) systems. Compared with the H² approach, the PSA is simpler in design but has a poorer performance index unless it adopts a parity vector of a very high order, which will lead to an unacceptable computational load. In this paper, a new approach to design a PSA based FD system in frequency domain is proposed, in which the optimal performance index of the H² approach can be realized with a low order PSA based residual generator and a simple narrowband filter. The new approach ensures a simple design form similar to that of the PSA, an optimal performance index as good as that of the H² approach, a low computational load and an easy online realization simultaneously. Keywords. Fault detection, H², optimization, parity space approach, robustness

In this paper, an active fault tolerant control (FTC) strategy is presented for linear dynamic systems. The robust observer-based fault detection and isolation (FDI) systems are applied to guide the reconfiguration of controller parameters to achieve the optimal control performance during different operating conditions of the system: fault-free, fault detected and fault isolated. The selection of design parameters is achieved using the linear matrix inequality (LMI) optimization technique.

In traditional parity space approaches, a parity vector with a low order means a simple online realization but a bad performance, while that with a high order leads to a good performance but an unacceptable calculation amount. In this paper, by introducing a simple scalar IIR (Infinite Impulse Response) filter, a new kind of parity relation based residual generator and the corresponding optimization approach are proposed. With the new approach, a residual generator can deliver a very good performance index but with a parity vector of low order. Simulation results are given.