This paper deals with the problem of fault estimation and accommodation for a class of networked control systems with nonuniform uncertain sampling periods. Firstly, the reason why the adaptive fault diagnosis observer cannot be applied to networked control systems is analyzed. Based on this analysis, a novel robust fault estimation observer is constructed to estimate both continuous-time fault and system states by using nonuniformly discrete-time sampled outputs. Furthermore, using the obtained states and fault information, a nonuniformly sampled-data fault tolerant control law is designed to preserve the stability of the closed-loop system. The proposed scheme can not only guarantee the impact of continuous-time uncertainties and discrete-time sampled estimation errors on the faulty system to satisfy a H 1 performance index but also repress the negative effect of the unknown intersample behavior of continuous-time fault by use of an inequality technique. Finally, simulation results are included to demonstrate the feasibility of the proposed method. Although no time delays and packet dropouts during the data transfer are assumed in the former NCS, it can also express a general framework of NCSs with packet dropouts. Considered the packet dropouts, the input and output signal are updated when the new information is arrived. If the sampling and updating intervals contain the packet dropouts' times, the nonuniformly sampled NCS (1), (3)-(4) can describe the NCSs with dropouts. This statement has been made in [14] and [25].
Remark 2According to the former proof, the core idea of the adaptive fault diagnosis observer is to take e x .t / and e f .t / apart to construct the Lyapunov function. Correspondingly, in the derivative of the Lyapunov function, there exists two cross items of e x .t /; e f .t /, but no quadratic item of e f .t /. Thus one has to choose Lyapunov matrices P , 1 and make equality (10) holds to remove the two cross items.