Songjiao Shi

Robust fault detection for a class of nonlinear time-delay systems

In this paper, the robust fault detection filter (RFDF) design problems are studied for nonlinear time-delay systems with unknown inputs. Firstly, a reference residual model is introduced to formulate the robust fault detection filter design problem as an H∞ model-matching problem. Then appropriate input/output selection matrices are introduced to extend a performance index to the time-delay systems in time domain. The reference residual model designed according to the performance index is an optimal residual generator, which takes into account the robustness against disturbances and sensitivity to faults simultaneously. Applying robust H∞ optimization control technique, the existence conditions of the robust fault detection filter for nonlinear time-delay systems with unknown inputs are presented in terms of linear matrix inequality (LMI) formulation, independently of time delay. An illustrative design example is used to demonstrate the validity and applicability of the proposed approach.

Actuator fault diagnosis for a class of time-delay systems

This paper presents a novel approach for the actuators fault diagnosis of time-delay systems by using an adaptive observer technique. The systems considered are subjected to an unknown input that represents either model uncertainty or external disturbances. At first, fault detection observer and fault diagnosis observer for linear actuators are designed. An extension to nonlinear actuators is then made, and a convergent adaptive diagnostic algorithm is developed. Finally, two numerical examples are given to illustrate the efficiency of the proposed method.

A state-delay system approach to fault detection for networked control systems

This paper considers the fault detection problem for networked control systems (NCSs) with both network-induced delay and data dropout. By transforming the NCS into a state-delay system, we can obtain a time-independent fault detection filter for the NCS, directly utilizing the fault detection methods for state-delay system. An observer-based fault detection filter (FDF) is firstly proposed for residual generation. Then a performance index is introduced to enhance the robustness of fault detection filter and, based on it, the fault detection filter design problem is formulated as an H infin optimization problem. Considering the unbounded network-induced delay (the worst-case transmission), a delay-independent solution of the optimization problem is derived by applying Lyapunov-Krasovskii approach. The residual evaluation problem is also considered. Finally, an illustrative design example is employed to demonstrate the validity of the proposed approach.

Active Fault-tolerant Control Design for a Class of Time-delay Systems

This paper deals with the problem of active fault-tolerant control design for a class of linear systems with time-delays. For a class of linear time delay system, firstly, adaptive observer was designed to estimate fault, then a new active fault-tolerant controller is designed which can guarantee that the controlled system keep stable in faulty status, thus the active fault-tolerant control design for this systems is realized. Finally, a numerical example is given to illustrate the efficiency of the proposed design method

A fault detection and isolation scheme based on parity space method for discrete time-delay system

A fault detection and isolation (FDI) scheme for discrete time-delay system is proposed, which can not only detect but also isolate the faults. A time delay operator nabla is introduced to deal with time-delay items. Residuals in the form of parity space can be deduced from the recursion of the system equations. Further more, a generalized residual set is created using the freedom of the parity space redundancy. Thus, both fault detection and fault isolation have been accomplished. The proposed method has been verified by a numerical example.

A new robust on-line fault diagnosis for nonlinear difference-algebraic systems

A new robust online fault diagnosis method based on least squares estimation for nonlinear difference-algebraic systems (DAS) with uncertainties is proposed. Based on the known nominal model of DAS, it firstly constructs an auxiliary system consisting of a difference equation and an algebraic equation, then based on the relationship between the state deviation and the faults in the difference equation and the relationship between the algebraic variable deviation and the faults in the algebraic equation, it identifies the faults on-line through least squares estimation. This method can not only detect, isolate and identify faults for DAS, but also give the upper bound of the error of fault identification.

Integrated Controller/Detector Design for State-delay Systems Based on Mixed GH 2 / H ∞ Control

This paper considers the integrated controller/detector design problem for time-delay systems with both exogenous disturbance and fault. Using mixed GH2/Hinfin control theory, the integrated controller/detector is designed. The GH2 norm is considered as a measure for fault detection objectives and the Hinfin norm is considered as a measure for control objectives. The sufficient conditions for the existence of integrated controller/detector and its design method are presented in terms of linear matrix inequality (LMI), independently of time delay. A numerical example is finally given to demonstrate the validity and applicability of the proposed approach

Hamilton-Jacobi inequality based reliable H/sup /spl infin// control for nonlinear systems

In this paper, the problem of reliable H/sup /spl infin// control for affine systems is addressed. First, the normal state, partial failure and outage of an actuator are simultaneously considered by introducing a new actuator model, then, two reliable H/sup /spl infin// controllers are proposed for two cases: one has only one faulty actuator in the set of all actuators, and the other has a certain number of faulty actuators in a pre-specified subset of all the actuators. The conditions for the existence of reliable H/sup /spl infin// controllers are presented. The analyses show that the resulting closed-loop control system is asymptotically stable and has certain disturbance attenuation ability.