Adel Tellili

Reliable H ∞ control of multiple time scales singularly perturbed systems with sensor failure

This paper studies the reliable H ∞ control for linear time-invariant multiparameter singularly perturbed systems against sensor failures. By time-scale decomposition, the full-order system is decomposed into slow and fast subsystems. After designing a reliable H ∞ controller for the global system, three reduced reliable H ∞ sub-controllers based on the slow and fast problems are obtained through the manipulation of the algebraic Riccati equations. The resulting control systems are reliable in that they provide guaranteed asymptotic stability and H ∞ performance when all control components are operational as well as when sensor failures occur.

Model-based fault diagnosis of two-time scales singularly perturbed systems

The aim of this paper is to detect and to isolate sensor faults in singularly perturbed systems (SPS), with emphasis on the use of slow subsystem. Firstly, we considered the fast subsystem as a modelling error by the approximation of the SPS with the slow subsystem. Structured residuals were generated, using robust parity space, to the fault diagnosis of the SPS. A second approach was to design a set of observer-based residuals based on the slow subsystem. In order to validate the proposed approaches, we applied the results on a F-8 aircraft example.

Fault Diagnosis and Reconfigurable Control of Singularly Perturbed Systems using GIMC Structure

paper proposes the extension of generalized internal model control (GIMC) based diagnosis and fault tolerant control to singularly perturbed system. This control method consists of two parts: a controller which guaranties nominal performance and works in the fault free case and a robustness controller to compensate the fault when a sensor failure is detected. This work describes the way to design such controllers for singularly perturbed systems so that the performance with the nominal controller may be guaranteed in the case of sensor failure.

Composite control of a delayed singularly perturbed system by using Lambert-W function

The composite state feedback control designed for singularly perturbed system SPS with small time-delay by using Lambert-W function is proposed in this paper. Based on the delayed slow subsystem (SS) and fast subsystems (FS) decomposition, we design a composite sate-feedback control. So the gain of delayed SS will be designed by using Lambert-W function and the gain of FS will be designed on the basis of classical pole placement method, and the two gains will be regrouped in global gain to design the delayed SPS. A numerical example is presented to illustrate the effectiveness of the proposed design approach.

Reconfigurable Control of Two-Time Scale Systems in Presence of Additive Faults

This work presents an adaptive approach for fault tolerant control of singularly perturbed systems, where both actuator and sensor faults are examined in presence of external disturbances. For sensor faults, an adaptive controller is designed based on an output-feedback control scheme. The feedback controller gain is determined in order to stabilize the closed-loop system in the fault free case and vanishing disturbance, while the additive gain is updated using an adaptive law to compensate for the sensor faults and the external disturbances. To correct the actuator faults, a state-feedback control method based on adaptive mechanism is considered. The both proposed controllers depend on the singular perturbation parameter e leading to ill-conditioned problems. A well-posed problem is obtained by simplifying the Lyapunov equations and subsequently the controllers using the singular perturbation method and the reduced subsystems yielding to an e-independent controller. The control scheme, designed based on the Lyapunov stability theory, guarantees asymptotic stability in presence of additive faults and external disturbances provided the singular perturbation parameter is sufficiently small. Finally, a numerical example is presented to demonstrate the effectiveness of the obtained results. DOI: http://dx.doi.org/10.5755/j01.itc.44.4.8532

Sensor Fault Diagnosis of Singularly Perturbed Systems Applied to F-8 Flight Dynamic

Abstract The paper outlines sensor fault-detection and isolation of singularly perturbed systems (SPS) using the slow subsystem. In deterministic case, the fast subsystem is considered as a modeling error by the approximation of the SPS with the slow subsystem. A second approach was to design a set of observer-based residuals using the slow subsystem. In stochastic case, the slow subsystem is used to approximate the initial system and to the sensor fault-diagnosis. The goal of the paper is to generate slow subsystem based residuals to fault-detection of SPS. We applied the results on a F-8 aircraft-dynamic to validate the proposed approaches.

Additive fault tolerant control of nonlinear singularly perturbed systems against actuator fault

Abstract This paper presents the design of an additive fault tolerant control for nonlinear time-invariant singularly perturbed systems against actuator faults based on Lyapunov redesign principle. The overall system is reduced into subsystems with fast and slow dynamic behavior using singular perturbation method. The time scale reduction is carried out when the singular perturbation parameter is set to zero, thus avoiding the numerical stiffness due to the interaction of two different dynamics. The fault tolerant controller is computed in two steps. First, a nominal composite controller is designed using the reduced subsystems. Secondly, an additive part is combined with the basic controller to overcome the fault effect. The derived ε - independent controller guarantees asymptotic stability despite the presence of actuator faults. The Lyapunov stability theory is used to prove the stability provided the singular perturbation parameter is sufficiently small. The theoretical results are simulated using a numerical application.

Diagnosis of delayed discrete-time singularly perturbed systems based on slow subsystem

This work presents an approach for fault diagnosis of discrete time singularly perturbed systems (SPS) with time-delay, called parity space in order to generate fault detection residual. In fact, to decompose the full system into slow and fast subsystems, we based on singular perturbation method. Then, we can use the reduced residual generated basing on slow subsystem in order to estimate and isolate faults of the global delayed SPS. A numerical example is presented to demonstrate the efficiency of the proposed approach in the case of sensor faults with different values of singular perturbation parameter epsilon.

Centralized and Decentralized Adaptive FTC of Interconnected and Networked Control System

In this work, we focus on monitoring and reconfiguration of an Adaptive Model Reference (MRA) Fault-Tolerant Control (FTC) for large-scale system. This particular class presents an interconnected and networked control system (INCS). Moreover, the system can be decomposed into N-interconnected subsystems communicating with network. Then the global output of INCS and one or more outputs of N-interconnected and networked control subsystems are attacked by sensor faults. Therefore, an active Fault-Tolerant (FT) approach, say the model reference adaptive control of linear systems, is used in order to guarantee not only the stability of an overall INCS globally, but also all local stabilities of N-networked control subsystems with strong interactions, delay and additive faults. Moreover, two architectures: centralized and decentralized adaptive controllers are designed to compensate the sensor faults for different internal structures of systems which are subject of this paper. The law adaptations which make the different faulty systems stable are given. A simulation example of an overall INCS consisting of three interconnected and networked control subsystems and involving stabilization of unstable steady-states is used to demonstrate the efficiency of the proposed approach.

Robust adaptive fault-tolerant control applied to interconnected systems

In this present article a centralized structure of an adaptive method to solve the problem of robust and fault tolerant control (FTC) for large-scale system linear, continuous and time invariant (LTI), against defects sensors and external disturbances is proposed. This class of system contain N-interconnected subsystems. In fact, it operates one architecture for the direct adaptive method. This is a centralized feedback controller. It is assured by some adaptation laws which are proposed to estimate the unknown potential of sensors faults, disturbances and controller parameters Online. Then, a class of centralized controllers return state is constructed to automatically compensate for the effects of faults and external disturbances based on information extracted. An adaptive mechanism from a scheme where active fault tolerant system is exploited. The proposed techniques are finally evaluated in the light of a simulation for an overall interconnected system that can be decomposed into two subsystems coupling.