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ABSTRACT: This paper deals with the problem of fault-tolerant control (FTC) for a class of nonlinear uncertain systems against actuator faults using adaptive logic-based switching control method. The uncertainties under consideration are assumed to be dominated by a bounding system which is linear in growth in the unmeasurable states but can be a continuous function of the system output, with unknown growth rates. Several types of common actuator faults, e.g., bias, loss-of-effectiveness, stuck and hard-over faults are integrated by a unified fault model. By utilizing a novel adaptive logic-based switching control scheme, the actuator faults can be detected and automatically accommodated by switching from the stuck actuator to the healthy or even partly losing-effectiveness one with bias, in the presence of large parametric uncertainty. In particular, two switching logics for updating the gain in the output feedback controllers are designed to ensure the global stability of the nominal (fault-free) system and the boundedness of all closed-loop signals of the faulty system, respectively. Two simulation examples of an aircraft wing model and a single-link flexible-joint robot are given to show the effectiveness of the proposed FTC controller. Copyright © 2010 John Wiley & Sons, Ltd.
International Journal of Robust and Nonlinear Control 06/2010; 21(4):404 - 428. · 1.55 Impact Factor
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ABSTRACT: In this paper, a high-gain nonlinear observer based fault diagnosis approach is proposed for a general class of nonlinear uncertain systems. The nonlinear system under consideration contains parameter uncertainties as well as Lipschitz-like nonlinearities and may be harmed by time-varying fault. The fault diagnosis algorithm is designed based on a new adaptive estimation method for estimation of the parameters related to faults. The main result is given in a constructive manner by developing a novel nonlinear adaptive observer, without resort to any linearization. The design of the proposed observer does not necessitate the resolution of any dynamics systems and its expression is explicitly given. Its global exponential convergence is ensured, which does not rely on solving any kind of dynamic Riccati equation. A simulation example is given to illustrate the efficiency of the proposed fault diagnosis method.
Decision and Control, 2009 held jointly with the 2009 28th Chinese Control Conference. CDC/CCC 2009. Proceedings of the 48th IEEE Conference on; 01/2010
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ABSTRACT: This note presents a filter design for a large class of multiple-input-multiple-output(MIMO) nonlinear uncertain stochastic systems with time-delay. A high-gain filer is proposed such that the dynamics of the estimation error is guaranteed to be stochastically exponentially ultimately bounded in the mean square (Yaz & Azemi, 1993; Zakai, 1967). For easiness of implementation and calibration, the gain of of the proposed filter does not necessitate the resolution of any dynamics systems and it expression is explicitly given, i.e., its calibration is achieved through the choice of a single parameter. A simulation example is given to illustrate the performance of the proposed filter.
Control Applications, (CCA) & Intelligent Control, (ISIC), 2009 IEEE; 08/2009
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ABSTRACT: This paper deals with the adaptive output control of a class of uncertain nonlinear systems with an unknown non-symmetric dead-zone nonlinearity. The nonlinear systems considered are dominated by a triangular system without zero dynamics satisfying polynomial growth in the unmeasurable states. An adaptive control scheme is developed without constructing the dead-zone inverse. The proposed adaptive scheme requires only the information of bounds of the slopes and the breakpoint of dead-zone nonlinearity. The novelty of this paper is that a universal-type adaptive output feedback controller is numerically constructed by using a sum of squares (SOS) optimization algorithm, which can globally regulate all the states of the uncertain systems without knowing the growth rate. An example is presented to show the effectiveness of this methodology.
Decision and Control, 2008. CDC 2008. 47th IEEE Conference on; 01/2009
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ABSTRACT: This paper studies the fault tolerant control (FTC) problem for a class of nonlinear discrete-time systems with guaranteed H<sub>infin</sub> performance objective in the presence of actuator faults. The mode of faults under consideration is typical aberration of actuator effectiveness. The novelty of this paper is that the effect of the nonlinear terms is described as an index in order to transform the FTC design problem into a semi-definite programming (SDP). The proposed optimization approach is to find zero optimum for this index. Combined with H<sub>infin</sub> performance index, the conceived multi-objective optimization problem is solved by using sum of squares method (SOS) in a reliable and efficient way. A numerical example is included to verify the applicability of this new approach for the nonlinear FTC synthesis.
American Control Conference, 2008; 07/2008
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ABSTRACT: This paper studies the fault tolerant control (FTC) problem for nonlinear systems, with guaranteed cost or H<sub>infin</sub> performance objective in the presence of actuator faults. The mode of faults under consideration is typical aberration of actuator effectiveness. To transform the FTC design problem into a semi-definite programming (SDP), the effect of the nonlinear terms is described as an index. The proposed optimization approach is to find zero optimum for this index. Combined with other performance indexes, the conceived multiobjective optimization is solved by sum of squares method (SOS) in a reliable and efficient way. Numerical examples are included to verify the applicability of this new approach for the nonlinear FTC synthesis.
Decision and Control, 2007 46th IEEE Conference on; 01/2008
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ABSTRACT: In this paper, the fault tolerant control problem of nonlinear systems against actuator failures is considered. By representing the open-loop nonlinear systems in a state dependent linear-like polynomial form and implementing a special class of Lyapunov functions, the above problem can be formulated in terms of state dependent linear polynomial inequalities. Semidefinite programming relaxations based on the sum of squares decomposition are then used to efficiently solve such inequalities.
Control Applications, 2007. CCA 2007. IEEE International Conference on; 11/2007
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ABSTRACT: This paper deals with the adaptive output feedback control problem of a class of uncertain nonlinear systems with an unknown non-symmetric dead-zone nonlinearity. The nonlinear system considered here is dominated by a triangular system without zero dynamics satisfying polynomial growth in the unmeasurable states. An adaptive control scheme is developed without constructing the dead-zone inverse. The proposed adaptive control scheme requires only the information of bounds of the slopes and the breakpoint of dead-zone nonlinearity. The novelty of this paper is that a universal-type adaptive output feedback controller is numerically constructed by using a sum of squares (SOS) optimization algorithm, which ensures the boundedness of all the signals in the adaptive closed-loop without knowing the growth rate of the uncertainties. An example is presented to show the effectiveness of the proposed approach.
Automatica.
