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ABSTRACT: In this study, a novel optimal anti-windup control scheme is proposed to resolve the input constraint problem for multi-input multi-output (MIMO) systems, without losing the good tracking performance as possible. Avoiding complex numerical calculation, the proposed optimal control scheme can systematically compress a huge control input within the range of the required restriction by adjusting well-designed weighted matrices for linear constrained systems. Combining a conventional linear quadratic analogue tracker (LQAT) with the proposed scheme, the anti-windup-based optimal analogue tracker not only possesses the advantage of the conventional LQAT, good tracking performance, but also effectively resolves the input saturation problem. For practical consideration, the proposed LQAT is implemented by adopting the prediction-based digital redesign technique to design an effective digital control of linear MIMO sampled-data systems under input constraints.
IET Control Theory and Applications 03/2011; · 0.99 Impact Factor
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ABSTRACT: The universal state-space adaptive observer-based fault diagnostics/estimator and the high performance tracker for the sampled-data non-linear slowly time-varying system with unanticipated decay factors in actuators/system states are proposed. The optimal linearisation technique is used to obtain the exact (local) linear model at each operating state for a non-linear system, so that the actuator and state fault detection and performance recovery of a sampled-data non-linear time-varying system can be accomplished. Additionally, an improved Kalman filter-based adaptive observer is proposed to achieve a better estimation-based performance recovery than the conventional one. A residual generation scheme and a mechanism for auto-tuning switched gain is also presented, so that the proposed methodology is applicable for the fault detection and diagnosis (FDD) for actuator and state faults to yield the high tracking performance recovery. For practical implementation, this study also takes advantage of the merit of digital redesign methodology to convert a theoretically well-designed analogue controller/observer with a high-gain property into its corresponding low-gain digital controller/observer without possibly losing the high tracking/estimation as well as FDD performance recovery. Examples are given to illustrate the effectiveness and performances of the provided methodology.
IET Control Theory and Applications 02/2011; · 0.99 Impact Factor
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Journal of Circuits, Systems, and Computers. 01/2011; 20:1571-1589.
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ABSTRACT: This paper presents the low-order multi-rate linear time-invariant decentralized trackers using the new observer-based sub-optimal method for a class of unknown sampled-data nonlinear time-delay system with closed-loop decoupling. For the unknown sampled-data nonlinear time-delay system, we assume that the inner time delay is clearly known. Under this prerequisite, the appropriate (low-) order decentralized linear observer for the unknown sampled-data nonlinear system is determined by the off-line observer/Kalman filter identification (OKID) method with artificial delay input and actual delay output. Then, the above observer has been further improved based on the proposed new observer-based sub-optimal approach. Sequentially, the decentralized tracker with the high gain property is proposed, so that the closed-loop system has the decoupling property. The proposed approach constructs complete mathematics method including the concept of optimal control theory and state-matching digital redesign technique and is quite useful for the complicated interconnected large-scale sampled-data nonlinear time-delay system with unknown system equation. Copyright © 2010 John Wiley & Sons, Ltd.
Optimal Control Applications and Methods 08/2010; 32(4):433 - 475. · 0.65 Impact Factor
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ABSTRACT: In this paper, a novel intelligent-based fault tolerant control (FTC) framework is proposed to solve the fault tolerant tracking control problem for unknown nonlinear multi-input multi-output (MIMO) systems. To eliminate the effect of faults, a neural network model adapted with the extended Kalman filter (EKF) is created to online identify the unknown systems, and then the steepest descent and evolutionary programming (EP) method is utilized to find a self-tuning proportional-integral-derivative (PID) controller for the adapted neural network. The resulted PID FTC controller can not only achieve the tracking objective but also can maintain the stability and the expected performance when faults occur in system. Finally, a numerical example is given to illustrate the effectiveness of the proposed methods.
Control and Automation, 2009. ICCA 2009. IEEE International Conference on; 01/2010
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ABSTRACT: A minimal realisation scheme for a class of multiple time-delay transfer function matrices with distinct poles is presented. Also, a simple minimal realisation method is developed for a specific two-input-two-output multiple time-delay system whose poles can be repeated. In addition, a state-space discretisation technique developed for a multivariable system with a single time delay is extended to a multivariable system with multiple time delays. Finally, it should be mentioned that the proposed approach is restricted to systems where multiple time delays arise only in the input and output, and not in the state. Illustrative examples are given to demonstrate the effectiveness of the proposed method.
IET Control Theory and Applications 10/2007; · 0.99 Impact Factor
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ABSTRACT: The optimal hybrid tracking control problem for analog neutral systems with multiple discrete and distributed time delays is discussed in this paper. In order to obtain good tracking performance and improve the drawback of conventional optimal control in selecting the weighting matrices, the observer with evolutionary-programming (EP)-based alternative digital redesign control technique is presented to find a low-gain digital tracker for hybrid control of the analog neutral system. A novel approach that combining the EP method and the high-gain property is proposed to search the optimal weighting matrices in the performance index to achieve the "best" tracking control for analog neutral systems for the first time. Finally, a numerical example is given to illustrate the proposed methods.
Control and Automation, 2007. ICCA 2007. IEEE International Conference on; 07/2007
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ABSTRACT: Based on the modified state-space self-tuning control (STC), a novel low-order tuner via the modified observer/Kalman filter identification (OKID) is proposed for stochastic fractional-order chaotic systems. The OKID method is a time-domain technique that identifies a discrete input-output map by using known input-output sampled data in the general coordinate form, through an extension of the eigensystem realization algorithm (ERA). First, the estimated system in the general coordinate based on the conventional OKID method is transformed to the one in an observer form to fit the state-space innovation form for the STC. Then, in stead of the conventional recursive least squares (RLS) identification algorithm used for STC, the Kalman filter as a parameter estimator with the state-space innovation form is presented for effectively estimating the time-varying parameters. Besides, taking the advantage of the digital redesign approach, the derivation of the current-output-based observer is proposed for the modified STC. As a result, the low-order state-space self-tuner with the high-gain controller property is then proposed for stochastic fractional-order chaotic systems, which the fractional operators are well approximated using the standard high integer-order operators. Finally, the fractional-order Chen and Roumlssler systems with stochastic system process and measurement noises are used as illustrative examples to demonstrate the effectiveness of the proposed methodology
Circuits and Systems I: Regular Papers, IEEE Transactions on 04/2007; · 1.97 Impact Factor
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ABSTRACT: This paper presents an observer-based weighting switch controller for dealing with the problem of cascaded systems with state saturation and external loads. This method improves the generally poor transition response and output deviation caused by state saturation and external loads. In order to maintain the state-saturation limits, we adopt the evolutionary programming optimal search technique to find the optimal switching parameters for the weighted switch controller. Also, a digital redesign method is utilized to replace a designed high-gain analog controller with a low-gain digital controller. It is shown that the digitally redesigned outputs closely track the analogously controlled outputs. The digital redesign technique is then extended to find the digital version of the continuous-time observer. An illustrative example is demonstrated to show the effectiveness of the proposed procedure.
ISA Transactions 02/2005; 44(1):93-115. · 1.11 Impact Factor
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ABSTRACT: In this paper, we propose a new dual-rate, observer-based control scheme utilizing digital redesign and a weighted switching
strategy for cascaded systems with saturating actuators and state constraints. The weighted switching approach, which uses
an evolutionary programming optimal search technique, improves the generally poor transition response caused by nonlinear
constraints on saturating actuators and state constraints. An inner loop state compensator is provided to correct the windup
effects on the actuator. The designed scheme can easily be implemented using digital processors and enables
us to improve the performance of cascaded systems with saturating actuators and state constraints. An illustrative example
is presented to demonstrate the effectiveness of the proposed methodology.
Circuits Systems and Signal Processing 01/2005; 24(1):53-82. · 0.82 Impact Factor
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ABSTRACT: A lifted prediction-based digital redesign method to discretize an analogue tracker for a sampled-data systems is presented. The developed lifted digital redesign method is then used to construct a full/reduced-order digital observer. The developed lifted observer-based digital tracker improves the intersample behaviour of the digitally redesigned sampled-data systems. An illustrative example of a hybrid multivariable system demonstrates the effectiveness of the proposed method.
International Journal of Systems Science 04/2004; 35(4):255-271. · 0.99 Impact Factor
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ABSTRACT: This paper deals with the problem of robust H<sub>∞</sub> filtering for a class of linear continuous-time interval systems with delay dependence. The problem aims at designing a stable linear filtering assuring asymptotic stability and a prescribed H<sub>∞</sub> performance level for the filtering error system. A sufficient condition for the existence of such a filter is developed in terms of linear matrix inequalities. A numerical example demonstrates the validity of the theoretical results.
Systems, Man and Cybernetics, 2003. IEEE International Conference on; 11/2003
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ABSTRACT: This paper deals with the problem of robust stability and robust H<sub>∞</sub> control for a class of uncertain neutral systems. The nonlinearities are assumed to satisfy the global Lipschitz conditions and appear in the term of perturbation. Attention first is focused on investigating a sufficient condition for designing a state feedback controller which stabilizes the uncertain neutral system under consideration of robust stabilization dependent of delay. Then, we show that it guarantees an H<sub>∞</sub>-norm bound constraint on the disturbance attenuation. The proposed results are given in terms of linear matrix inequalities. An example is worked out to illustrate the validness of the theoretical results.
Systems, Man and Cybernetics, 2003. IEEE International Conference on; 11/2003
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ABSTRACT: This paper addresses how a variable coefficient, two-dimensional (2D)
multiple-input, multiple-output system described by second-order partial differential
equations (PDEs) can be converted to a discrete variable coefficient Roesser model (RM).
The following important question for its practical application is addressed: How does the
choice of the finite difference operators for each differential operator and the respective
integral intervals determine whether it is possible to arrive at a formulation according to
the RM? This problem has not yet been addressed in generality. The results presented
give a clear procedure to follow in the application of a finite difference discretization. The
proposed prescription covers some important aspects, such as the state-space structure of
variable coefficient difference equations, setting the states of the RM, and modeling of the
RM, all of which are clearly interdependent. The proposed state-space modeling of a 2D
system described by a PDE provides a powerful tool for analysis, design, and processing
of variables and processes depending on two independent variables, one of which may
be time. In particular, the model is very useful for 2D system control, such as observer
design, optimal filter design, and state-feedback control methodologies presented in the
literature.
Circuits Systems and Signal Processing 09/2003; 22(5):423-463. · 0.82 Impact Factor
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ABSTRACT: This paper presents a new observer-based sub-optimal digital tracker for the continuous-time system with input and state time delays. We directly convert the continuous-time input-state delayed system into an equivalent discrete-time input-state delayed model and its extended discrete-time delay-free model. In addition, we directly discretize the linear quadratic performance index specified in the continuous-time domain into an equivalent decoupled discrete-time performance index using the newly developed extended delay-free model. As a consequence, the well-developed discrete-time optimal control theory for discrete-time delay-free system can be applied to determine the optimal digital tracker for the continuous-time input-state delayed system. When the states of the continuous-time input-state delayed system are not available for measurements, we develop a sub-optimal digital observer for the original continuous-time input-state delayed system using the state-matching digital redesign technique and the digital-to-analog model conversion technique. As a result, the proposed observer-based linear quadratic digital tracker is able to make the output of the digitally controlled continuous-time input-state delayed system sub-optimally track the desired reference signals. An illustrative example is presented to demonstrate the effectiveness of the proposed design methodology. Copyright © 2003 John Wiley & Sons, Ltd.
Optimal Control Applications and Methods 06/2003; 24(4):197 - 236. · 0.65 Impact Factor
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ABSTRACT: The stability for cellular neural networks (CNNs) with time-varying delay is introduced by using a linear-matrix inequality. A sufficient condition related to the global asymptotic stability for delay CNNs is proposed. It is shown that the condition relies on the dependence of the delay. This condition is less restrictive than that given in the literature.
IEEE Transactions on Circuits and Systems I Fundamental Theory and Applications 06/2003;
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ABSTRACT: The cascaded conventional anti-wind-up (CAW) design method for integral controller is discussed. Then, the prediction-based digital redesign methodology is utilized to find the new pulse amplitude modulated (PAM) digital controller for effective digital control of the analog plant with input saturation constraint. The desired digital controller is determined from existing or pre-designed CAW analog controller. The proposed method provides a novel methodology for indirect digital design of a continuous-time unity output-feedback system with a cascaded analog controller as in the case of PID controllers for industrial control processes with the presence of actuator saturations. It enables us to implement an existing or pre-designed cascaded CAW analog controller via a digital controller effectively.
ISA Transactions 02/2003; 42(1):73-88. · 1.11 Impact Factor
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ABSTRACT: We first deal with the robust stability of uncertain linear stochastic differential delay systems. We then extend the proposed theory to discuss the robust stabilization of uncertain stochastic differential delay systems.
Decision and Control, 2002, Proceedings of the 41st IEEE Conference on; 01/2003
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IEEE Transactions on Circuits and Systems I Fundamental Theory and Applications 01/2003;
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ABSTRACT: In this paper, discretized quadratic optimal control for
continuous-time two-dimensional (2D) systems is newly proposed. It
introduces a new state vector (a new virtual control input) to directly
convert the original continuous-time 2D quadratic cost function into a
decoupled discretized form. As a result, a new virtual discrete-time 2D
model with the new virtual control input is constructed to indirectly
find the desired discretized quadratic optimal regulator for the
continuous-time 2D system. The recently developed dynamic programming in
discrete-time 1D descriptor form is utilized to determine the desired
discretized quadratic optimal regulator. This method provides a novel
approach for discretized quadratic optimal control of continuous-time 2D
systems. An illustrative example is presented to demonstrate the
effectiveness of the proposed procedure
IEEE Transactions on Circuits and Systems I Fundamental Theory and Applications 02/2002;
