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Control Theory & Applications, IET

Issue 8 • Date May 15 2014

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Displaying Results 1 - 13 of 13
  • Integrated fault-tolerant control methodology for non-linear dynamical networked control systems subject to time-varying delay

    Page(s): 535 - 545
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    This study deals with the problem of designing an integrated fault-tolerant control (FTC) methodology for non-linear dynamical networked control systems subject to time-varying delay. For the convenience of residual generation, influence caused by network-induced delay is transformed into time-varying uncertainty, which facilitates further manipulation. A fault diagnosis scheme is utilised for fault detection and isolation. On the basis of the uncertainty and fault information obtained by the fault diagnosis procedure, an FTC component is developed to compensate for the effects of uncertainty and fault. In the absence of fault, a nominal controller is employed to deal with the system uncertainty. After fault detection estimator is activated, the controller is reconfigured to guarantee the boundedness of all the system signals until the fault is isolated. After the fault is isolated, the controller is reconfigured to improve the control performance by using the fault information generated by the isolation module. In addition, the stability of the proposed scheme is rigorously investigated. Finally, a simulation example is utilised to illustrate the performance of the proposed scheme. View full abstract»

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  • Synchronised tracking control for multiple strict-feedback non-linear systems under switching network

    Page(s): 546 - 553
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (565 KB)  

    This study addresses a synchronised tracking problem for multiple strict-feedback systems with different non-linear functions under a jointly switching directed graph topology. A group with a stationary leader or with a dynamic leader is considered separately and each follower only shares information with its neighbours locally. For the case with each leader, the authors propose each distributed consensus algorithm based on the dynamic surface design to guarantee the consensus between the followers and the leader in any dimensional space where the leader's velocity and the derivatives of non-linear functions of neighbours are not required to implement the controller even if the order of followers increases. In particular, it is shown from the Lyapunov-based analysis that consensus errors are cooperatively semi-globally uniformly ultimately bounded and the consensus tracking is achieved in the presence of the stationary leader under the switching jointly connected interaction network and in the presence of the dynamic leader under the directed switching network. View full abstract»

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  • New approach to derivative calculation of multi-valued logical functions with application to fault detection of digital circuits

    Page(s): 554 - 560
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    This study investigates the directional derivative of multi-valued logical functions with application to fault detection of multi-valued digital circuits. Firstly, the authors study the calculation problem of directional derivatives of multi-valued logical functions by using the semi-tensor product. Several new results and a new algorithm are obtained to calculate the directional derivative. Then, the achieved results are applied to the fault detection of multi-valued digital circuits. A complete test set of stuck-at faults is obtained. Finally, two illustrative examples are presented to demonstrate the effectiveness of the authors' method. View full abstract»

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  • Robust and decentralised output regulation of switched non-linear systems with switched internal model

    Page(s): 561 - 573
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (529 KB)  

    This study investigates the global robust output regulation problem for a class of switched non-linear systems with stabilisable and unstabilisable subsystems. First, this study proposes a new concept, namely switched internal model, as an extension of the concept of non-switched internal model, which provides a tool for solving the output regulation problem of switched non-linear systems. Also, the authors show that the problem of output regulation boils down to a global robust regulation problem of an appropriately switched augmented system via a switched internal model. Then, the global robust regulation problem under a class of switching signals with average dwell time is solved by using the average dwell time method, which leads to the solution of the problem of global robust output regulation. Further, the authors apply this type of switched internal models above to solve the global decentralised output regulation problem for a class of large-scale switched non-linear systems with stabilisable and unstabilisable subsystems. An example is provided to demonstrate the effectiveness of the proposed approach. View full abstract»

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  • Fault-tolerant output synchronisation control of multi-vehicle systems

    Page(s): 574 - 584
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (765 KB)  

    This study presents a fault-tolerant output synchronisation control approach for a class of non-linear multi-vehicle systems. Firstly, adaptive fault diagnosis observers are designed for vehicle systems by utilising local measurements. Adaptive thresholds for distributed fault-detection of each vehicle system are derived. Then an adaptive fault estimation algorithm is proposed. Using the online obtained fault information, an adaptive fault-tolerant control protocol is designed to ensure the output synchronisation of the networked vehicle systems. It is proved that the proposed active fault-tolerant control protocol is capable of maintaining the output synchronisation performance of the multi-vehicle systems, at an acceptable level, in the presence of faults. Finally, simulation results are presented to show the effectiveness of the proposed algorithms. View full abstract»

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  • Robust transcale decentralised estimation fusion for multisensor systems based on wavelet packet decomposition

    Page(s): 585 - 597
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (629 KB)  

    In this study, an effective wavelet packet decomposition (WPD)-based robust transcale decentralised estimation fusion algorithm is proposed for multisensor systems. The standard state-space models of wavelet packet coefficients at the coarsest scale decomposition layer are established by Haar WPD. Based on the above models, the decentralised H filtering fusion formulae is employed to obtain the fusion estimates at the coarsest scale decomposition layer, and these estimates are then used to reconstruct the estimates at the finest scale by an inverse WPD transform. At last, the feasibility analysis of the proposed algorithm is given. Two simulation examples are presented to illustrate the effectiveness of the proposed algorithm. View full abstract»

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  • How BIBO stability of LTI fractional-order time delayed systems relates to their approximated integer-order counterparts

    Page(s): 598 - 605
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    Time delay generates exponential transcendental terms in characteristic equations. Subsequently, the applied methods are narrow to assess the stability map of delayed fractional-order systems with vanishing fractions. In this case, it is convenient to approximate these equations with its integer-order counterparts to design controllers or investigate features of the systems. However, delay can cause enormous differences between characteristic of these two equations. This study offers a method to survey analytically the stability of fractional-order time delayed linear time invariant systems with infinitesimal fractions. In this method, equations are transferred to an explicit expression which enables one to analyse stability of retarded, neutral and even integer-order systems simultaneously. View full abstract»

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  • New mixed-delay-dependent robust stability conditions for uncertain linear neutral systems

    Page(s): 606 - 613
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    In this study, mixed-delay-dependent robust stability problem is investigated for uncertain linear neutral systems with mixed delays. The existing stability conditions are obtained by employing the information of neutral delay and discrete delay independently, and are conservative to some extent. Different from most existing methods, this study attempts to introduce the interconnected information between neutral delay and discrete delay. Based on such an idea, the simple stability and robust stability conditions are firstly proposed by integral inequality method, then improved stability and robust stability conditions are obtained by incorporating delay-decomposition idea and augmented Lyapunov-Krasovskii functional. Theory analysis and examples show the benefits of the proposed techniques and conditions. View full abstract»

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  • Linear matrix inequalities-based membershipfunction-dependent stability analysis for non-parallel distributed compensation fuzzy-model-based control systems

    Page(s): 614 - 625
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (998 KB)  

    This study investigates the stability of fuzzy-model-based (FMB) control system, which is formed by a Takagi-Sugeno (T-S) fuzzy model representing a non-linear plant and a fuzzy controller connected in a closed loop. The proposed fuzzy controller considers a higher design flexibility that the premise membership functions and the number of fuzzy rules are allowed to be not the same as those of the T-S fuzzy model. By employing simple membership functions and a smaller number of fuzzy rules, the complexity of the fuzzy controller can be reduced to facilitate its implementation. Based on the Lyapunov stability theory, a membership-function-dependent (MFD) stability analysis is proposed to develop stability conditions in the form of linear matrix inequalities (LMIs) to determine the system stability and facilitate the control synthesis. The information of the membership functions is brought to the MFD LMI-based stability conditions, which are dedicated to the FMB control system under consideration. It is thus the proposed MFD stability analysis result is more relaxed compared with the existing membership-function-independent stability analysis results. A simulation example is given to illustrate the effectiveness of the proposed approach. View full abstract»

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  • Non-fragile state-feedback control of uncertain piecewise-affine slab systems with input constraints: a convex optimisation approach

    Page(s): 626 - 632
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    The main contribution of this work is to propose a design technique for state-feedback control of continuous-time piecewise-affine (PWA) systems that is robust not only to the system uncertainties, but also to variations of the controller gains. More specifically, this study presents sufficient conditions to synthesise a robust non-fragile PWA controller that exponentially stabilises the closed-loop equilibrium point. Furthermore, these conditions are cast as an optimisation problem subject to a set of linear matrix inequalities (LMIs), which can then be solved efficiently. In addition, a set of LMI conditions are derived to ensure that the control input will always meet a pre-assigned upper bound. Simulation results demonstrate the effectiveness of the proposed approach. View full abstract»

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  • On overshoot and integrators

    Page(s): 633 - 640
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (490 KB)  

    An extension of previous results concerning the effect of integrators on the closed-loop response overshoot is presented. It is shown that if the open-loop transfer function contains more integrators (i.e. [1/s]) than the Laplace transform of the reference signal, then the resulting output response must exhibit overshoot, assuming that a one degree-of-freedom control configuration is used. Several corollaries are also derived. The obtained results are applicable to minimum and non-minimum phase linear systems, and also strictly proper and non-strictly proper linear systems. A non-overshooting output tracking controller is then proposed for linear chain of integrators, whose structure and performance are analysed. View full abstract»

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  • Finite-time stability of quantum systems with impulses

    Page(s): 641 - 646
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (208 KB)  

    In this study, the authors investigate finite-time stability (FTS) and FTS at one target state (FTST) of quantum systems with impulses which are governed by the Schrödinger equation. New results for the mentioned quantum systems with impulses in the form of sufficient conditions of FTS and FTST are proposed. One numerical simulation is presented to illustrate the effectiveness of the obtained theoretical results. View full abstract»

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  • Convergence of switched linear systems with time-delay in detection of switching law

    Page(s): 647 - 654
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1170 KB)  

    This study studies the stabilisation of second-order switched linear systems in which delays are present in detection of switching law. For stabilisable second-order switched linear systems and constant time-delay the authors find under which values of time-delay the switched system is stable under the same switching law. Hence, they prove the existence and uniqueness of a value of time-delay that satisfies that if time-delay is less, the system is stable and, if time-delay is greater, the system is not stable. Moreover, a method of estimating this value is obtained. Finally, a numerical example is presented in order to illustrate the results. View full abstract»

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IET Control Theory & Applications is devoted to control systems in the broadest sense, covering new theoretical results and the applications of new and established control methods.

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