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Control Theory & Applications, IET

Issue 6 • Date April 12 2012

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Displaying Results 1 - 14 of 14
  • Exponential stability analysis for positive systems with delays

    Page(s): 761 - 767
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (308 KB)  

    This study investigates the exponential stability analysis problem for continuous-time and discrete-time positive linear systems with delays. For given decay rate, necessary conditions for exponential stability of such systems are presented based on the asymptotical stability results of positive linear time-delay systems, and sufficient conditions are provided by using Lyapunov-Krasovskii functional method. It is shown that, the exponential stability with given decay rate of positive linear time-delay systems has to do with the delays. Some illustrative examples are given to show the correctness of the obtained theoretical results. View full abstract»

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  • Parameter estimation of periodically switched linear systems

    Page(s): 768 - 775
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (509 KB)  

    This study is concerned with parameter estimation of a special class of switched linear systems (SLSs), namely, periodically switched linear systems (PSLSs). General identification methods that do not explore switching sequence patterns may perform poorly in estimation accuracy and implementation efficiency. In this work, we first analyse input and output (I/O) data sequences and then establish the connection between the periodicity and I/O data sequence. This allows us to obtain an accurate estimation of the switching sequence period p0. We prove that the correctness of data classification is almost surely guaranteed. In implementation, we propose two efficient strategies, namely, the reverse order search and finite data selection, to improve the computational efficiency. Moreover, we provide both offline and online methods to estimate p0 and the parameters. The effectiveness of these methods are demonstrated in simulations. View full abstract»

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  • Optimal tuning rules for proportional-integral-derivative and fractional-order proportional-integral-derivative controllers for integral and unstable processes

    Page(s): 776 - 786
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1083 KB)  

    A set of tuning rules for standard (integer-order) proportional-integral-derivative (PID) and fractional-order PID controllers for integral and unstable processes is presented in this study. Based on a simple model of the process, the tuning rules have been devised in order to minimise the integrated absolute error. Both set-point tracking and load disturbance rejection tasks are considered. The achieved performance indexes can also be used for the assessment of the controller performance. A remarkable feature of the optimisation procedure employed for integral processes is highlighted. The provided results allow the user to quantify, for a given process, the performance improvement that can be obtained by using the fractional controller instead of the integer one. View full abstract»

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  • Hα filtering for discrete-time affine non-linear descriptor systems

    Page(s): 787 - 795
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (251 KB)  

    In this study, the authors consider the H-filtering problem for discrete-time affine non-linear descriptor systems. Two types of filters are discussed; namely, (i) singular, (ii) normal and sufficient conditions for the solvability of the problem in terms of disrete-time Hamilton-Jacobi-Isaacs equations (DHJIEs) are presented. The results are also specialised to linear systems, in which case the DHJIEs reduce to a system of linear-matrix-inequalities (LMIs). Examples are also presented to illustrate the results. View full abstract»

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  • Mean square detectability of multi-output systems over stochastic multiplicative channels

    Page(s): 796 - 802
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (243 KB)  

    This study addresses the mean square detectability problem for multi-output networked systems via single packet or multiple packets transmission, where a multiplicative white noise model the unreliability of output channels. For the single packet case, by adopting the bisection technique, the authors give the critical value (lower bound) of mean square capacity for ensuring mean square detectability. For the m-parallel multiple packets transmission strategy, a necessary and sufficient condition on overall mean square capacity for mean square detectability in terms of the Mahler measure or topological entropy of the plant is presented, under the assumption that the given network resource can be allocated among all the output channels. Applications in erasure-type channel and channel with stochastic sector-bounded uncertainty are provided to demonstrate the results. View full abstract»

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  • Dynamic output feedback control for Markovian jump systems with time-varying delays

    Page(s): 803 - 812
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (275 KB)  

    This study investigates the problems of delay-dependent H output feedback control for Markovian jump systems with time-varying delays. Firstly, the improved delay-dependent stochastic stability is obtained by constructing a new Lyapunov-Krasovskii functional. Neither free-weighting matrix approach nor model transformation is involved in the derivative of the criterion. Then, a new bounded real lemma (BRL) for Markovian jump systems is established. Based on the proposed BRL, a full-order dynamic output feedback controller is designed to ensure the stochastic stability and a prescribed H performance level for the closed-loop systems. Finally, two numerical examples are provided to demonstrate the effectiveness of the proposed approaches. View full abstract»

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  • A connectivity-preserving flocking algorithm for multi-agent dynamical systems with bounded potential function

    Page(s): 813 - 821
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    Without assuming that the communication topology can remain its connectivity frequently enough and the potential function can provide an infinite force during the evolution of agents, the flocking problem of multi-agent systems with second-order non-linear dynamics is investigated in this study. By combining the ideas of collective potential functions and velocity consensus, a connectivity-preserving flocking algorithm with bounded potential function is proposed. Using tools from the algebraic graph theory and matrix analysis, it is proved that the designed algorithm can guarantee the group of multiple agents to asymptotically move with the same velocity while preserving the network connectivity if the coupling strength of the velocity consensus term is larger than a threshold value. Furthermore, the flocking algorithm is extended to solve the flocking problem of multi-agent systems with a dynamical virtual leader by adding a navigation feedback term. In this case, each informed agent only has partial velocity information about the leader, yet the present algorithm not only can guarantee the velocity of the whole group to track that of the leader asymptotically, and also can preserve the network connectivity. Finally, some numerical simulations are provided to illustrate the theoretical results. View full abstract»

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  • Adaptive state estimation for stochastic delay systems with state-dependent Markovian switching

    Page(s): 822 - 828
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    This study is concerned with an adaptive state estimation problem for a class of stochastic delay systems with state-dependent Markovian switching. Since the upper bound of parameters related to a transition rate of stochastic Markovian jump system is assumed to be unknown, an adaption law is developed to estimate such an unknown parameter. A class of adaptive state estimator is proposed such that not only the estimated parameter is bounded almost surely but also the estimated state error is mean-square exponentially stable. Finally, a numerical example is given to show the validity of the results. View full abstract»

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  • Robust fractional order proportion-plus-differential controller based on fuzzy inference for permanent magnet synchronous motor

    Page(s): 829 - 837
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (777 KB)  

    Owing to the simplicity and effectiveness, the proportional-integral-differential (PID) controller is widely used in the control of permanent magnet synchronous motor (PMSM). However, the disadvantage of the PID controller is its poor capacity in dealing with system uncertainties. The authors propose a robust fractional order proportion-plus-differential (FOPD) controller for the control of PMSM. To enhance the robustness, the control effort of FOPD controller acts on an acted function (AF) instead of tracking error directly. A tuning method is used for the gains of FOPD controller and a fuzzy logic inference algorithm (FLIA) is designed to obtain the parameters of AF. Some simulation and experimental results show that the proposed control scheme not only achieves favourable tracking performance, but also is robust with regard to external load disturbance and parameter variation. View full abstract»

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  • Decentralised output-feedback control for high-order stochastic non-linear systems

    Page(s): 838 - 846
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (257 KB)  

    In this study, the problem of decentralised output-feedback stabilisation is investigated for the first time for a class of large-scale high-order stochastic non-linear systems. By developing a decentralised high-gain homogeneous domination approach, we can completely relax the power order restriction which has been the common assumption for global stabilisation of high-order stochastic non-linear systems. It is shown that under some general conditions, the equilibrium of the closed-loop system is globally asymptotically stable (GAS) in probability when the drift and diffusion vector fields vanish at the origin. The efficiency of the output-feedback controller is demonstrated by a simulation example. View full abstract»

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  • Marginalised iterated unscented Kalman filter [Brief Paper]

    Page(s): 847 - 854
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (556 KB)  

    In this study, the authors investigate the role of iteration in the unscented Kalman filter (UKF) with additive measurement noise and propose a novel filter referred to as the marginalised iterated unscented Kalman filter (MIUKF). In each iteration of the MIUKF, the new sigma points are regenerated and propagated through the same measurement update strategy as the UKF. In order to guarantee the state to be statistically independent with the measurement noise, the state variables are augmented with the measurement noise. Since the measurement noise is additive, the measurement function is conditionally linear of the augmented state, then the marginalised unscented transformation is investigated to reduce the computational burden. Compared with the traditional iterated UKF, the MIUKF is more rigorous in terms of efficiency and accuracy. The simulation results agree well with the theoretical analyses. View full abstract»

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  • Controllability and observability of switched linear systems with continuous-time and discrete-time subsystems [Brief Paper]

    Page(s): 855 - 863
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (223 KB)  

    In this study, the authors focus on the controllability and observability of switched linear systems composed by continuous-time and discrete-time subsystems. Necessary and sufficient conditions for controllability and observability are obtained. A simple example is proposed to illustrate the effectiveness of the current theoretical results. View full abstract»

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  • Add-on type loop shaping controller design for high precision track following in hard disc drives (hdds) [Brief Paper]

    Page(s): 864 - 867
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (309 KB)  

    In this study, the authors present a systematic design method of the add-on type loop shaping scheme for high precision track following with plant modelling perturbations in HDDs. The proposed controller minimises the standard deviation of the position error signal (PES) of certain closed-loop transfer function while satisfying the robust stability condition in HDDs. Compared with the conventional H control, the proposed method yields estimated plant states, which can be used for estimator-based controller design. Also, the proposed control method can be implemented in a parallel manner by performing a partial-fraction expansion for easy implementation. The effectiveness and practicality of our work is demonstrated through various experimental results. View full abstract»

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  • Improved delay-range-dependent stability criteria for linear systems with interval time-varying delays [Brief Paper]

    Page(s): 868 - 873
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (186 KB)  

    This study provides new delay-range-dependent stability criteria in the forms of linear matrix inequalities (LMIs) for systems with interval time-varying delays. Two cases concerning whether the derivative of the time delay is known are studied. A new estimation method is developed to estimate the non-linear time-varying coefficients derived from Jenson's integral inequality more tightly than the existing ones. Along with convex combination and delay partitioning method, less conservative stability criteria are provided by utilising the new estimation method. Numerical examples are given to illustrate the effectiveness of the proposed method. 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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