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Control Theory & Applications, IET

Issue 1 • Date January 2 2014

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Displaying Results 1 - 8 of 8
  • Robust fault detection for discrete-time stochastic systems with non-homogeneous jump processes

    Page(s): 1 - 10
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (284 KB)  

    The problem of robust fault detection (RFD) is studied for a class of discrete-time stochastic systems with non-homogeneous jump processes. First, a filter-based residual signal generator is constructed. To guarantee the sensitivity to faults and robustness against unknown inputs, both H performance and a new performance index are considered. Then an FD filter, which minimises the influences of the disturbances, modelling uncertainties and increases the sensitivity to faults, is designed. A sufficient condition for ensuring the existence of RFD filter in terms of linear-matrix inequalities is established. A simulation is carried out, illustrating that the proposed RFD filter can detect the faults after their occurrences in a timely manner. View full abstract»

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  • Discrete inventory control in systems with perishable goods-a time-delay system perspective

    Page(s): 11 - 21
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (663 KB)  

    This study considers the problem of providing efficient control of periodic-review production-inventory systems with perishable goods. The stock storage and replenishment is modelled as a first-order process with delay subject to external perturbations. The study investigates formally the classical delay compensation mechanisms used in inventory control and shows deficiencies of inventory position and Smith predictor-based concepts in the context of systems with deteriorating stock. Then, a new dead-time compensation mechanism is developed and non-linear control law synthesised. The proposed control scheme is proved robust with respect to arbitrary demand and delay variations. View full abstract»

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  • Linear parameter-varying modelling and control of an offshore wind turbine with constrained information

    Page(s): 22 - 29
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (840 KB)  

    This study deals with linear parameter-varying modelling and output-feedback H control design for an offshore wind turbine. The controller is designed with consideration that not all the information in the feedback loop will be used. This constraint is incorporated into the design procedure. Constrained information means that a special zero-non-zero pattern is forced upon the gain matrix. The constrained controller is obtained based on parameter-dependent Lyapunov functions and formulated in terms of linear-matrix inequalities. Since the functions are dependent on the wind speed and accurate wind speed measurements are rarely available in practice, an extended Kalman filter is used to estimate the wind speed. The controller is designed in such a way that it should maintain its stability and performance even if one of the sensors in the feedback loop should malfunction. The control objectives are to mitigate oscillations in the structure and drivetrain, to smoothen power/torque output in addition to keep the closed-loop system stable. This should be achieved by means of individual blade pitch. A traditional procedure for designing a controller for such a system is to choose an operating point and assume it works in a suitable way under the influence of turbulent wind. In this study, the wind turbine model is obtained from the software fatigue, aerodynamic, structural and turbulence (FAST). To design the controller, the model is linearised about several operating points. The degrees of freedom in the linearised model are chosen according to the controller objectives. The linear models are valid within the span of operating points. Finally, the controller is tested on the fully non-linear system under the influence of turbulent wind and a scenario where one of the sensors in the feedback loop is malfunctioning. The closed-loop response of the presented controller is compared to the closed-loop response of the baseline controller included in - he FAST package along with a controller designed based on a single linearised model. View full abstract»

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  • Finite-time cluster synchronisation of markovian switching complex networks with stochastic perturbations

    Page(s): 30 - 41
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (690 KB)  

    In this study, the authors study the finite-time cluster synchronisation problem for a class of Markovian switching complex networks with stochastic noise perturbations. By constructing the suitable stochastic Lyapunov-Krasovskii functional, using finite-time stability theorem, inequality techniques and the properties of Weiner process, sufficient conditions are obtained to ensure finite-time cluster synchronisation for the complex networks with or without time delays. The effects of control parameters on cluster synchronisation speed and time delays are also analysed. Since finite-time cluster synchronisation means the optimality in convergence time and has better robustness and disturbance rejection properties, this study has important theory significance and practical application value. Finally, numerical examples are examined to illustrate the effectiveness of the analytical results. View full abstract»

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  • Robust fault reconstruction via learning observers in linear parameter-varying systems subject to loss of actuator effectiveness

    Page(s): 42 - 50
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (852 KB)  

    In this study, the problem of robust fault reconstruction in polytopic linear parameter-varying systems, subject to loss of actuator effectiveness and external disturbances, is investigated using a learning observer (LO). A polytopic LO is proposed to achieve system state estimation and actuator fault reconstruction at the same time. The proposed LO is sensitive to incipient faults because no chattering is induced. Both constant and time-varying faults can be accurately reconstructed and detected. Moreover, simultaneous fault reconstruction and detection can be performed using a single LO because the reconstructed fault signal can be employed as a fault alarm. The stability and convergence of polytopic LO and the uniformly ultimately boundedness of the dynamic error system is proved using Lyapunov stability theory and H techniques. A systematic design of the LO is effectively solved using standard linear-matrix-inequality techniques. At last, simulation results on a satellite system for attitude control verify the effectiveness of the proposed fault-reconstruction approach. View full abstract»

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  • Leaderless and leader-following consensus for heterogeneous multi-agent systems with random link failures

    Page(s): 51 - 60
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (337 KB)  

    This study investigates the heterogeneous consensus problem for multi-agent systems with random link failures between each agent. The discrete-time heterogeneous multi-agent systems are described by first-order and second-order dynamics, and the communication network is assumed to be directed with fixed topology. Since each link between the agents is subject to failure with a certain probability, the control protocol is designed considering the random link failures. The random link failures are presented by a Bernoulli probability sequence, that is, the control protocol for failure occurrence is designed using the one step previous data that is sent by adjacency neighbouring agents. The control protocol for heterogeneous multi-agent systems is designed for first-order dynamics and second-order dynamics using the Lyapunov method. The mean square stability is shown for leaderless and leader-following heterogeneous multi-agent systems in terms of a set of linear matrix inequalities, and some simulation results are provided to verify the effectiveness of the proposed methods. View full abstract»

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  • Bounded synchronisation of singularly perturbed complex network with an application to power systems

    Page(s): 61 - 66
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (929 KB)  

    This study is concerned with the bounded synchronisation of singularly perturbed complex network. If the reduced network is boundedly synchronised, the authors obtain, by using partially contracting theory, an explicit bound for small perturbation parameter to guarantee the bounded synchronisation of singularly perturbed complex network. Moreover, the authors present a sufficient condition such that the reduced network is boundedly synchronised. Although this sufficient condition is difficult to test directly for general networks, it can be tested for power networks based on some existing results. The effectiveness of the proposed results is demonstrated via power networks. View full abstract»

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  • Robust finite-time stability and stabilisation of switched positive systems

    Page(s): 67 - 75
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (363 KB)  

    This study is concerned with robust finite-time stability and stabilisation of a class of switched positive systems. By using the multiple linear copositive Lyapunov function approach, sufficient conditions of finite-time stability and finite-time boundedness are constructed, respectively. l1-gain is used to analyse the disturbance attenuation performance of the systems, and a finite-time weighted l1-gain is obtained under bounded exogenous disturbances. Then, the problem of robust finite-time stabilisation of non-autonomous systems with a weighted l1-gain is solved. All the proposed conditions are formulated in linear programming. Finally, two illustrative examples are given to show the validity of the theoretical 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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