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This study is concerned with the static output-feedback stabilisation problem of discrete-time networked control systems. If the controlled plant is a discrete-time system, the networked control system with time-varying network-induced delays and data packet dropouts in the transmission is modelled as a discrete-time system with time-varying delays in the state. The network-induced delays are assumed to have both an upper bound and a lower bound. Next, an asymptotic stability condition for the networked control systems is established, which depends on the upper and lower bounds of delay times. Then, three approaches to the static output-feedback controller are proposed, where the effect of both network-induced delays and data packet dropouts has been considered. Furthermore, the robust stability condition and controller design method for such networked control systems with structured uncertainties are presented. All the results are formulated in the terms of linear matrix inequalities (LMIs), which are numerically very efficiently solved via LMI toolbox in the Matlab. Finally, three examples are worked out to illustrate the feasibility and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The problem of estimating feasible parameter sets for linear discrete-time systems with unknown-but-bounded noise is investigated. Considering that the feasible parameter set of a linear discrete-time system with bounded noise is a convex polytope and that a convex polytope can be triangulated into a limited number of simplexes with good properties, the authors propose an exact triangulation description method for the feasible parameter set. A convex polytope triangulation algorithm is introduced and a recursive algorithm of estimating the feasible parameter set in correspondence with the system description is developed. Simulation examples show the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The controllability problem of high-order linear time-invariant (LTI) continuous-time swarm systems is investigated. A necessary and sufficient condition for complete controllability of homogeneous swarm systems is given. The controllability of graph is important and is analysed in detail. The concept of formation controllability is proposed and the relationship between complete controllability and formation controllability is studied. [ABSTRACT FROM AUTHOR]

In this study, the problem of designing regular robust l2–l∞ filter for a class of linear singular discrete-time systems with norm-bounded uncertainties is investigated. A class of regular linear filters is fully analysed, then necessary and sufficient conditions of robust admissibility are established. Guaranteed l2–l∞ performance of the filtered system is provided and expressed in terms of the solution of strict linear matrix inequalities (LMIs). The cases of full- and zeroth-order realisable filter are derived as limiting cases of design. Numerical examples are worked out to illustrate the theoretical development. [ABSTRACT FROM AUTHOR]

This study presents a dynamic post-filtering approach to a single-input-single-output sampled-data variable structure output feedback control problem. Given a sliding surface, Σ(x)=0 (x being the system state vector), designed through standard procedures with the assumption of full state accessibility, a dynamic filter, denoted post-filter, is employed to synthesise Σ(x) by means of output variable alone. In contrast with a state observer, the post-filter is invariant of the matched disturbances; and it requires only partial information of the system parameters. Thus, the robustness property of the variable structure system is retained. Let T be the sampling period. A sampled-data realisation of the post-filter is done by zero-order hold. Depending on the system relative degree, either Σk or Σk-1 can be obtained for implementing the variable structure control law. A discrete-time switching-type control law, which is originally designed to satisfy the continuous-time reaching condition, will lead to a quasi-sliding motion, forming a boundary layer of thickness O(T) about the sliding surface. The stability of the post-filter is ensured if the system output is in minimum phase and that the sliding mode dynamics are chosen properly. [ABSTRACT FROM AUTHOR]

This paper studies the simultaneous fault detection and control problem for linear uncertain discrete-time systems. A design procedure dealing with polytopic uncertainties is proposed for residual generation, where both the fault detection objectives and some control objectives are considered simultaneously through certain performance indexes. To cope with the fault sensitivity performance index in a given frequency range directly, the generalised KYP lemma is introduced in this framework. A two-step procedure is adopted to obtain the solutions through satisfying a set of linear matrix inequalities. A numerical example is given to illustrate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

Based on the satisfactory fault-tolerant control strategy, the problem of reliable guaranteed cost control with multiple criteria constraints is investigated for a class of uncertain discrete-time systems subject to sensor faults. The state-feedback controller is developed by linear matrix inequalities approach such that, for all admissible parameters uncertainties and possible sensor faults, the given upper bounds on the amplitudes of control input signals be ensured, all the closed-loop poles be placed into the pre-specified regional disk, and the expected quadratic cost performance index as well as the given H∞ norm index of disturbance rejection level be guaranteed, simultaneously. Thus, with the above multiple criteria constraints, the resulting closed-loop system can provide satisfactory stability, transient property, external disturbance attenuation level and quadratic cost performance, despite the possible sensor faults. [ABSTRACT FROM AUTHOR]

Issues of observer design for a class of Lipschitz nonlinear discrete-time systems with time-delay and disturbance input are addressed, where the Lipschitz condition is expressed in a componentwise rather than aggregated manner. It has been shown that both full-order and reduced-order robust H∞ observers can be obtained by means of the same convex optimisation procedure with minimisation of the disturbance attenuation upper bound γ>0. It is also shown that for a prescribed H∞-norm upper bound γ>0, the tolerable Lipschitz bounds can be obtained by another convex optimisation procedure. A numerical example is presented to show the effectiveness of the developed approach. [ABSTRACT FROM AUTHOR]

The problem of robust l2–l∞ filtering for switched linear discrete-time systems with polytopic uncertainties and time-varying delays is investigated. The time delay is assumed to be time-varying and bounded, which covers constant delay and mode-dependent constant delays as special cases. A robust switched linear filter is designed based on the mode-switching idea and a parameter-dependent stability approach such that the corresponding filtering error system is robustly asymptotically stable and achieves a prescribed l2–l∞ performance index for all admissible uncertainties. The existence conditions for such a filter, dependent on the upper and lower bounds of time-varying delays, are formulated in terms of a set of linear matrix inequalities. By solving that corresponding convex optimisation problem, the desired filter is obtained and an optimal l2–l∞ noise-attenuation level bound of the resulting filtering error system is guaranteed as well. A numerical example is given to show the feasibility and potential of the theoretical results. [ABSTRACT FROM AUTHOR]

The authors present an enhanced composite nonlinear feedback (CNF) control technique for discrete-time systems with input saturation and with external disturbances. The conventional CNF control is proven to be capable of yielding better transient performance in tracking control for systems with input saturation. However, when the given system has external disturbances as in most practical situations, the conventional CNF control yields some steady-state errors in the resulting output response. The enhanced CNF technique presented is an extension of the conventional one. It retains the good transient properties of the conventional CNF control and at the same time has the additional capacity for eliminating steady-state bias because of unknown constant disturbances. A numerical example and practical disk drive servo system design are provided to demonstrate the effectiveness of this control technique. Experimental results show that the new design yields a huge improvement over classical approaches. [ABSTRACT FROM AUTHOR]

The dynamic output feedback guaranteed cost control problem is investigated for a class of uncertain discrete-time systems with multiple time-varying state delays and norm-bounded parameter uncertainties. Attention is focused on the design of the dynamic output feedback controllers such that the resulting closed-loop system is asymptotically stable and an adequate level of performance is also guaranteed. Delay-dependent sufficient conditions for the existence of the desired guaranteed cost controllers are derived without involving model transformation and bounding technique for cross terms, and these conditions are formulated in terms of nonlinear matrix inequalities. An iterative algorithm involving convex optimisations is presented to solve these nonlinear matrix inequalities. Finally, a numerical example is given to demonstrate the effectiveness of the proposed results. [ABSTRACT FROM AUTHOR]

The problem of the delay-dependent stability of linear systems with multiple time delays is discussed. A new method is first presented for a system with two time delays, in which free weighting matrices are used to express the relationships among the terms of the Leibniz–Newton formula. Next, this method is used to show the equivalence between a system with two identical time delays and a system with a single time delay. Then, a numerical example verifies that the criterion given is effective and is a significant improvement over the existing ones. Finally, the basic idea is extended to a system with multiple time delays. [ABSTRACT FROM AUTHOR]

The problem of sampled-data state reconstruction in linear time invariant systems is considered. A new full order observer structure that can generate intersample state estimation is introduced. The observer synthesis is carried out using the H∞ framework and is shown to have some important advantages over the classical lifting technique that has been used to study similar problems. A simulation example illustrates the application of the proposed design in the fast rate fault detection problem. [ABSTRACT FROM AUTHOR]

The two-dimensional (2-D) system theory iterative learning control (ILC) techniques for linear time-invariant discrete systems are extended to the cases of linear time-variant discrete systems. By exploiting the convergent property of 2-D linear time-variant discrete systems with only one independent variable, a kind of 2-D system theory ILC approach is presented for linear time-variant discrete systems. Sufficient conditions are given for convergence of the proposed ILC rules. Two numerical examples are used to validate the ILC procedures. [ABSTRACT FROM AUTHOR]

A computationally efficient linear matrix inequality (LMI)-based criterion for the global asymptotic stability of discrete-time systems in a state-space realisation with state saturation nonlinearities is presented. The criterion turns out to be an improved generalised version of a previously reported LMI-based criterion. The extension of the approach to a situation involving partial state saturation nonlinearities is performed. [ABSTRACT FROM AUTHOR]

The optimal updating law of the problem of optimal higher-order iterative learning control is given explicitly and the convergence of the tracking errors is proved. Two examples show that the convergence of the optimal higher-order iterative learning control is faster than that of the optimal one-order iterative learning control. [ABSTRACT FROM AUTHOR]

The restricted structure optimal deconvolution filtering, smoothing and prediction problem for multivariable, discrete-time linear signal processing problems is considered. A new class of discrete-time optimal linear estimators is introduced that directly minimises a minimum variance criterion but where the structure is prespecified to have a relatively simple form. The resulting estimator can be of much lower order than a Kalman or Wiener estimator and it minimises the estimation error variance, subject to the constraint referred to above. The numerical optimisation algorithm is simple to implement and the full-order optimal solutions are available as a by-product of the analysis. Moreover, the restricted structure solution may be used to compute both IIR and FIR estimators. A weighted H2 cost-function is minimised, where the dynamic weighting function can be chosen for robustness improvement. The signal and noise sources can be correlated and the signal channel dynamics can be included in the system model. The algorithm enables loworder optimal estimators to be computed that directly minimise the cost index. The main technical advance is in the pre-processing, which enables the expanded cost expression to be simplified considerably before the numerical solution is obtained. The optimisation provides a direct minimisation over the unknown parameters for the particular estimator structure chosen. This should provide advantages over the simple approximation of a high-order optimal estimator. The results are demonstrated in the estimation of a signal heavily contaminated by both coloured and white noise. [ABSTRACT FROM AUTHOR]

A matrix-analytic approach is applied to analyse both the long-term and the short-term drop behaviour of a router with an RED scheme. The bursty nature of packet drop is examined by means of conditional statistics with respect to alternating congested and non-congested periods. All of the four related performance measures are derived by conditional statistics, including the long- term drop probability, and the three short-term measures comprising average length of a congested period, average length of a non-congested period, and the conditional packet drop probability during a congested period. [ABSTRACT FROM AUTHOR]