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Control Theory and Applications, IEE Proceedings -

Issue 4 • Date 8 July 2005

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Displaying Results 1 - 19 of 19
  • On the interpretation and practice of dynamical differences between Hammerstein and Wiener models

    Page(s): 349 - 356
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    It is suggested that the differences between the Hammerstein and Wiener models be interpreted and understood in terms of the system eigenvalues. In particular, it is shown that the Wiener representation should be preferred when the system dynamics vary with the operating point. Conversely, when only the system gain varies with the operating point, Hammerstein models generally outperform the Wiener representation. The paper also points out connections between such models and the more general non-linear autoregressive model with exogenous inputs (NARX) polynomial representation. From a practical control engineering point of view, the results presented seem to be more helpful than other ways of distinguishing between such model types. The main ideas are illustrated by means of three examples that use simulated and measured data. View full abstract»

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  • Decoupling control design via linear matrix inequalities

    Page(s): 357 - 362
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (271 KB)  

    A new method for the design of multivariable internal model control (IMC) is proposed, aimed at obtaining good loop performance and small loop couplings based on linear matrix inequalities (LMIs). The decoupling design with performance constraints is formulated into an optimisation problem with LMI constraints, and thus the problem can be solved effectively. Robust stability is analysed and simulations show that good control performance can be achieved. View full abstract»

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  • Stator flux and torque decoupling control for induction motors with resistances adaptation

    Page(s): 363 - 370
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (207 KB)  

    An adaptive state feedback control has been designed for direct torque and stator flux regulation with a fifth-order model of an induction motor. The control design is based on exact input-output decoupling linearisation via non-linear state feedback. To achieve decoupling control, it is shown that the tracking dynamics with respect to the outputs (stator flux amplitude and electrical torque) is asymptotically stable at an admissible operating equilibrium. In the adaptive control, the uncertainty in the resistances of the stator and the rotor is considered, and the adaptation law is design to guarantee the boundedness of parameter estimation and output regulation performance. Finally, simulation results are presented to demonstrate the availability of the proposed controller. View full abstract»

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  • Validation of an interconnected high-gain observer for a sensorless induction motor against a low frequency benchmark: application to an experimental setup

    Page(s): 371 - 378
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (455 KB)  

    An interconnected high-gain observer and a flux estimator are presented for the elucidation of the angular speed and load torque of an induction motor. Because of observation difficulties at low frequencies, both the observer and the estimator are tested and validated against reference trajectories derived using a proposed benchmark. This is true even in the case where the motor state is unobservable. Experimental results to validate the proposed benchmark criteria are presented. View full abstract»

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  • Two-stage identification with applications to control, feature extraction, and spectral estimation

    Page(s): 379 - 386
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (431 KB)  

    A two-stage identification scheme is proposed for multivariable systems for applications including spectral estimation, and signal and system model estimation. The statistics of the signal and of the corrupting noise are taken as unknown, except that the signal is assumed to have a rational spectrum. First, a very high-order model is estimated and then a reduced-order model is derived from the higher-order model. An algorithm based on theory and heuristics is developed to select a set of frequencies where the signal-to-noise ratio is high. A reduced-order model is obtained from the best weighted least-squares fit at the selected frequencies. View full abstract»

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  • Decentralised adaptive control for large-scale non-linear systems with unknown high-frequency-gain signs

    Page(s): 387 - 391
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (165 KB)  

    For the first time, a decentralised adaptive control scheme for large-scale non-linear systems is proposed, which does not require a priori knowledge of subsystems' high-frequency-gain signs. In each local adaptive controller, a Nussbaum-type function is incorporated, and its argument is tuned online via an appropriately designed update law. The stability of the closed-loop system is analysed. It is shown that all signals in the closed-loop system are bounded, and that asymptotic regulation is achieved. View full abstract»

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  • Dynamic sliding mode control design

    Page(s): 392 - 396
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (167 KB)  

    Dynamic sliding mode control and higher order sliding mode are studied. Dynamic sliding mode control adds additional dynamics, which can be considered as compensators. The sliding system with compensators is an augmented system. These compensators (extra dynamics) are designed for achieving and/or improving the system stability, hence obtaining desired system behaviour and performance. Higher order sliding mode control and dynamic sliding mode control yield more accuracy and also reduce and/or remove the chattering resulting from the high frequency switching of the control. It is proved that certain J-trajectories reach a sliding mode in a finite time. A sliding mode differentiator is also considered. View full abstract»

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  • Fault detection for Markovian jump systems

    Page(s): 397 - 402
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (185 KB)  

    The paper deals with the robust fault detection problem for a class of discrete-time linear Markovian jump systems with an unknown input. By using a general observer-based fault detection filter as residual generator, the robust fault detection filter design is formulated as an H-filtering problem, in which the filter matrices are dependent on the system mode, i.e. the residual generator is a Markovian jump linear system as well. The main objective is to make the error between residual and fault (or, more generally, weighted fault) as small as possible. A sufficient condition to solve this problem is established in terms of the feasibility of certain linear matrix inequalities (LMI), which can be solved with the aid of Matlab LMI Toolbox. A numerical example is given to illustrate the effectiveness of the proposed techniques. View full abstract»

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  • One-bit processing for digital control

    Page(s): 403 - 410
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (261 KB)  

    The paper presents a new methodology and architecture for digital control. Control laws can be efficiently implemented with one-bit signals at both the input and output. ΔΣ modulation is used to shape either analogue or multi-bit digital signals into 1-bit format. The 1-bit signals can be applied directly to physical systems, i.e. pulse-density modulation. A modified canonic controller structure is developed, in which there are no multipliers. Some problems arising from sampling and quantisation are discussed. As an example, a practical 1-bit processing architecture for DC motor control is presented. View full abstract»

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  • Zero-moment point trajectory modelling of a biped walking robot using an adaptive neuro-fuzzy system

    Page(s): 411 - 426
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1043 KB)  

    A bipedal architecture is highly suitable for a robot built to work in human environments since such a robot will find avoiding obstacles a relatively easy task. However, the complex dynamics involved in the walking mechanism make the control of such a robot a challenging task. The zero-moment point (ZMP) trajectory in the robot's foot is a significant criterion for the robot's stability during walking. If the ZMP could be measured on-line then it becomes possible to create stable walking conditions for the robot and here also stably control the robot by using the measured ZMP, values. ZMP data is measured in real-time situations using a biped walking robot and this ZMP data is then modelled using an adaptive neuro-fuzzy system (ANFS). Natural walking motions on flat level surfaces and up and down a 10° slope are measured. The modelling performance of the ANFS is optimized by changing the membership functions and the consequent part of the fuzzy rules. The excellent performance demonstrated by the ANFS means that it can not only be used to model robot movements but also to control actual robots. View full abstract»

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  • Ackermann-like eigenvalue assignment formulae for linear time-varying systems

    Page(s): 427 - 434
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (224 KB)  

    Eigenvalue assignment techniques for linear time-varying systems are presented as a way of achieving feedback stabilisation. For this, novel eigenvalue concepts, which are the time-varying counterparts of conventional (time-invariant) eigenvalue ideas, are introduced. Ackermann-like formulae for both SISO and MIMO linear time-varying systems are proposed. It is believed that these techniques are the generalised versions of the Ackermann formulae for linear time-invariant systems. The advantages of the proposed Ackermann-like formulae are that they neither require the transformation of the original system into a phase-variable form nor the computation of the eigenvalues of the original system, and they can allow the closed-loop system to have desired eigenvalue trajectories rather than fixed eigenvalue locations. Two examples are given to demonstrate the capabilities of the proposed techniques. View full abstract»

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  • Application of generalised polynomials to the decoupling of linear multivariable systems

    Page(s): 435 - 442
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (193 KB)  

    Properties of generalised polynomials and generalised polynomial matrices are applied to the problem of the decoupling with Λ-stability of linear square multivariable systems, i.e. decoupling of linear systems with closed-loop poles in a region Λ of the complex plane. We present first some extensions of well known results about generalised polynomials, which are basically defined as rational functions with poles in a symmetric region of the extended complex plane. Then, an application of the concepts to the problem of decoupling with Λ-stability of linear square multivariable systems is presented. The conditions for this problem to have a solution are stated in terms of the row and global zero structure of the system out of the region Λ. View full abstract»

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  • Explicit solutions to optimal control problems for constrained continuous-time linear systems

    Page(s): 443 - 452
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (301 KB)  

    An algorithmic framework is presented for the derivation of the explicit optimal control policy for continuous-time linear dynamic systems that involve constraints on the process inputs and outputs. The control actions are usually computed by regularly solving an on-line optimisation problem in the discrete-time space based on a set of measurements that specify the current process state. A way to derive the explicit optimal control law, thereby, eliminating the need for rigorous on-line computations has already been reported in the literature, but it is limited to discrete-time linear dynamic systems. The currently presented approach derives the optimal state-feedback control law off-line for a continuous-time dynamic plant representation. The control law is proved to be nonlinear piecewise differentiable with respect to the system state and does not require the repetitive solution of on-line optimisation problems. Hence, the on-line implementation is reduced to a sequence of function evaluations. The key advantages of the proposed algorithm are demonstrated via two illustrative examples. View full abstract»

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  • New results on robust control design of discrete-time uncertain systems

    Page(s): 453 - 459
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (242 KB)  

    The paper considers the problem of robust control redesign of a class of linear discrete-time systems with norm-bounded parametric uncertainties and controller-gain perturbations. In both cases of additive and multiplicative perturbations, the control objective is to design a resilient feedback-stabilisation schemes using guaranteed cost control and H control approaches. The problem under consideration is cast as convex optimisation over linear matrix inequalities which led to the derivation of necessary and sufficient conditions for closed-loop robust quadratic stability. Three system examples are provided to illustrate the theoretical developments. View full abstract»

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  • Semi-global stabilisation of a class of non-minimum phase non-linear output-feedback systems

    Page(s): 460 - 464
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (150 KB)  

    The stabilisation of non-linear systems with unstable zero-dynamics is considered. The non-linear systems are assumed to be transformable to the non-linear output feedback form. The control design starts from the state feedback, and the state variables associated with the zero-dynamics are stabilised first. The state feedback control design is then carried out using backstepping. An observer with linear error dynamics is constructed with a design parameter which can be set at any positive value. The dynamic output feedback control is then designed, by substituting the state in state feedback control with the observed one and imposing a saturation on the control input. The saturation level depends on the domain of the initial state. The proposed control design asymptotically stabilises the system for any prescribed domain of the initial state. View full abstract»

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  • Observer-based controller for position regulation of stepping motor

    Page(s): 465 - 476
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (559 KB)  

    The design of a controller-observer scheme for the exponential stabilisation of a permanent magnet stepper motor is proposed. The technique is based on sliding-mode techniques and nonlinear observers. Representing the stepper motor model as a singularly perturbed nonlinear system, a position regulation controller is obtained. Since this controller depends on the mechanical variables, load torque and equilibrium point, under the assumption that the rotor position is available for measurement, an observer design is presented to estimate the angular speed and load torque. Furthermore, a stability analysis of the closed-loop system is also made to provide sufficient conditions for the exponential stability of the full-order closed-loop system when the angular speed and load torque are estimated by means of the observer. The proposed scheme is applied to the model of a permanent-magnet stepper motor. View full abstract»

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  • Computing finitely reachable containable region for switching systems

    Page(s): 477 - 486
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (297 KB)  

    In this paper the practical stability issue of a switching system is discussed in terms of solving a containability problem and an attraction problem. A novel computational procedure based on nonlinear programming is presented to compute a containable region, in which each trajectory from inside cannot move out under a given single-step-lookahead control policy. How to decide whether the obtained containable region is finitely reachable from a point outside the region is then examined. The proposed approach is demonstrated on a two-tank system. View full abstract»

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  • Guaranteed-cost control of a linear uncertain system with multiple time-varying delays: an LMI approach [comment]

    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (81 KB)  

    The commenter states that the matrix function in the above paper (Nian, and Feng, IEE Proc. Control Theory Appl., 2003, 150, (1), p. 17-22) is incorrectly defined. View full abstract»

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  • Erratum

    Page(s): 488
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (93 KB)  

    First Page of the Article
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