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Control Theory & Applications, IET

Issue 3 • Date February 17 2011

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Displaying Results 1 - 12 of 12
  • Vision-based adaptive guidance law for intercepting a manoeuvring target

    Publication Year: 2011 , Page(s): 421 - 428
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (367 KB)  

    This article introduces an adaptive guidance law for intercepting a manoeuvring target using information from an imaging seeker. The relative missile-target kinematics is represented in the line-of-sight (LOS) frame, and the image information - instead of the relative range - is introduced to formulate the interception problem as an adaptive control problem with an unknown control coefficient. Considering the target-s acceleration as a time-varying bounded external disturbance, an estimator with an adaptive property is derived. It is proven that the proposed guidance law can guarantee the LOS angular rates global uniform ultimate boundedness during the terminal course. The effectiveness of the proposed guidance law has been demonstrated in simulations for two kinds of typical manoeuvring targets. View full abstract»

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  • New results on stability and stabilisation of systems with interval time-varying delay

    Publication Year: 2011 , Page(s): 429 - 436
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (147 KB)  

    This study is concerned with the stability and stabilisation for systems with interval time-varying delay. First, by appropriately choosing Lyapunov functional and using Finsler's lemma, a new delay-dependent stability criteria involving the minimum and maximum delay bounds is obtained. Second, new results for delay-dependent stabilisation of systems with interval time-varying delay are provided on the basis of a linear matrix inequality (LMI) framework. Both state- and observer-based output feedback controllers are designed. Differing existing design approach of observer-based controller, a single-step approach is proposed to overcome the drawback of the two-step LMI approach often encountered in the literature, and the conditions are also delay dependent. Numerical examples are given to demonstrate the effectiveness and the benefits of the proposed method. View full abstract»

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  • Linear quadratic Gaussian control with quantised innovations Kalman filter over a symmetric channel

    Publication Year: 2011 , Page(s): 437 - 446
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (329 KB)  

    This study discusses the quantised linear quadratic Gaussian (LQG) control problem for linear stochastic systems. A symmetric channel that connects the sensor and the controller is considered. Given a quantiser that is applied on the most recent innovation of the measurement, it is shown that the well-known separation principle remains valid. Based on a quantised innovations Kalman filter, a suboptimal LQG controller is given in terms of the solutions of two Riccati difference equations associated, respectively, with the state estimation and the standard linear quadratic regulator control. The corresponding approximate suboptimal cost is also derived. An illustrative example is included to demonstrate the effectiveness of the proposed controller. View full abstract»

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  • Optimal anti-windup digital redesign of multi-input multi-output control systems under input constraints

    Publication Year: 2011 , Page(s): 447 - 464
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1601 KB)  

    In this study, a novel optimal anti-windup control scheme is proposed to resolve the input constraint problem for multi-input multi-output (MIMO) systems, without losing the good tracking performance as possible. Avoiding complex numerical calculation, the proposed optimal control scheme can systematically compress a huge control input within the range of the required restriction by adjusting well-designed weighted matrices for linear constrained systems. Combining a conventional linear quadratic analogue tracker (LQAT) with the proposed scheme, the anti-windup-based optimal analogue tracker not only possesses the advantage of the conventional LQAT, good tracking performance, but also effectively resolves the input saturation problem. For practical consideration, the proposed LQAT is implemented by adopting the prediction-based digital redesign technique to design an effective digital control of linear MIMO sampled-data systems under input constraints. View full abstract»

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  • Adaptive neural network output feedback control for a class of non-affine non-linear systems with unmodelled dynamics

    Publication Year: 2011 , Page(s): 465 - 477
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (349 KB)  

    In this study, an output feedback-based adaptive neural controller is presented for a class of uncertain non-affine pure-feedback non-linear systems with unmodelled dynamics. Two major technical difficulties for this class of systems lie in: (i) the few choices of mathematical tools in handling the non-affine appearance of control in the systems, and (ii) the unknown control direction embedded in the unknown control gain functions, in great contrast to the standard assumptions of constants or bounded time-varying coefficients. By exploring the new properties of Nussbaum gain functions, stable adaptive neural network control is possible for this class of systems by using a strictly positive-realness-based filter design. The closed-loop system is proven to be semi-globally uniformly ultimately bounded, and the regulation error converges to a small neighbourhood of the origin. The effectiveness of the proposed design is verified by simulations. View full abstract»

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  • Observer-based output feedback control for discrete systems with quantised inputs

    Publication Year: 2011 , Page(s): 478 - 485
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (267 KB)  

    This study is concerned with the problem of observer-based output feedback control for discrete-time systems with quantised inputs. Firstly, a new necessary and sufficient condition is established to guarantee the asymptotic stability of the closed-loop system. However, the condition is presented in terms of a matrix inequality that depends on quantisation parameters varying over certain intervals. To solve this problem, a new quantisation-density-dependent necessary and sufficient condition is derived. Based on such a condition, both full- and reduced-order observer-based quantised feedback controllers are designed via a single-step approach. Finally, numerical examples are given to show the effectiveness of the author's method. View full abstract»

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  • Output feedback adaptive neural control for a class of non-affine non-linear systems with a dynamic gain observer

    Publication Year: 2011 , Page(s): 486 - 497
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (437 KB)  

    Output feedback adaptive neural control is investigated for non-affine non-linear systems with zero dynamics using implicit function theorem, mean value theorem and neural network (NN) parametrisation by exploiting the explicit Lipschitz property of radial basis function NNs for function approximation. The control approach developed is based on non-separation principle design. A new dynamic gain observer is introduced to estimate the unmeasurable states of the system. The observer gain and the neural controller are simultaneously tuned according to output tracking error. With the universal approximation property of NN and the simultaneous parametrisation both for the NN approximation and the controller, restrictive conditions, such as Lipschitz assumption, strictly positive realness condition and contracting assumption are not required. Semi-globally uniformly ultimate boundedness for the steady-state and transient performance is guaranteed, and simulation results demonstrated the effectiveness of the proposed scheme. View full abstract»

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  • Decentralised state estimation for linear systems with unknown inputs: A consensus-based approach

    Publication Year: 2011 , Page(s): 498 - 506
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (383 KB)  

    A new method is proposed to identify the parameters of the low-frequency error (LFE) of the star sensor. The LFE is one of the most dominant error sources in the high-precision attitude determination system for the satellite. It is shown that the gyroscope bias estimate, which is obtained by processing the star sensor measurement in the stellar inertial attitude determination Kalman filter, represents the variation in the LFE. As the LFE is a periodic signal, the LFE parameters can be identified from the frequency spectrum of the gyroscope bias estimate. The identified parameters are used for the LFE compensation, such that the effect of the LFE to the attitude estimate is partly eliminated. The efficiency of the proposed method is illustrated through numerical simulations with the use of the real gyroscope data. View full abstract»

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  • Separation principle for networked control systems with multiple-packet transmission

    Publication Year: 2011 , Page(s): 507 - 513
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (194 KB)  

    The authors investigate a class of observer-based discrete-time networked control systems (NCSs) with multiple-packet transmission where random packet dropouts occur independently in both the sensor-to-controller (S/C) and controller-to-actuator (C/A) channels. The authors first propose and prove the separation principle for the NCSs where packet dropouts in the C/A and S/C channels are governed by two independent Markov chains, respectively. Secondly, the authors derive a sufficient condition, in terms of linear matrix inequalities (LMIs), for stabilisation control of the Markov chain-driven NCSs. The authors also derive the necessary and sufficient condition for stabilisation control of the memoryless process-driven NCSs as a special case. A numerical example is provided to illustrate the effectiveness of our method. View full abstract»

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  • Robust adaptive formation control and collision avoidance for electrically driven non-holonomic mobile robots

    Publication Year: 2011 , Page(s): 514 - 522
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (215 KB)  

    This study proposes a robust adaptive formation controller for electrically driven non-holonomic mobile robots to achieve desired formation tracking and collision avoidance with static and moving obstacles. The projection algorithm is employed to estimate the time-varying velocities of the leader robot. The robust adaptive technique is adopted to deal with parametric uncertainties and external disturbances. Moreover, the avoidance function is used to avoid the collisions even though many obstacles exist within the detection region of the mobile robot. It is shown using Lyapunov stability theory that formation errors are uniformly ultimately bounded and collision avoidance is guaranteed. Simulations are included to illustrate the control method. View full abstract»

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  • Powers of parametric interval uncertain matrix

    Publication Year: 2011 , Page(s): 523 - 534
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (533 KB)  

    This study addresses methods for finding lower and upper boundaries of powers of parametric interval uncertain matrix. Two results are presented. As the first result, a method to find the exact lower and upper boundaries of powers of single-parametric interval matrix is established. As the second result, the lower and upper boundaries of powers of general interval matrix are evaluated. Three numerical examples and one application example are presented to validate the method and analysis proposed in this study. View full abstract»

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  • Existence of a common quadratic lyapunov function for discrete switched linear systems with m stable subsystems

    Publication Year: 2011 , Page(s): 535 - 537
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (86 KB)  

    The problem on the existence of a common quadratic Lyapunov function (CQLF) for discrete switched linear systems with m stable subsystems is considered. System matrices are Schur stable. A necessary condition for the existence of a CQLF and a sufficient condition for the non-existence of a CQLF are derived, respectively. Numerical examples are presented 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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