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Control Theory & Applications, IET

Issue 10 • Date July 5 2012

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Displaying Results 1 - 24 of 24
  • Strong stabilisation by output feedback controller for linear systems with delayed input

    Publication Year: 2012 , Page(s): 1329 - 1340
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (284 KB)  

    This study addresses the strong stabilisation problem for continuous-time linear systems with an unknown input delay via dynamic output feedback controllers. A new criterion for dynamic output feedback stabilisability is proposed in terms of matrix inequalities with the separation of the controller gain with the Lyapunov matrix and the system matrices. Based on these new characterisations, an iterative algorithm is given to design the dynamic output feedback controllers with the initial values obtained by some proposed state feedback stabilisation methods. The effectiveness and merits of the proposed approach are shown through several examples. View full abstract»

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  • Robust dynamic bumpless transfer: an exact model matching approach

    Publication Year: 2012 , Page(s): 1341 - 1350
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (409 KB)  

    This study considers the problem of dynamic bumpless transfer for uncertain controller switched systems. The robust dynamic bumpless transfer is firstly concerned. With a set of pre-given controllers, design conditions on robust dynamic bumpless transfer are formulated under which the switched system will perform a smooth transition at the transfer moment. These conditions consist of two parts including several linear matrix equations (LMEs) and two linear matrix inequalities (LMIs), each part derived is based on exact model matching and L1 control, respectively. Furthermore, the condition for guaranteeing the closed-loop system to be robustly stable under arbitrary bumpless transfer is discussed. Lastly, a numerical example and a practical simulation example on the ramjet engine control system are given to illustrate the practicability of the proposed method. View full abstract»

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  • Adaptive observer design for the uncertain Takagi-Sugeno fuzzy system with output disturbance

    Publication Year: 2012 , Page(s): 1351 - 1366
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1982 KB)  

    The study proposes an adaptive fuzzy observer for the uncertain Takagi-Sugeno (T-S) fuzzy system with output disturbance. First, an augmented fuzzy model is built by integrating the system state and the output disturbance together as new variables. Then, the desired adaptive fuzzy observer is designed to estimate the unavailable system state and the unknown output disturbance simultaneously. Based on Lyapunov theory and linear matrix inequalities (LMIs) tools, two main conditions are derived under which the fuzzy observer is designed. Finally, the procedure of the observer design is summarised and the effectiveness of the designed observer is demonstrated with a numerical example. View full abstract»

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  • Fault detection and identification of aircraft control surface using adaptive observer and input bias estimator

    Publication Year: 2012 , Page(s): 1367 - 1387
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2917 KB)  

    A fault detection and isolation (FDI) algorithm is proposed for the stuck fault detection of an aircraft with multiple control surfaces. The proposed FDI approach is composed of an adaptive observer and a bias estimation algorithm. The adaptive observer is designed for the stuck fault detection of the control surfaces, and the bias estimation algorithm is used to estimate the stuck position of the corresponding control surface. The bias estimation algorithm is designed using an unscented Kalman filter. Non-linear back-stepping control is applied. Also, to achieve the fault-tolerant property without redesigning the controller, control allocation technique is used. A non-linear aircraft model with the multiple control surfaces is considered. Numerical simulations are performed to demonstrate the performance of the proposed FDI algorithm. View full abstract»

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  • Fault tolerant control with Hα performance for attitude tracking of flexible spacecraft

    Publication Year: 2012 , Page(s): 1388 - 1399
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (925 KB)  

    A fault-tolerant control scheme with thruster redundancy is developed and applied to perform attitude tracking manoeuvres for an orbiting flexible spacecraft. Based on the assumption of bounded elastic vibrations, an adaptive sliding mode controller is proposed to guarantee that all the signals of the resulting closed-loop attitude system are uniformly ultimately bounded in the presence of an unknown inertia matrix, bounded disturbances and unknown faults. An H performance index is introduced to describe the disturbance attenuation performance of the closed-loop system. This approach is then extended to the problem of elastic vibration without knowledge of the bounds a priori. The presented approach addresses thruster saturation limits and the desired thruster force is guaranteed to stay within the limit of each thruster. Extensive simulation studies have been conducted to demonstrate the closed-loop performance benefits compared to conventional control schemes. View full abstract»

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  • Decoupled Stein iterations to the discrete-time generalized Riccati equations

    Publication Year: 2012 , Page(s): 1400 - 1409
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    The authors investigate the numerical solution of a set of discrete-time generalised Riccati equations. The class of discrete-time non-linear equations involves in various control problems for discrete-time stochastic systems and it can be considered as an important tool for solving optimisation control for such type systems. A new procedure for computing the maximal solution and the stabilising solution is proposed by Dragan et al. (`Iterative algorithm to compute the maximal and stabilising solutions of a general class of discrete-time Riccati-type equations`, Int. J. Control, 2010, 83, (4), pp. 837-847). In this study, the authors introduce a new iterative procedure based on the solution of a Stein matrix equation for computing the maximal and the stabilising solution. The convergence properties of the new iteration are proved. Sufficient conditions for computing the maximal solution and the stabilising solution are derived. Finally, some numerical examples are presented to illustrate the feasibility of the proposed algorithm. View full abstract»

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  • Transportation task-oriented trajectory planning for underactuated overhead cranes using geometric analysis

    Publication Year: 2012 , Page(s): 1410 - 1423
    Cited by:  Papers (14)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (957 KB)  

    The authors present a novel off-line trolley trajectory planning method for the payload horizontal transferring task of underactuated overhead cranes. The proposed approach is feasible and efficient for crane control. Specifically, the coupling behaviour between the actuated trolley motion and the unactuated payload swing is successfully addressed via some rigorous geometric analysis in the phase plane. Based on this, an analytical three-segment acceleration trajectory (i.e. a trapezoid velocity trajectory) is firstly obtained by carefully considering the practical constraints of crane control. To tackle the infinite jerk (discontinuity) problem as well as to show the flexibility of the proposed geometric analysis-based method, the authors then introduce some transition mechanisms to smoothen the acceleration trajectory, and to construct two types of modified acceleration trajectories. For any given transferring task, the proposed trajectory planning approach provides a novel mechanism to determine the parameters of the trajectories so that the transportation indexes, including the permitted payload swing, transferring efficiency and so on, can be met without much difficulty. Both simulation and experimental results are exhibited to illustrate the effectiveness and feasibility of the proposed approach. View full abstract»

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  • Classical and quantum-inspired electromagnetism-like mechanism and its applications

    Publication Year: 2012 , Page(s): 1424 - 1433
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2318 KB)  

    In this study, we propose a novel evolutionary computing method that is called quantum-inspired electromagnetism-like mechanism (QEM). QEM is based on the electromagnetism theory and uses the characteristic of quantum computation. We compare with quantum-inspired evolutionary algorithms (QIEA) and the other traditional heuristic algorithms to solve 0/1 knapsack problem. Meanwhile, we can also find the shortest tour length of 16 cities travelling salesman problem (TSP). The experimental results show that the QEM can rapidly and efficiently obtain the optimal solution of combinatorial optimisation problems. To conclude, QEM is an efficient solution for optimal control and adaptive control in stochastic/hybrid systems. View full abstract»

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  • Hα robust fuzzy dynamic observer-based controller for uncertain Takagi-Sugeno fuzzy systems

    Publication Year: 2012 , Page(s): 1434 - 1444
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (290 KB)  

    This study considers the problem of robust controller design for uncertain Takagi-Sugeno (T-S) fuzzy systems with H performance through fuzzy dynamic observer (FDO). Dynamic observer is an alternative structure for classical observer which can be regarded as a general form of a usual observer and has additional degrees of freedom in the observer structure. In this study first the idea of dynamic observer in linear systems is extended to T-S fuzzy systems and it is shown that FDO can be used effectively for tackling the drawbacks of the existing methods of classical observer-based robust controller design. Strict linear matrix inequality (LMI) conditions are presented for designing robust H observer-based controller even in the presence of uncertainties in system matrix, input and output matrices simultaneously by employing FDO. Finally, efficiency of the proposed design method is shown in simulation results. View full abstract»

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  • Output tracking control with enhanced damping of internal dynamics and its output boundedness for static synchronous compensator system

    Publication Year: 2012 , Page(s): 1445 - 1455
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1099 KB)  

    This study investigates an important and challenging problem in non-linear systems: achieving output tracking control with a tolerable error bound as well as providing enhanced damping control of the internal dynamics. This problem is solved by using a damping controller in an input-output linearised static synchronous compensator system. The controllability and observability analyses direct the authors how to determine the damping controller gain. The proposed controller provides improved damping for lightly damped internal dynamics with degraded but tolerable output tracking performance. Finding a parameter-dependent Lyapunov function for the zero dynamics of error dynamics proves the stability of the damped internal dynamics in the time-invariant and time-varying systems. Stability of the closed-loop system is established by designing a composite Lyapunov function and it ensures that the tracking error of the output, in the approximated input-output linearised system, remains within a specified bound. Through stability analysis, the damping controller and the desired reference trajectory providing uniform boundedness of tracking error in output can be designed. View full abstract»

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  • Controllability and observability in non-linear flow reservoir model - RETRACTED

    Publication Year: 2012 , Page(s): 1456 - 1467
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (24 KB)  

    [This paper has been withdrawn by the publisher]. In this study, the authors analyse and interpret the controllability and observability properties of a non-linear two-phase flow reservoir model, with particular focus on the saturation dynamics. They investigate the extent to which such models are controllable and observable; and how these properties are affected by well locations, geological heterogeneities and fluid properties. It is shown that well configuration and fluid front dynamics are significant factors that affect the extent to which a non-linear two-phase flow reservoir model is controllable and observable. Overall, these findings are very promising and further demonstrate the applicability of systems theoretic in this subject area. View full abstract»

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  • A unified dual-stage actuator control scheme for track seeking and following in hard disk drives

    Publication Year: 2012 , Page(s): 1468 - 1477
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1497 KB)  

    This paper presents a unified approach to track seeking and following control for a dual-stage actuator (DSA) hard disk drive (HDD) system. Based on a doubly coprime factorisation (DCF) method, the DSA controller and the closed-loop dynamics are expressed explicitly in terms of two design parameters. This greatly simplifies the optimisation of design parameters in meeting desired specifications. We then address how to use the design parameters to deal with specific problems in the DSA, that is, control allocation for disturbance rejection and trajectory planning for track seeking. Simulated results are also presented to verify the effectiveness of the proposed DSA controller. Compared with previous works, the proposed approach can fulfil track seeking and following tasks by a single controller without switching. Moreover, the unified controller can achieve desirable performances for both tasks that are equivalent to that by two separate conventional controllers. View full abstract»

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  • Single agent control for multi-agent dynamical consensus systems

    Publication Year: 2012 , Page(s): 1478 - 1485
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (385 KB)  

    The problem of controlling a single agent in a multi-agent consensus system is studied in order to make states of all agents in the system follow a common reference signal. It is shown that if every two agents in a given system are connected and a reference signal is a step function, then every controller locally stabilising one single agent gives rise to a successful tracking of all agents. When a proportional control is employed, the relations between overall tracking performance, interconnection topology and the choice of a controlled agent are analytically investigated. A numerical study is also performed to substantiate theoretical findings. View full abstract»

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  • Predictive control of nonlinear visual servoing systems using image moments

    Publication Year: 2012 , Page(s): 1486 - 1496
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (942 KB)  

    The visual servoing architectures with an eye-in-hand configuration, composed of a 6-d.o.f. manipulator robot and a video camera, are categorised as high-coupled and nonlinear systems. For this reason, in order to have a stable and convergent behaviour, advanced techniques like predictive control are needed. These types of techniques can solve the potential problems that can appear in classical (image-based visual servoing) while different type of constraints for visual servoing system can be fulfilled easier. Three different visual predictive control architectures based on image moments are proposed. The model for the image moments predictor used in the first architecture is an extension of a local model point features predictor. The second predictive approach uses an image moment-based predictor to describe the future behaviour of the system over a certain camera velocity scenario directly in the image moments space. In order to have a faster convergence and in the same time a desired behaviour of the servoing system, a reference trajectory is employed. This represents the main contribution of the last predictive control technique proposed in this study. A Matlab simulator was developed and all the visual servoing architectures described in the study were implemented. The simulation results showed that all the proposed visual predictive control approaches are stable and convergent when dealing with visual servoing tasks, but the best performances were assigned to the reference trajectory-based image moments architecture. View full abstract»

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  • Actuator fault detection and adaptive accommodation control of flexible-joint robots

    Publication Year: 2012 , Page(s): 1497 - 1507
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (623 KB)  

    This study presents a fault detection and adaptive accommodation control scheme for flexible-joint (FJ) robots with model uncertainties and multiple actuator faults. It is assumed that the value and occurrence time of multiple actuator faults are unknown. A fault detection scheme is designed to detect the first actuator fault of uncertain FJ robots and the fault detectability characterising the class of actuator faults is analysed. Then, we design an adaptive fault accommodation control scheme with prescribed performance bounds, which characterise the convergence rate and maximum overshoot of tracking errors to accommodate the actuator faults and to compensate the effect caused by them. The proposed accommodation controller is developed based on the dynamic surface design and the adaptive technique. From the Lyapunov stability theorem, it is proved that all signals of the closed-loop system are semiglobally uniformly ultimately bounded and tracking errors are preserved within prescribed performance bounds regardless of actuator faults that occur after the first fault detection. A simulation example of a three-link FJ robot is provided to illustrate the effectiveness of the proposed scheme. View full abstract»

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  • Synchronisation of chaotic neural networks with unknown parameters and random time-varying delays based on adaptive sampled-data control and parameter identification

    Publication Year: 2012 , Page(s): 1508 - 1515
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (349 KB)  

    This study investigates the synchronisation problem of chaotic neural networks with unknown parameters and random time-varying delays. By introducing a stochastic variable with Bernoulli distribution, the neural networks with random time-varying delays is transformed into one with deterministic varying delays and stochastic parameters. A simple and robust adaptive sampled-data controller is designed such that the response system can be synchronised with a drive system with unknown parameters by using suitable parameter identification and the Lyapunov stability theory. The proposed synchronisation criteria are easily verified and do not need to solve any linear matrix inequality. Numerical simulations are carried out to demonstrate the effectiveness of the established synchronisation laws. View full abstract»

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  • Suboptimal strategy for the finite-time linear-quadratic optimal control problem

    Publication Year: 2012 , Page(s): 1516 - 1521
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (450 KB)  

    In this article the authors study analytically the impact of the optimal constant feedback gain of the steady-state linear-quadratic optimal control problem to the corresponding finite-time linear-quadratic optimal control problem. Contributions of the study are 3-fold: (i) conditions for applicability of this suboptimal procedure are presented; (ii) a formula for the performance loss because of this practical implementation (use of the constant instead of the time-varying gain) is derived; and (iii) a technique based on the prescribed degree of stability that can be successfully used in practice is discussed. Examples are included to demonstrate the performance loss owing to this simplified approximate (suboptimal) linear-quadratic finite-horizon optimal control problem implementation. View full abstract»

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  • Finite-time stochastic stability and stabilisation of linear discrete-time Markovian jump systems with partly unknown transition probabilities

    Publication Year: 2012 , Page(s): 1522 - 1526
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    This study deals with the problems of finite-time stochastic stability and stabilisation with partly unknown transition probabilities for linear discrete-time Markovian jump systems (MJP). The definition of finite-time stochastic stability for discrete-time MJP is firstly given. Based on it, a sufficient condition is proposed to guarantee that the state of the system does not exceed a certain threshold in mean-square sense during a specified time interval. The above result is then extended to the finite-time stochastic stabilisation case. By introducing some free-weighting matrices, the proposed method leads to less conservatism compared with the existing ones. Two numerical examples are given to illustrate the effectiveness of the proposed methods. View full abstract»

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  • Coding scheme based on boundary function for consensus control of multi-agent system with time-varying topology

    Publication Year: 2012 , Page(s): 1527 - 1535
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (309 KB)  

    The relationship between control and communication is becoming more and more important in multi-agent system. Besides consensus protocol, the coding scheme is also a part of the system design. In this study, the boundary function method is proposed for the coding scheme design to solve quantised consensus problem of multi-agent system under channels with time-varying connected topology. Two cases of channels with time-varying topology are considered: (i) channels connecting agents (controllers) and actuators and (ii) channels connecting neighbouring agents. To obtain convergence conditions for consensus problems, a relation between incidence matrices of any two connected graphs is used for the first case and an expression of the boundary function is developed for the second case. Since the quantiser is parameterised by the boundary function and the channel data rate, constraint expressions that include the channel data rate and the system convergence rate are obtained to show the tradeoff between control and communication performances. View full abstract»

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  • Enumeration of reachable states for arbitrary marked graphs

    Publication Year: 2012 , Page(s): 1536 - 1543
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (351 KB)  

    This study develops the theory to enumerate the reachable states of marked graphs that are a simple subclass of Petri nets where every place has a single input and output transition without the construction of a reachability graph (RG), which, as far as the authors know, does not receive much attention in the previous studies. Usually, it is necessary to enumerate all the reachable states of a plant to be controlled. However, the construction of an RG suffers from the state explosion problem. This study tackles the problem for a special class of Petri nets by expressing and finding the number of reachable states in an algebraic way. View full abstract»

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  • Robust adaptive fault-tolerant control for uncertain linear systems with actuator failures

    Publication Year: 2012 , Page(s): 1544 - 1551
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (694 KB)  

    This study is concerned with the robust adaptive fault-tolerant compensation control problem for linear systems with parameter uncertainty, disturbance and actuator faults including outage, loss of effectiveness and stuck. It is assumed that the lower and upper bounds of actuator efficiency factor, the upper bounds of disturbance and the unparametrisable time-varying stuck fault, are unknown. Then, according to the information from the adaptive mechanism, the effect of actuator fault, exogenous disturbance and parameter uncertainty can be eliminated completely by designing adaptive state feedback controller. Furthermore, it is shown that the solutions of the resulting adaptive closed-loop system are uniformly bounded, the states converge asymptotically to zero. Finally, two examples are given to illustrate the effectiveness and applicability of the proposed design method. View full abstract»

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  • Robust controllability of linear systems with multiple delays in control

    Publication Year: 2012 , Page(s): 1552 - 1556
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (135 KB)  

    The considered problem is robust controllability of linear systems with both multiple delays in control and structured parametric uncertainties. Under the assumption that the linear nominal system with multiple control delays is controllable, a sufficient condition is proposed to preserve the assumed property when system uncertainties are introduced. The application of the proposed sufficient condition is demonstrated in two examples. View full abstract»

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  • Rendezvous of mobile agents with constrained energy and intermittent communication

    Publication Year: 2012 , Page(s): 1557 - 1563
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (227 KB)  

    This study addresses the rendezvous problem for networks of mobile agents with limited energy and intermittent communication. An energy-aware rendezvous protocol is developed which can prevent the agents from depleting their energy. Moreover, the agents with the least energy among their neighbours are allowed to remain static to conserve energy under the proposed protocol. A necessary condition and a sufficient condition are also derived for achieving rendezvous. Finally, numerical examples are presented to illustrate the main results. View full abstract»

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  • Comments on 'Controllability of periodic systems: continuous and discrete'

    Publication Year: 2012 , Page(s): 1564 - 1566
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (118 KB)  

    This note shows that necessities of Theorems 1 and 3-5 in the above study cannot be derived by the proof method presented by the authors. Two counterexamples are given to validate the conclusion. 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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