Online ISSN
1751-8652
Print ISSN
1751-8644
IET Control Theory & Applications
Volume 6, Issue 11, 19 July 2012
Volumes & issues:
Volume 6, Issue 11
19 July 2012
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- Author(s): S. Patra ; G. Ray ; S. Sen
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1567 –1576
- DOI: 10.1049/iet-cta.2011.0313
- Type: Article
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In this study, an attempt has been made to design an output feedback controller for local stabilisation of uncertain linear time-invariant plant with bounded control inputs. The design is accomplished via parametric H∞ loop-shaping control by describing the uncertainty as perturbations to normalised coprime factors of the shaped plant. The shaped plant is designed based on the closed-loop design specifications by appropriately choosing the weighting transfer function matrices. For the existence of stabilising controller, a set of sufficient conditions has been derived in linear matrix inequality framework and subsequently, a region of attraction is estimated such that the control inputs never exceed the pre-specified bounds. To illustrate the effectiveness of the proposed method, a numerical example has been elucidated. - Author(s): W. Xie
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1577 –1582
- DOI: 10.1049/iet-cta.2011.0362
- Type: Article
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The study deals with the quadratic L2-gain performance linear parameter-varying realisation of parametric transfer functions and state-feedback gain scheduling control. It is shown that any parametric transfer function, which has L2-gain performance with a bound for all constant parameters values, admits a state space realisation guaranteeing quadratic L2-gain performance with the bound under arbitrary parameter variations. A reasonably general procedure is provided to find such a realisation with linear matrix inequality optimal technique. Furthermore, according to the realisation, the state-feedback gain scheduling control design is also dealt with. Finally, a simple numerical example is given to illustrate the efficiency of the proposed method. - Author(s): G. Wen ; Z. Duan ; Z. Li ; G. Chen
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1583 –1593
- DOI: 10.1049/iet-cta.2011.0156
- Type: Article
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In this study, the problem of stochastic consensus in multi-agent systems of non-linear dynamical agents with state-dependent noise perturbations and repairable actuator failures is investigated. By appropriately constructing a Lyapunov function and using tools from the stochastic differential equations theory, it is proved that mean-square consensus in the closed-loop multi-agent systems with a fixed strongly connected topology can be achieved exponentially if the coupling strength of relative states among neighbouring agents is larger than a threshold value depending on the actuator failure rate. The convergence rate is also analytically given. The results are then extended to the more general case where the communication topology only contains a directed spanning tree. Numerical simulations are finally provided to illustrate the effectiveness of the theoretical analysis. - Author(s): A.V. Papadopoulos ; M. Maggio ; S. Negro ; A. Leva
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1594 –1602
- DOI: 10.1049/iet-cta.2011.0632
- Type: Article
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System-theoretical methods are already used for the control of computing systems, but much more can be done exploiting said methods for their ‘design’. This requires to express in control-theoretical terms desires and specifications that originate in the computer science domain, which may not be immediate. It also requires to accept that part of the addressed system be modified, which may pose some acceptance problems. However, if those issues are handled correctly, the payback is often very relevant. This study demonstrates the above ideas in the context of resource allocation. - Author(s): Y. Tong ; C. Wang ; L. Zhang
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1603 –1609
- DOI: 10.1049/iet-cta.2011.0293
- Type: Article
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This study investigates the stabilisation problem of discrete-time switched positive linear systems by means of piecewise linear copositive Lyapunov functions. Two stabilisation strategies are designed under time- and state-dependent switching cases, respectively. The former case aims at determining an upper bound of the minimum dwell time to guarantee that the underlying system is stable for any switching signal with dwell time greater than this bound. The latter case is focused on deriving a state-dependent switching law stabilising the underlying system from the solution of a family of so-called linear copositive Lyapunov–Metzler inequalities. In each case, a sufficient stabilisation condition is given first, then based on which an associated guaranteed cost is further proposed. A practical system derived from the distributed power control in communication networks is given to illustrate the effectiveness and applicability of the theoretical results. - Author(s): E. Capello ; D. Sartori ; G. Guglieri ; F. Quagliotti
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1610 –1619
- DOI: 10.1049/iet-cta.2011.0275
- Type: Article
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In this study a novel robust approach for proportional integrative derivative gain evaluation is proposed. This approach, which can be considered in the class of H∞ loop shaping methods, is applied to tune the gains of a multi-loop autopilot for mini unmanned aerial vehicles. Nominal stability, nominal performance, robust stability and robust performance of the system are assessed. Root locus method and loop shaping techniques are combined in order to guarantee compliance with robustness requirements and to obtain satisfying flying qualities. Simulation results demonstrate that the method is easy to implement, good robustness and flying performances can be achieved despite a conflicting requirement between these two characteristics. - Author(s): J. Ma ; Z. Zheng ; D. Hu
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1620 –1632
- DOI: 10.1049/iet-cta.2011.0394
- Type: Article
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In this study a modular approach to the robust reconfigurable flight control system design for an overactuated aircraft is proposed. The structure of the proposed scheme consists of three parts: a backstepping controller module, a robust control allocator and an online actuator effectiveness estimator. Firstly, the backstepping control law is developed for the strict feedback form of an Aero-Data Model in Research Environment aircraft to produce the desired commands. Furthermore, a novel robust optimisation-based control allocation algorithm is proposed to distribute the commands among redundant actuators with the consideration of control effectiveness uncertainties. Lastly, the control effectiveness factors are introduced to denote the healthiness of the actuators, and the least trimming squares-based estimator is designed for online estimation of the actuator effectiveness. With the proposed scheme, good tracking performance, robustness and reconfigurable capability are achieved. Evaluation of the overall system is accomplished by numerical simulation with various conditions, including adverse scenarios where actuator failures occur. The results show the effectiveness of the proposed scheme. - Author(s): G.A. Ramos and R. Costa-Castelló
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1633 –1644
- DOI: 10.1049/iet-cta.2011.0272
- Type: Article
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Repetitive control has proven to be an efficient control technique in power factor correction by active filtering. Unfortunately, this technique shows a dramatic performance decay when the network frequency is not exactly known or it varies with time. In order to overcome the varying/uncertain frequency problem, a robust high-order repetitive control strategy can be used; however, most internal models obtained by these approaches are unstable. Although this fact does not compromise the closed-loop stability, practical problems can arise during the implementation. This study proposes and studies a stable second-order odd-harmonic repetitive control system, presents a stability analysis of high-order internal models and describes the performance degradation of the standard repetitive control in terms of the active filter (AF) application. In this way, an experimental validation has been carried out implementing the proposed internal model in a shunt AF current controller. As a result, this high-order controller allows dealing with the grid frequency variations without using adaptive schemes. - Author(s): H.K. Lam ; L.D. Seneviratne ; X. Ban
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1645 –1653
- DOI: 10.1049/iet-cta.2011.0310
- Type: Article
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This study investigates the stability of parameter-dependent polynomial-fuzzy-model-based (PDPFMB) control systems. A parameter-dependent polynomial fuzzy model is proposed to represent a non-linear plant. A parameter-dependent polynomial fuzzy controller is then employed to stabilise the non-linear plant. The stability of PDPFMB control systems is investigated using the sum-of-squares (SOS) technique based on a parameter-dependent Lyapunov function candidate. With the consideration of the information of system parameters, parameter-dependent SOS-based stability conditions are obtained to determine the system stability and polynomial feedback gains. A feasible solution to the stability conditions can be obtained numerically using the third-party Matlab toolbox SOSTOOLS. Unlike the membership functions, as the system parameters are not single signed functions, the traditional analysis approach obtaining the stability conditions cannot be applied. Instead, the membership functions and system parameters are considered as symbolic variables for the construction of the parameter-dependent SOS-based stability conditions. A simulation example is given to demonstrate the merits of the proposed approach. - Author(s): M.S. Mahmoud and S.A. Hussain
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1654 –1660
- DOI: 10.1049/iet-cta.2011.0388
- Type: Article
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The problem of resilient stabilisation for a class of continuous-time uncertain systems having norm-bounded parametric uncertainties is investigated. Both static and dynamic output-feedback resilient controller design is considered. The goal is to robustly quadratically stabilise the uncertain plant considering the controller gain perturbations. Sufficient conditions for the existence of static output feedback and dynamic output feedback resilient controllers are derived in terms of linear matrix inequalities. A numerical example for each type of controllers is illustrated to demonstrate their effectiveness. - Author(s): D.-W. Gong ; Y. Zhang ; C.-L. Qi
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1661 –1670
- DOI: 10.1049/iet-cta.2011.0513
- Type: Article
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Localising an odour source is of considerable importance in real-world applications. A modified particle swarm optimisation (PSO) algorithm was presented in this study as an effective cooperative strategy among robots to guide them to search for an odour source. In this algorithm, the whole search space is divided into several grid cells with each cell saving positions that have been detected by robots. In the phase of searching for an odour plume, each robot locating at a cell obtains a repulsive force proportional to the number of positions saved by this cell. To improve the efficiency of particles in traversing the plume, two cognitive factors of PSO are dynamically adjusted according to the effect of wind on self-cognition and social cognition of a particle. In addition, simulated annealing is incorporated into the update of a particle’s local leader to prevent premature convergence of the swarm. The proposed algorithm, implemented using MATLAB, was applied to localise the odour source in four typical simulation scenes formed by Fluent, and compared with previous methods. The experimental results show that the proposed algorithm can guide a multi-robot system to localise the odour source rapidly and accurately. - Author(s): A. Maghsoudi and M. Jahed
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1671 –1681
- DOI: 10.1049/iet-cta.2011.0449
- Type: Article
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Although ‘Needle steering’ is considered a challenge in needle insertion strategies, needle control becomes a crucial training tool for evaluating surgeon’s skills in such critical incision. In this study, a model-based dynamics equation for the needle movement through the soft tissue is developed. In the proposed control scheme, the force estimation calculated through the simulated tissue deformation data and the dynamic finite element as the tissue model, is used as the force feedback. To point out the role of mechanical properties of the soft tissue, an inverse dynamics control method is used to demonstrate the system performance in presence of uncertainty in tissue mechanical parameters. Moreover, it is shown that the uncertainty in the tissue mechanical parameters dramatically affects the system performance as well as causing instability. Hence subsequently, a robust control approach is designed to compensate for the undesirable effect of parameter uncertainty in the system. - Author(s): J.-M. Yang and S.W. Kwak
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1682 –1689
- DOI: 10.1049/iet-cta.2011.0339
- Type: Article
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In this study, the authors present a novel scheme of fault-tolerant control for asynchronous sequential machines. The considered asynchronous machine is subject to permanent faults, for which the system remains in the faulty condition indefinitely after the occurrence of fault inputs. The main objective is to design an observer and a corrective controller, so that the stable-state behaviour of the closed-loop system can maintain the normal input/output behaviour despite the adversarial effect of fault inputs. It is shown that existence of such a controller depends on a certain structural redundancy of the asynchronous machine. As a case study, the authors apply the proposed control scheme to the implementation of an asynchronous Johnson counter with redundant bits. Experimental results demonstrate the applicability of the proposed fault-tolerant controller to real digital systems working in a faulty environment. - Author(s): X.-W. Jiang ; Z.-H. Guan ; G. Feng ; Y. Wu ; F.-S. Yuan
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1690 –1698
- DOI: 10.1049/iet-cta.2011.0329
- Type: Article
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In this study, the optimal tracking performance of multiple-input multiple-output (MIMO) networked control systems is investigated. The system under consideration is finite-dimensional, linear time-invariant over an additive white Gaussian noise (AWGN) channel between the controller and the plant. The power of the tracking error is adopted as the measure of the performance and is minimised subject to the channel input power constraint searching through all stabilising two-parameter controllers. It is shown that, under the channel input power constraint, the optimal tracking performance is closely dependent on non-minimum phase zeros, unstable poles of the plant and the characteristics of the signals and the channel. Finally, computer simulations are provided to illustrate the analytical results obtained. - Author(s): L.-W. Lee and I.-H. Li
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1699 –1714
- DOI: 10.1049/iet-cta.2011.0434
- Type: Article
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An adaptive sliding-mode controller developed from an orthogonal Haar wavelet is proposed for a pneumatic servo control system experiment to overcome its non-linear and time-varying characteristics. To achieve real-time control of the pneumatic servo system, the orthogonal Haar wavelet is employed to quickly and accurately fit a non-linear function, thus bypassing the model-based prerequisite. The adaptive laws for the coefficients of the Haar wavelet series are derived from a Lyapunov function to guarantee system stability. One of the authors’ purposes is to enhance the stability, reliability and working performance of the pneumatic servo system. Hence, the H∞ tracking technique is incorporated into the conventional adaptive sliding-mode control method [Haar wavelet-based adaptive sliding-mode controller with H∞ tracking performance (HWB-ASMC + H∞)] to attenuate the vibration of servo valve, which is caused by the chattering effect. The authors also show that the proposed HWB-ASMC + H∞ is robust against approximated errors, un-modelled dynamics and disturbances, and can reduce the control chattering problem. The advantages of the proposed method include that no system dynamic models being required to achieve the controller design and no trial-and-error efforts are needed in selecting an approximation function. Consequently, practical experiments on a pneumatic servo system are successfully implemented with different position tracking profiles, which validates the proposed method. - Author(s): G. Ning ; D. Yang ; L. Tie ; K.-Y. Cai
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1715 –1721
- DOI: 10.1049/iet-cta.2011.0346
- Type: Article
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In this study, the authors consider the problem of Nash equilibrium solutions of multi-agent game of information warfare in complex networks, of which the inner dynamics are nonlinear, the interactions among vertex states are with time delays, and vertex states are also with persistent disturbances. A successive approximation approach is used to obtain an optimal control law for different agents in the network systems. An illustration example is presented to demonstrate the characteristic of multi-agent game in networks. - Author(s): L.C. Henriksen ; M.H. Hansen ; N.K. Poulsen
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1722 –1734
- DOI: 10.1049/iet-cta.2011.0488
- Type: Article
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This study presents a wind turbine controller able to handle both hard and soft constraints, typically on actuators but also on other components of the wind turbine, if needed. An issue especially relevant during extreme events or for under-dimensioned actuators. The presented controller is based on model predictive control, a control method well suited for constraint handling. The performance of the presented controller during an extreme operating gust is compared to that of a proportional–integral controller with integrator anti-windup. Furthermore, the presented controller’s capability to operate in both partial and full load operation and to switch between the two modes of operation is demonstrated by additional test cases.
Local stabilisation of uncertain linear time-invariant plant with bounded control inputs: parametric H∞ loop-shaping approach
Quadratic L2-gain performance linear parameter-varying realisation of parametric transfer functions and state-feedback gain scheduling control
Stochastic consensus in directed networks of agents with non-linear dynamics and repairable actuator failures
General control-theoretical framework for online resource allocation in computing systems
Stabilisation of discrete-time switched positive linear systems via time- and state-dependent switching laws
Robust assessment for the design of multi-loop proportional integrative derivative autopilot
Modular robust reconfigurable flight control system design for an overactuated aircraft
Power factor correction and harmonic compensation using second-order odd-harmonic repetitive control
Fuzzy control of non-linear systems using parameter-dependent polynomial fuzzy model
Improved resilient feedback stabilisation method for uncertain systems
Localising odour source using multi-robot and anemotaxis-based particle swarm optimisation
Needle dynamics modelling and control in prostate brachytherapy
Fault diagnosis and fault-tolerant control of input/output asynchronous sequential machines
Optimal tracking performance of networked control systems with channel input power constraint
Wavelet-based adaptive sliding-mode control with H∞ tracking performance for pneumatic servo system position tracking control
Nash equilibrium of time-delay interaction complex networks subject to persistent disturbances
Wind turbine control with constraint handling: a model predictive control approach
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- Author(s): A. Ghosh and S.K. Das
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1735 –1740
- DOI: 10.1049/iet-cta.2011.0358
- Type: Article
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This study achieves superior multi-channel output gain margin (MOGM), compensation of continuous-time, linear time-invariant (LTI), non-minimum-phase, unstable, multi-input-multi-output (MIMO) plants by first input–output decoupling these in open-loop and then effecting zero placements of the decoupled loops using single-input-single-output (SISO) periodic feedback. The condition that allows this controller to yield arbitrarily large MOGM is also found out. An example is considered to illustrate the design procedure and the capability of this controller. - Author(s): Y. Wang ; X. Shi ; G. Wang ; Z. Zuo
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1741 –1744
- DOI: 10.1049/iet-cta.2011.0529
- Type: Article
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The problem of finite-time stability for a class of continuous-time switched systems with impulse effects is studied in this article. A criterion is proposed which ensures that the system’s state trajectory remains in a bounded region of the state space over a pre-specified finite-time interval if the authors give a bound on the initial condition. Contrary to the existing results on finite-time stability of switched systems, the average dwell time approach, rather than the Lyapunov-based ones, is utilised to realise such a purpose. The difference between the finite-time stability and the Lyapunov stability is clearly shown. A numerical example is given to illustrate the proposed design method. - Author(s): X. Nian ; X. Wang ; Y. Wang ; Z. Sun
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1745 –1751
- DOI: 10.1049/iet-cta.2011.0541
- Type: Article
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This study deals with the problem of delay-dependent stability for fuzzy neutral system. The matrix decomposition technique is used to deal with the cross terms. The main results are extended to the fuzzy neutral system with time-varying uncertainties. The stability criteria proposed in this study, which are expressed by linear matrix inequalities, are with simple form and have less slack variables. Numerical examples are given to illustrate the effectiveness of the authors’ methods. - Author(s): Y. Fan ; G. Feng ; Q. Gao
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1752 –1757
- DOI: 10.1049/iet-cta.2011.0479
- Type: Article
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In multi-agent control systems, coordination of agents often relies critically on the connectivity of the underlying communication network. This study analyses the problem of preserving connectivity with bounded control inputs for multi-agent systems. Firstly, a general potential-based control framework is investigated and sufficient conditions for achieving rendezvous while preserving connectivity are presented. Then, based on the modification of the potential-based control, a novel bounded control law with very mild design requirements is proposed and the issues of preserving connectivity, the agent group rendezvous, and the input bound of the controller are discussed. The effectiveness of the proposed control law and the boundedness of the inputs are illustrated by numerical examples. - Author(s): Y. Hu ; P. Li ; J. Lam
- Source: IET Control Theory & Applications, Volume 6, Issue 11, p. 1758 –1765
- DOI: 10.1049/iet-cta.2011.0324
- Type: Article
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This study considers the state consensus problem of multi-agent systems by virtue of novel simultaneous stabilisation techniques, where the distributed controller is proposed using relative outputs of the agents. A new consensus analysis condition is derived by studying the corresponding simultaneous stabilisation problem. Based on the analysis result, a necessary and sufficient condition is then established to ensure the consensus achievement of multi-agent systems, where the controller gain matrix is parameterised by a positive definite matrix, which is independent of the Lyapunov matrices. Iterative approaches are also developed to solve the design conditions, and to optimise the initial values with the solvability of the original problem improved. Further results are obtained for the dynamic output-feedback case. Finally, a numerical example is given to show the effectiveness of the obtained results.
Decoupled periodic compensation for multi-channel output gain margin improvement of continuous-time MIMO plants
Finite-time stability for continuous-time switched systems in the presence of impulse effects
Delay-dependent stability for fuzzy neutral system via state matrix decomposition
Bounded control for preserving connectivity of multi-agent systems using the constraint function approach
Consensus of multi-agent systems: a simultaneous stabilisation approach
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