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Control Theory & Applications, IET

Issue 6 • Date June 2009

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Displaying Results 1 - 17 of 17
  • Traffic network hybrid feedback controller via 0-1 classification of PWARX system with hierarchy

    Publication Year: 2009 , Page(s): 605 - 616
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (445 KB)  

    A new design method for the traffic network hybrid feedback controller is proposed. In the proposed method, the piece-wise auto regressive exogenous (PWARX) classifier describes a nonlinear feedback control law of the traffic control system, where the output of a previously developed controller is reproduced applying the 0-1 classifications of the PWARX system. A new performance criterion is presented here to consider directly the covariance of the traffic network controller output y. The proposed method is a hierarchical classification procedure, where the cluster splitting process is introduced to the cluster with the worst classification performance (which includes 0-1 mixed values of y). The cluster splitting process is followed by the piecewise fitting process to compute the cluster guard and dynamics, and the cluster updating process to find new centre points of the clusters. The usefulness of the proposed method is verified through some numerical experiments. View full abstract»

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  • Robust adaptive control of a class of nonlinearly parameterised time-varying uncertain systems

    Publication Year: 2009 , Page(s): 617 - 630
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (267 KB)  

    A robust adaptive control is presented for a class of time-varying nonlinear uncertain systems which have a fractional nonlinearly parameterised structure. The proposed design is based on robust adaptive backstepping and neural network approximation. The unknown time-varying parameters in the fractional nonlinear functions are estimated using a smooth projection algorithm and estimation errors are robustly compensated for by the additive terms in the proposed virtual and actual controls. Neural networks are employed to approximate the completely unknown bounding functions of the disturbance terms, and their weights as well as approximation errors are adaptively tuned. It is proved that the proposed robust adaptive control can ensure the semi-global uniform ultimate boundedness of all the closed-loop system signals. The control performance can be improved by an appropriate choice of the design parameters. Simulation results are provided to verify the effectiveness of the proposed design. View full abstract»

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  • Memory state feedback controller design for singular systems with multiple internal constant point delays

    Publication Year: 2009 , Page(s): 631 - 641
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    The problem of delay-dependent stabilisation for singular linear continuous-time systems with multiple internal incommensurate constant point delays is investigated. The condition when a singular system subject to point delays is regular independent of time delays is given and it can be easily tested with numerical or algebraic methods. Based on the Lyapunov-Krasovskii functional approach and the descriptor integral-inequality lemma, a sufficient condition for delay-dependent stability is obtained. The main idea is to design multiple memory state feedback control laws such that the resulting closed-loop system is regular independent of time delays, impulse free and stable via solving matrix inequality problem. An explicit expression for the desired memory state feedback control law is also given. Finally, a numerical example is presented to illustrate the effectiveness and the availability for the proposed method. View full abstract»

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  • Active fault-tolerant fuzzy control design of nonlinear model tracking with application to chaotic systems

    Publication Year: 2009 , Page(s): 642 - 653
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (370 KB)  

    The active fault-tolerant control (FTC) design problem for nonlinear model tracking based on the Takagi and Sugeno (T-S) fuzzy model is dealt with. For a nonlinear active FTC system, two random processes with Markovian transition characteristics are introduced to model the system component failure process and the fault detection and isolation (FDI) decision process used to reconfigure the control law, respectively. The random behaviour of the FDI process is conditioned on the failure process state. First, the T-S fuzzy model is employed to exactly represent the FTC system and the nonlinear reference model. A fuzzy controller is used to generate the FDI-decision-dependent control signal. As a result, an error fuzzy system with two Markovian jump parameters is obtained. Then, based on a stochastic Lyapunov function, a linear matrix inequality approach to the fuzzy control design is developed such that the error system is exponentially stable in the mean square and an Hinfin model-tracking performance is guaranteed. Finally, the proposed design method is successfully applied to the chaotic model-tracking control between Lorenz system and Rossler system. View full abstract»

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  • Computing the controllability radius: a semi-definite programming approach

    Publication Year: 2009 , Page(s): 654 - 660
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (178 KB)  

    A semi-definite programming (SDP) approach to compute the controllability radius is proposed in this paper. The initial nonconvex optimisation problem is transformed into the minimisation of the smallest eigenvalue of a bivariate real or trigonometric polynomial with matrix coefficients. A sum-of-squares relaxation leads to the SDP formulation. A similar technique is used for the computation of the stabilisability radius. The approach is extended to the computation of the worst-case controllability radius for systems that depend polynomially on a small number of parameters. Experimental results show that the proposed methods compete well with previous ones in a complexity/accuracy trade-off. View full abstract»

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  • Hα-filtering and state feedback control for discrete-time switched descriptor systems

    Publication Year: 2009 , Page(s): 661 - 670
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    The problem of Hinfin filtering for a class of discrete-time switched systems with unknown inputs is investigated. By using a switched Lyapunov function, sufficient conditions for the solution of this problem are obtained in terms of linear matrix inequalities. Filtering is envisaged both with proportional and proportional integral observers. In addition, the results obtained in observer design are transposed to the controller design for switched descriptor systems. The control of a switched uncertain descriptor system is also treated. A numerical example is given to illustrate the presented results. View full abstract»

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  • Automated manufacturing system: virtual-nets or non-virtual-nets?

    Publication Year: 2009 , Page(s): 671 - 680
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (316 KB)  

    Proving liveness for automated manufacturing systems such as systems of simple sequential processes with resources (S3PR) has been mind boggling. This is because deadlock-freeness does not imply liveness in general. In an earlier paper, it was shown that the virtual first-order structure (VFOS) is the key structure to make some transitions not live. A virtual-net (non-virtual-net) or V-net (NV-net) is a net with (without) VFOS. It was proposed to enlarge the class of NV-nets to NV+-nets to include S3PR by imposing conditions upon VFOS. Showing that S3PR belongs to neither NV-nets nor V-nets, it was proposed that a new large class of resource allocation systems called S+PR and proved that it belonged to NV+-nets. There is no need to prove the liveness of an NV+-net without emptiable siphons, if it is an ordinary Petri net as in traditional techniques is shown. The absence of the above conditioned VFOS serves as one regulation structural mechanism ensuring a siphon to be controlled other than that based on the trap or invariant concept. View full abstract»

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  • Adaptive tracking control of high-order non-holonomic mobile robot systems

    Publication Year: 2009 , Page(s): 681 - 690
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (385 KB)  

    A backstepping-based tracking control design for uncertain mobile robot systems with non-holonomic constraints is presented. For avoiding the singularity and the necessity of the repeated differentiation of the virtual controller, high-degree polynomials of the affine functions are generally included in many existing kinematic controllers. That unfortunately would cause the possible blowup of the actuators for high-order kinematic systems (e.g. a trailer-type mobile robot) in high-speed motions. Regarding this, an exponentially modulated linear stabilising function is included in this design to alleviate such a difficulty. Next at the dynamic design level, an adaptive control algorithm is developed for attaining the global asymptotic tracking stability of the overall closed-loop system. Two case studies of a unicycle-like and a trailer-type wheeled mobile robots are conducted in the final to demonstrate the effectiveness of the proposed design. View full abstract»

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  • A stein matrix equation approach for computing coprime matrix fraction description

    Publication Year: 2009 , Page(s): 691 - 700
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (188 KB)  

    This paper is concerned with the coprime matrix fraction description of linear systems. Analytical solutions are obtained by solving a Stein matrix equation with nilpotent coefficient matrix. An explicit solution consisting of finite summations to the Stein matrix equation is also provided. The proposed approach can be easily transformed into a numerically reliable algorithm if the Stein matrix equation is solved in a numerically stable way. The parametric eigenstructure assignment problem is reconsidered to illustrate the application and efficiency of the proposed approach. View full abstract»

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  • Computed torque control-based composite nonlinear feedback controller for robot manipulators with bounded torques

    Publication Year: 2009 , Page(s): 701 - 711
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (321 KB)  

    On the basis of the classical computed torque control method, a composite nonlinear feedback (CNF) design method for robot manipulators with bounded torques is presented. The resulting controller consists of two loops. The inner loop is for the full compensation for manipulators nonlinear dynamics and the outer loop is the CNF for stabilisation and performance enhancement. Stability analysis is carried out with an estimate of the domain of attraction specified in the presence of actuator saturation. In addition to the guaranteed stability properties, the controller takes advantage of a varying damping ratio induced by the CNF control. The varying damping ratio allows fast transient response without overshoot and compensates the effect of the frictions. It also takes advantage of the high-gain action embedded in the outer loop to compensate the friction effect. Simulation results demonstrate the effectiveness of the proposed design. View full abstract»

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  • Optimal real-time collision-free motion planning for autonomous underwater vehicles in a 3D underwater space

    Publication Year: 2009 , Page(s): 712 - 721
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (351 KB)  

    One approach to designing an optimal real-time collision-free trajectory for autonomous underwater vehicles (AUVs) that move in a 3D unknown underwater space presented here. By explicitly considering the kinematic model of AUVs, a class of feasible trajectories is derived in a closed form, and is expressed in terms of two adjustable parameters for the purpose of collision avoidance. Then, a collision avoidance condition is developed to determine a class of collision-free trajectories. Finally, a performance index is established to find an optimal trajectory from the class. All the steps can be implemented in real-time. The advantages of the proposed approach are: (1) The 3D motion planning problem is reduced to a 2D problem. Instead of directly searching in a 3D space, one only needs to determine two parameters in their plane. Therefore computational efforts are greatly reduced, which is suitable for real-time implementation; (2) The vehicle's kinematic model is explicitly considered, and all boundary conditions are met. After the parameters are determined, the trajectory and controls are explicitly solved in closed forms. This method is shown to be effective by computer simulations. View full abstract»

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  • Robustness analysis of input shaping commands for two-mode flexible systems

    Publication Year: 2009 , Page(s): 722 - 730
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (821 KB)  

    A robustness evaluation of input-shaping techniques to reduce residual vibration of two-mode flexible systems is presented. Using a benchmark two-mode system, the robustness problem is illustrated by first applying input shapers designed for only one mode. These simple shapers are effective for a wide array of two-mode systems because the amplitude of the second mode is often small, perhaps near the noise level. However, single-mode shapers are ineffective when the second mode contributes substantial oscillation amplitude. Therefore the robustness analysis for both single- and two-mode input shapers reveals an inherent compromise between shaper robustness to parameter uncertainties and rise time of the command. A specified-insensitivity shaper can result in command profiles that are significantly more robust to modelling errors than profiles produced with alternative input shapers. The robustness evaluation is verified with a numerical simulation of double-pendulum dynamics and experimentally validated on a 10 ton industrial bridge crane. View full abstract»

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  • Delay-dependent robust hα control for uncertain singular systems with multiple state delays

    Publication Year: 2009 , Page(s): 731 - 740
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (197 KB)  

    The problem of delay-dependent robust H infin control for uncertain singular systems with multiple state delays has been studied. Firstly, using linear matrix inequality (LMI) approach, an improved delay-dependent criterion is given to ensure the singular system to be regular, impulse free and stable with H infin performance. Based on this criterion, the problem is solved via state feedback controller, which guarantees that the closed-loop system is not only regular, impulse free and stable, but also satisfying a prescribed H infin performance condition for all admissible uncertainties. Finally, numerical examples are given to illustrate the effectiveness of the proposed method. View full abstract»

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  • Global robust stability of interval delayed neural networks

    Publication Year: 2009 , Page(s): 741 - 749
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (215 KB)  

    In recent years, the problem of global robust stability of Hopfield-type interval delayed neural networks has received considerable attention. A number of criteria for the global robust stability of such networks have been reported in the literature. On the basis of the idea of dividing (in respect of both the connection weight matrix A and the delayed connection weight matrix B) the given interval into two intervals, four new criteria for the global robust stability of such networks are established. The criteria are in the form of linear matrix inequality and, hence, computationally tractable. The criteria yield a less conservative condition compared with many recently reported criteria, as is demonstrated with an example. View full abstract»

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  • Stability analysis of T-S fuzzy control systems using parameter-dependent lyapunov function

    Publication Year: 2009 , Page(s): 750 - 762
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (987 KB)  

    The system stability of T-S fuzzy-model-based control systems with a parameter-dependent Lyapunov function (PDLF) is investigated. As PDLF approach includes information of the membership function (time derivatives of membership functions), it has been reported that relaxed stability conditions can be achieved compared to the parameter-independent Lyapunov function (PILF). To investigate the system stability, the non-linear plant is represented by a T-S fuzzy model. Various non-parallel distribution compensation (PDC) fuzzy controllers, which can better utilise the characteristic of the PDLF, are proposed to close the feedback loop. To relax the stability conditions, an improved PDLF is employed. Some inequalities are proposed to relate the membership functions and its time derivatives, which allow the introduction of some slack matrices to facilitate the stability analysis. Stability conditions in terms of linear matrix inequalities are derived to aid the design of stable fuzzy-model-based control systems. Simulation examples are given to illustrate the effectiveness of the proposed non-PDC fuzzy control schemes. View full abstract»

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  • Average dwell-time approach to L2 gain control synthesis of switched linear systems with time delay in detection of switching signal

    Publication Year: 2009 , Page(s): 763 - 771
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (206 KB)  

    For switched linear systems with time delay in detection of switching signal, the authors investigate its L2 gain control synthesis problem via off-line-type switched state feedback by average dwell-time approach, that is identifying an average dwell time to guarantee that switched system is exponentially stable with an L2 gain less than chi. The authors first establish an estimation on the state transition matrix of switched systems. Then, based on this concise estimation and some famous mathematical inequalities such as Minkowski's integral inequality and Cauchy-Schwartz inequality, the authors prove that there exists a switched state-feedback controller such that switched system has an L2 gain less than chi for any switching signal with average dwell time greater than a given constant. Finally, an example is given to illustrate our results. Our results complement and generalise those results given in the works of Xie and Wang, Ji et al. and Xie and Chen. View full abstract»

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  • Application of absolute stability theory to robust control against loss of actuator effectiveness

    Publication Year: 2009 , Page(s): 772 - 788
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (329 KB)  

    The problem studied here is passive fault tolerant control (FTC) for actuator faults as a result of loss of effectiveness. This FTC problem is formulated in the dasiaabsolute stability theory frameworkdasia. Based on this formulation, different tools from absolute stability theory are applied. Four controllers are proposed for four problem settings: (a) LTI certain plants, (b) uncertain LTI plants, (c) LTI models with input saturations and (d) non-linear affine single-input plants. The proposed controllers are tested on the hovercraft numerical example. View full abstract»

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