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Control Theory and Applications, IEE Proceedings -

Issue 4 • Date 24 July 2003

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Displaying Results 1 - 16 of 16
  • Optimal control of multirate sampled-data feedback systems via a polynomial approach

    Page(s): 433 - 442
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    The linear quadratic Gaussian design of multirate-sampled multivariable feedback systems using input-output models is described. The theoretical emphasis is placed upon the formulation of augmented representations in which each variable is specified at its associated sample instants throughout one cycle of the sequence of sampling operations. The structures of the polynomial matrices utilised illuminate the causality issues involved and facilitate the acquisition of the optimal control solution from coupled diophantine equations. View full abstract»

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  • Robust vertical takeoff and landing aircraft control via integral sliding mode

    Page(s): 383 - 388
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (355 KB)  

    Reduced equivalent systems have inherent closed-loop poles at the origin in the sliding mode for conventional sliding mode control (SMC). A systematic design strategy is developed for arbitrarily placing all SMC closed-loop poles. The speed control of a vertical takeoff and landing aircraft whose aerodynamic parameters vary considerably during flight is investigated. An outstanding output tracking performance and robustness against system parameter uncertainties and external disturbances are achieved. View full abstract»

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  • Hierarchical fuzzy logic controller for a flexible link robot arm performing constrained motion tasks

    Page(s): 355 - 364
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (405 KB)  

    An examination is performed on the dynamics and control issues for a robotic manipulator with link structural flexibility modelled during the execution of a task that requires the robot tip to contact fixed rigid objects. A multi-time-scale fuzzy logic controller is applied to this system. The large-scale system is decomposed into a finite number of reduced-order subsystems using the singular perturbation approach. A hierarchical ordering of fuzzy rules is used to reduce the size of the inference engine. Real-time implementation of fuzzy controllers can help reduce the burden of large-sized rule sets by fusing sensory data before input and the system's output to the inference engine. Using this approach the control of the force and position of the robot end point is possible while the end-effector moves on the constraint surface. View full abstract»

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  • Delay-dependent guaranteed cost control for uncertain discrete-time systems with delay

    Page(s): 412 - 416
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (229 KB)  

    A guaranteed cost control problem for a class of discrete-time linear state-delayed systems with norm-bounded uncertainties is considered. Attention is focused on the design of memoryless state feedback controllers such that the resulting closed-loop system is asymptotically stable and an adequate level of performance is also guaranteed. By using a descriptor model transformation of the system and Moon's inequality for bounding cross terms, new delay-dependent sufficient conditions for the existence of the guaranteed cost controller are presented in terms of linear matrix inequalities. Three numerical examples are given which show that the proposed method can even produce a lower guaranteed cost than the delay-independent methods. View full abstract»

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  • Instrument fault detection and compensation scheme for direct torque controlled induction motor drives

    Page(s): 376 - 382
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (279 KB)  

    The effects of instrument faults in direct-torque-control-based induction motor drives are analysed and an instrument fault detection isolation scheme (IFDIS) for the drives is proposed. The IFDIS detects and isolates the incipient fault(s) of a speed sensor and current sensors in real-time. The scheme consists of an adaptive gain scheduling observer as a residual generator and a special sequential test logic unit. Although the IFDIS is a single observer scheme, it has the function of fault isolation that normally only a multiple-estimator-based IFDIS possesses. Simulation results show the detection and isolation performance of the IFDIS and the applicability of the scheme to fault tolerant control system design. View full abstract»

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  • Hybrid control of biped robots in the double-support phase via H approach and fuzzy neural networks

    Page(s): 347 - 354
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (310 KB)  

    A quadratic stabilisation fuzzy neural network hybrid control scheme is proposed for biped robots in the double-support phase. First, the authors considered the holonomic constraints. The walking locomotion of biped robots in the double-support phase is modelled as a reduced order position/force hybrid model, which integrates the position/force hybrid model with the reduced-order model. Then a new fuzzy neural network hybrid control scheme is presented, in which H approach, inverse system method and variable structure control are used to attenuate the effect of external disturbances and parametric uncertainties. Simulation results are reported in order to show the performance of the proposed control scheme. View full abstract»

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  • Improved eigenvalue sensitivity for finite-precision digital controller realisations via orthogonal Hermitian transform

    Page(s): 365 - 375
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (322 KB)  

    An improved eigenvalue sensitivity is presented for digital controller realisations via the orthogonal Hermitian transform, subject to finite word length (FWL) effects. This approach can preserve the stability of the closed-loop system when the designed stabilising digital controllers are actually implemented with FWL by using the mode of fixed-point arithmetic. A performance index defined by eigenvalue sensitivity of the closed-loop system is evaluated by the mixed matrix-2/ Frobenius norms, so that the eigenvalues of the closed-loop system, from infinite precision after using an FWL implemented digital controller, become limited precision, the influence suffered is minimal. Then, the optimal similarity transformation for the controller is obtained via the orthogonal Hermitian transform. Thus, a minimum bit number used for implementing the stabilising digital controllers can be obtained from the performance index and the optimal similarity transformation under certain stability criteria. The main contributions are that this approach provides an analytical closed-form solution for the optimal transformation and leads to the implementation of the stabilising controllers with a lower bit number when using this optimal one. Finally, a numerical example is used to illustrate the effectiveness of the proposed scheme. View full abstract»

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  • Stability analysis of impulsive control systems

    Page(s): 331 - 334
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (221 KB)  

    A comparison theorem for the asymptotic stability of impulsive differential systems is presented. Based on this result, less conservative conditions for the asymptotic stability of impulsive control systems with impulses at fixed times are derived. The results are used to design an impulsive control for a class of nonlinear systems, that improves and extends the existing results. The class of nonlinear systems considered is also enlarged. View full abstract»

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  • Approaches for dynamic modelling of flexible manipulator systems

    Page(s): 401 - 411
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (415 KB)  

    An investigation into the dynamic modelling of flexible manipulator systems with different mechanical structures and actuation mechanisms is presented. Dynamic models of the systems are developed based on the assumed modes method considering linear displacements, quadratic displacements and the finite element method. Simulation and experimental exercises are performed with bang-bang torque and smooth displacement driven manoeuvres. To investigate the effects of centrifugal forces, slow and fast trajectories are implemented. Simulation and experimental results of the response of the flexible manipulators are presented in the time and frequency domains. Moreover, model validations are carried out by comparing the results to assess the performance of the modelling approaches. View full abstract»

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  • Parallel branch and bound algorithm for computing maximal structured singular value

    Page(s): 417 - 420
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (222 KB)  

    In the paper, a parallel branch and bound algorithm has been developed, which computes the maximal structured singular value μ without tightly bounding μ for each frequency, and thus significantly reducing the computational complexity. View full abstract»

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  • Reduced-order PIM methods for digital redesign

    Page(s): 335 - 346
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (383 KB)  

    Complexity increase is common in modern global redesign methods and is tackled in this paper with a specific reference to the concept of plant input mapping. The paper proposes new global digital redesign techniques that rely on linear algebra to constrain the complexity of the resulting sampled-data control system while taking into account the plant dynamics and the topology of the continuous-time (CT) control system, and apply to any stable linear, time-invariant CT control system. Complexity is constrained in two ways. First, each discrete-time (DT) controller transfer function in the loop has an order which is fixed by the designer. Second, the number of DT controllers present in the loop is constrained by the designer. The proposed global digital redesign methods can be readily applied by the control designer as they require neither sophisticated mathematics nor stringent conditions for their application. The effectiveness of the proposed techniques is shown via numerical examples. View full abstract»

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  • Noise response of detection filters: relation between detection space and completion space

    Page(s): 443 - 447
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (234 KB)  

    An analysis is presented of the noise response of detection filters with zero-mean gaussian white noise. The major focus is placed on the relation between eigenvalues and error covariance. By similarity transformation it is shown that assigning the eigenvalues associated with a detection space does not affect the noise response of a completion space or other detection spaces. Based on this relationship, a brief optimisation procedure is given for an optimal problem in terms of the error covariance. View full abstract»

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  • Control of a pressure tank system using a decoupling control algorithm with a neural network adaptive scheme

    Page(s): 389 - 400
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (323 KB)  

    The design of a multivariable adaptive decoupling controller and its application to a real-time pressure tank system is presented. The pressure tank is highly coupled and nonlinear. The developed algorithm allows the noise disturbance to be coloured and uses a modification of the Hopfield neural network to identify and track the system parameters. The control algorithm is tested, first in a simulation using an identified model and secondly in a real-time application to a pressure tank system. A very good control performance is reported. View full abstract»

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  • Delay-dependent stability analysis of singular linear continuous-time system

    Page(s): 325 - 330
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (243 KB)  

    The paper deals with the class of singular linear continuous systems. By decomposing the singular linear system with time-delay into slow and fast subsystems, linear matrix inequality (LMI)-based delay-dependent stability and stabilisation conditions are established, and an LMI-based algorithm to design a memoryless state feedback control that stabilises the system is provided. Two numerical examples are solved to show the usefulness and validness of the theoretical results. View full abstract»

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  • Repetitive control design for linear systems with time-varying uncertainties

    Page(s): 427 - 432
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (247 KB)  

    The design of a repetitive control system for linear systems with time-varying norm-bounded uncertainties is presented. Using a Lyapunov functional for the time-delay systems, a sufficient condition is derived in terms of either an algebraic Ricatti inequality or a linear matrix inequality (LMI), which ensures robust stability of the repetitive control system. Based on the derived condition, we show that the repetitive controller design problem can be reformulated as an optimisation problem with an LMI constraint of the free parameter. View full abstract»

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  • State observer for MIMO nonlinear systems

    Page(s): 421 - 426
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (254 KB)  

    A state observer design for a special class of MIMO nonlinear systems which has a block triangular structure is presented. For this purpose an extension of the existing design for SISO triangular systems to MIMO cases is performed. Since the gain of the proposed observer depends on both the nonlinear and linear parts of the system, it improves the transient performance of the high gain observer. Also, by using a generalised similarity transformation for the error dynamics, it is shown that under a boundedness condition, the proposed observer guarantees the global exponential convergence of the estimation error. Finally, an illustrative example is included to show the validity of the design approach. View full abstract»

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