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Control Theory and Applications, IEE Proceedings -

Issue 6 • Date 22 Nov. 2004

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Displaying Results 1 - 16 of 16
  • Process fault isolation for linear systems with unknown inputs

    Publication Year: 2004 , Page(s): 720 - 726
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (271 KB)  

    A systematic and straightforward fault estimation approach for process fault detection, isolation and accommodation is presented. The approach includes the design of a reduced-order observer and an algebraic fault estimator. The observer is designed for an unknown input and fault-free system, which is obtained by co-ordinate transformations of original systems with unknown inputs and faults. The observer information is devoted to the fault estimation for fault detection and isolation. The fault estimates can be used to form an additional control input to accommodate the fault. The suggested scheme is verified through simulation studies performed on the control of a vertical takeoff and landing aircraft in the vertical plane. View full abstract»

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  • Active control of jet mixing

    Publication Year: 2004 , Page(s): 763 - 772
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1079 KB)  

    A control law to improve jet flow mixing is presented. The control law employs a pair of actuators at the jet nozzle exit that act on the shear layers near the corners by blowing and subtracting fluid in an anti-symmetric fashion and a sensor downstream or at the nozzle exit with a time delay that measures the pressure difference across the nozzle diameter. A 2-D jet flow is numerically simulated along with massless/mass particles and a passive scalar. The mixing enhancement produced by these controllers is demonstrated visually by snapshots of the vorticity, streaklines, particle distribution and scalar field. Probability function for the particles and the scalar field are constructed, which serve as an index of mixing quality and the effectiveness of the controllers. This closed-loop control law successfully alters the jet flow and improves the mixing of particles with mass and passive scalar. View full abstract»

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  • Set-valued estimation approach to recursive robust H filtering

    Publication Year: 2004 , Page(s): 773 - 782
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (355 KB)  

    A recursive robust H filtering algorithm is proposed for a discrete-time uncertain linear system subject to the sum quadratic energy constraint. This type of uncertainty description can accommodate a large class of uncertainties. A set-valued estimation approach is used to tackle the problem. To this end, an augmented energy constraint is produced by combining an energy constraint on the H-norm condition of the error dynamics and an inequality relationship between the uncertainty input and output. The robust H filtering problem is formulated as finding the set of estimates that satisfy the augmented constraint. The solutions are given in terms of ellipsoids whose centres are the minimums of the indefinite quadratic function defined by the augmented constraint. Krein space estimation theory is utilised to efficiently deal with the minimisation problem of the indefinite quadratic function it is shown that the robust H filter is simply a special form of, the Krein space Kalman filter. The proposed robust filter has basically the same structure as the information form of a Kalman filter and therefore needs only a small computational effort is required in its implementation. In addition, it can be reduced into versions of robust and nominal filters by tuning the relevant parameters. Numerical examples are presented that verify that; (i) the proposed filter guarantees robustness in the presence of parametric uncertainties; and (ii) its bounding ellipsoidal sets of filtered estimates always contain true states. View full abstract»

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  • Fuzzy logic enhanced robust torque controlled induction motor drive system

    Publication Year: 2004 , Page(s): 754 - 762
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (335 KB)  

    A closed-loop torque controlled induction motor drive system is presented which can function as a controllable source of torque with a fast dynamic response and thus it can achieve an adequate control performance. The proposed drive system includes an accurate and robust flux and torque estimator and a direct fuzzy controller to enhance the torque regulation. The proposed flux and torque estimators keep the machine field oriented and can overcome any problem created by changes in the transformation and torque ripples. The fuzzy controller can achieve an adequate control performance with a high bandwidth torque control. Simulation and experimental results are presented to show the effectiveness of the proposed drive system. View full abstract»

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  • Computational method to analyse the stability of interval matrices

    Publication Year: 2004 , Page(s): 669 - 674
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    A method is proposed to compute a lower bound to the stability margin of an interval matrix family, thus also providing a sufficient condition for stability. The method is based on Gershgorin's theorem and on the optimal selection of the eigenvectors of the nominal system; the optimisation considerably improves previous bounds reported in the literature. The analytical results make the solution extremely simple. Numerical experiments show that several problems involving uncertain systems can be solved efficiently by the proposed method as compared to other methods proposed in the literature. View full abstract»

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  • Pseudo-linear controllers for systems with saturated actuators

    Publication Year: 2004 , Page(s): 783 - 789
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    The design of controllers with a pseudo-linear structure for continuous and discrete-time systems under actuator saturation is considered. The proposed method is based on a practical optimisation framework, and in general can be applied in combination with different control system designs. As an example, a particular class of H2-type fixed-order anti-windup dynamic controllers is considered in detail. The method is illustrated by its application to a high-powered laser example. View full abstract»

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  • Pole assignment in a disk for linear systems by static output feedback

    Publication Year: 2004 , Page(s): 706 - 712
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (284 KB)  

    A systematic approach for pole assignment in a disk for continuous or discrete-time linear systems using a static output control law is proposed. It is shown that if the open-loop system satisfies certain structural conditions, a static output feedback gain can be easily computed, using a formula that simply involves the original system matrices and the parameters that define the disk. Among the conditions the system has to satisfy, the key one relies on a minimum phase argument. Square and non-square, proper and non-proper systems are considered. The main results are derived invoking the limiting behaviour of the optimal linear quadratic regulator for discrete-time systems. Some other implications are also presented. View full abstract»

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  • Method for detecting spectral changes in the frequency domain

    Publication Year: 2004 , Page(s): 713 - 719
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (767 KB)  

    The use of frequency response estimates for change detection is considered. The class of faults considered affects the spectral properties of the system. Spectral changes are detected as deviations in the frequency response, through the choice of a suitable residual. Taking into consideration the statistical nature of a finite-time estimator, a χ2 detector is then designed for the residual. The performance of the fixed sample size detector is compared with a conventional cumulative sum algorithm, and found to be better. A DC motor is used as an implementation example to illustrate the performance and properties of the detector. View full abstract»

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  • Analytical decoupling control design for dynamic plants with time delay and double integrators

    Publication Year: 2004 , Page(s): 745 - 753
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (422 KB)  

    Two control schemes are proposed to control dynamic plants with time delay and double integrators. One adopts the H2 optimal controller, whereas the other utilises a conventional derivative controller for the setpoint tracking in an open-loop control manner. Both of the proposed control schemes are of the two-degree-of-freedom control structure and use an identical disturbance estimator to construct the closed-loop between the plant input and output for load disturbance rejection. In consequence, the setpoint response is decoupled from the load disturbance response. The disturbance estimator is obtained by proposing a desired closed-loop complementary sensitivity function according to the H2 optimal performance objective. The closed-loop robust stability is analysed and corresponding sufficient and necessary conditions are also provided in the presence of the plant multiplicative uncertainty. Consequently a rule-of-thumb for tuning the single adjustable parameter of the disturbance estimator is presented. Finally, illustrative examples are included to show that a good performance can be obtained using the two proposed control schemes, especially the proposed closed-loop for the load disturbance rejection, which can also be successfully utilised to reject ramp-type load disturbances in industrial and chemical processes with one integrator. View full abstract»

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  • An enhanced fuzzy PD controller with two discrete nonlinear tracking differentiators

    Publication Year: 2004 , Page(s): 675 - 682
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (378 KB)  

    An enhanced fuzzy PD (EFPD) controller by incorporating two discrete nonlinear tracking differentiators (TDs) into a conventional fuzzy PD controller is proposed. This work is motivated by the fact that the performance of the controlled system is limited by how to select a high-quality differential signal in the presence of noise, based on the noncontinuous measured position signal only. The proposed TD is constructed based on the fact numerical integration can provide more stable and accurate results than numerical differentiation in the presence of noise. The proposed EFPD controller is easy to implement, and exhibits better control performance than conventional fuzzy controllers, with especially high robustness against noise. Comparative simulations and experiments with a linear observer performed on a permanent-magnet synchronous motor system are presented to demonstrate the better performance of the controller. View full abstract»

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  • Reliable control of uncertain delayed systems with integral quadratic constraints

    Publication Year: 2004 , Page(s): 790 - 796
    Cited by:  Papers (14)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (478 KB)  

    The reliable control design problem for uncertain systems with time delays as well as actuator failures in the input channels is discussed. A sufficient condition is established such that the closed-loop system stability and a time-domain integral quadratic constraint are satisfied for both a normal system and a system with possible actuator failures. A reliable state feedback controller is synthesised within the framework of linear matrix inequalities. Simulation results on a test example are presented to validate the proposed design method. View full abstract»

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  • Design of a stable sliding-mode controller for a class of second-order underactuated systems

    Publication Year: 2004 , Page(s): 683 - 690
    Cited by:  Papers (63)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    A stable hierarchical sliding-mode control method for a class of second-order underactuated systems is presented. The ideas behind the method are as follows. First, the underactuated system is divided into two subsystems. For each part a first-level sliding surface is defined. For these two first-level sliding surfaces, a second-level sliding surface is defined. The sliding-mode control law is derived using Lyapunov law. The control law can drive the subsystems toward their sliding surfaces and attain their desired values, and implement antidisturbance control. The asymptotic stability of all the sliding surfaces is proved theoretically, and simulation results show the controller's validity and its adaptive abilities for all kinds of extraneous disturbances. View full abstract»

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  • Estimation of parameters in a linear state space model using a Rao-Blackwellised particle filter

    Publication Year: 2004 , Page(s): 727 - 738
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (701 KB)  

    A Rao-Blackwellised particle filter is used in the estimation of the parameters of a linear stochastic state space model. The proposed method combines the particle filtering technique with a Kalman filter using marginalisation so as to make full use of the analytically tractable structure of the model. Simulation studies are performed on a simple illustrative example and the results demonstrate the effectiveness of the proposed method in comparison with the conventional extended-Kalman-filter-based method. The proposed method is then applied in the estimation of the parameters in a railway vehicle dynamic model for condition monitoring and the desired results have been obtained. View full abstract»

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  • Delay-dependent output-feedback stabilisation of discrete-time systems with time-varying state delay

    Publication Year: 2004 , Page(s): 691 - 698
    Cited by:  Papers (96)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (296 KB)  

    The output-feedback stabilisation problem is solved for discrete-time systems with time-varying delay in the state. A stability condition is first proposed, which is dependent on the minimum and maximum delay bounds. Based on this easily verifiable stability condition, the problems of stabilisation by static and dynamic output-feedback controllers are solved within the linear matrix inequality (LMI) framework. Since the obtained conditions for the existence of admissible controllers are not expressed as strict LMI conditions, the cone complementary linearisation procedure is exploited to solve the nonconvex feasibility problem. In addition, the obtained results, including stability analysis, static output-feedback stabilisation and dynamic output-feedback stabilisation are further extended to discrete time-delay systems with norm-bounded uncertain parameters. Numerical examples are also presented to illustrate the applicability of the developed results. View full abstract»

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  • Dynamic stabilising controllers for linear time-invariant systems and multirate control

    Publication Year: 2004 , Page(s): 739 - 744
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (270 KB)  

    For a given linear time-invariant plant-compensator pair in a closed-loop, it is shown that, if a simple matrix equation holds, the closed-loop system behaves like a functional observer of a linear function of the state of the plant. If such a function can be used to augment the plant output, it is possible to use a static output feedback from the augmented output, thus obtaining as a closed-loop system the restriction of the original one to a suitable invariant subspace. A dual result holds too, ensuring stabilisation by static output feedback with an augmented input. If the plant output/input cannot be augmented, the use of multirate samplers/holders is proposed in order to equivalently augment the outputs or inputs of the controlled plant, thus making the technique suitable even if no additional sensors/actuators can be placed on the plant. The proposed multirate controllers are either static or asymptotically stable, and thus strongly stabilise the plant. View full abstract»

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  • Stabilising controller design for uncertain systems with time-varying input delay

    Publication Year: 2004 , Page(s): 699 - 705
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (275 KB)  

    The design problem of a robust stabilisation controller for a class of uncertain systems with time-varying input delay is considered. The reduction method, a first-order transformation and the cone complementarity method are combined to produce a memory robust controller design method that does not need to exactly know the time delay. In the proposed method, only information on the variation range of the time delay is needed to design the controller. The effectiveness and less conservative nature of the proposed method is shown by a numerical example. View full abstract»

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