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Control Theory and Applications, IEE Proceedings -

Issue 4 • Date Jul 2002

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Displaying Results 1 - 14 of 14
  • Nonlinearities in NARX polynomial models: representation and estimation

    Publication Year: 2002 , Page(s): 343 - 348
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (449 KB)  

    It is shown how nonlinearities are mapped in NARX polynomial models. General expressions are derived for the gain and eigenvalue functions in terms of the regressors and coefficients of NARX models. Such relationships are useful in grey-box identification problems. The results are illustrated using simulated and real data View full abstract»

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  • Regional flux target with minimum energy

    Publication Year: 2002 , Page(s): 349 - 356
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (483 KB)  

    An extension of a gradient controllability problem to the case where the target subregion is a part of the boundary of a parabolic system domain is discussed. A definition and some properties adapted to this case are presented. The focus is on the characterisation of the control achieving a regional boundary gradient target with minimum energy. An approach is developed that leads to a numerical algorithm for the computation of optimal control. Numerical illustrations show the efficiency of the approach and lead to conjectures View full abstract»

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  • Computing the frequency response of systems affinely depending on uncertain parameters

    Publication Year: 2002 , Page(s): 311 - 315
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (386 KB)  

    The computation of the frequency response of systems depending affinely on uncertain parameters can be reduced to that of all its one-dimensional edge plants while the image of such an edge plant at a fixed frequency is an arc or a line segment in the complex plane. Based on this conclusion, four computational formulas of the maximal and minimal (maxi-mini) magnitudes and phases of an edge plant at a fixed frequency are given. The formulas, besides sharing a simpler form of expression, concretely display how the extrema of the frequency response of the edge plant relate to the typical characteristics of the arc and line segment such as the centre, radius and tangent points of the arc, the distance from the origin to the line segment etc. The direct application of the results is to compute the Bode-, Nichols- and Nyquist-plot collections of the systems which are needed in robustness analysis and design View full abstract»

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  • Adaptive tracking controller design for robotic systems using Gaussian wavelet networks

    Publication Year: 2002 , Page(s): 316 - 322
    Cited by:  Papers (19)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (462 KB)  

    An adaptive tracking control design for robotic systems using Gaussian wavelet networks is proposed. A Gaussian wavelet network with accurate approximation capability is employed to approximate the unknown dynamics of robotic systems by using an adaptive learning algorithm that can learn the parameters of the dilation and translation of Gaussian wavelet functions. Depending on the finite number of wavelet basis functions which result in inevitable approximation errors, a robust control law is provided to guarantee the stability of the closed-loop robotic system that can be proved by Lyapunov theory. Finally, the effectiveness of the Gaussian wavelet network-based control approach is illustrated through comparative simulations on a six-link robot manipulator View full abstract»

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  • Control of integral processes with dead-time. 1. Disturbance observer-based 2 DOF control scheme

    Publication Year: 2002 , Page(s): 285 - 290
    Cited by:  Papers (13)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (419 KB)  

    A disturbance observer-based control scheme (a version of 2 DOF internal model control) which is very effective in controlling integral processes with dead time is presented. The controller can be designed to reject ramp disturbances as well as step disturbances and even arbitrary disturbances. When the plant model is available only two parameters are left to tune. One is the time constant of the set-point response and the other is the time constant of the disturbance response. The latter is tuned according to the compromise between disturbance response and robustness. This control scheme has a simple, clear, easy-to-design, easy-to-implement structure and good performance. It is compared to the best results (so far) using some simulation examples View full abstract»

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  • Nonlinear adaptive control via sliding-mode state and perturbation observer

    Publication Year: 2002 , Page(s): 269 - 277
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (549 KB)  

    The paper presents a nonlinear adaptive controller (NAC) for single-input single-output feedback linearisable nonlinear systems. A sliding-mode state and perturbation observer is designed to estimate the system states and perturbation which includes the combined effect of system nonlinearities, uncertainties and external disturbances. The NAC design does not require the details of the nonlinear system model and full system states. It possesses an adaptation capability to deal with system parameter uncertainties, unmodelled system dynamics and external disturbances. The convergence of the observer and the stability analysis of the controller/observer system are given. The proposed control scheme is applied for control of a synchronous generator, in comparison with a state-feedback linearising controller (FLC). Simulation study is carried out based on a single-generator infinite-bus power system to show the performance of the controller/observer system View full abstract»

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  • LMI approach to digital redesign of linear time-invariant systems

    Publication Year: 2002 , Page(s): 297 - 302
    Cited by:  Papers (14)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (419 KB)  

    A simple design methodology for the digital redesign of static state feedback controllers by using linear matrix inequalities is presented. The proposed method provides close matching of the states between the original continuous-time system and those of the digitally redesigned system with a guaranteed stability. Specifically, the digital redesign problem is reformulated as linear matrix inequalities (LMIs) and solved by a numerical optimisation technique. The main feature of the proposed method is that the closed-loop stability of the digitally redesigned system is explicitly guaranteed within the design procedure using the LMI-based approach. A numerical example of the position control of a simple crane system is presented View full abstract»

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  • Input-output based pole-placement controller for a class of time-delay systems

    Publication Year: 2002 , Page(s): 323 - 330
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (581 KB)  

    A controller structure valid for SISO plants involving both internal and external point delays is presented. The control signal is based only on the input and output plant signals. The controller allows finite or infinite spectrum assignment. The most important feature of the proposed controller is that it only involves the use of a class of point-delayed signals. Thus the controller synthesis involves less computational cost than former methods. Since the plant control input is generated by filtering the input and output plant signals, this controller structure is potentially applicable to the adaptive case of unknown plant parameters View full abstract»

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  • Structural interpretation of matched pole-zero discretisation

    Publication Year: 2002 , Page(s): 257 - 262
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (451 KB)  

    Deals with matched pole-zero discretisation, which has been used in practice for hand calculations in the digital redesign of continuous-time systems but available only in the transfer-function form. Since this form is inconvenient for characterising the time-domain properties of sampled-data loops and for computerising the design of such systems, a state-space formulation is developed. Under the new interpretation, the matched pole-zero model is shown to be structurally identical to a hold-equivalent discrete-time model, where the generalised hold takes integral part, thus unifying the most widely used discretisation approaches. An algorithm for obtaining the generalised hold function is presented. The hold-equivalent structure of the matched pole-zero model clarifies several discrete-time system properties, such as controllability and observability, and their preservation or loss with a matched pole-zero discretisation. With the proposed formulation, the matched pole-zero, hold-equivalent, and mapping models can now all be constructed with a single schematic model View full abstract»

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  • Variable structure control of a photovoltaic energy converter

    Publication Year: 2002 , Page(s): 303 - 310
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (615 KB)  

    The variable structure control of a DC-to-DC converter in photovoltaic applications is presented. The feasibility of establishing stable constant-voltage and constant-current sliding modes is stressed. Further, their ability to satisfy the control objectives, i.e. maximum power tracking or power regulation, is analysed. In addition, different control laws are obtained by combining these sliding motions, thereby improving their individual performances. The capability of these control laws to steer the state trajectories towards the sliding surfaces from any initial condition, as well as the stability of the sliding regimes, is investigated View full abstract»

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  • Hamiltonian modelling and nonlinear disturbance attenuation control of TCSC for improving power system stability

    Publication Year: 2002 , Page(s): 278 - 284
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (457 KB)  

    To tackle the obstacle of applying passivity-based control (PBC) to power systems, an affine non-linear system widely existing in power systems is formulated as a standard Hamiltonian system using a pre-feedback method. The port controlled Hamiltonian with dissipation (PCHD) model of a thyristor controlled serial compensator (TCSC) is then established corresponding with a revised Hamiltonian function. Furthermore, employing the modified Hamiltonian function directly as the storage function, a non-linear adaptive L2 gain control method is proposed to solve the problem of L2 gain disturbance attenuation for this Hamiltonian system with parametric perturbations. Finally, simulation results are presented to verify the validity of the proposed controller View full abstract»

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  • Sliding-mode control scheme for a class of continuous chemical reactors

    Publication Year: 2002 , Page(s): 263 - 268
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (450 KB)  

    The synthesis of a robust control law for regulation control of a class of relative-degree-one nonlinear systems is presented. The control design is based on a sliding-mode uncertainty estimator, developed under a framework of algebraic-differential concepts. The closed-loop stability for the underlying closed-loop system is achieved via averaging techniques. Robustness of the proposed control scheme is proved in the face of noise measurements, model uncertainties and sustained disturbances. The performance of the proposed control law is illustrated with numerical simulations, comparing the proposed controller with a well tuned PI controller View full abstract»

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  • Control of integral processes with dead-time. 2. Quantitative analysis

    Publication Year: 2002 , Page(s): 291 - 296
    Cited by:  Papers (12)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (401 KB)  

    For part 1, see ibid., p.285-90, (2002). Several different control schemes for integral processes with dead time resulted in the same disturbance response. It has already been shown that such a response is subideal. Hence, it is necessary to quantitatively analyse the achievable specifications and the robust stability regions. The control parameter can be quantitatively determined with a compromise between the disturbance response and the robustness. Four specifications: (normalised) maximum dynamic error, maximum decay rate, (normalised) control action bound and approximate recovery time are used to characterise the step-disturbance response. It is shown that any attempt to obtain a (normalised) dynamic error less than τm is impossible and a sufficient condition on the (relative) gain-uncertainty bound is √(3)/2 View full abstract»

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  • Approach to adaptive neural net-based H control design

    Publication Year: 2002 , Page(s): 331 - 342
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (618 KB)  

    An approach is investigated for the adaptive neural net-based H control design of a class of nonlinear uncertain systems. In the proposed framework, two multilayer feedforward neural networks are constructed as an alternative to approximate the nonlinear system. The neural networks are piecewisely interpolated to generate a linear differential inclusion model by which a linear state feedback H control law can be applied. An adaptive weight adjustment mechanism for the multilayer feedforward neural networks is developed to ensure H regulation performance. It is shown that finding the control gain matrices can be transformed into a standard linear matrix inequality problem and solved via a developed recurrent neural network View full abstract»

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