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Control Theory and Applications, IEE Proceedings -

Issue 2 • Date Mar 2000

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Displaying Results 1 - 13 of 13
  • Crisp-type fuzzy logic controller using Dubois and Prade's parametric t-norm-sum-gravity inference methods

    Publication Year: 2000 , Page(s): 167 - 175
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (640 KB)  

    The input/output relationship of a class of crisp-type fuzzy logic controllers (FLCs) using parametric t-norm-sum-gravity inference method is examined. The explicit mathematical form of reasoning surface using Dubois and Prade's parametric t-norm is addressed. Reasoning surfaces of crisp-type FLCs are proved to be composed of a two-dimensional multilevel relay and a local position-dependent nonlinear compensator. The influence of the α value, the parameter of Dubois and Prade's parametric t-norm, on the reasoning surfaces is also investigated View full abstract»

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  • Observer-based neuro identifier

    Publication Year: 2000 , Page(s): 145 - 152
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    A new online identification method is presented. The identified nonlinear systems have partial-state measurement. Their inner states, parameters and structures are unknown. The design is based on the combination of a model-free state observer and a neuro identifier. First, a sliding mode observer, which does not need any information about the nonlinear system, is applied to obtain the full states. A dynamic multilayer neural network is then used to identify the whole nonlinear system. The main contributions of the paper are: a new observer-based identification algorithm is proposed; and a stable learning algorithm for the neuro identifier is given View full abstract»

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  • Receding horizon H predictive control for systems with input saturation

    Publication Year: 2000 , Page(s): 153 - 158
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    A receding horizon H predictive control method is derived by solving a min-max problem in nonrecursive form. The min-max cost index is converted to a quadratic form which, for systems with input saturation, can be minimised using quadratic programming (QP). Stability conditions and H norm bounds on disturbance rejection are obtained. Without input saturation, stabilising terminal weights guaranteeing finite H norm bounds always exist, but the guaranteed H norm bound may be conservative; this is remedied through the use of closed-loop prediction. Feasible sets for state and disturbances are derived, for which stability can be guaranteed. The algorithm and weight selection procedures are given in terms of LMI View full abstract»

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  • Control of state-constrained linear dynamical systems: anti-reset windup approach

    Publication Year: 2000 , Page(s): 159 - 166
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (720 KB)  

    An alternative controller design method for state-constrained control systems is presented, where the concept of the anti-reset windup (ARW) strategies is used. The proposed controller design procedure is composed of two steps. First, a linear controller is designed to show a desirable nominal performance by ignoring state constraints. Then, an additional compensator is designed to mitigate the adverse effects due to state constraints. The paper focuses on the effective design method of the additional compensator. By minimising a reasonable performance index, the proposed compensator is expressed explicitly in plant and controller parameters. The resulting dynamics of the compensated controller exhibits the dominant part of linear closed-loop systems, which can be seen from the singular perturbation model reduction theory. The proposed method guarantees the total stability of overall resulting systems if linear controllers were constructed to meet certain conditions View full abstract»

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  • Process identifier and its application to industrial control

    Publication Year: 2000 , Page(s): 196 - 204
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (740 KB)  

    Many industrial controllers use the relay experiment to estimate the system ultimate data for three-term controller tuning. However, for some systems the relay experiment describing function analysis can produce poor estimates. The paper reports a new and more accurate method of finding system frequency response data including the system ultimate data. A full demonstration of the accuracy attainable by the new method is presented. The new method was motivated by a phase-locked loop concept. The additional flexibility to find gain and phase margins, or the peak resonance frequency is demonstrated. The paper includes the application of the module to closed-loop system identification and a brief discussion of the LabVIEW implementation View full abstract»

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  • ANNNAC-extension of adaptive backstepping algorithm with artificial neural networks

    Publication Year: 2000 , Page(s): 177 - 183
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    The adaptive backstepping algorithm is a well-known scheme for the design of nonlinear adaptive controllers. The two main drawbacks associated with this algorithm are that the nonlinear system must be linearly parameterised in the unknown or uncertain parameters and that the nonlinear functions must be exactly known. To avoid these problems, an extension of the backstepping algorithm with a specific type of artificial neural networks (ANN) called radial basis function networks (RBF), is proposed. This extension leads to a new control scheme: namely artificial neural network nonlinear adaptive control (ANNNAC). To further clarify the approach, a simple example is studied and the simulation results demonstrate clearly the power of this extension View full abstract»

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  • Robust state estimator of stochastic linear systems with unknown disturbances

    Publication Year: 2000 , Page(s): 224 - 228
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    The design of a filtering algorithm when an unknown disturbance exists is described. An alternative method to solve the disturbance estimation problem is proposed, which is to reformulate it to a tracking problem by using the relation of the filter update. The reformulation of the problem makes it possible to use an effective sliding surface and fast estimate against arbitrary disturbance. A disturbance estimator using the discrete sliding mode is designed and improved by introducing a prediction parameter. In addition, a disturbance detection algorithm having a moderate calculation cost is designed using filter update and innovations. The normalised testing parameter makes it possible to use the standard chi-square table to determine the threshold level. The stability of the suggested algorithm is given and simulation results are included to demonstrate the effectiveness of the proposed technique View full abstract»

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  • Stabilisation of discrete-time interconnected systems under control constraints

    Publication Year: 2000 , Page(s): 137 - 144
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    The problem of stabilising a discrete-time large-scale uncertain system where the norms of the decentralised controls are bounded by prespecified constants is considered. The uncertainty is supposed to be cone-bounded, but not necessarily matched. A nonlinear controller is proposed, which guarantees the exponential stability of the whole system, if the bounds of uncertainties are not too large. If the nominal part of the subsystems is nonlinear, the nominal free system is supposed to be exponentially stable. If the nominal system is linear and time invariant this assumption can be omitted and substituted by controllability View full abstract»

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  • Restricted-structure LQG optimal control for continuous-time systems

    Publication Year: 2000 , Page(s): 185 - 195
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (740 KB)  

    A novel LQG optimal-control problem is developed for continuous-time systems, where the structure of the controller is assumed to be fixed a priori. The controller may be chosen to be of reduced order, lead/lag or PID forms, and the optimal causal controller is required to minimise the usual LQG cost index. The theoretical problem considered is to obtain the causal, stabilising, controller, of a prespecified form, that minimises an LQG criterion. The underlying practical problem of importance is to obtain a simple method of tuning low-order controllers given only an approximate model of the process. The robustness of the solution can be improved by tuning the controller using QFT methods View full abstract»

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  • Adaptive iterative learning control of uncertain robotic systems

    Publication Year: 2000 , Page(s): 217 - 223
    Cited by:  Papers (48)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (484 KB)  

    A distinct feature of the proposed AILC scheme is that uncertain parameters are estimated in the time domain whereas repetitive disturbances are identified and compensated in the iteration domain. The bounds of the parameters are not required to be known a priori, and the learning control gain can be adjusted independently of the parameter adaptation gain. The overall closed-loop stability and uniform error convergence in the iteration domain are established without any acceleration measurements or their estimated values. The proposed AILC scheme is a balanced combination of the conventional adaptive control and the iterative learning control, where the shortcomings of each scheme are complemented. The validity of the scheme is confirmed through a simulation example View full abstract»

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  • Robust fuzzy control for robot manipulators

    Publication Year: 2000 , Page(s): 212 - 216
    Cited by:  Papers (12)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (304 KB)  

    A robust fuzzy control is developed for robot manipulators to guarantee both global stability and performance. Robot dynamics under consideration may include large nonlinear uncertainties, such as nonlinear load variations and unmodelled dynamics. Fuzzy sets are chosen based on performance requirements and stability regions of the control system. For each fuzzy set, a sub-control is designed based on nonlinear robust control design using Lyapunov's direct method; this is blended with others into a final fuzzy control. The resulting control provides not only robust and global stability, but also more accurate control performance than fuzzy controls obtained from constant sub-controls. The proposed design is applied to a robot trajectory control problem and compared with a standard nonlinear robust controller. The simulation results show that the proposed control is effective and yields superior tracking performance View full abstract»

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  • Disturbance attenuation in linear systems via dynamical compensators: a parametric eigenstructure assignment approach

    Publication Year: 2000 , Page(s): 129 - 136
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (596 KB)  

    A simple approach is proposed for disturbance attenuation in multivariable linear systems via dynamical output compensators based on complete parametric eigenstructure assignment. The basic idea is to minimise the H2 norm of the disturbance-output transfer function using the design freedom provided by eigenstructure assignment. For robustness, the closed-loop system is restricted to be nondefective. Besides the design parameters, the closed-loop eigenvalues are also optimised within desired regions on the left-half complex plane to ensure both closed-loop stability and dynamical performance. With the proposed approach, additional closed-loop specifications can be easily achieved. As a demonstration, robust pole assignment, in the sense that the closed-loop eigenvalues are as insensitive as possible to open-loop system parameter perturbations, is treated. Application of the proposed approach to robust control of a magnetic bearing with a pair of opposing electromagnets and a rigid rotor is discussed View full abstract»

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  • Geometric analysis of missile guidance command

    Publication Year: 2000 , Page(s): 205 - 211
    Cited by:  Papers (8)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    An approach is followed for analysing flight control command for tactical missile guidance with a variable manoeuvering target. The moving orthogonal coordinate system of classical differential geometry curve theory is similar to the stability axis system utilised in atmospheric flight mechanics. Based on this similarity, the Frenet-Serret formula is used to study the characteristics of a pseudomissile pointing velocity vector and used to design a new control command for tactical missile guidance. The closed-form solution for the rate of rotation of the line of sight vector, characteristic of the pseudomissile pointing velocity vector, together with a miss vector are used to study the capture capability of this control command. The region of miss is derived in terms of the tangential component of the kinematics equation. A sufficient initial condition, which can guarantee capture under arbitrary target manoeuvres with bounding information is proposed View full abstract»

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