摘要:

Multirate output controllers are a new type of controller which detect the ith output of the plantNitimes and change the plant input once during a periodT0. Important features of this type of controller include equivalent realization of state feedback and strong stabilization. Above all, they distinguish themselves from multirate input controllers in that they appear more suitable for industrial application. Nevertheless, there are some potential problems that can degrade the operation of the controller. In this paper, these problems are highlighted and approaches to avoid them are provided.

ISSN:0020-7179    

DOI:10.1080/00207179108953662

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

System identification plays an extremely important role in the self-tuning controller. As the recursive least squares (RLS)identification technique has the advantages of simple calculation and good convergence properties, it is the preferred technique for use in the design of the self-tuning controllers. However, use of RLS identification in a real-time environment does raise some problems such as the speed of parameter convergence, identification going to ‘sleep’, covariance matrix ‘blow up’, biased identification, etc. This paper deals with the problems which may arise in the practical use of the RLS identification technique. These issues are the summary of several years' experience of designing self-tuning controllers with RLS identification technique for power system applications. Although some of these issues are difficult to analyse, they are quite effective in dealing with the practical problems.

ISSN:0020-7179    

DOI:10.1080/00207179108953663

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A class of systematic distributed control design methods suitable for large-scale interconnected power systems is presented in this paper. The design methods are based on: (i)distributed implementations of centralized control systems; (ii) model reduction of dynamical systems; and (iii) modelling of the interactions between the subsystems comprising the global control system. In these schemes the control task is decomposed into local subtasks. The function of each subtask is to generate the required local control input so that, collectively, the centralized performance of the global system is preserved. The local control input is composed of a control signal generated from local state feedback and a corrective control signal generated from low-order dynamic and, in some schemes, static compensators. The structure of these compensators is determined from the reduced-order model of the global closed-loop control system and from derived models of the interactions among the subsystems. A two-area interconnected power system is considered for the application of the proposed distributed control schemes. Results of time simulation studies show that the performance of the power system under the distributed control schemes presented in this paper are almost identical with the centralized one.

ISSN:0020-7179    

DOI:10.1080/00207179108953664

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A systematic methodology that facilitates the modelling of a non-linear dynamic system for the purposes of controller design is described and applied to the forced Van der Pol oscillator. The non-linear model is represented as a set of linear time-invariant models. This results in a nominal linear model with a quantified parameter uncertainty. This information is applied in conjunction with the quantitative feedback theory (QFT)control design method to produce a controller which meets the performance specifications. The controller is verified with non-linear simulation and experimentation. The method reduces the number of iterations required to design practical controllers for non-linear systems considerably compared with trial and error methods.

ISSN:0020-7179    

DOI:10.1080/00207179108953665

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A complete analysis of loop transfer recovery problem using full order observer based controllers for general not necessarily left invertible and not necessarily minimum phase systems is considered. The analysis here, while showing that neither exact nor asymptotic loop transfer recovery is in general possible, focuses on three fundamental issues. The first issue is concerned with what can and what canot be achieved for a given system and for an arbitrarily specified target loop transfer function, while the second issue is concerned with the development of necessary and/or sufficient conditions a target loop has to satisfy so that it can be either exactly or asymptotically be recovered for a given system. The third issue deals with the development of method(s)to test whether recovery is possible in a given subspace of the control space or not, i.e. to test whether projections of target and achievable sensitivity and complimentary sensitivity functions onto a given subspace match each other or not. Such an analysis pinpoints the limitations of the given system for the recovery of arbitrarily specified target loops via observer based controllers. These limitations are the consequences of the structural properties (i.e. finite and infinite zero structure, and invertibility) of the given system. Furthermore, the analysis discovers a multitude of ways in which freedom exists to shape the loops in a desired way as close as possible to the target shapes. Also, possible pole zero cancellations between the eigenvalues of the controller and the input and/or output decoupling zeros of the plant are characterized.

ISSN:0020-7179    

DOI:10.1080/00207179108953666

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

This Part focuses on the design of full order observer based controllers for the recovery of target loop transfer function or sensitivity and complimentary sensitivity functions when the given system is not necessarily left invertible and not necessarily of minimum phase. Four design tasks are considered. The first task concerns with arbitrarily specified target loop transfer functions and develops an observer design which has the capability to shape the inevitable recovery error according to the designer's needs whenever they are feasible. The second task considers observer design for exactly recoverable target loop transfer functions. The third task is similar to the second one in that it makes use of the specific properties of the target loop transfer function, but it considers observer design for asymptotically recoverable target loop transfer functions. The fourth task can be thought of as a generalization of the second and third tasks, and it considers observer design so that the achieved and target sensitivity and complimentary sensitivity functions match each other either exactly or asymptotically over a given subspace of the control space whenever it is possible. For all these tasks, observer design constraints and the available design freedom are reviewed. In view of the available freedom, possible specifications on the time-scale and/or eigenstructure of the observer dynamic matrix are formulated. In the case of first task, the conventional approach of designing observer based controllers by Kalman filter formalism which requires solving algebraic Riccati equations, is shown to have several fundamental limitations. A method of design based on asymptotic time-scale and eigenstructure assignment (ATEA) developed here overcomes these limitations. For the other tasks, no design methods other than the ones developed here are available in the literature. All the developed design methods are implemented in a ‘Matlab’ software package. A bank of examples illustrate that the proposed methods of design are capable of directly exploiting all the available freedom so as to achieve the desired results.

ISSN:0020-7179    

DOI:10.1080/00207179108953667

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

In an attempt to achieve more realistic control objectives, the weighting matrices in the standard LQ1 problem are usually chosen by the designer in anad hocmanner. This paper shows several optimal control design problems that minimize a quadratic function of the control vector subject to multiple inequality constraints on the outputL2norms,L∞norms, covariance matrix, and the maximum singular value of the output covariance matrix. The solutions of all four of these problems reduce to standard LQI control problems with different choices of weights. This paper shows how to construct these different weights. The practical significance of these results is that many robustness properties relate directly to these four entities. Hence the given control design algorithm delivers a specified degree of robustness to both parameter errors and disturbances. The results are presented in the deterministic terms of the linear quadratic impulse (LQI)for continuous and discrete systems problem rather than the stochastic LQG problem. The results are easily transferable to the LQG problem.

ISSN:0020-7179    

DOI:10.1080/00207179108953668

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A general and concise formulation is given of the loop transfer recovery (LTR) design problem based on recovery errors. Three types of recovery errors are treated, open loop recovery, sensitivity recovery and input-output recovery errors. The three corresponding versions of the asymptotic recovery problem turn out to be equivalent, since the minimization of the recovery errors all amount to the minimization of a certain matrix, the recovery matrix. Using the recovery error definitions, simple necessary and sufficient conditions for the controllers are derived both for the exact and asymptotic recovery cases. This general recovery formulation covers all known observer based compensator types as special cases. The conditions given in this setting are effectively the aim of all known LTR design methods. The recovery formulation is interpreted in terms of a model-matching problem as well, which is examined by means of theQ-parametrization. It is shown how the general controller obtained by theQ-parametrization can be written as a Luenberger observer based controller. In all cases,ncontroller states suffice to achieve recovery. The compensators are characterized for errors both on the input- and on the output-node (dual case).

ISSN:0020-7179    

DOI:10.1080/00207179108953669

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The dynamic performance of a robot manipulator is directly dependent on the efficiency of the controller and the dynamic model of the robot. This paper addresses the fundamental issue of how much manipulator dynamics information should be included in the manipulator dynamic model for control such that the manipulator will achieve the desired system performance under a proportional-plus-derivative control scheme. An efficient minimax simplification scheme has been developed which automatically generates simplified closed-form manipulator motion equations in symbolic form while maintaining the desired manipulator system performance under a proportional-plus-derivative controller. The scheme involves the identification and selection of basis functions that represent the dynamic coefficients in the dynamic model. These basis functions consist of a linear combination of the product terms of sinusoidal and polynomial functions of the generalized coordinates and form a Chebyshev set on the workspace of the manipulator. A multi-layered decision scheme is developed for selecting significant basis terms in each layer for each dynamic coefficient. The linear combination of these significant basis terms is then utilized to construct each simplified dynamic coefficient based on the minimax approximation technique. A verification of the proposed scheme on a Stanford robot arm is included for discussion.

ISSN:0020-7179    

DOI:10.1080/00207179108953670

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The scope of this paper is to develop a methodology for a time invariant, single rate, approach to optimal multirate regulator design. The proposed method is developed employing a time invariant expanded discrete time model for the multirate system capable of providing all the information between sampling instants needed to compute the corresponding control weighting matrices for each base rate interval and then to accumulate all the control effort at the last base rate sampling interval for which all sampling switches are synchronized. In this way, the design of an optimal multirate regulator reduces to an equivalent single rate design of the same dimensionality as the original sampled system

ISSN:0020-7179    

DOI:10.1080/00207179108953671

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor