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Volume 136
Issue 2
IEE Proceedings D (Control Theory and Applications)
Volume 136, Issue 2, March 1989
Volumes & issues:
Volume 136, Issue 2
March 1989
Decoupling in nonlinear systems: from linearity to nonlinearity
- Author(s): L.C.J.M. Gras and H. Nijmeijer
- Source: IEE Proceedings D (Control Theory and Applications), Volume 136, Issue 2, p. 53 –62
- DOI: 10.1049/ip-d.1989.0008
- Type: Article
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A standard approach for dealing with synthesis problems in nonlinear control systems consists in linearising the nonlinear system around a specific working point and, then, solving the synthesis problem for the obtained linear system. To what extent the resulting linear controller is a good approximate solution for the nonlinear problem is, of course, questionable. In the paper, the authors discuss, as an example, the input/output decoupling problem. It is shown that, under fairly general conditions, the solvability requirements for the nonlinear and the corresponding linear problem are the same. The authors also characterise those linear solutions which are first-order solutions for the nonlinear problem. Simulations on a few fairly simple exam ples illustrate the results obtained.
Lower bounds for the stability margin of linear continuous systems based on weighted performance criteria
- Author(s): P. Agathoklis and V. Sreeram
- Source: IEE Proceedings D (Control Theory and Applications), Volume 136, Issue 2, p. 63 –67
- DOI: 10.1049/ip-d.1989.0009
- Type: Article
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In the paper, lower bounds for the stability margin of linear continuous systems with unknown system parameters are developed. These lower bounds are obtained as a function of the weighted performance criteria computed from the measurements of the system's impulse response. The properties of the proposed method are discussed and it is shown that the bounds can be improved by increasing the order of the weighting factor. The method is illustrated by a numerical example.
Homotopy method for solving algebraic Riccati equations
- Author(s): S.-S. Wang and C.-T. Pan
- Source: IEE Proceedings D (Control Theory and Applications), Volume 136, Issue 2, p. 68 –72
- DOI: 10.1049/ip-d.1989.0010
- Type: Article
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In the paper, a new method is presented for solving algebraic Riccati equations. The proposed method possesses an almost globally convergent characteristic and, hence, is very suitable for finding the Riccati equation solution of an ill conditioned control system. The new method is simple and easy to implement. Some typical numerical examples are also given for illustration.
New computationally efficient formula for backward-pass fixed-interval smoother and its UD factorisation algorithm
- Author(s): K. Watanabe and S.G. Tzafestas
- Source: IEE Proceedings D (Control Theory and Applications), Volume 136, Issue 2, p. 73 –78
- DOI: 10.1049/ip-d.1989.0011
- Type: Article
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A new UD factorisation-based backward-pass fixed-interval smoother that is numerically reliable and stable is derived for linear stochastic discrete-time systems. A computationally efficient recursion of a classic backwardpass smoother is first obtained, so that the smoother can exclude the well known short-comings of the classic version and utilise the outputs of a forward-pass information filter. This recursion formula is then applied to construct the UD smoother using three fundamental UD algorithms. It is shown that, compared with Bierman's backward-pass UD smoother, the present UD smoother can provide an improvement in computation speed and computer storage for time-invariant systems, as well as the forward-pass UD smoother, but cannot avoid the computation of an inversion of the state-transition matrix for time-varying systems.
A class of discrete-time models for a continuous-time system
- Author(s): T. Mori ; P.N. Nikiforuk ; M.M. Gupta ; N. Hori
- Source: IEE Proceedings D (Control Theory and Applications), Volume 136, Issue 2, p. 79 –83
- DOI: 10.1049/ip-d.1989.0012
- Type: Article
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An equivalence class, called the T-equivalence class in this study, is introduced for discrete time models of a continuous-time system, such that any member of this class has the same input/output characteristics when the discrete-time interval approaches zero. This concept provides a systematic way of viewing the relationship between the discrete and continuous-time systems.
Engine control system using a cylinder pressure sensor
- Author(s): Y. Hata ; K. Ikeura ; T. Morita ; T. Abo
- Source: IEE Proceedings D (Control Theory and Applications), Volume 136, Issue 2, p. 84 –88
- DOI: 10.1049/ip-d.1989.0013
- Type: Article
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Individual cylinder combustion control systems using a cylinder pressure sensor have already been introduced to realise highly tolerant system to the variability of engine components, fuel quality and environmental conditions. The paper deals with such an application of a cylinder pressure sensor to air/fuel ratio control, which is to control air/fuel ratio to the lean limit of engine stability. To detect the engine stability limit, some statistical signal processing method was applied to the detected peak pressure crank angle position Θpmax. By using this method, this system needs only relative cylinder pressure value to detect Θpmax, hence a practical piezoelectric type washer transducer was good enough for this application.
Approach to pole assignment by centralised and decentralised output feedback
- Author(s): M. Tarokh
- Source: IEE Proceedings D (Control Theory and Applications), Volume 136, Issue 2, p. 89 –97
- DOI: 10.1049/ip-d.1989.0014
- Type: Article
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The paper presents a method for output feedback pole assignment in both centralised and decentralised systems. For the nth-order m-input l-output system (A, B, C), the existence of a solution to the pole-assignment problem is determined by checking the rank of a certain matrix E formed from the matrices CAiB, i=0, 1, …, n−1. It is shown that when rank(E)=n, it is possible to assign min(n, ml) poles by constant output feedback. The solution to the nonlinear equations required for pole assignment is obtained by, first, converting the nonlinear equations into a set of linear equations and, then, applying an iterative numerical method. The pole assignment condition and the method of solution are extended to decentralised systems using constant or dynamic output feedback. In particular, it is shown that, when an N-station decentralised system satisfies a certain rank condition, min poles can be assigned using decentralised constant output feed back, where mj and lj are the number of local inputs and outputs, respectively. Lower bounds on the order of centralised and decentralised dynamic compensators for pole assignment are also established.
Self-tuning control in the presence of periodic disturbance
- Author(s): K.W. Lim ; C.C. Hang ; C.H. Lee
- Source: IEE Proceedings D (Control Theory and Applications), Volume 136, Issue 2, p. 98 –104
- DOI: 10.1049/ip-d.1989.0015
- Type: Article
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A pseudo-feedforward method is proposed for adapting an incremental self-tuning controller to reject periodic disturbances. The algorithm begins with an estimate of the disturbance frequency. The amplitude and phase of the disturbance are estimated by augmenting the parameter estimation vector. The estimated disturbance can then be used as a feedforward term with the self-tuning controller. A second stage allows for the estimate of the disturbance frequency to be improved using the estimated amplitude. The algorithm has been shown to be robust in simulation examples and on a pilot heat exchanger.
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