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1887

IEE Proceedings D (Control Theory and Applications)

Volume 135, Issue 2, March 1988

Volumes & issues:

Volume 135, Issue 2

March 1988

Linear system reduction using approximate moment matching
Stability and performance bounds for the linearisation-based analysis and design of multivariable nonlinear systems
  • Author(s): D. Valsamis ; D.H. Owens ; J.O. Gray
  • Source: IEE Proceedings D (Control Theory and Applications), Volume 135, Issue 2, p. 79 –89
  • DOI:  10.1049/ip-d.1988.0012
  • Type: Article
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  • p. 79 –89 (11)
    The paper is concerned with the derivation of useful results that complement the linearisation-based analysis and design of multivariable systems with measurement nonlinearity. The approach is based on the closed-loop linearised system descriptions and certain nonlinearity related parameters representing sector and/or incremental sector properties, and also enables the consideration of nonlinearities with discontinuities at the origin. Nonlinear-system stability and performance is assessed on the basis of the stability and performance of the corresponding linearised system and certain easily computable sufficient conditions representing BIBO and asymptotic stability conditions, as well as absolute and derivative performance bounds. The results depend on useful linearised system descriptions such as the L∞ operator norm, thus offering the advantages of meaningful assessments and overall computational simplicity.
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Application of nonlinear system transformations to control design for a chemical reactor
Self-tuning control of hypotension during ENT surgery using a volatile anaesthetic
  • Author(s): R.K. Millard ; C.R. Monk ; C. Prys-Roberts
  • Source: IEE Proceedings D (Control Theory and Applications), Volume 135, Issue 2, p. 95 –105
  • DOI:  10.1049/ip-d.1988.0014
  • Type: Article
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  • p. 95 –105 (11)
    The generalised minimum-variance self-tuning controller of Clarke and Gawthrop has been used to regulate induced hypotension (reduced blood pressure) in 34 patients undergoing ENT surgery, by automatic adjustment of the inhaled concentration of the volatile anaesthetic agent isoflurane. The purpose of the investigation was: to assess the use of self-tuning control (STC) as an aid to the anaesthetist in normal clinical situations; to obtain information in an acceptable manner to illuminate the clinical situation and any signal conditioning, sources of outliers, and other possible problems to be met therein; to see to what extent STC compares with manual adjustments by an anaesthetist (10 patients); to provide a basis for the design of a stand alone controller for use in anaesthesia which would enable comparison with other drugs in the same situations; and to provide controlled conditions for measurement of various physiological variables of interest to anaesthetists. In summarising our investigations and experiences from an engineering standpoint the potential of STC methods in clinical applications is indicated, and some ways of improving the performance of our implementation are discussed.
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Decoupling and data sensitivity in singular systems
New pole assignment algorithm with reduced norm feedback matrix
  • Author(s): R.G. Cameron
  • Source: IEE Proceedings D (Control Theory and Applications), Volume 135, Issue 2, p. 111 –118
  • DOI:  10.1049/ip-d.1988.0016
  • Type: Article
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  • p. 111 –118 (8)
    A new algorithm is described for the assignment of closed loop poles in linear time invariant multivariable systems. The approach is similar to the well known dyadic pole placement methods, but does not usually result in a unity rank controller. The algorithm can be put into iterative form in the sense that open loop poles can be relocated or preserved so that by repeating the assignment process, all of the open loop poles can be reassigned. There are only very mild constraints on the destinations of the poles. The paper also shows how any unused degrees of freedom can be exploited to reduce the control effort needed to achieve the pole assignment. Results are given for both the state and the output feedback cases.
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Modified algorithm for steady-state integrated system optimisation and parameter estimation
Parameter-bounding identification algorithms for bounded-noise records
  • Author(s): S.H. Mo  and  J.P. Norton
  • Source: IEE Proceedings D (Control Theory and Applications), Volume 135, Issue 2, p. 127 –132
  • DOI:  10.1049/ip-d.1988.0018
  • Type: Article
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  • p. 127 –132 (6)
    In the identification of dynamical models from noisy observations, an adequate stochastic characterisation of the noise is often unavailable, either because there are relatively few observations and little prior information, or because the noise behaviour is complicated, e.g. nonstationary. An alternative approach to identification has been suggested, which uses bounds on the noise instead of a stochastic description. From the noise bounds in a specified model structure, each observation yields a pair of bounds in parameter space. A succession of observations thus identifies a feasible parameter region rather than a point estimate of the parameters. This paper suggests combined use of two standard algorithms for parameter-bounding identification, outer-bounding by linear programming, and ellipsoidal outer-bounding. The former is expensive in computation but may result in a more accurately defined feasible parameter region. The latter is cheap, but often unsatisfactory on its own because it gives only a loose approximation to the parameter region. Various combined uses of the two methods are described and tested.
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Robustness analysis of discrete-time adaptive control systems using input-output stability theory: a tutorial
Leak detection and location in gas pipelines
Adaptive model following control of electrohydraulic velocity control systems subjected to unknown disturbances
  • Author(s): J.S. Yun  and  H.S. Cho
  • Source: IEE Proceedings D (Control Theory and Applications), Volume 135, Issue 2, p. 149 –156
  • DOI:  10.1049/ip-d.1988.0021
  • Type: Article
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  • p. 149 –156 (8)
    This paper considers the velocity control problem of nonlinear hydraulic servo systems subjected to unknown and time-varying external load disturbances. Hydraulically operated processes are usually represented by a hydraulic actuator-load system whose dynamic characteristics are complex and highly nonlinear, owing either to the flow-pressure relationships of the hydraulic system or to a load system motion itself. Furthermore, these characteristics are sometimes unknown owing to the uncertainty in external load disturbances to the processes. Therefore, the conventional approach to the controller design of these systems may not assure satisfactory control performance. To obtain better performance an adaptive model following control scheme was derived based upon Lyapunov's direct method [8]. In order to deal with the uncertainties that are associated with the plant dynamics and the unknown disturbances, this method uses a small ultimate bound of the state error as an adaptation criterion. A series of simulation studies were performed to demonstrate the effectiveness of this controller. The results show that the proposed AMFC is fairly robust to unknown and timevarying external load disturbances, yielding improved performance characteristics when compared with a suboptimal PID controller with constant feedback gain.
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Controller designs for model-plant parameter mismatch

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