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IEE Proceedings D (Control Theory and Applications)

Volume 131, Issue 6, November 1984

Volumes & issues:

Volume 131, Issue 6

November 1984

Complex sectors and multivariable on-axis and off-axis circle criteria
  • Author(s): B. Kouvaritakis  and  R. Husband
  • Source: IEE Proceedings D (Control Theory and Applications), Volume 131, Issue 6, p. 209 –220
  • DOI:  10.1049/ip-d.1984.0035
  • Type: Article
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  • p. 209 –220 (12)
    Earlier work has shown that frequency-dependent real sector conditions, together with a suitable decomposition of the transfer function matrix of a linear time-invariant system G(jω), enable the extension of the circle criterion to the multivariable case. The present paper proposes the use of complex rather than real sectors, and utilises the extra degrees of freedom introduced into the problem to improve the measure of deviation from normality, and thus reduce the diameter of the circles of the criterion. The new circles will not necessarily have their centres on the real axis and thus the approach yields a set of smaller and shifted circles, which provide a useful test for the stability of nonlinear multivariable feedback systems. This approach is also shown to be suitable for the improvement of multivariable off-axis circle type of results.
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Parameter estimation of system dynamics with modulation-type noise—application to the modelling of the dynamic relationship between the EMG and force transients in muscle
  • Author(s): P.J. Lago  and  N.B. Jones
  • Source: IEE Proceedings D (Control Theory and Applications), Volume 131, Issue 6, p. 221 –228
  • DOI:  10.1049/ip-d.1984.0036
  • Type: Article
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  • p. 221 –228 (8)
    In most of the well known procedures for parameter estimation of system dynamics, it is assumed that disturbances acting on the system are additive and independent of the input to the system. In mathematical modelling of biological systems, this assumption is often unreasonable; in addition, to accomodate the variety of phenomena present in biological systems, developments of existing parameter estimation techniques are required. Of the existing methods of system parameter estimation, those based on the ‘instrumental variables’ principle are among the simplest and most useful in practical applications. An algorithm based on this principle is developed for the parameter estimation of linear systems with modulation-type noise. The application of the technique is illustrated in the modelling of the dynamic relationship between the electrical and mechanical activity of muscle.
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Erratum: Online optimisation of the free parameters in discrete adaptive control systems
Pole assignment in decentralised systems: a structural approach
Optimal variable-structure controller for DC motor speed control
  • Author(s): Yuan-Yih Hsu  and  Wah-Chun Chan
  • Source: IEE Proceedings D (Control Theory and Applications), Volume 131, Issue 6, p. 233 –237
  • DOI:  10.1049/ip-d.1984.0039
  • Type: Article
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  • p. 233 –237 (5)
    A new technique, based on the theory of variable-structure systems, is proposed for the speed control of a separately excited DC motor. A systematic procedure for selection of the switching hyperplane in the design of variable-structure controllers is developed, by minimising a quadratic performance index in the sliding-mode operation. The proposed control scheme is illustrated by digital simulation of a separately excited DC motor. It is shown that use of optimal variable-structure controllers can greatly improve the transient performance of the system, while still keeping the steady-state error at zero.
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Time-optimal control algorithm for microprocessor with asymmetrical bounds
  • Author(s): I. Serra ; L. Moreno ; E. Luque
  • Source: IEE Proceedings D (Control Theory and Applications), Volume 131, Issue 6, p. 238 –242
  • DOI:  10.1049/ip-d.1984.0040
  • Type: Article
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  • p. 238 –242 (5)
    A microprocessor-based time optimal control algorithm is presented. The method is based on the bang-bang approach which incorporates an asymmetrical control strategy to allow load disturbance. The implementation is carried out in such a way as to minimise the number of real-time computations. A relationship involving the sampling period, the asymmetrical value and the amplitude disturbance has been developed. The time-response deterioration as a consequence of the asymmetrical control signal is also evaluated. The method has been applied to a second-order process, and experimental results are presented.
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Model reduction of linear multivariable control systems via frequency matching
  • Author(s): L.R. Pujara  and  K.S. Rattan
  • Source: IEE Proceedings D (Control Theory and Applications), Volume 131, Issue 6, p. 243 –247
  • DOI:  10.1049/ip-d.1984.0041
  • Type: Article
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  • p. 243 –247 (5)
    A computer-aided method for model reduction of linear multivariable continuous control systems via frequency matching is presented in the paper. The objective is to obtain a simplified transfer function matrix from a given large-order transfer function matrix, so that the vital characteristics of the given system are retained in the simpler system. This is accomplished by matching the frequency responses of the given and the reduced systems by means of the weighted mean square error. As a result of this minimisation, formulas for computing the optimal coefficients for the simplified transfer function matrix are obtained. The technique is illustrated by a numerical example and the results are compared with those in the literature.
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Low-order modelling via discrete stability equations
  • Author(s): C.P. Therapos
  • Source: IEE Proceedings D (Control Theory and Applications), Volume 131, Issue 6, p. 248 –252
  • DOI:  10.1049/ip-d.1984.0042
  • Type: Article
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  • p. 248 –252 (5)
    The continuous-time stability equation method is extended to reduce the order of discrete stable high-order transfer functions. The operations of the proposed method are carried out entirely in the z domain. Thus, use of the bilinear transformation is avoided, and considerable savings in computation are achieved. Furthermore, all the desired properties of the stability equation method, such as stability preservation, satisfactory approximation at large times, estimation of the reduced order and accurate preservation of the oscillation frequencies are retained.
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Robust stability of diagonally dominant systems
Parameter estimation from noncontiguous data
  • Author(s): P.J. Gawthrop
  • Source: IEE Proceedings D (Control Theory and Applications), Volume 131, Issue 6, p. 261 –266
  • DOI:  10.1049/ip-d.1984.0044
  • Type: Article
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  • p. 261 –266 (6)
    A ‘linear-in-the-parameters’ representation is derived for a data set formed by concatenating a number of input-output data records which, although arising from the same system, are not contiguous in time. As well as parameters describing the system, further ‘splicing parameters’ arise from the discontinuities in the concatenated data records at the joins. This representation gives rise to a method of ‘data splicing’ which enables system parameters to be recursively identified from the concatenated data records. The method is particularly useful when each individual data record is not, by itself, sufficient to identify the system parameters. The method is developed for noise-free differential equation models, but the basic principles are more widely applicable. An illustrative example is given.
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On using orthogonal functions with singular systems
Numerical inversion of multidimensional Laplace transforms via block-pulse functions
Reply: Numerical inversion of multidimensional Laplace transforms via block-pulse functions

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