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1887

IEE Proceedings D (Control Theory and Applications)

Volume 134, Issue 5, September 1987

Volumes & issues:

Volume 134, Issue 5

September 1987

Convergence analysis of least-squares identification algorithm for unstable systems
  • Author(s): J. Jiang  and  R. Doraiswami
  • Source: IEE Proceedings D (Control Theory and Applications), Volume 134, Issue 5, p. 301 –308
  • DOI:  10.1049/ip-d.1987.0049
  • Type: Article
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  • p. 301 –308 (8)
    The convergence behaviour of a least-squares equation error identification algorithm applied to an unstable time-invariant system is analysed. It is shown that, to obtain a uniform rate of convergence for all the parameter estimates of an ARMA model, an unbounded probing signal input is necessary. However, with the bounded probing signal input, the convergence of AR parameter estimates alone is ensured. It is also shown explicitly that, for unstable systems with a bounded probing signal input, the speed of convergence of AR parameter estimates is much faster than that for stable systems, but the convergence rate of MA parameter estimates is so slow that it is difficult to obtain them in a reasonable time span. The practical issues of unstable system identification, as well as the relationship between the robustness of the algorithm with respect to measurement noise and the relative stability of the system are also discussed. Finally, simulation results are included to illustrate the convergence behaviours.
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A system for partitioned control of a robot
  • Author(s): J. Billingsley
  • Source: IEE Proceedings D (Control Theory and Applications), Volume 134, Issue 5, p. 309 –316
  • DOI:  10.1049/ip-d.1987.0050
  • Type: Article
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  • p. 309 –316 (8)
    Many robots contain a microprocessor controller per axis, linked to a supervisory minicomputer contained within the manufacturer's package. In the paper it is proposed that a defined bus structure and protocol can give public access to similar controllers, enabling the supervisory and geometric computations to be performed on a standard desk-top machine of the current commercial type. The proposed protocol allows for evaluation of a cubic interpolation function in the controller cards, so that a fit can be made to two past and two future sets of target co-ordinates. A command coding scheme is suggested which will give close liaison between controllers and a supervisory computer. Design details are given of an ongoing practical project based on adding such a controller to the mechanical portion of the Mitsubishi RM-501 robot. Kinematic equations are derived, showing the restriction of the 5-axis robot. Expressions are found for evaluating coefficients to be used in a simple recursive computation, giving an exact cubic fit to a succession of four target points. An outline is given of the hardware structure of the interface, of the handshake which synchronises the movements of the various axes, and of the interrupt levels assigned to the controllers' tasks.
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Decentralised design of robust controllers
  • Author(s): D. Petkovski
  • Source: IEE Proceedings D (Control Theory and Applications), Volume 134, Issue 5, p. 317 –326
  • DOI:  10.1049/ip-d.1987.0051
  • Type: Article
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  • p. 317 –326 (10)
    The paper presents a procedure for improving the feedback properties, including robustness, of a decentralised multivariable feedback system designed by a quadratic index optimisation methodology. The procedure allows the possibility of adding extra controllers which can be used to fine-tune the closed-loop behaviour of the nominal control system. Although attention is focused on the quadratic index methodology, the basic approach can be applied to adjust the design parameters of any decentralised design methods. The methodology and design procedure are illustrated by considering two numerical examples, including a 9th-order power system with a five-terminal DC network configuration.
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Book review: An Introduction to Identification
New table to implement Routh's stability test and matrix continued fraction expansion and inversion
  • Author(s): C.P. Therapos
  • Source: IEE Proceedings D (Control Theory and Applications), Volume 134, Issue 5, p. 327 –332
  • DOI:  10.1049/ip-d.1987.0053
  • Type: Article
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  • p. 327 –332 (6)
    A new table of numbers, obtained by rearranging the well known Routh stability array, is used to perform Routh's stability test. The proposed table, with slight modifications, can also be used to expand a known rational transfer function matrix into one of the three Cauer-form continued fractions, or, conversely, to invert a given Cauer-form continued fraction. In all the aforementioned applications, the recursive relations presented for the construction of the proposed table seem better than the relevant Routh-type relations, as one may follow more easily the values of the indices appearing in the formulas, while the number of the variables involved is significantly decreased. Moreover, from the programming point of view, they guarantee a reduction of the required memory, nearly by half, and a faster execution of the corresponding program. These advantages are achieved without increase of the number of numerical operations or in the complexity of the existing techniques.
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Book review: Programmable Controllers for Factory Automation
Multivariable servo-system design technique using sensitivity as a design parameter
Continuous-time quadratic regulators and pseudo-continuous-time quadratic regulators with pole placement in a specific region
  • Author(s): S. Leang Shieh ; M. Hani Dib ; Ganesan Sekar
  • Source: IEE Proceedings D (Control Theory and Applications), Volume 134, Issue 5, p. 338 –346
  • DOI:  10.1049/ip-d.1987.0056
  • Type: Article
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  • p. 338 –346 (9)
    A linear optimal quadratic regulator is developed, for optimally placing the closed-loop poles of multivariable continuous-time systems within the common region of an open sector, and the left-hand side of a line parallel to the imaginary axis in the complex s-plane, without explicitly utilising the eigenvalues of the open-loop systems. Also, a pseudo-continuous-time state-space method is developed, for finding the linear suboptimal quadratic regulator which suboptimally places the closed-loop poles of multivariable discrete-time systems within the common region of a circle, and the logarithmic spiral in the complex z-plane. An illustrative example is presented to demonstrate the effectiveness of the proposed procedures.
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Book review: Flight Simulation

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