Transactions of the Institute of Measurement and Control

Sahin, B.; Ceyhan, H.

doi: 10.1177/014233129601800401pmid: N/A

In this work, axisymmetric, viscous, steady, incompressible and laminar flow through square-edged orifices has been studied. A numerical solution of the steady-state vorticity transport equation has been obtained from the two-dimensional Navier-Stokes equations. Finally, streamline patterns, vortex formations and separated flow regions have been predicted.The effects of orifice plate thickness and Reynolds number on the flow characteristics have been investigated numerically and experimentally. The Navier-Stokes equations have also been integrated in order to compute the pressure distributions through the orifice. From these results, the orifice discharge coefficient has been computed and examined as the Reynolds number and the orifice plate thickness were varied. A comparison has been made between the experimental results, the numerical predictions and available experimental results. The predicted flow discharge coefficient values agreed closely with the experimental results.

Takahashi, Yoshihiko; Hayase, Minoru

doi: 10.1177/014233129601800402pmid: N/A

A new control scheme based on H∞ control theory is proposed for precise positioning. In comparison with PID control, the validity of the proposed scheme has been confirmed by simulations at the micron scale. The effects of disturbances such as Coulomb friction and mechanical resonance mode are treated explicitly at the controller design stage. The proposed control scheme exhibits rapid response with good suppression of the effects of resonance vibration and Coulomb friction. Root locus simulation results for the closed-loop transfer function have shown that H∞ control is able to stabilise the mechanical resonance frequency mode, whereas PID control is not. Frequency response simulation results for the closed-loop transfer function of H∞ control have shown that the cut-off frequency increases and the mechanical resonance mode stabilises simultaneously when the H∞ norm condition, γ, is decreased.

Wang, Feng-Sheng; Yeh, Chi-Liang; Wu, Yieng-Chiang

doi: 10.1177/014233129601800403pmid: N/A

An interactive multiobjective optimisation method was introduced in this study to tune satisfactory modes of a PID controller. An interval process was modelled by a set of transfer functions in this study. In general, such processes could not be handled by a PID controller which was tuned by a single-objective optimisation method. A trade-off tuning rule based on multi-objective optimisation methods was introduced to overcome this drawback. The robust stability for this multi-modelling control system performed by the multi-objective optimisation approach was automatically guaranteed. Extension to cascade control systems was also developed.

Coulbeck, Bryan; Ulanicki, Bogumil; Rance, John P.; Deviatkov, Vladimir V.; Kosov, Sergei; Glukhovsky, Iosiff

doi: 10.1177/014233129601800404pmid: N/A

Automating the pressure control of typical Russian types of water distribution systems can result in greater than average benefits. The potential exists for improving the system efficiency and reliability while reducing the on-line operational manning requirements. To this end the paper presents modelling and simulation studies of the current semi-manual and the proposed fully automatic pressure control schemes for the Zelenograd water supply system. Dynamic operational simulations are an essential feature of the project. However, it was necessary to enhance the network hydraulic simulator, to include pressure feedback controls, in order to produce acceptable results. Analyses of the operational requirements and the simulation results provide a basis for the design of an improved controller using an expert system approach. A major part of the paper covers the methods in use for obtaining an adequate set of control rules for the Zelenograd system. Extended time period operational simulations are used to verify the rules and to compare the results with those of existing practice. There are expectations of immediate benefits in terms of operating economies. Typically these will arise from reductions in water leakage, electricity charges and control manpower. Work is now proceeding on actual implementation using a combination of expert system and fuzzy logic methods.

Whalley, R.

doi: 10.1177/014233129601800405pmid: N/A

Mechanical system and electrical circuit models represented by the matrix quadratic are considered. Parameter variations which may be due to modelling uncertainties or coefficient adjustments are incorporated. The characteristic-zero excursions induced by modelling changes are investigated. A typical application where the frictional dampers can be adjusted to provide efficient oscillatory regulation is outlined.

Webster, C.A.G.

doi: 10.1177/014233129601800406pmid: N/A

Spherical retroreflectors are customarily constructed of cemented hemispheres made from conventional glasses. With the recent availability of glass with a refractive index close to 2 the possibility exists of making such a reflector out of a simple sphere. A refractive index of exactly 2.0 is optimum for reflecting a beam of zero width. For finite beam widths, better overall performance is obtained with an index slightly less than 2.0.

Baglio, Salvatore; Graziani, Salvatore; Pitrone, Nicola

doi: 10.1177/014233129601800407pmid: N/A

In this paper a new intelligent sensor for distance measurements is proposed. Both optical and acoustical sensors are adopted. Fuzzy data fusion methodologies have been applied in order to integrate the distance estimates of the different sensors. The introduced intelligent measurement system allows high quality distance estimation to be obtained in a wide operating range with low sensitivity to environmental noise. The experimental set-up and the metrological characterisation of the measuring system are reported.