bluuebunny/crossref_metadata_2025 huggingface dataset:
Input stimulus design for model discrimination in human respiratory control
Authors: Swanson George D.
Published: August 2008

The existence of a set of alternative models, all competing to characterise respiratory controller structure, leads naturally to a model discrimination problem. This paper considers the problem of input design for enhancing model discrimination. Both empirical and formal methods are considered. The empirical methods utilise frequency domain model characteristics. The formal methods utilise the time domain model responses. Using a class of models given by linear differential equations with time delays, an input consisting of a sum of sinusoidal components under a power constraint is considered. A procedure for designating the power spectrum of the signal is developed. Furthermore, a procedure for obtaining a binary signal with a similar spectrum is illustrated. These concepts are applied to input design for discrimination among models that characterise respiratory control during exercise.
Calibration and data reduction in microprocessor based process chromatographs
Authors: Villalobos Richard
Published: August 2008

A process gas chromatograph system is described which employs microprocessors in the analyser and data processor to sample and digitise the detector signal, and measure peak height or area by five different methods. Additionally, three methods of baseline correction and five methods for calibration and calculation of results are user programmable from a panel with alpha numeric display using an interactive conversational dialogue with the operator. Some considerations relating to noise filtering and non-zero baseline correction are discussed.
A reconfigurable parallel processing structure for adaptive state estimation
Authors: Al-Dabass D.
Published: August 2008

The computational requirement of adaptive state estimation is examined, and a previously proposed chain parallel processor is extended to satisfy these requirements. An example is programmed in detail to illustrate the flexibility of the structure. During each integration cycle, the processing elements operate in a single-instruction stream mode by accessing a common program, they then re-configure and operate in a multi-instruction stream mode to execute the second part of the algorithm.
A microcomputer algorithm for open loop step motor control
Authors: Hine D. , Burbridge L.
Published: August 2008

The Digital Differential Analyser is an algorithm which, has been known for many years but has been somewhat neglected. With the advent of cheap computing power in the form of microprocessors, however, such an algorithm deserves reconsideration. This paper describes the use of the DDA to control the point to point motion of a step motor. The algorithm is developed in detail and its surprisingly complex operation is investigated by both a test-bed situation and by a detailed simulation.

The algorithm is developed to a point where it is suitable for widespread practical application in the field of incremental motion control.
A structure load alleviation control system for a large aircraft
Authors: McLean D. , Prasad R.A.
Published: August 2008

By using active control technology (ACT) on a large flexible aircraft it is possible to effect some alleviation of dynamic loads to which the wing is subjected when the aircraft performs some commanded manœuvre or when it encounters unwanted atmospheric turbulence. The design of such a load alleviation control scheme by means of linear optimal control theory is described in this paper. Of particular concern are the effects upon the aircraft's structural behaviour of using impaired optimal feedback control caused either by the use in the design method of simpler mathematical models to describe the aircraft dynamics, or by the practical impossibility of obtaining for measurement the complete state vector of the aircraft, or by the failure of particular motion sensors. A simple algebraic method of accounting for the deficit in steady-state load values, which occurs as a result of having to use such reduced- order feedback control, is presented in addition to several results which illustrate the effectiveness of the load alleviation scheme when the aircraft encounters turbulence.
Controller selection and tuning
Authors: Hind E.C.
Published: August 2008

Rational methods are developed for the tuning of ideal continuous action controllers for set point changes using Proportional, Proportional plus Derivative, Proportional plus Integral and Proportional plus Integral plus Derivative control actions. For two or three term controllers, maximum gain methods are used together with the open loop frequency response of the uncompensated system. The methods have an analytical foundation andprovide considerable insight into the controller tuning. For the first time a set of mathe matical criteria are proposed for the selection of continuous action controllers.
The reduction of transfer function matrices to generalised diagonally dominant form
Authors: Nwokah O.D.I.
Published: August 2008

A key problem in the Rosenbrock Nyquist .Array is how to determine a pre-compensator matrix K(s) of as simple form as possible so that, given any plant transfer matrix G(s), the composite matrix Q(s) = G(s)K(s) has a suitable structure. One such suitable structure is diagonal dominance and another is the Hadamard condition, which is a generalisation of diagonal dominance. This paper gives a systematic method for making Q(s) Hadamard by suitable choice of K(s).
Optimal control-system design for solar-tracking concentrators
Authors: Cho H.S. , Lee C.W. , Cho Y.J.
Published: August 2008

An optimal control procedure is presented for minimising the sun tracking error of solar concentrators. The sun tracking system is a point-focusing collector which is subject to wind disturbance. The optimal control law considered herein is a proportional plus integral control, and the following two feedback schemes are used for the controller implementation: 1. state estimation via an observer; and 2. suboptimal control The observer is constructed to estimate the unmeasurable tracking error variables and designed optimally to minimise the deviation of estimated errors from actual error values. The suboptimal control, on the other hand, uses only the output variables available from sensor. Investigation of the comparative performances of the two schemes indicates that sub-optimal control is only marginally inferior and could therefore provide a satisfactory and cost-effective solution under the conditions assumed.
Control and management
Authors: Wilson B.
Published: August 2008

The argument of the paper is that a management- control system (containing people) is fundamentally different from a process-control system (containing hardware). Given this difference, the methods of analysis and design appropriate to management- control systems need also to be fundamentally different. A modelling language and associated methodology which have been derived from a continuing programme of action research are illustrated in the paper and are suggested as one way in which the problems of the analysis and design of management control systems can be tackled.
Management control systems-analogies with process control systems as an aid to improved performance
Authors: Lunt S.T.
Published: August 2008

The paper describes a number of analogies between management control systems and corresponding systems for the control of process variables in industry. Examples are included from the management control field, and indications are given of some of the ways in which improved performance might result from a more complete understanding of basic ideas.
Investigation into the adaptive control of a fermentation process
Authors: Waterworth G. , Swanick B.H.
Published: August 2008

The availability of a batch-fed yeast fermentation plant provided an opportunity to investigate the performance of an adaptive control scheme for the plant. From observation and measurement of plant outputs, the structure of a model describing the plant dynamics was established. A solution of the model allowed comparisons to be made with the actual plant operation. While the simulation did not reflect the behaviour of the plant precisely it did provide sufficient information to structure a parameter estimation procedure within a state-variable framework. Using the estimator, the multivariable pseudo linear descriptions of the nonlinear model were identified from input and output data and these were passed to a suboptimal controller whose feedback gains were adjusted to minimise a performance index. Results are presented identifying the appropriate model structure and the operation of the multivariable adaptive controller. The work suggests that the application of the adaptive technique to an online configuration will improve the present semiautomated control approach to this problem.
A correlation function peak tracking system
Authors: Jordan J.R. , Manook B.A.
Published: August 2008

A search and track system for detecting the peak position of a correlation function can be simply implemented and a high resolution result can be obtained. Unfortunately it is difficult to assure industrial users that such a system will only lock on to the most significant peak of the function. In this paper a peak tracking system is described which is forced to search around the most significant peak position by using a second correlator to set the length of the shift register used by the tracking loop. The second correlator must be a digital correlator (eg, the overloading counter correlator) giving a reliable, coarse indication of the position of the most significant peak.
Component evaluation by means of voltage and current measurements
Authors: Riggs W. , Evans W.A.
Published: August 2008

The complex nature of real electronic components is examined, and their evaluation by means of voltage and current measurements is discussed. An electronic component meter based on these principles is described. Careful partitioning of hardware and software has led to an instrument with relatively little analogue electronic circuitry.
Manual tuning of controllers using set point changes
Authors: Hind E.C.
Published: August 2008

Techniques are presented for the manual tuning of controllers on unidentified processes using Proportional plus Derivative, Proportional plus Integral and Three Term controllers. Successful tuning procedures are achieved by providing clear and rational objectives coupled with easily understood methods of achieving those objectives. Theoretical bases are given for the two main methods - the maximum gain method and the minimum integral method- thus providing an understanding of manual tuning not previously available and bridging one of the important gaps between the theory and the practice of control engineering.
Oscillations in relay systems
Authors: Atherton D.P.
Published: August 2008

This paper surveys the application of a frequency-domain method, initially presented by Tsypkin, and its extensions for the evaluation of free and forced oscillations in relay systems. It is shown that in a single-loop system containing a relay with no dead zone, the solution for a limit cycle is obtained from a single, nonlinear algebraic equation which can be solved graphically in a similar manner to the approximate describing function approach. For a relay with dead zone or other more complicated situations, such as multi-pulse oscillations or systems with multiple relays, more than one nonlinear algebraic equation must be solved to obtain the free or forced oscillation solutions. Details of general computer programs for obtaining these solutions are given. Several solutions can exist, which may correspond to stable or unstable limit cycles, and a necessary and sufficient condition for determining the stability of the oscillations is given.
The movement of circular cylindrical bodies while under the action of a liquid jet
Authors: Penny P.H.G. , Neve R.S.
Published: August 2008

A number of industries use machines to sort or to separate mixed components. A simple two-dimensional mathematical model is presented which enables designers to predict the movement of a cylindrical body while it is under the impact of a liquid jet. The calculated results compare well with experimental values. Improvements in the mathematical model are discussed.
The KPC multichannel correlation signal processor for velocity measurement
Authors: Keech R.P.
Published: August 2008

To date, cross-correlation flowmeters have not achieved commerical importance, and this is believed to have been due primarily to oversimplified assumptions concerning the statistical nature of flow-derived signals. A detailed analysis of signals from flow-modulated ultrasonic beams has led to a set of parameters that a correlation signal processor must satisfy for reliable measurement of flow velocity. This paper describes these parameters and their implementation in the Kent Process Control correlation signal processor, forming the heart of a commercial flow-velocity meter. A new concept of multichannel correlation is utilised, whereby further statistically independent data inherently present in the flow are correlated simultaneously to yield a multichannel correlation function. This technique gives a reduction in response time to sudden changes of flow velocity, extends the operating range and allows greater flexibility in transducer configurations to give improved flow interrogation. The theory of operation of the multichannel correlation signal processor is given, with particular emphasis on the analysis of practical correlation functions and the system response to nonstationary data processed under changing flow conditions.
Photoplethysmography- fundamental aspects of the optical properties of blood in motion
Authors: Roberts V.C.
Published: August 2008

This paper outlines a simplified theory to explain the behaviour of photoelectric plethysmographs used for the measurement of blood flow in the skin. The paper reports the finding that light diffusing through blood, from a source outside a blood vessel, can diffuse preferentially in the direction of motion of the blood, and that this preferential diffusion is likely to arise from a combination of the plasma skimming which occurs at the vessel wall and from the orientation effects of the erythrocytes in motion.
Dynamic measurements of small displacements by laser interferometry
Authors: Ohtsuka Yoshihiro
Published: August 2008

A descriptive survey of optical noncontact detection of small dynamic displacements is made from the practical point of view of the use of laser interferometry. Photodetection processes are mentioned briefly for the purpose of understanding the time-averaging effect on the time-varying optical interference. Principles of optical homodyne, heterodyne, and two-frequency interferometry are reviewed for measurements of small dynamic displacements. Merits and demerits of these detection techniques are discussed by consideration of the minimum detectable amplitude for a simple harmonic motion.
Modelling of drying of an abrasive-paper strip
Authors: Božičević J. , Kraijević M.
Published: August 2008

A mathematical model of the drying of an abrasive-paper strip is derived; the behaviour of the simulated model is studied and compared with the behaviour of the real process. An optimisation procedure is developed for the estimation of optimal conditions for drying, ie minimising the time taken while ensuring the optimum quality of the product.
Time-optimal positioning control with limited values of the parameters
Authors: Schillinger J.
Published: August 2008

In order to improve the response to commands and disturbances of a time-optimal positioning control system with limited values of the parameters, a new concept for a velocity director with position feedback has been developed. The proposed solution is suitable for realisation with a microprocessor, and its distinction lies in its insensitivity to variations of parameters, better response to disturbances and lower costs. Important constituents of the hardware and software are described.
Systems identification in biology
Authors: Carson E.R. , Finkelstein L.
Published: August 2008

The nature of system identification in biological systems is analysed, in order to show what are the special features of biological systems in relation to the identification process, and to reveal what general lessons for measurement and control can be learned from the quantitative study of biological systems. Approaches to be adopted in the identification process are ou tlined, highlighting the importance of adopting an appropriate mathematical model. It is shown that biological systems constitute a paradigm for the application of identification procedures in the observational sciences generally. The paper sets the scene for the four application studies which follow, illustrating the application of identification methods to mechanical parameters of the lung, to elements of the neuromuscular system, to the blood pressure control system and in pharmacokinetics.
System identification of the blood pressu re control system by low frequency neural stimulation
Authors: Kitney R.I. , Gerveshi C.M.
Published: August 2008

This paper describes the identification of the control structure of that section of the blood pressure control system which relates cardiac depressor activity to heart rate, arterial blood pressure and respiration. Using pulse frequency modulated PRBS techniques, the parameters of the closed loop frequency and impulse responses of the baroreceptor (pressure transducer) control loop were estimated, thereby gaining a more detailed understanding of the dynamics of the baroreceptor system.
Economic performance control
Authors: Benson R.S.
Published: August 2008

Current computing technology allows the continuous display of economic performance measures in the control room to be a real practical possibility. This paper explores the possibilities and implications of this on plant control.
Modelling a complex biological system: the human cardiovascular system — 2. Model validation, reduction and development
Authors: Leaning M.S. , Pullen H.E. , Carson E.R. , Al-Dahan M. , Rajkumar N. , Finkelstein L.
Published: August 2008

Model valadity is a multi-faceted concept which is expressed as a set of validity criteria related to different modelling objectives. These criteria form the basis of a validation methodology for biological models - an integral part of the modelling methodology presented in the preceding paper. This is applied to the model of the human cardiovascular system. By means of model decomposition and reconstruction, validation occurs at a number of levels and includes empirical, theoretical and heuristic tests. In general, the model is shown to have reasonable validity in terms of its objectives; it is an adequate representation of the human cardiovascular system under certain conditions. Although some defects may be traced to the modelling of neural control, the model has an important role in the conception and testing of different hypotheses for such control. In conclusion, the two papers support the thesis that mathematical models, used wisely, are effective and necessary tools in complex systems research.
The application of microwave-frequency spectrometry, permittivity and loss measurements to chemical analysis
Authors: Alder J.F. , Brennan M.F. , Drew P.K.P. , Thirup G.
Published: August 2008

The frequency dependence of the interaction between microwave radiation and matter gives chemical information concerning both the bulk and molecular structure of gases, solids and liquids. Such chemical analysis has been investigated over the last four decades, but has only recently become generally accessible through the introduction of low-cost, microwave solid-state devices. The theory is reviewed, for both pure and mixed substances, to show the link between the electrical and chemical approaches. The principles, hardware and chemical physics of microwave rotational spectroscopy for multicomponent gas analysis are discussed. Microwave permittivity measurements as applied to two component mixtures are described with particular reference to the determination of the moisture content of natural products. Remote sensing of hydro-meteors is attracting increasing attention, especially in regard to propagation of microwaves in the millimetre regions.
Algorithms for digital control
Authors: Forsythe W.
Published: August 2008

This paper presents a new method of deriving a digital algorithm to represent a given continuous transfer function. It has the advantage over other methods currently in use that computation time may be taken into account, if required, when deriving the coefficients of the algorithm. This is often necessary in on-line control, for example. The same feature makes the method especially useful when interpolation or extrapolation is needed, and when dealing with dead time.
Signal processing for automatic optical su rface inspection of steel strip
Authors: Hill W.J. , Norton-Wayne L. , Finkelstein L.
Published: August 2008

This paper reports on a continuing collaborative research project involving the Instrument Systems Centre (now the Measurement and Instrumentation Centre) of the City University, the British Steel Corporation, and the Sira Institute, and concerned with automatic optical surface inspection for cold rolled steel strip. The steel surface is interrogated by a high-speed laser scanning system and the resulting multi-channel response signal is processed to achieve detection, delineation (ie, boundary extraction), and identification (by type) of significant surface defects. Processing is organised in a hierarchy, using multiple matched filters and modified image processing operations for detection and delineation, and the techniques of automatic pattern recognition for identification. Extensive studies in computer simulation are described for the development and evaluation of this processing system. The resulting structure is relevant to many similar problems of plain surface inspection.
Resolved motion rate control of a materials-handling machine
Authors: Hewit J.R. , Love J.G.
Published: August 2008

Resolved motion rate control - a technique developed for controlling robotic manipulators - is applied here to an industrial vehicle used for the handling of materials.

An on-board microprocessor is used to compute trigono metrical transformations necessary to achieve co-ordinated movement of servo-valves which control the hydraulic cylinders.

It is shown that, by this method, the operator's task is significantly eased, bringing potential benefits in speed of operation and safety.
Sampling systems for on-stream x-rayanalysers in ore-dressing plants
Authors: Hughes D.V.
Published: August 2008

Sampling systems for on-stream analysers in ore-dressing plants must be designed to take into account the requirements of the analyser and the conditions prevailing in the process.

The accuracy of the analysis provided by the analyser is determined by process factors such as ore type and grinding. For process control and development, the required sample accuracy is a relative sampling error less than 1%.

Static primary samplers give acceptable accuracy for normal sulphide ores up to a particle size of 85% - 150μm. This covers the needs of most small-to-medium size concentrators. The size of the sample error in static samplers is discussed.

Other methods available are immersion of the analyser probe and the use of automatic samplers. Experience of both is reported.
Whole-cycle control of AC power to small electric heaters
Authors: Fenna D.S.
Published: August 2008

When a triac is used to control the flow of AC power to a heater, burst control is preferred to phase-angle control, but cannot be used if the thermal system reacts quickly to changes in heat input. This paper describes an arrangement which allows zero-voltage triggering of the triac, so avoiding the problems associated with phase control, but is usable with plants whose thermal time-constants are as short as 5 s (with 50Hz supply) or less. Its hardware requirements are no more than those of burst or phase control. Schematic circuits are given for use with both digital and analogue control systems.
Errors in th e simulation of pressure transients in a hydraulic system
Authors: Maudsley D.
Published: August 2008

The describing dynamic equations for pressure transients in a closed pipe are non-linear partial differential equations. No closed form of solution exists and, consequently, simulation techniques must be used to effect a solution. The partial differential equations must be discretised, at least to ordinary differential equations using a finite difference scheme. It is shown in the paper that finite differencing introduces a source of error into the simulation. The errors takes the form of different frequencies of a disturbance being propagated through the finite difference scheme with a shift in phase and attenuation from the true solution. It is shown that, for a linear system, the distortion can be quantified. Errors can be minimised by a correct choice of the number of discrete segments. A simple example of a non-linear system is included to illustrate the technique.
Factors affecting the reliability of microelectronics in severe offshore environments
Authors: Buchanan G. , Whittington H.W.
Published: August 2008

The feasibility of large, unmanned, offshore wind and wave energy convertors will be greatly enhanced by the availability of highly reliable electronic systems to provide on-board control and condition monitoring systems. However, there is a danger that the extreme environmental conditions found offshore will adversely affect the reliability of electronic systems.

This paper quantifies the reduction in reliability to be expected due to the offshore environment and also compares the environmental effect with all other known factors which can reduce the reliability of electronic components and systems.

It is concluded that, important as the environmental factor is, its effect can be swamped by other factors such as equipment temperature and packaging technique. The design of reliable electronic systems for use offshore is possible without incurring military-type costs by following a few basic design rules. Ideally, offshore systems should be designed from the component level up, following these rules, rather than by simply sealing 'onshore systems' in watertight boxes.
Optimal control of the activated sludge process
Authors: Marsili-Libelli Stefano
Published: August 2008

This paper assesses the potential benefits of optimal control applied to the activated sludge wastewater treatment process. The optimal control approach is motivated by the need to compromise between treatment efficiency and operational costs. In this sense this approach differs from a previous activated-sludge control scheme, in which only control effectiveness was taken into account. Two separate control problems are addressed, with differing scope and methodologies, but still in the optimality context. Dissolved oxygen control is considered first, and a discrete-time optimal output regulator is designed. Then the attention is focused on recycle sludge manipulation for which two different feedback schemes are evaluted. From the simulations it appears how the effectiveness of a control scheme depends almost entirely on a proper choice of the cost functional.
Application of a computer to asymmetric flow measurement in circular pipes
Authors: Salami L.A.
Published: August 2008

Experimental investigations into asymmetric flo w measurement are usually found to be time consuming and the results generally inconclusive, especially if the error being investigated is within the limits of the accuracy of the ultimate flow measuring device used in the investigation. Therefore, a computer method has been developed in which asymmetric flow measurement has been studied using theoretical velocity profiles. The basic conclusions of the approach have been found to be in agreement with the experimental evidence. Apart from the considerable savings in time, it has also permitted areas in asymmetric flow measurement, which have been hitherto very difficult to investigate experimentally, to be tackled.
Optimisation methods for economic dispatch in electric power systems
Authors: Sterling M.J.H. , Irving M.R.
Published: August 2008

The application of constrained optimisation methods to the problem of economic dispatch in power systems is considered, and a unified presentation of problem formulations and appropriate solution methods is given. In particular, the methods of merit-ordering, linear programming, quadratic programming, and recursive quadratic programming are described. It is shown that the application of increasingly sophisticated methods leads to a more secure and economic dispatch of power generation. Experience with computer optimisation is presented, and the various methods are compared in terms of computational overhead, accuracy of modelling, availability of appropriate measurements, and suitability for networks of different sizes and characteristics.
Optimisation and analysis of gas supply networks
Authors: Lo K.L.
Published: August 2008

This paper reviews the methods of gas-flow analysis and defines the optimisation problems in the gas engineering field. The formulations involving the two principal solution methods to the optimisation problems are given. These are the linear programming approach and the non-linear programming approach. The choice of solution methods and their relative advantages are discussed The final section of the paper deals with a possible future area of research with regard to hierarchical control in the gas engineering field. The discussion concentrates on methods of decomposition and possible computer configurations.
Leakage reduction by optimised control of valves in water networks
Authors: Sterling M.J.H. , Bargiela A.
Published: August 2008

The problem of minimisation of leakages due to overpressure in a water distribution network is considered, and an algorithm for computation of the optimal valve controls based on the sparse revised Simplex method is presented. Computational experience indicates that the method has low memory and processor time requirements and is suitable for online implementation on minicomputer systems. The economy of the optimal valve control policy is shown by comparison of the volume of leakages for uncontrolled, manually controlled and optimally controlled networks.
A multivariable controller with self-selecting of setpoints for an industrial compressor set
Authors: Boutton C. , Richards R.J.
Published: August 2008

A compressor control system simulation is described. Multivariable control algorithms are used, with switches in controller gain to compensate for nonlinearities and to allow a wider operating range. A novel feature is the selection of setpoints inside the control algorithm to allow rapid disturbance rejection, and gradual recovering of efficient operation.
On-line mass spectrometry: a review
Authors: Scrivens J.H.
Published: August 2008

The technique of on-line mass spectrometry is placed in its historical context indicating how increased reliability of vacuum systems and electronic developments have led to its reinstatement as a viable on-line analytical tool. The basic principles of mass spectrometry are discussed, indicating how the instruments may be classified with reference to their source, analyser and detector components. The advantages of using mass spectrometry for process analysis are discussed.

A survey of the literature concerning on-line mass spectrometry is given, indicating its range of applications. The current limitations of the various types of commercial instrument available are discussed, and some opinions are expressed as to the likely future development of the instrumentation.

Computer control and data processing are particularly relevant in this technique, and a review of current philosophies is undertaken together with an indication of their implications in the cost and efficiency of a total instrument package. A view is expressed of the current status of the technique as a practical process instrument indicating maintenance calibration and technical supervision requirements.
Correction of pyrometric measu rements of fu rnace tu be temperature: a viable proposition
Authors: van Oorschot B.P.J.
Published: August 2008

The systematic errors that occur during furnace tube temperature measurements with pyrometers can be very large indeed. The feasibility of using a correction technique to compensate for these systematic measurement errors is evaluated. It is concluded that it is not possible to realise this objective in practice. However, a qualitative assessment of the magnitude of these systematic measurement errors can be made by means of a simple mathematical model; the model is described.
The measurement of air-flow characteristics using a five-hole Pitot probe in conjunction with a microcomputer
Authors: sahin B. , Ward-Smith A.J.
Published: August 2008

The use of a five-hole Pitot tube in conjunction with a microcomputer for the experimental investigation of air-flow patterns is described. The paper discusses the use of the equipment for the measurement of local velocity, static pressure and flow direction in non-uniform three-dimensional flow fields.
Model reduction for closed-loop performance
Authors: Thompson S.
Published: August 2008

This paper presents a procedure for finding reduced order SISO models which will have similar closed-loop characteristics to those of the original system. The reduction method is based on frequency data which are fitted using Levy's complex-curve-fitting technique. When appropriate, a time delay may also be introduced into the reduction. All the procedures have been incorporated into a package of microcomputer programs.
Modelling sampled-data systems: a historical outline
Authors: Bissell C.C.
Published: August 2008

The earliest attempts at mathematically modelling the behaviour of sampled-data control systems appear to have taken place in the first decade of this century in the context of steam engine governing. This early work is reviewed, and the appearance, immediately after the 1939-45 War, of a mature theory of sampled-data signals and systems is discussed.
Positive-displacement meters for liquids
Authors: Baker Roger C. , Morris M. Vivien
Published: August 2008

After brief descriptions of the most common industrial types of meter and a review of the relevant literature, various aspects of a typical meter are analysed. These include the effects of temperature, pressure and orientation. A governing equation is derived and the behaviour of calibrators is analysed.

Dimensions of a typical meter design are used to obtain values for coefficients in the governing equation and the expansion due to changes in temperature and pressure. Consideration is given to the causes of 'back-slip'. The paper includes a general discussion of instrument accuracy, slippage tests and the use of the derivations for developing a computational prediction.
Extraction of symmetrical components in the presence of harmonics
Authors: Vasu E. , Sankaran P. , Rao V.V.B.
Published: August 2008

A new microprocessor-based symmetrical component analyser, readily useful for power system application under non-sinusoidal conditions, is described. Use of simple look-up table saves time otherwise required for software multiplication. The instrument stabilises within one cycle of the wave and provides as output the sequence components of the fundamental. Experimental results demonstrating the utility of the instrument are presented on a model system with fifth-harmonic being allowed in the unbalanced 3-phase currents.
The detection and location of foreign metal objects i n conveyed products
Authors: Abbas H.J. , Brewster R.L.
Published: August 2008

The efficiency of materials-processing plants can be seriously affected by the presence of foreign metal objects in the process material. Such objects can arise from machine damage or by contamination before processing begins. The work was originally motivated by a requirement to detect the presence of tramp iron in coal for use in electricity-power generating stations to prevent damage to coal-crushing machinery. There are many other applications, however, in which contamination by metal objects may have serious repercussions.

This paper describes an inductive-loop detector apparatus that not only detects the presence of metallic objects but is also able to discriminate between ferrous and non-ferrous objects and to locate the position of the object on both the length and the width of the conveyor belt. This permits ferrous objects to be located within non-ferrous metals and vice-versa, and also makes the removal of the object a relatively simple matter.

Details of the loop design are given, together with details of the signal processing required to give the type and position information relating to the foreign metal object. Some results of tests carried out on the laboratory prototype are included at the end of the paper.
Multi-axis step motor control
Authors: Dunlop G.R.
Published: August 2008

The problems associated with step motor driven multi-axis numerical control machinery are examined. Commensurate positioning on two axes is discussed in detail and the results are extended to the control of step motors on six or more axes. A controller design based on a microcomputer and a single VLSI peripheral circuit for each pair of controlled axes is presented. This results in a considerable hardware saving as well as reducing the computational requirements for the numerical control machinery.
Modelling of bioreactors
Authors: Howell John A.
Published: August 2008

Biochemical reactors pose special problems in that they are essentially concerned with living systems. The consequences of this is that the bio transformations are complex and require detailed consideration, especially since instabilities can easily occur if the concentration of species is not controlled carefully. A discussion of the issues is presented and the principal factors identified. This is then used as a basis for analysing the dynamic models suitable for state variable models for on-line computer control.
A method for the identification of system modes
Authors: Brandin B.A. , Hind E.C.
Published: August 2008

A frequency-response method allowing the identification of system modes, given the system transfer function (or Bode diagram), is presented. The method has been developed as an integral part of a controller tuning technique based on the recursive identification of the most oscillatory mode of the systems to be tuned. The method is based on the Bode diagram of the system to be identified and uses the rate of change of phase angle with frequency. Its implementation and limitations are discussed and a numerical example is given. The method is referred to as the 'slope method for identification',
The dynamic modelling of differential pressure transmitters
Authors: Cartledge Jane , Bentley J.P.
Published: August 2008

The paper describes the dynamic modelling of two force-balance differential-pressure transmitters, one pneumatic and one electronic. In both cases an experimental transmitter transfer function is found from frequency response tests. This is then compared with a theoretical transfer function calculated from the differential equations describing the principles of transmitter operation.

The theoretical transfer function for the pneumatic transmitter is fourth order; there is reasonable agreement between theoretical and experimental transfer-function coefficients. A more detailed model of the adjustable fluid damping mechanism is necessary for closer agreement to be obtained. The theoretical transfer function describing the electronic transmitter is third order, with close agreement between experimental and theoretical transfer-function coefficients.

The bandwidth of the electronic differential-pressure transmitter tested was between 0 and 0.3 Hz compared with a bandwidth of between 0 and 3 Hz for the pneumatic transmitter. This large difference is mainly attributable to the electronic transmitter having a larger damping constant and a demodulator low-pass filter with a long time constant.
A survey of recursive identification algorithms
Authors: Hunt K.J.
Published: August 2008

The paper gives an introduction to and comparison of the four recursive identification algorithms most commonly used in self-tuning control. The paper demonstrates that the algorithms are very similar, and a simple simulation example is used to compare the algorithms and to give some insight into the suitability of each method for a particular problem. Choice of algorithm is seen to depend on four factors: model complexity, noise/signal ratio, convergence rate, and computational expense.
Characteristics of the twin-wire resistance-probe water manometer
Authors: Liu C.Y. , Ng K.L. , Poo A.N.
Published: August 2008

This paper investigates the practicality of using depth probes in the two arms of a water manometer for measuring pressure differences. The main feature of the design is the capability to measure low-pressure differences, accurately, at low cost. From the extensive performance tests conducted, it is found that the output voltage from the resistance-probe manometer is linearly proportional to the difference in pressure. A sensitivity and accuracy of measurement of 50 m V/mm and 0.5 Pa (about 0.05 mm of water), respectively, have been achieved. Good linearity and low drift have also been observed.
Limits of detection of ion-selective electrodes: theory and practice
Authors: Midgley D.
Published: August 2008

The limit of detection of an ion-selective electrode is usually described in the literature in a far less rigorous way than is practised for other techniques of chemical analysis. There is no need for this discrepancy either theoretically or practically, since electrodes are used for the analysis of highly pure waters at concentrations below those implied by the conventional 'limit'and their sensitivities at extreme dilution can in many cases be predicted theoretically from the known chemistry of the system. Near the limit of detection the emf of an electrode no longer changes in a Nertistian manner, i e, in proportion to log (concentration), and other calibration functions are described. The performance characteristics of commercial ion-selective electrodes are summarised and briefly discussed.
Effects of processing conditions o n platinum resistance temperature detectors
Authors: Atherton A.
Published: August 2008

Routine control of platinum resistance temperature detector manufacture includes (among many other factors) surveillance of resistance values, typically at 0° C (R0) and 100° C (R100) , on the finished product, In addition to the use of such measurements in applying acceptance and selection criteria, careful inspection of these data can also provide some insight into the nature of certain systematic changes in R0 and R100 produced by manufacturing procedures or by other, subsequently imposed, processing conditions. There exists, therefore, the possibility of monitoring systematic effects as a means of assessing improvements in product consistency brought about by process developments or as a diagnostic technique for incidental fault conditions that may have arisen. This paper presents analyses of various sets of production-related and experimental data to illustrate the extent to which systematic changes in R0 and R100 can occur under various circumstances. Exploitation of this type of information is not discussed in detail because of its dependence upon various interacting conditions and material properties that are specific to each case.
Education and training of engineers and scientists in measurement and instrumentation in relation to metrology
Authors: Finkelstein L.
Published: August 2008

The paper presents an analytical view of the education and training of engineers and scientists in measurement and instrumentation in relation to metrology, It discusses the process of formation and the way in which metrologisis are formed. It emphasises the role of applied physics and of measurement and instrumentation technology in their formation. It discusses the nature and scope of the latter as a teachable discipline.
The scope of metrology in industry and manpower needs
Authors: Jones O.C.
Published: August 2008

A modern industrial society depends upon the availability of a sound metrological infrastructure for its success. In the UK this is provided by the metrologists and standards laboratories that contribute to the National Measurement System. Although it is known that the total cost of measurement activity is very high, there is a surprising dearth of detailed information about the numbers of metrologists in the NMS, their qualifications, and the roles that they play. Consequently, although there is general agreement as to the existence of a shortage of skilled metrologists, it is not clear what should be done to rectify the situation.

In this paper the role of the metrologist is first briefly discussed. It is concluded that recent rapid advances in technology have created the need for a new breed of gnetralagist, who must combine the traditional skills of his predecessors with a more flexible approach and a greater breadth of coverage. He must also be computer literate. Estimates are then presented for both the total number of metrologists in the NMS and the number that should be trained annually.
A low-order modelling method for Z-domain transfer functions
Authors: Morgan C.
Published: August 2008

When digital computer-based parameter estimation techniques are used to identify linear, dynamic systems, the results are usually obtained in the form of a high order Z-domain transfer function. For many practical applications, however, a model transfer function of second or third order is sufficient to represent the prominent features of the system dynamics.

A computationally simple transfer function reduction method, based on the Matsuburu time delay theorem, is presented herein. This method is compared with a recently reported Padé approximation approach in both the time and frequency domains.
A spatial distribution of light intensities as a monitor of refractive index
Authors: Thomas E.
Published: August 2008

The results of earlier experiments suggest that a linear relationship exists between the optical signal passing through liquids in the refractive index range 1.3 to 1.6 when the liquid couples two multi-mode optical fibre cables, An analogue transmission system has been constructed, with a solid state camera and a computer as the basis of the detector system, in order to examine in detail the emission from the receiver optical fibre cable. The measurements obtained and the empirical equations deduced from them, suggest the possibility of an intrinsically safe technique for monitoring the refractive index of liquids that are non-absorbent in the red region of the optical spectrum.
The effects of an air pocket on the performance of a twin-wire resistance probe manometer
Authors: Tou S.K.W. , Liu C.Y. , Ng K.L.
Published: August 2008

An alternative design of twin-wire resistance probe manometer uses air trapped in one manometer tube to permit differential pressure measurements. The paper investigates the effects of initial size of trapped air pocket and its thermodynamic properties on the performance of the manometer, and suggests a calibration curve.
Modelling and microcomputer control of a nonlinear pneumatic servomechanism
Authors: Chiu P.C. , Leung T.P.
Published: August 2008

A mathematical model is proposed for a low-pressure experimental pneumatic servomechanism which exhibits hysteresis characteristics at the torque motor and the servo spool valve assembly, nonlinear mass flow through the spool valve opening, and friction at piston and rod-end seals. Systems parameters are determined experimentally and correlated empirically. A single-board microcomputer is used for both servomechanism control and data acquisition purposes. The model predicts the experimental responses of three control algorithms with good accuracy. In particular, the response of PD with hysteresis compensation control shows no overshoot and minimal steady-state error when a step change of reference input is applied.