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In this paper, the effect of the method of control on the transfer function of two-phase servomotors is investigated. The methods of control considered are the amplitude, time-phase, frequency, voltage-frequency, pulse-width and space-phase control. Torque equations are derived for different methods. The motor gain and time-constant are determined from the torque-speed and speed-signal characteristics. The servomotor torque, speed, time-constant and gain — and their dependence on the signal magnitude — are compared for the different methods of control. It is shown that for the same value of the signal, the motor time-constant may vary between 2·2 msec and 45 msec and the gain may be increased six times if the method of control is changed.

This work forms part of a study into reflection behaviour within a duct directed towards the understanding of the problems associated with metering pulsating gas flows. A novel application of correlation analysis is used to predict the shape of the reflected wave from an opening of finite thickness. The incident wave is in the form of a pseudo-random binary sequence pressure pulse sequence which enables incident and reflected waves to be distinguished one from the other. It is shown that for waves of small amplitude, reflections do not occur in like shape to that of the incident wave. These shapes are influenced by both the amplitude of the incident wave and the geometry of the opening. It is believed that this technique makes an original contribution to the study of reflection behaviour and the use of correlation analysis.

For some years the Authors' company has engaged in the design and manufacture of closed-loop hydraulic control systems. The hydraulics form a high performance system of considerable power. But the control is exercised electrically through the agency of a servo valve. This note describes the development of an electronic system for this application. Although originally rather specialised in purpose, the system has in the course of development become universal. Advantage has been taken of recent improvements in electronic techniques and at the time of writing the system is as advanced as any. Nonetheless, the speed at which electronics develops nowadays is such that some parts of the system may get outdated, and superseded. It has already happened once in the course of the work that a major invention the Integrated Circuit — has made obsolete an entire concept using discrete components before the development was complete. The same can happen again.

In the optimal control of any physical process about its operating point, a requirement of prime importance is the identification of the process parameters. This requires the realisation of both the static and dynamic characteristics of the control system. A method of identifying multi-variable non-linear systems is presented in this paper. The method uses correlation techniques around the tracked operating point of the system. The correlation method uses several uncorrelated maximal length (pseudo-random) sequences of small amplitude as test signals. This facilitates on-line identification during the normal process operation. A further advantage of this method is that a system identification may be made in the presence of noise and other inherent disturbances. The technique is first applied to a multi-variable system containing cubic non-linearities and then to one containing four hysteresis elements. Finally, an identification was made of the non-linear cross-coupling dynamics between the roll and yaw axes of an aircraft.

To extend the range of usefulness of a water calibrated metering constriction in the field of gas flow measurement, a method is described for determining the expansion coefficient (∈) which does not involve measurement of gas flow rate, while the precision of the method is such as to achieve accuracy tolerances of the order ±0· 30%. When used in conjunction with flow coefficients appropriate to incompressible flow, the flow coefficient appropriate to compressible flow is determined with an overall tolerance well within the limits ±0· 5% over a range of ∈ of 1 > ∈ > 0· 90.

Results are presented showing how the performance of wedge-probes at low Mach number may be affected by the geometry of the front pressure tapping recess in the leading edge and also by the shape of the leading edge.

Low carbon soft iron is used in the manufacture of relays. An instrument is described which can grade the coercive force of such steel with a minimum of sample preparation. Satisfactory correlation is found between results obtained from the grader described and classical testing methods.

A control model of accommodation and convergence has been developed further, in accordance with the physiology of the eye. It is argued on control theory grounds for accommodation, and more tentatively for convergence, that effort is able to be exerted on both sides of a resting point which lies at an intermediate position between the extremes of the range. Thus convergence and active divergence, in addition to positive and negative accommodation, are examined.

A résume of the theory of fluid flow measurement is given in a concise manner. The statistical method of evaluating overall system accuracy is discussed and the standard deviation values for various sources of error are quantified. The results of calculations using the formulae and quantitative data are presented graphically to indicate the accuracies for different methods of measurement at different rates of flow. Other likely sources of error are discussed.

A method is described to overcome the errors in diode function generators when operating at voltages considerably lower than the maximum, without a significant increase in the number of sections required. The technique, based on varying section length, produces a maximum error in each section which is nearly a constant percentage of the local value. An application of this to the production of a square root network is analysed in detail and the results are presented in graphical form to allow the designer to select a combination of accuracy and the number of sections for any particular problem. Several units have now been constructed using commercial components and the experimental results are in excellent agreement with the predicted values of error. The method has been found to be a simple and inexpensive way of producing fixed function generation with a considerable improvement in accuracy.

A review of some previous studies of pulsating air flow through orifices in pipes is presented. In particular, the authors comment on the significance of inertia effects, the use of Strouhal number as a non-dimensional parameter, and the effect of phase change on time-dependent variables. Attention is drawn to the possible importance of the previously neglected interaction between the effects of orifices as acoustical filters and as meters of pulsating flow. Using complex variable analysis, a theoretical model based on plane acoustic waves yields, for resonance conditions, relationships between frequency, pressure and geometry variables. These were investigated experimentally for a 1-in diameter pipe with different orifice diameters for a range of frequencies up to 180 Hz. The results indicate that accurate derivation of mass flow rates from pressure measurements across an orifice in a pipe depends on taking into account the effects of wave action at all frequencies. This would avoid the rig-dependent limitations to which experimental work on pulsating gas flow through an orifice in a pipe is subject.

The use of interferometry for heat transfer studies enables a complete field of view to be quantitatively examined at one time without disturbing the temperature distribution being measured. The Mach-Zehnder interferometer described has an elliptical field, with a 15cm minor axis and is capable of accommodating test chambers 102cm in length using the full field of view. The sensitivity of the instrument for various air pressures and temperature distributions within the test cell has been evaluated. The use of the instrument for identifying isotherms in the neighbourhood of a heated slab supported on skid bars is described. A Moiré technique which eliminates the effects of imperfections in the interferometer plates has also been used.

La vulnerabilidad de un asentamiento ante cualquier situación y ámbito territorial, es una preocupación, debido entre otras cuestiones a su fuerte influencia en las políticas de desarrollo de gestión frente a desastres o eventos adversos externos que afectan el normal desarrollo de las personas; de ahí que diagnosticar la calidad ambiental de una urbanización en áreas espaciales específicas, como es el caso de las urbanizaciones periféricas, posibilita analizar aquellos factores que influyen en la vulnerabilidad de estas y formular recomendaciones para implementar políticas ambientales que mitiguen los riesgos. Partiendo de que la vulnerabilidad es una noción dinámica que examina los factores de riesgos, se presenta un instrumental para la evaluación ambiental de los Asentamientos Poblacionales Periféricos (APP), en las condiciones particulares de la ciudad Santiago de Cuba, donde se ha considerado esta componente dentro de sus indicadores evaluativos. Se expone el instrumental de referencia y su sistema categorial: variables, subvariables; parámetros evaluativos y escala de valores, lo que constituye la esencia del instrumental teórico diseñado; de igual forma se presentan los histogramas y matrices que conforman el instrumental práctico de evaluación. El mismo servirá para evaluar asentamientos en funcionamiento y para el diseño de nuevos, pudiendo ser generalizado a otros territorios. Palabras claves: Asentamientos poblacionales periféricos;calidad ambiental; vulnerabilidad.The vulnerability of settlement before any situation and territorial scope, is a concern, due inter alia to their strong influence on the development policies of management to disaster or adverse external events affecting the normal development of the people; Summary to diagnose the environmental quality of urbanization in a discrete space, as it is the case of the peripheral housing estates, allows analyze those factors that influence the vulnerability of these and make recommendations for implementing environmental policies that mitigate the risks. On the basis of that vulnerability is a dynamic concept that examines the risk factors, continues an instrumental for environmental assessment of settlements population peripherals (APP), in particular the conditions of the city Santiago de Cuba, where it has considered this component in its evaluative indicators. You expose instrumentation reference and his categorical system: variable, subvariables, evaluative parameters and scale of values, which is the essence of the instrumental designed theorist; likewise are histograms and arrays that comprise the instrumental assessment workshop. It will serve to assess settlements in operation and for the design of new ones, and can be generalized to other territories. Key words: Peripheral population settlements; environmental quality; vulnerability

El proyecto se basó en el diseño y montaje de una planta piloto para la extracción química de Quitina y proteínas a partir de desechos de crustáceos (camarón y langostino). Se determinó el contenido de humedad del material y las condiciones experimentales óptimas de volumen y concentración de los reactivos involucrados en el proceso. Además, se realizó un análisis técnico y económico del mismo. Los resultados mostraron que la materia prima tiene un alto contenido de humedad entre 68-80% y que las condiciones experimentales para la obtención de Quitina dependen fuertemente de las características del material. Bajo estas condiciones se obtuvo una recuperación mayor del 98% para el caso de caparazón de camarón y de aproximadamente un 58% en el caso del langostino. Por otro lado, para la extracción de proteínas se encontró que la mayor producción ocurre a pH 4.0 y con soluciones provenientes del proceso de desproteinización, sin trituración previa de la materia prima. El estudio técnico proporcionó información básica sobre los costos e inversión del proceso operativo, datos sobre las instalaciones y los equipos asociados al proceso productivo. El análisis económico mostró que se debe tener una inversión inicial de US $ 10,520.94 para el montaje de la planta piloto y de US $ 4,852.58 para gastos de transporte y operación por seis meses. Palabras claves: caparazón de camarón; langostino; método químico; planta piloto; proteínas, quitina.DOI: http://dx.doi.org/10.5377/nexo.v22i2.42Nexo: Revista Científica Vol. 22, No. 02, pp.45-55/Diciembre 2009

Al implementar y desarrollar proyectos con intervención en los recursos naturales los cuales presentan problemas de uso y escasez, normalmente existe competencia entre usuarios y portadores de interés. La Gestión Integral de los Recursos Hídricos, promueve el uso, desarrollo y seguimiento coordinado del recurso e integra el enfoque de involucramiento de actores claves. En la ejecución del Proyecto TwinLatin (Hermanamiento de Cuencas) se retoma el concepto de participación ciudadana y la cuál se aplicó durante todas las fases de la investigación. Asimismo se desarrollaron métodos cualitativos, tales como diagnósticos, talleres, entrevistas y conversatorios. Involucrando activamente en diferentes niveles a los actores que tienen incidencia en la protección de la cuenca. Palabras claves: Gestión integral; recursos hídricos; involucramiento; actores; participación ciudadana.DOI: http://dx.doi.org/10.5377/nexo.v23i1.36Nexo: Revista Científica Vol. 23, No. 01, pp.27-32/Mayo 2010

Safeguards, for costly and hazardous chemical plants, are often provided by means of alarm or automatic shutdown systems. The adequacy of this protection—which is a measure of the capability of the newly installed system in shutting down the plant on the occurrence of a hazardous condition, and its effectiveness over the long term (its reliability)—may be judged by an independent safety assessment. Both qualitative and quantitative aspects of safety analysis are involved in an assessment, the quantitative approach being of particular use where there is a need to compare the anticipated reliability of the proposed system with a numerically specified, reliability requirement. Some of the techniques used in the assessment procedure are discussed in the paper and, by way of example, the performance of a typical shutdown system is assessed and its adequacy judged against a hypothetical plant fault condition.

A technique suitable for the rapid synthesis of the duplicator class of feedback control systems is developed. Simultaneous requirements of maximum percentage overshoot, bandwidth and velocity constant, such as commonly specified in instrument servomechanisms, are satisfied by the technique, which uniquely defines the compensation terms required to satisfy the specification. The techniques make use of the fact that many feedback control systems, irrespective of order, are dominated by a few system poles and zeros, and therefore places either one system zero, and two system poles, or an integrating dipole and two system poles in the dominant part of the s plane. Straight-line approximations to the Bode plot of amplitude ratio only are used in conjunction with a dummy transfer function, the coefficients of which are obtained directly from the performance specification by means of a universal chart. Digital computer results are given in verification of the accuracy of the technique.The approach is sufficient for the design of feedback control systems for which a linear or small perturbation model is adequate, provided the open loop dynamics can be approximated by the straight-line Bode plot. If the small perturbation model is inadequate, but a linear design approach is still chosen, the technique may be used to define trial systems for subsequent detailed nonlinear studies on the analogue computer.

The main concern is with the applications of a radar dopplermeter which has recently become available. Laboratory trials have been carried out to investigate its use in the process industries especially as a potential interrogating unit in a control system. Useful features, and some of the disadvantages are exposed and comparisons are made between dapplermeters using radar and laser sources. These and other techniques are under patent application.

Instruments and systems developed at the Water Pollution Research Laboratory and elsewhere, for the continuous measurement of those parameters which are of most significance in water pollution research are discussed. Particular attention is given to instruments and systems which are also of value in sewage-works operation or in the water-quality monitoring stations now being set up by River Authorities and the Water Resources Board. Recent developments such as equipment for monitoring organic matter and ammonia are described and the commercial availability of equipment based on developments at the Laboratory indicated. The possible value in this context of the recently available specific-ion electrodes is also considered.

Examination of trends during the past 30 years shows that human engineering principles, when overlooked or suppressed, had to user reaction which must be heeded if optimum design is to be obtained. Data is presented to show that when the instrument becomes too small or too large there is a noticeable user reaction. For example, many users appear to demand process instruments that are larger than those permitted by the German DIN system of dimensions which was decided many years ago, before the widespread use of process control instruments. Electronic and digital techniques do not change fundamentals of human engineering but widen the scope for data presentation. As operators are a continuing requirement the paper considers some of the questions awaiting answers in the areas of display and total system reliability.

A method of designing controllers for multivariable systems is described which regards the problem from an implicit reference model point of view. The rules for the design are found to be very simple to apply and involve only proportional and integral terms if all the system state variables are available. The method is demonstrated by means of two examples, one being a second order system with two inputs and two outputs, the other being a fourth order system also with two inputs and two outputs.

The equivalent gain concept of a mono-variable non-linear stochastic process is used to evaluate the linear matrix equivalent of a multi-variable non-linearity having n independent inputs and m outputs. It is shown that if the n inputs are restricted to separable class of processes (which includes Gaussian random signals and also sinusoidal wave forms but is much wider), then the distortion terms produced by the non-linearity and by cross modulation have zero cross-correlation with any of the input signals.

The common distributed parameter thermal processes that can be modelled by the cascade of a time constant and a transit delay (ie: boilers without superheaters, furnaces, ovens, vats, torches, fluidised beds, etc) are discussed. These are often multiposition controlled by solenoid valves, tapped transformers and similar discontinuous control elements. It is well known that if controller sensitivity, process gain, process parameters, and transducer locatons are arbitrarily combined these processes can exhibit instability. Over the years empirical design rules have been developed to determine such critical parameters as process gain, controller sensitivity, transducer type and location and the like. This paper uses a describing function approach to establish a facile technique for determining the stability criteria of such processes in terms of the controller parameters. This is then developed into a graphical display that gratly simplifies the design procedures associated with thermal processes and their control and instrumentation.

The equations of motion for the rotameter and turbinemeter are derived and the errors resulting from pulsating flow are investigated. Measurements of errors are given and the application of the results to practical problems is indicated.

Flow velocity can be derived directly from the transit time of natural turbulence signals between two transducers spaced along the direction of flow. The transit time is determined by cross-correlating the transducer outputs with either a special purpose correlator or an on-line computer. Advantages are that the time delay can be measured absolutely by the correlator, the flowmeters are relatively insensitive to the effects of up-stream disturbances, the transducers do not obstruct the flow, and suspensions and slurries can be metered. Results are presented for flow measurement of sand/water slurries using electrical conductivity and ultrasonic transducers, and for heavily loaded gaseous suspensions using capacitance transducers. A low cost mass flowmeter has been devised in which the mass flow of solids in a pneumatic conveyor is derived from measurement of variations in concentration intensity due to turbulence. Results are given for mass flow measurement of foodstuffs (flour, wheat and beans), pulverised fuel, cement and chemicals.

A qualitative model of an autonomic effector control loop is presented, showing the components of information transmission. With reference to the pupil-light reflex and accommodation it is argued that injection of drugs such as pilocarpine forms an input to the forward loop of the system, whereas drugs such as DFP and cycloplegics cause a change in gain. In these terms their effect on accomodative-convergence may be understood. Competition between certain miotic drugs as well as dose-response non-linearity is explained by reference to the model. It is proposed that under some conditions, properties of the open-loop system are responsible for denervation-sensitization.

An analytical solution to the batch distillation equations for packed columns is presented. The dynamic model thus formed has been compared with experimental results for a 4-inch packed column separating a binary mixture. The computer time for a solution was only a few seconds, thus rendering the model useful for on line optimisation purposes.

Of all gases oxygen plays a unique part in human existence. Without it, life as we know today, could not exist. The nature and the measurement of oxygen has, therefore, always been a challenge to scientists throughout the ages. Modern technological advances, both in industry and medicine, over the past quarter of a century, have resulted in demands for increased accuracy in oxygen measurement. The application of oxygen analysers ranges from the measurement of the atmosphere inside an incubator containing a premature baby, to the monitoring of oxygen content in the process streams on giant chemical plants to ensure safe operation.

La presente investigación consistió en el diseño y aplicación de una metodología para la evaluación de la calidad del medio construido en asentamientos humanos urbanos. El proceso metodológico inició con el establecimiento del estado del arte sobre la materia, destacando los aspectos conceptuales sobre la sustentabilidad como máxima aspiración a lograr en la evaluación de un asentamiento y determinando los componentes significativos de la problemática objeto de trabajo. Posteriormente se caracterizó el sistema vigente de asentamientos urbanos en Nicaragua y se determinaron los asentamientos objeto de estudio. Se identificaron las clasificaciones tipológicas existentes sobre los asentamientos humanos urbanos nicaragüenses, las cuales se completaron mediante la propuesta de una nueva forma de agrupación según la estructuración de los componentes, lo que permitió la selección de los asentamientos donde se aplicó el instrumental. A continuación se desarrolló la metodología de evaluación conformado por el instrumental teórico, los histogramas de evaluación ambiental y las matrices de evaluación de la calidad. Se finalizó el proceso de validación del instrumental diseñado, aplicándose a cuatro asentamientos seleccionados, con base en una muestra del 5% del total de asentamientos de la zona de estudio elegida. Se valoraron los resultados obtenidos, relacionándolos con otros análisis del área, lo que posibilitó demostrar su efectividad y eficacia. Palabras claves: asentamientos humanos urbanos; hábitat urbano; medio construido; calidad ambiental.DOI: http://dx.doi.org/10.5377/nexo.v22i1.41Nexo: Revista Científica Vol.22, No.01, pp.23-31/Agosto 2009

In a brief period, lasers have developed from curiosities of the physics laboratory to tools suited to incorporation in complex instrumentation systems. One line of progress has been through the applications of holography and holographic interferometry to engineering metrology where the potential of a precision comparator is realized without a convenient means of using it. The process, however, has formed a basis for development and the progress of holographic metrology is reviewed leading to more general concepts better described as “Coherent Optical Metrology”. The authors' latest developments in this area are described where, by means of a coherent optical sampling technique, three dimensional data is coded onto an electronic video waveform. The method is based on speckle pattern interferometry with optical to electronic interfacing by means of a modified closed-circuit television arrangement. With this instrumentation, most of the measurement facilities of holography are retained without many of the inconveniences arising from photographic recording. The data is processed electronically and displayed or presented in a form suitable for viewing or to actuate a stage of process control.

The aim of this paper is to establish a simple method for the calculation of the transfer function parameters of the capacitor servomotor. The equivalent circuits of a group of twelve capacitor servomotors of widely different parameters are simulated on a transformer analogue network analyser. An empirical formula expressing the reference voltage in terms of the motor speed, control voltage and the capacitance value is obtained. A torque equation for the capacitor servomotor is deduced by introducing the obtained formula in the torque equation of the two-phase servomotor derived by Saleh and Yuferov. The gain and time-constant of the capacitor servomotor are deduced from the proposed torque equation. Effects of the control voltage, as well as the effects of the capacitive reactance on the gain and time-constant, are also discussed. The torque-speed characteristics of a drag-cup capacitor servomotor are computed for different values of the control voltage and different capacitances using the proposed torque equation, and compared with those obtained experimentally. The experimental results are in good agreement with the theoretical calculations.

A self-adaptive instrument servomechanism has been devised to enable airflow direction to be automatically determined when using a hot wire anemometer for flow measurements. In the anemometer, used for measuring air velocity and turbulence, a fine wire acts as the sensing element. The wire is maintained at constant temperature by an automatically balancing bridge circuit, the voltage across which is a measure of the rate at which the flow is cooling the wire. When the probe from such an instrument is rotated through 360° in an air stream the voltage/angle characteristic is as shown in Fig. 1; with the wire axis along the flow direction the bridge voltage is a well-defined minimum while a less definite maximum voltage is obtained with the wire normal to the flow. Location of the successive minima or maxima is achieved by a hill-climbing method. The device has been developed for taking measurements in two dimensional flow within the rotors of certain fans where difficulties of access preclude the use of any probe having a large head.

When using thermocouples directly connected to ultra-violet galvanometers for recording temperature transients, the low-voltage outputs necessitate the use of galvanometers with low natural frequencies. This puts a limitation on the overall dynamic performance. In a particular application, the user has to select the damping resistor for the galvanometer and the work describes how this is done so that the system is optimised for minimum integrated errors during a transient. The transient considered was of an exponential type which occurs frequently in practice and it is shown that the correct damping ratio and hence damping resistor for the galvanometer depends upon the non-dimensional parameter defined by the product of the natural frequency of the galvanometer and the time constant of the exponential. The results show that the usual value of damping ratio of 0·64 based on minimum sinusoidal distortion has to be modified for best dynamic performance. However, if the non-dimensional parameter is sufficiently large, higher values of damping can be used, which produce a large trace with acceptably small errors.

En este trabajo, se elaboró una interfaz gráfica que determina por medio de simulación en estado estacionario el número de platos necesarios en el proceso de destilación multicomponente, así como la composición en el flujo de destilado y fondos de una torre de destilación utilizando métodos cortos. La interfaz gráfica de usuario, se construyó en el lenguaje de programación Python 2.5, permite presentar los datos de entrada y salida para el caso de columnas de destilación operando en régimen permanente. Los resultados del uso de la interfaz gráfica muestran una forma simple de realizar diseños preliminares de torres de destilación y su potencialidad como material de apoyo para el estudio y comprensión de conceptos básicos en destilación multicomponente. En un trabajo posterior se podrá visualizar el desempeño del modelo dinámico a través de perturbaciones programadas en las condiciones de operación. Palabras claves: destilación multicomponente; métodos cortos; interfaz gráfica de usuario; Phyton 2.5.In this work, we developed a graphical interface that determines by steady-state simulation the number of plates required for multicomponent distillation process and the composition of distillate and bottoms flow of a distillation tower using short-cut methods. The graphical user interface was built in the programming language Python 2.5, allows to present the input and output data for the case of distillation columns operating in steady state. The results of using the graphical interface shows a simple way to make preliminary designs of distillation towers and its potential as support material for the study and understanding of basic concepts in multicomponent distillation. In a later work it will can display the dynamic model performance through scheduled disturbances in operating conditions. Keywords: multicomponent distillation; shorcut methods;graphical user interface; Phyton 2.5.

This paper was included in the programme of the Hertfordshire Local Section with the prime objective of interesting people new to the process control field, but the author has blended into the framework views which will engage the interest of the more experienced also. The paper is not designed as a substitute for text book study.

A mathematical formulation is developed for obtaining the frequency responses from known sampled impulse responses of linear dynamical systems. This is done by assuming a straight line approximation from one sampled point to the next and performing the usual Fourier Transformation for this interval. This is repeated for all sampled points and the results are summed together. In practice sampled impulse responses can be obtained using correlation techniques. The frequency responses as obtained above are then processed by a generalised method, developed by the authors, to determine the transfer functions. The unique feature of this method is that the transfer functions can be obtained from the frequency responses without any idea about the actual order of the system and its poles and zeroes. However, the actual principle employed, that of complex curve fitting, is already a well established technique. Finally, many examples are presented which show the validity of the methods where impulse responses are exact and also corrupted by errors. The treatment is restricted to systems which have a finite dc gain. The numerical calculations are processed on an ICT 1905 computer.

The paper is in two sections. The first attempts to describe what an ideal man/machine interface might be in the control room; the second deals with a hardware implementation that could lead to the improved interface. Because the distribution of data is all important in any implementation of an advanced man/machine interface, a method of data distribution is synthesised similar to an associative memory in a computer system. Since the derivation of the system concept for the ‘Data Highway’ by the author, several similar systems have been proposed in recent literature.

Rod and bar has been rolled for many years without the benefit of any form of gauging beyond the holding of a piece of wood against the moving stock. Quality control at present depends on retrieving processed material after cooling and using micrometer measurements to make mill adjustments. Valuable time is lost before any alteration in mill parameters is revealed and setting up is time consuming without rapid feedback of rolled diameter. Furthermore, any form of gauge control is not possible without the rapid determination of the diameter and profile of rolled material. The driving force behind automatic control of rod and bar mills and the considerable loss of revenue incurred by wastage of stock and in setting-up time has driven many investigators to examine ways and means of measuring rod and bar diameters. Over the past two years many schemes have been evaluated and some instruments will be commercially available shortly. This paper seeks to review the more interesting developments that have taken place in this area over the past two years.

An internal combustion engine speed control system has been investigated to determine the possibility of using a model-reference adaptive control device to maintain constant dynamic behaviour of engine speed irrespective of engine load and environmental conditions. A conventional type of speed control arrangement has been used in the primary loop and an auxiliary loop has been introduced which biases the engine throttle mechanism by an amount which is proportional to the derivative of engine speed. The constant of proportionality is the parameter which is being changed by the adaptive loop. The results of the engine tests showed good correlation with those obtained in a simulation study and clearly showed that for certain installations the incorporation of a model-reference loop into a conventional speed control system would result in improved engine dynamic behaviour.

It is shown that low order models can be used to predict adequately the transient response sensitivity of high order linear systems, thus leading to a great reduction in time and complexity during analogue or digital computation, as well as facilitating the understanding of the sensitivity functions themselves. Experimental results on an analogue model of a sixth order aircraft blind landing system confirm the adequacy of the procedure. In this instance the use of the low order model eliminates six integrators from the analysis and it is to be expected that higher order systems will lead to even greater savings. The example used to illustrate the procedure is the practical problem of setting parameter tolerances given acceptable bounds of transient performance. A new low order model is introduced, and when compared with alternative models proposed elsewhere in the literature is found to give an encouraging accuracy of prediction. The new model is particularly useful if the sensitivity analysis is undertaken on an analogue computer.