bluuebunny/crossref_metadata_2025 huggingface dataset:
Solids-concentration measurement and flow measurement of slurries and sludges using ultrasonic sensors with random data analysis
Authors: Balachandran W. , Beck M.S.
Published: August 2008

An instrument has been developed for on-line monitoring of suspended-solids concentration of slurries and sludges in hostile environments. A narrow and parallel ultrasonic beam, projected across the pipe diameter, interacts with the flowing sample, and the inhomogeneities present in the sample scatter the ultrasound, resulting in amplitude modulation of the transmitted beam. The average modulation index (depth of modulation) of the received ultrasound signal is shown to be a function of suspended solids-concentration, flow velocity and mean particle size. In a constant-velocity system, if the mean particle size remains constant, then the received signal will be proportional to suspended-solids concentration. A closed-loop system using a phase-locked loop is used to give good acoustic stability. This instrument could also be used for on-line monitoring of suspended-solids concentration in a variable-velocity system by compensating for the velocity changes using the cross-correlation techniques described in Part 2.
Station-keeping control system for a helicopter with a suspended load
Authors: Tsitsilonis L. , McLean D.
Published: August 2008

The problem of automatically controlling the stationary position in hovering fligh of a load suspended from a helicopter is first outlined with reference to some of the past and present-day flight-control systems designed to achieve its solution. Next, a detailed mathematical model of a particular helicopter-and-load combination is described before a discussion of a proposed control system to provide optimal load positioning, even in the presence of acute atmospheric turbulence. Some numerical problems that can arise in the determination of such solutions are indicated, and several results are discussed which illustrate the effectiveness of the proposed scheme.
Use of a microprocessor in a proposed flight-control system
Authors: McLean D. , Prasad R.A.
Published: August 2008

A design proposal for a large transport-aircraft control system for alleviating structural loads due to commanded manoeuvres or atmospheric turbulence is described. Because the order of the least-complex mathematical model representing aircraft dynamics is large, reduced-order feedback control is proposed. Flight integrity is secured by using a microprocessor for control-gain reconstitution in the event of controller failure, and, for the occurrence of sensor failure, to synthesise an observer to reconstruct missing feedback signals.
Minimal models of glucose/insulin dynamics in the intact organism
Authors: Bergman R.N. , Cobellit C. , Toffolo G.
Published: August 2008

One of the major goals in metabolic physiology is the development of methods to quantify specific processes involved in carbohydrate metabolism regulation in the intact organism. In this paper we propose a novel non-invasive (as compared to other techniques) approach for estimating in vivo glucose-insulin dynamic interactions. The rationale of the approach lies in the interpretation of glucose/insulin dynamic data, obtained after a system perturbation, with two mathematical models: particular attention is devoted to the selection of these two models. A minimal, or parsimonious, modelling strategy is proposed, that is, the two models are selected out of two series of physiologically based models, respectively; six of glucose disappearance; and six of insulin secretion and kinetics, according to a set of specific criteria. The two chosen minimal models of glucose metabolism and insulin secretion permit a quantitative insight into the metabolic state of an intact organism by providing accurate estimates of parameters such as insulin sensitivity and pancreatic sensitivity to glucose. Possible physiological and clinical uses of the two models for in vivo quantitative studies of glucose/insulin interactions are discussed, together with the insight that these models seem to provide into the intimate nature of metabolic control .
Optimal self-tuning control systems: theory and application
Authors: Grimble M.J. , Fung P.T.K. , Johnson M.A.
Published: August 2008

This paper covers the estimation aspects of self-tuning theory and examines the success of the methodology on a dynamic ship-positioning problem. The parameter-estimation algorithms for self-tuning are given their conceptual roots in the theory of statistics, particularly the properties of sufficiency, unbiasedness and efficiency. The particular system description is manipulated into a form suitable for the application of the discrete Kalman filtering methodology. Finally, recursive estimation formulae are given, and their numerical implementation is discussed. Some remarks on suitable rules for forgetting factors are also given. Bringing together the control and estimation theory results in the self-tuning controller per se. The two types: self-tuning with explicit, or implicit identification are considered in some detail. Finally, the application of a self-tuning controller to a dynamic ship-positioning problem is presented. The characteristic adaptation by the controller to different wave conditions is illustrated.
A complete proof of Bristol's relative gain array
Authors: Wang S. , Munro N.
Published: August 2008

Bristol has defined a matrix called the Relative Gain Array, as a measure of steady-state interaction for a given multivariable system, and gave a proof for the 2-input 2-output case. In this note, we provide a complete proof for the general case of an m -input m-output system.
Laser-Doppler methods for the assessment of microcirculatory blood flow
Authors: Nilsson G.E. , Tenland T. , Ake Öberg P.
Published: August 2008

A new principle for the measurement of microcirculatory blood flow is described. The laser Doppler flowmeter u tilises the fact that a laser light beam incident on tissue is scattered in static structures as well as in moving red cells. Light beams scattered in moving red cells undergo a frequency shift according to the Doppler effect, while beams scattered in static tissue alone remain unshifted in frequency. If shifted and unshifted light is mixed on a photodetector surface, beat notes are produced. The power spectral density of these beat notes is determined by red cell concentration and velocity. From the alternating portion of the photocurrent, an output signal that is related to flux of red cells in a specific tissue volume can be calculated. Some applications of the method are presented.
On-line identification of mechanical parameters of the lung
Authors: Linkens D.A. , Rimmer S.J.
Published: August 2008

The subject of this paper is the use of a microcomputer for on-line estimation of mechanical parameters of the lungs. The identification is based on measurements of airflow at the mouth using a pneumotachograph and oesophageal pressure obtained via a balloon catheter. A simple mathematical model for lung mechanics is used which includes terms for airways resistance, dynamic pulmonary compliance and a non- linear turbulence factor. The method of identification is a steepest-descent gradient algorithm based on equation- error formulation of the problem. The stability of the method has been verified via Liapunov theory, and the tracker was originally implemented in analogue form. It has been shown to give good dynamic tracking performance, with settling times in the order of a few breathing cycles. Good correlations between manual off-line estimation and the on-line steepest-descent tracker have been obtained in both human and guinea-pig trials. Recently, the estimation algorithm has been transferred to a Research Machines 380Z microcomputer and applied to neo-natal data for rapid assessment of apnoea. Two versions of programmes have been implemented, one of which gives an on-line printer listing of lung parameters based on either inspiratory or expiratory data. The other version uses four DA C channels to give analogue chart recording data Examples are shown of simultaneous six-channel recordings comprising the primary pressure and flow signals, estimated airways resistance and pulmonary compliance, tidal volume and minute volume. The effect of apnoea on these parameters, together with heart rate, can be assessed using this on-line identification method.
An introduction to the application of system identification techniques to elements of the neuromuscular system
Authors: Rosenberg J.R. , Murray-Smith D.J. , Rigas A.
Published: August 2008

A simplified account of the organisation of the neuromuscular system is presented. An important component of this system, the 'muscle spindle', is a complex sensor that responds to imposed length changes and is thought to provide information which is important in the control of movement and in the maintenance of posture. The structure of the muscle spindle and its response to various inputs are described. The multi-input and multi-output nature and non-linear behaviour of the muscle spindle are emphasised, both in terms of continuous and pulse- coded quantities. The methods of pre-processing of pulse-coded signals from nerves, and the identification techniques currently applied by neurophysiologists for the estimation of the parameters of linearised models of the muscle spindle, are presented and assessed. New developments in the identification of point-process systems are shown to be applicable to some aspects of muscle-spindle behaviour. This approach, based upon point-process parameters, is applied to an analysis of the output signal of a muscle spindle under a variety of input conditions and to the estimation of a transfer function of the muscle spindle subjected to a point-process input. A description of one non-linearity and the effects of an additional input are also presented.
Computer control technology - past, present and probable future
Authors: Williams Theodore J.
Published: August 2008

This survey paper reviews the field of computer control from its inception in the late 1950s to the present and note the trends in hardware, software and applications, Based on this it projects present trends in these areas to predict the foreseeable fu ture of the field. In particular the present very strong trends toward distributed and hierarchical control systems based on microprocessors and recent developments in communications techniques is followed. In the software area the probable effect of the new ADA language is discussed along with the developments in specific problem and applications oriented languages.
The application of self-tuning control
Authors: Clarke D.W.
Published: August 2008

Thanks to cheap computing power, self-tuning control has matured rapidly from an academic topic to a position in which it can be seriously considered as an alternative to the ubiquitous PID regulator for many industrial process-control loops. The purpose of this paper is to discuss some of the key ideas in self-tuning - from the point of view of an industrial control engineer without excessive use of mathematics. The use of predictive control laws is explored first in the non-adaptive context in which the closed-loop response, the control input behaviour, and the response to load disturbances can be (to a certain extent) individually tailored by the user. This is contrasted with the usual tuning of PID coefficients based on the subjective evaluation of control performance. The role of adaptation is then discussed in terms of its possible applications, for example for commissioning fixed controllers or for keeping a critical loop tightly tuned. Some of the likely pitfalls in applying adaptive control are outlined, and alternatives to the approach based on discrete-time predictor theory are briefly mentioned.
Modelling a complex biological system: the human cardiovascular system—1. Methodology and model description
Authors: Leaning M.S. , Pullen H.E. , Carson E.R. , Finkelstein L.
Published: August 2008

Mathematical models are powerful tools for investigating and understanding complex systems. Their use must be guided by knowledge of their potentialities and limitations and a well-based approach to the modelling process. Such is embodied in an integrated methodology for model formulation, identification and validation which has emerged from practical modelling as well as historical studies. The methodology in operation is illustrated by application to the formulation of a model of the human cardiovascular system, its neural control and the effect of drugs. The derivation of the model is described in depth and a complete model listing is given. The companion paper develops a validation methodology and applies it to the cardiovascular model.
Using linear potentiometers in place of sine/cosine potentiometers
Authors: Williams P.
Published: August 2008

Techniques are described that enable linear potentiometers to perform some of the functions which usually require sine/cosine potentiometers. The primary advantage is lower cost but, in some cases, the use of linear helical (multiturn) potentiometers also permits greater resolution. Applications of these techniques in phase shift circuits are discussed.
A review of the evolution and development of solid-electrolyte oxygen sensors
Authors: Kocache R.M.A.
Published: August 2008

The paper traces the origins of the relevant developments that have led to the emergence and contributed to the evolution of the solid-electrolyte oxygen sensor. Its main features are discussed in general, and a number of different sensor designs are then critically examined.
Modelling and control studies of the activated sludge process at Norwich Sewage Works
Authors: Beck M.B.
Published: August 2008

In general, studies of the control of the activated sludge process have focused on the design of single-loop controllers able to suppress higher-frequency disturbances and provide minimum-variance performance about a precisely-defined, constant set-point. This paper addresses some of the complementary problems of control. It considers the slower dynamical components of activated sludge process behaviour, the detection of and response to conditions of process failure, control within imprecisely-defined 'domains' of performance, and (by implication) the concept of switching performance from one such domain to another. For these purposes the paper discusses the construction of a relatively complex microbiological model for the activated sludge process. The results of using this model in simulation studies of a fuzzy controller are then presented. These preliminary results are encouraging and suggest that, in spite of the substantial current limitations on process knowledge, there are many novel aspects of activated sludge process control yet to be explored.
Experimental improvement of the mathematical model of the process of suspension polymerisation
Authors: Lukec D. , Božičević J.
Published: August 2008

A theoretical mathematical model of the process of suspension polymerisation is developed and then improved by experimental estimation of reaction-rate constants and initiator efficiency. The verification of the simulation model has shown its good approximation of the real process.
PID algorithms and their computer implementation
Authors: Clarke D.W.
Published: August 2008

Three-term or PID regulators are deservedly popular in industrial control systems. They give satisfactory performance for a wide class of processes, they are readily understood by technical plant personnel, and they are easy to implement using analogue or digital hardware. Stable elimination of offset due to load-disturbances is a principal control requirement, as in many cases processes are operated continuously at a fixed set-point Often this is achieved by the PI terms alone, though derivative action can be added for plant with excessive phase lag. In practice, however, nonlinear behaviour such as actuator saturation is a critical component of overall performance.

This report discusses various forms of the PID regulator (positional, incremental, cascade, etc) and their closed-loop properties. Practical features such as avoidance of 'integral windup' and 'derivative kick' are described. The ways in which the PID algorithm can be discretised for use in a digital computer are outlined, together with appropriate Fortran coding. The effect of choice of sample interval on the discretised performance is analysed. Often the interval is chosen to be as short as possible given the computational power available; the influence of this on quantisation noise and offset is discussed

Various filters are used in a discrete PID algorithm, including the anti-aliasing filter and a filter on derivative action. The properties of these filters are investigated and some interesting nonlinear filters, such as 'spike' filters are presented .
Feasibility of measuring reactive forces during peg/hole assembly
Authors: Martin K.F.
Published: August 2008

This paper deals with the possibility of measuring the two separate reaction forces when a peg is inserted into a hole. It is assumed that means are available of measuring the resultant force exerted due to the reaction forces acting on the peg. The solution is intractable if the two forces are regarded as being totally unrelated to normal directions, but in a real situation this is not the case, and a solution that allows realistic estimates of the forces is proposed.
A modern approach to classical control
Authors: Thompson S.
Published: August 2008

The title of the paper refers to a package of microcomputer SISO programs which have been used to complement a course in control engineering given to undergraduate mechanical engineering students. Descriptions of both the course and package are given. Also described is the method of incorporating the package into the course by means of tutorials and class demonstrations. Some comments on the implication of the impact of microcomputers in teaching are also made.
Two tutorial examples of multivariable control system design
Authors: Limebeer D.J.N. , Maciejowski J.M.
Published: August 2008

Two tutorial examples are presented which illustrate different methods of designing practical multivariable control systems using frequency-domain techniques. In the first case eigen vector alignment techniques are used to manipulate and shape the generalised Nyquist diagrams, while in the second case LQG theory in conjunction with singular value plots is employed. In both cases the designs are carried out on a modern computer-aided control-system design package.
An approximate spectrum analyser
Authors: Jordan J.R. , Moulton G.A. , Whittington H.W.
Published: August 2008

A simple hardware approximate spectrum analyser is described which is obtained by replacing the sine and cosine modulating functions used in a complex demodulator by a square-wave approximation. Measured approximate power spectra show a defined pattern of small sub-harmonic error terms. If the maximum input frequency is limited to F then no errors wall be incurred over the range F/3 to F. Experimental and theoretical results are presented describing the effect of sweep time on the measured speetrum. The simplicity of the hardware involved allows a parallel array of complex demodulators to be created and, when the individual elements of the array are swept over adjacent frequency bands, a greatly reduced measurement time is obtained.
Measurement of plant growth in three dimensions
Authors: Jones D.I. , Stedham D.J. , Sackville-Hamiltont N.R.
Published: August 2008

An instrument is described for producing accurate three-dimensional maps of various plant forms. Allied with a flexible data logging system, the instrument has been shown to increase biologists' data-collecting capability by a factor of between 10 and 100 over manual methods. Substantial improvements in the quality and continuity of the measurements, as well as sheer quantity, have made it possible to produce plant maps which would not otherwise be feasible.
Compensation in pneumatically actuated servomechanisms
Authors: Moore P.R. , Weston R.H. , Thatcher T.W.
Published: August 2008

This paper describes the features of a pneumatically actuated servomechanism which has been designed for the point-to-point positioning of payloads. The servomechanism utilises low cost computer control and interface electronics to facilitate software compensations for system time delays and non-linearities. The compensation algorithms hve been designed and developed with reference to a linearised model of pneumatic servodrives, which allows for variation in transfer function with load position. Application of these algorithms has allowed a substantial improvement in static performance and dynamic characteristics to be realised for drives incorporating various forms of pneumatic servo valves, pneumatic actuators and load systems. This offers a significant opportunity for commercial exploitation of the pneumatic servodrive. The paper describes the method by which compensation is achieved and references experimental data, which have been obtained by using a standardised evaluation procedure.
Recursive estimation for non-linear Weiner systems by on-line implementation of Bayes' rule
Authors: Jacobs O.L.R.
Published: August 2008

Bayes'rule can be directly applied to estimation using noisy non-linear measurements in real systems. This requires an on-line computer to implement numerical computation of conditional probability distributions and their statistics: suitable machines are now routinely available for distributions of low dimensionality.

Practical numerical problems can arise in connection with grid-scaling, prediction, and dimensionality. Gaussian approximation is well known as a way to avoid the first two of these: numerical results are included which demonstrate the power of this approximation. The main contribution of the paper is a novel linearisation which avoids the curse of dimensionality in Wiener systems where several random variables are observed through a noisy non-linear function of their weighted sum.

The work was motivated by case studies and is justified by examples from simulations and experimental studies. Analysis to guarantee reliability of the method is not yet available.
A study of the closed-loop structure of multivariable feedback control systems
Authors: Forsythe W. , Danisman H. , Eissa M.A.
Published: August 2008

A method of analysis for feedback systems with multiple inputs and outputs is presented, based on the transfer-function matrix representation. It allows the direct computation of any transfer function tij relating the ith input to the jth output, given the forward and feedback transfer function matrices G (s) and H (s), and sets out clearly the relationship between the numerator and denominator of such a transfer function.

The derivation of the method from first principles, starting with the system connection matrix, is felt to impart a certain insight into the behaviour of such complex structures.
Identification of combined viscous and Coulomb friction - a numerical comparison of least-squares algorithms
Authors: Stanway R. , Mottershead J.E.
Published: August 2008

In this paper the authors present a numerical comparison of three least-squares techniques - Gauss-Newton, quasi-linearisation and non-linear filtering - for identifying viscous and Coulomb friction parameters in a single-degree-of-freedom vibrating system.
Experimentation for the dynamic response of industrial temperature sensors
Authors: Chohan R.K. , Kerlin T.W.
Published: August 2008

The apparatus for the determination of dynamic response of industrial temperature sensors developed and used by the authors is briefly described. Extensive testing of typical sensors has been carried out. The apparatus described here allows testing in various liquids and dry/moist air.
Modelling the dynamics of regenerative catalytic reactors
Authors: Heggs P.J.
Published: August 2008

Regenerative catalytic reactors (RCRs) are proposed as novel catalytic systems especially for reversible reactions. At least two reactor vessels are required for continuous operation, and each reactor operates intermittently and transiently. When one reactor is operating, the temperature level in the other one is being regenerated. This RCR system is mathematically, modelled by a two-phase heterogeneous representation, and a numerical solution is proposed which is stable and convergent. The transient nature of an RCR system for the catalytic dehydrogenation of ethylbenzene to styrene is used to illustrate the operating characteristics. This system is shown to produce a higher conversion of ethylbenzene to styrene than a steady-state adiabatic configuration using the same amount of catalyst.
Controlling SO2 emissions during start-up of multi-bed sulphuric acid converters
Authors: Mann R.
Published: August 2008

The catalytic converter in sulphuric acid plant is normally designed to work high conversions to avoid recycle, and the associated integrated heat recovery system makes the process relatively tightly constrained. Because of this, considerable care is needed during start-up in order to avoid excessive emissions which would fail to satisfy criteria set by the factory inspectorate.

For a fast, clean start-up it is necessary to have a detailed appreciation of the reactor dynamics; the simulation developed here demonstrates how this can be done. In parti cular, it is possible to explore the level of detail necessary to enable operational policies for start-up to be explored. It is shown that, by suitable programming of the flow rates in the system, appropriate to the initial bed temperatures, clean fast start-ups are possible which avoid excessive stack gas emissions of sulphur dioxide.
The statistical properties of the number of observations used for proving meters in dynamic flow measurements
Authors: Berman M. , Prowse D.B.
Published: August 2008

Quantitative evidence is presented to show that the present practice in meter proving, of taking proof runs until two consecutive runs check each other within a pre-established variation, may be unreliable. It is shown that, if the number of consecutive runs required is increased from two to five, say, then the precision of the meter factor is increased and the probability of missing an initial transient is significantly decreased. The 'cost' of the alternative procedure, as measured by the average number of observations required, is shown to be small.
Methods of quantitative validation fo r dynamic simulation models
Authors: Butterfield M.H. , Thomas P.J.
Published: August 2008

Four examples, taken from nuclear-power-station experience are described, where model-distortion techniques have been applied successfully. These examples are:

(i) Validation of a power-station model for the prediction of behaviour followirag a trip;

(ii) validation of a nuclear-reactor model for the purposes of control-system design;

(iii) validation of a pump run-down model; and

(iv) validation of a model for a hydraulic accumulator.
An investigation of an SDLC-based remote monitoring and control system
Authors: Birch M.R. , Lucas J.
Published: August 2008

There is a large and increasing demand for remote monitoring and control systems in such applications as pipelines, reservoir systems, sewerage systems and shopping centres, where there are numerous inputs and outputs spread over a large physical area. To monitor and control these inputs and outputs, at a local level, devices known as outstations are used. The outstations are, in turn, controlled by a centralised master station.

The purpose of this paper is to investigate the use of the SDLC protocol for controlling the flow of data around such a system. The SDLC protocol is a modern bit-oriented protocol which offers an efficient method for ordering the flow of data around a communication system, As the SDLC protocol places no restrictions on the length or content of the messages sent over the communications link, it offers a very convenient method of communication. It also offers a comprehensive method of detecting any errors that may occur in the communication link, which is of vital importance in any control system.

An SDLC software package is described which makes communication between stations extremely easy and reliable. Many applications of remote monitoring and control may now be envisaged, such as factory automation. To take advantage of these new applications, a cheap out-station with built-in modem was designed and constructed. The use of the SDLC software package in hostile environments has been made possible by the introduction of Hamming error-correcting codes. This also widens the number of possible applications for which the SDLC software package may be used,
Radio and microwave frequency techniques for on-line analysis
Authors: Carr-Brion K.
Published: August 2008

Non-intrusive methods of on-line analysis are of particular value in those industries such as food manufacture and biotechnology, where sterility, plant integrity and ease of cleaning are of major importance. Radio frequency and microwave techniques, such as capacitance, NMR and ESR, being by their nature deeply penetrating, are attractive candidates to meet this requirement. Their current uses are described - mainly for moisture measurement- and their future potential examined. It appears that not only is this significant but that there exists a real need for further development and engineering of suitable industrial systems.
Dynamic mathematical model of the fluid catalytic cracking process
Authors: Božičevic J. , Lukec D.
Published: August 2008

A theoretical dynamic mathematical model of the fluid catalytic cracking process is described and the corresponding simulation model developed and verified by means of experimental data collected from commercial plant. The application of the simulation model in studying process behaviour and control has shown an excellent representation of the real process.
On-line Golden Section search to optimise the photoelectronic behaviour of amorphous silicon
Authors: Küppers U.
Published: August 2008

A one-dimensional optimisation strategy - the Golden Section search method -was applied to optimise the photoelectronic behaviour of amorphous silicon. Within a fixed interval of search (150°C-300°C) the substrate temperature was changed continuously. The transient amplitude resulting from in situ time resolved photoconductivity measurements was monitored and evaluated as the quality value of the search problem. Process apparatus, measurement equipment and computer were closed-loop connected as a first step in Computer Aided Process Optimisation (CAPO). For the system investigated, it was found that a maximum in the quality value results after four search steps.
Optimal steering control of an auto-guided-vehicle with two motored wheels
Authors: Ock Hyun Kim
Published: August 2008

An optimal control procedure is presented for steering an Auto-Guided- Vehicle (AGV) which has two motored wheels on its left and right side. Steering, running and stopping are enabled by controlling the motor speed independently.

An optimal proportional-plus-integral control is employed to eliminate steady-state error which is sustained by a simple proportional control for tracking a circular path. A simple and readily-implemented suboptimal control is also examined. The suboptimal control gives comparable performance and therefore provides an effective approach for industrial application of the AGV.

Effects of design parameters of the AGV such as forward velocity, wheel radius and position of sensor are investigated. It is shown that within the practicable values the controlled performance improves rapidly but with an increase of those parameters then the improvement becomes negligible, which suggests base values for the parameters.
Flow imaging for multi-component flow measurement
Authors: Plaskowski A. , Beck M.S. , Krawaczynski J.S.
Published: August 2008

Multi-component flow measurement is of increasing importance for resource exploitation, energy conservation, and biochemical process applications. Conventional flowmeters which endeavour to average a property of the flow over the pipe cross-section are unsuitable for accurate measurement in the many cases where the component distribution is spatially and time varying in a statistically non-stationary manner. Flow imaging which, like medical tomographic imaging, gives a cross-sectional image of the component distribution leads to the possibility of a much more accurate measurement.

The paper describes the basic theory of flow imaging and the system arrangement necessary for its implementation. We also describe a specific arrangement using pulsed ultrasound echo transducers and an acoustic backprojection algorithm for image reconstruction. This shows that a 12-transducer view system can resolve a long single 6-mm diameter void parallel to the axis in a physical model corresponding to a liquid/gas flow in a 78-mm diameter pipe.
On the use of small scale aircraft models for dynamic wind tunnel investigation of stability and control
Authors: Cook M.V.
Published: August 2008

An experimental facility for the dynamic investigation of the stability and control characteristics of small scale model aircraft in a wind tunnel is described. Some typical results for a conventional and unconventional aircraft configuration are presented.
Transient analysis of thermostatic expansion valves for refrigeration system evaporators using mathematical models
Authors: James K.A. , James R.W.
Published: August 2008

An investigation into the behaviour of a thermostatic expansion valve used to control the refrigerant flow into an evaporator was undertaken using a thermodynamically based mathematical model. The emphasis of the paper is on the behaviour of its sensor, which is a remote bulb charged with a refrigerant liquid/vapour mixture. The model was used to test the influence of simplifying assumptions and to determine the simplest model that could be an adequate representation of the TEV. Possible applications for the simplified models are discussed.
Dynamic modelling of a three-axis pneumatic robot
Authors: Czarnecki C.A. , Ashworth M.J. , Towill D.R.
Published: August 2008

To serve any useful function, the model of a system must reflect the salient features of that system and reproduce, to within an acceptable degree of accuracy, the performance which is observed when it is in operation. When the system is a robot, active in three dimensions, the modelling is comparatively complex and the determination of the values to be attributed to the mechanical parameters and to the coefficients which quantify the interactive torques is far from trivial.

As a prelude to the design of a controller which is effective throughout the operating envelope of the robot, the paper describes an investigation into the feasibility of simplifying the modelling procedure without incurring a penalty by way of a significant deterioration in performance prediction. If sufficiently accurate, this tentative model will form the basis of a probabilistic model of reduced complexity which will contain the uncertainty of motion which is exhibited by the robot in operation.

Essentially, the estimation of the model parameters follows a two-stage process. On the assumption that the Lagrangian expressions defining a simplified mechanical configuration will describe adequately the actual motion of the robot, a preliminary estimation is made by use of a recursive least-squares technique which provides directly the coefficients of the continuous-time model. This is followed by a sequence of trials carried out on both the preliminary model and on the real system, and so arranged as to emphasise the contribution of each coefficient in turn. By comparison of their responses, the model coefficients are then tuned to achieve an acceptable matching.

In addition to inherent cross-coupling, the industrial robot on which the investigation was conducted has nonlinearities introduced by way of pneumatic actuators with complex flow-rate characteristics and which operate in a bang-bang manner. The investigation has shown that the procedure is quite feasible and that the quality of response prediction which was achieved is impressive.
Automatic gas-jet parameter estimation for high precision spacecraft attitude control systems
Authors: Dodds S.J. , Milne P.A.
Published: August 2008

A simple and easily implemented method is presented here for automatic on-board estimation of a critical parameter of the control jet (thruster) impulse transfer characteristic. This facilitates optimal control with regard to thruster lifetime, fucel consumption and pointing accuracy, despite uncertainties in the thruster performance, The new estimator facilitates automatic, in-orbit adaptation of the attitude control system to slow changes in the control jet characteristics, thereby maintaining optimal performance.

The parameter estimator is intended for microprocessor implementation and assumes the use of a state estimator. Attention is restricted to a single, isolated axis. No difficulty is envisaged in developing the technique further to cater for three-axis stabilised spacecraft with significant inter-axis coupling

The parameters to be determined are the intercepts on the characteristics of each control jet relating the actual jet firing time to that demanded.

A mismatch in these parameters gives rise to a state estimator transient following a jet firing. This provides the stimulus to the parameter estimator, which is basically a resettable pure integrator. The intercept estimate is updated by an amount proportional to the integral of the state estimator error taken over a finite period, commencing at the beginning of the jet firing. Suitable choice of the gain of proportionality yields dead-beat parameter estimation.

Besides compensating for jet firing time mismatch, the control system is shown to be capable also of compensating for uncertainties in the thrust level for short turn-on times.
A test-bed facility for hybrid i c-engine/battery-electric road vehicle drive trains
Authors: Bumby J.R. , Masding P.W.
Published: August 2008

This paper describes the design and development of a test-bed facility for hybrid internal-combustion-engine/battery-electric vehicle power trains. The control hierarchy within the microprocessor control systems is discussed, and the influence this has on the software design is described. The instrumentation and computer software systems necessary for both data acquisition and drive train control are described. It is shown that drive train control over an urban cycle can be successfully achieved using a modified proportional-plus-integral controller.
The applicability of the IPTS-68 interpolation equations to PRTs which have low temperature coefficients of resistance
Authors: Atherton A.
Published: August 2008

A calibration exercise provided a preliminary investigation into the compatibility with IPTS-68for temperatures below 0°C of thermometers with low temperature coefficients. Further data, obtained for temperatures up to 300°C, support a previous hypothesis that divergence from the IPTS-68 is largely a result of stem-heat-transmission errors.
The management of complexity — keynote paper
Authors: Robb Fenton F.
Published: August 2008

Recent developments in managerial cybernetics, systems thinking and practice address the issues of growing complexity in organisations and between them and their environments. This paper will set the scene for consideration of these methodologies by defining the general area of interest, stressing the importance and urgency of the subject and indicating in what ways management currently fails to cope with complexity.
Systems methodologies as complementary tools for managing situational complexity
Authors: Jackson M.C.
Published: August 2008

This paper identifies a certain class of systems methodologies - those which seek to be tools for managing of complexity. This class contains four distinct types of systems approach: hard; cybernetic ; soft; and critical Each of these differs from the others in the way it understands complexity and the way it attempts to alleviate the problems posed by complexity. It is argued, following from this, that different forms of complexity respond to treatment from different systems methodologies. A classification of systems approaches is then constructed on this basis. The classification should help practitioners, since, if they are able to identify the nature of the complexity they face, it will assist in the choice of an appropriate systems methodology for managing that complexity. It should also help systems theorists to recognise the complementary nature of their work and give meaning to the otherwise somewhat empty formula that systems science is a unified endeavour concerned with managing situational complexity.
TRACER- a practical construct for dealing with complexity in human interactive systems
Authors: Stewart R.W.
Published: August 2008

The aim of this paper is to show how methodological ideas can be developed from theoretical first principles of complexity, by presenting TRACER, a practical construct for dealing with complexity in human interactive systems. Utilising the concept of a human interactive system life cycle exhibiting discrete phases, it can be seen that the use of a methodologically driven approach can be instrumental in the development of the life and success of a system.

The two elements of TRACER are considered.

1 The TRA CER Construct which utilises three linked dimensions: human requirements of the system; human understanding of the system; and capability of the participants in the system.

2 The TRACER Methodology, with discrete but interactive stages of translation, rapport, assessment, comparison, evaluation and recognition.

TRACER is eclectic in nature, using techniques from psychology, sociology and cross-cultural studies in order to understand the nature of complexity and human capability to interact with system demands. Using examples within a system to show generic structural attributes (eg, system/ human communication network) and task specific attributes (e g, perception), methods for understanding and controlling complexity are shown to change the dimensions of a human interactive system life cycle.
Control system design: a survey of personal computer software
Authors: Linkens D.A.
Published: August 2008

A review is given of some of the CAD software for control system design and analysis available for personal computers. The computers considered comprise 8-bit and 16-bit machines typified by the BBC and IBM PC ranges. The software described covers the area of simulation, control design, and system identification, together with special topics such as graphics pre-processors. The simulation packages concentrate on continuous systems, but some mention is made of discrete system packages used, typically,in the manufacturing process industries. The design packages mainly cover single- variable control systems, but some attention is given to multivariable design. The identification packages only cover the single- variable case. Tables are presented to give some idea of relative performance, and to assist in software selection.
A fast algorithm for the on-line estimation of polarity correlation using binary patterns
Authors: Harba M.I.A. , Ali F.A.
Published: August 2008

An algorithm which utilises the binary patterns of the polarity-sampled input signals for polarity correlation is presented. When programmed on a Z-80 microprocessor operating at 4 MHz, a double precision correlator which estimates 128 correlation coefficients with a maximum allowable sampling rate of about 2.5 kHz is realised. All the operations are performed on-line, except for an interval of about 15 ms of off-line processing to estimate the correlation coefficients from the binary patterns. This interval is constant, irrespective of the signal interval used.

The efficiency of this algorithm is derived from the ability of microprocessors to handle 8 bits of data simultaneously, and from the fact when the sampling rate: input-signal bandwidth ratio is high (> 15, for the random signal tested) then only a limited set of input signal binary patterns are obtained. The resulting correlator was tested on real natural signals (the Electromyographic signal (EMG)).
Harry Frankfurt's metaphysics of care
Authors: Jouan Marlène
Published: August 2008

Harry Frankfurt's conception of care and love has largely been considered a seductive theory of personality, but an untenable and irresponsible theory of moral normativity. Contrary to that interpretation, this article aims at showing that it is possible to remain faithful to Frankfurt's metaphysical premises while not falling into some moral relativism. First, by comparing Frankfurt's and Heidegger's conceptions of care, I show that Frankfurt's subordination of ethics to carology apparently commits him to a neutral foundationalism. In the next step, I argue that his calling into question of the relation between rationality and morality does indeed subject moral normativity to some subjective and contingent limits. And finally, I show that the objections raised against such a conclusion can be answered by shifting Frankfurt's frontier between contingency and necessity and by exploiting his concept of wholeheartedness.
Republican confusion and liberal clarification
Authors: Rogers Melvin L.
Published: August 2008

Proposed as an alternative political philosophy to liberalism, contemporary republicanism articulates a systematic theory of freedom as non-domination. Does it make sense, however, to think about the difference between liberals and republicans along the lines of freedom? This article answers in the negative, maintaining that the distinction is purchased at the cost of misdescribing liberal theory. Focusing on the work of Quentin Skinner and Philip Pettit, I maintain that the mischaracterization takes place at two levels. The first is the link that is drawn between Thomas Hobbes and classical and contemporary liberals. The second has to do with republicans' refusal to acknowledge the normative framework in which liberal freedom takes root and is made politically defensible. This framework, I argue, comprises a constellation of other concepts, such as consent, publicity and the rule of law, that are part and parcel of liberal freedom. Once these features are taken into consideration, what emerges is a view of liberalism that means something less than being free from any and all constraints, but which also means something more than being free from actual interference.
Using attachment theory with offenders
Authors: Ansbro Maria
Published: August 2008

Attachment theory has routinely been considered essential for those working with children. However, contemporary literature and research on attachment offers some compelling insights for work with offenders, particularly in the way that empathy is developed and mood is regulated.
Work for the benefit of the community as a criminal sanction in Spain
Authors: Blay Ester
Published: August 2008

Work for the benefit of the community as a criminal sanction was first introduced into Spanish legislation by the 1995 criminal code. However, orders have not been implemented as expected and the gap between the written law and the law in action has been considerable. Regulation and implementation of orders pose serious problems, which reflect more general trends of criminal policy and practice in Spain. After briefly describing the regulation and implementation of work for the benefit of the community orders, this article focuses on the main problems they present and discusses them in the context of wider policy issues.