bluuebunny/crossref_metadata_2025 huggingface dataset:
“I Whitened My Face, That They Might Not Know Me”
Authors: Paul Ronald
Published: November 2007

The aim of this essay is to explore the process of racial adaptation to the image of the Other—of the “White Mask” that is adopted by the Black man—as it is revealed in one of the most famous early slave autobiographies: Olaudah Equiano's The Interesting Narrative of the Life of Olaudah Equiano, or Gustavus Vassa, the African, Written by Himself. Over the years, critics have reiterated the historic, documentary significance of Equiano's work. The author instead looks more critically at the contradictions in racial consciousness—alienation and identification—that Equiano's self-portrayal tries to resolve. He also argues that Equiano's condition of psychological dualism corresponds to what Frantz Fanon, in his seminal work Black Skin, White Masks, sees as a denial of the Black self and adoption of the false racial identity of the White Other.
Biased Experimental Fineness and Maturity Results
Authors: Montalvo Joseph G. , Von Hoven Terri M. , Davidonis Gayle
Published: November 2007

In an earlier paper, we developed models and performed computer simulations to understand the variability in coefficients of determination (R2) between fineness and maturity, micronaire and fineness, and micronaire and maturity of cotton. We subsequently concentrated on derivation and testing of several diagnostic models to enhance the R2 and provide information about the analytical quality (accuracy) of the results. We then introduced modeling of biased fineness and maturity results. Error functions were derived based on micronaire values, specifically, Lord's micronaire model. This paper demonstrates testing of a key diagnostic model on two different sample sets of 21 cottons. The results from one sample set — analyzed on the fineness and maturity tester — fit the model. Results from the other sample set — analyzed on both the advanced fiber information system (AFIS) A-2 and AFISPRO — demonstrate a lack of fit to the diagnostic model. This lack of fit is due to bias in the AFIS fineness and maturity measurements compared to the more traditional Lord's micronaire model. As a consequence of the bias, the dynamic range of the AFIS raw data for both fineness and maturity is very narrow. Results are confirmed by image analysis.
Changes in Youth Smoking, 1976–2002
Authors: Pampel Fred C. , Aguilar Jade
Published: November 2007

During the past several decades, smoking prevalence among youth has fluctuated in puzzling and unexpected ways. To help understand these changes, this study tests seven explanations: (a) compositional changes, (b) sample selection, (c) adult smoking, (d) social strain, (e) cigarette prices, (f) tobacco advertising, and (g) other drug use. Figures on smoking prevalence come from the Monitoring the Future (MTF) Surveys from 1976–2002, whereas figures on aggregate determinants for the same time period come from government publications. Graphs of the time-series trends to determine temporal correspondence and time-series regression models to test for statistical influence reveal two variables that have expected effects. Increases in cigarette prices reduce smoking, particularly in the most recent years, and higher marijuana initiation (or use) is associated with greater smoking during most of the time period. However, much of the change in youth smoking, particularly the most recent rise and fall, remains unexplained.
The application of short-term adaptive forecasting techniques in energy management for the control of electrical load
Authors: McDonald J.R. , Lo K.L. , Sherwood P.M.
Published: November 2007

The philosophy of Energy Management has been developed in order to improve operational and economic efficiencies in the supply of electrical energy at the times of peak demands. These peaks last for only a short time and are costly for the supply authority. Energy Management attempts to shift the use of electrical energy from the times of peak demand to those times where the level of the load is relatively low.

There are two distinct divisions within Energy Management which fulfil this requirement: indirect and direct load control. First, through the pricing of electricity, large industrial and commercial consumers can react indirectly in response to pre-published tariffs or to spot prices. Second, the supply authority could employ direct control of suitable domestic appliances. This would require a communications facility between the supplier and the consumer terminal equipment which could be remotely controlled. This paper analyses and simulates the effects of the introduction of a direct load-control strategy. The load to be controlled would be domestic appliances which are modelled by employing a stochastic approach. This would identify the available level of controllable load at any time of the day.

The principal effects of Energy Management are the improvement of system load factors and the reduction of peak loads, thus improving the supply economies and efficiencies. For the consumer, Energy Management could reduce the energy costs for domestic customers with minimal inconvenience, provided that the control strategy is chosen with care.

The paper presents an adaptive-time-series model for short-term load forecasting and incorporates the appliance models in order to estimate the expected response of the domestic load to transmitted control signals. Simulations of simple control strategies are presented showing the avoidance of potentially difficult conditions of simultaneous reconnection of the controlled load.
Use of a conductivity heat-flow meter in fluidised-bed boilers
Authors: Andersson B.-Å. , Johnsson F. , Leckner B.
Published: November 2007

The usefulness of a conductivity type of heat-flow meter for measurements in fluidised-bed boilers is investigated. The design and the calibration of the meter are described. Results from measurements of the local heat tranfer at the walls of fluidised-bed boilers are presented. An error analysis shows that the accuracy of the heat-flow meter is ±9%.
The selection of resistors for precise analogue instrument circuits: a statistical method
Authors: O'Connor B.
Published: November 2007

A method involving a computer is described for selecting resistors for precise analogue instrument circuits. A statistical analysis is carried out which provides formulae for calculating the probability of non-duplication of resistors, and also the predicted discrepancy for specified group and batch sizes. Theoretical and actual values are compared: the agreement is such that the theoretical formulae can be used confidently to specify batch sizes to obtain indicated discrepancies for given group sizes. The method is of practical importance in selecting closely matched resistor ratios, and matched resistors, for precise analogue circuits.
Interactive graphics-based computer-aided system dynamic modelling
Authors: Bailey W.N. , Abdullah F.
Published: November 2007

A computer package MEDIEM (Multi-Energy-Domain-Interactive-Element-Modelling) has been developed for the purpose of interactive modelling of multi-energy domain systems. Model entry is effected interactively, using a mouse, by drawing a 'structure graph' from a set of defined elements in a fixed menu display. This allows rapid and efficient model development from which time and/or frequency-response information can be displayed. The package can be applied to mechanical, electrical, thermal and fluid systems (inclusive of energy conversion) provided that they can be treated on a lumped parameter basis. The paper illustrates the features of MEDIEM by way of simple examples covering electrical circuits, hydraulically coupled tanks, a vehicle suspension system, an electro-mechanical vibrator and two feedback control systems.
Mathematical insight through system dynamics
Authors: Prior Donald E. , Moscardini Alfredo O.
Published: November 2007

This paper considers how the precise world of mathematics is applied to fuzzy ambiguous real-life problems. System dynamics modelling for novice modellers is described, and a comparison made with mathematical modelling, using a simple physics problem as an example. The special place of time in modelling is examined. A key question of the paper is the purpose of modelling- is it to permit meaningful calculations within certain predefined accuracy limits, or is it to understand as many causal mechanisms as possible within the modeller's mental limits?
Identification and performance simulation of a hybrid i.c.-engine/battery electric automotive power train. Part 1: The i.c. engine
Authors: Masding P.W. , Bumby J.R.
Published: November 2007

This paper, and its companion Part II, describes the modelling and simulation of the drivetrain components in a hybrid i. c. -enginelbattery electric car. In this part particular attention is paid to describing the hybrid drive system and the identification procedure used to obtain discrete z-transfer functions of the system components. A full physical analysis of the i.c. engine is described and used, along with the identification procedure, to identify discrete transfer functions relating engine torque and speed to accelerator demand. A comparison of experimental and simulated data confirms the validity of the identified transfer functions. With these transfer functions, and those produced in the companion paper for the electric traction system, it is possible to design a main hybrid vehicle control unit which can both schedule, and control, the torque from either, or both, the i. c. engine and the electric traction motor in a smooth manner.
Multi-microprocessor control of processes with pure time delay
Authors: Mitchell R.J.
Published: November 2007

In 1967 a novel scheme was proposed for controlling processes with large pure time delay (Fellgett et al, 1967) and some of the constituent parts of the scheme were investigated (Swann, 1970; Atkinson et al, 1973). At that time the available computational facilities were inadequate for the scheme to be implemented practically, but with the advent of modern microcomputers the scheme becomes feasible. This paper describes recent work (Mitchell, 1987) in implementing the scheme in a new multi-microprocessor configuration and shows the improved performance it provides compared with conventional three-term controllers.
Integrated microprocessor control of a hybrid i.c. engine/battery-electric automotive power train
Authors: Masding P.W. , Bumby J.R.
Published: November 2007

This paper describes the development of a fully integrated microprocessor control system for a hybrid i. c. -enginelbattery-electric automotive power train. Torque control systems for the internal-combustion engine and the electric-traction motor are designed using digital transfer functions and indirect methods of torque measurement. Root-locus methods are used in all designs to provide fast, critically damped closed-loop response. In all cases simple proportional-plus-integral control proved sufficient to achieve this. An overall cycle speed controller allows the laboratory test system to be exercised over any test driving cycle and offers the ability to carry out sophisticated power sharing and transmission shifting strategies.
Towards a general procedure for dynamic model development
Authors: Foss A.M.
Published: November 2007

Offering a modelling and simulation has resulted in supplying models of various types in various application areas, for numerous purposes and to many clients. To provide this service cost-effectively, it is highly desirable to idendtify patterns so that a general procedure for model development may be derived.

It is useful to look at the related, but more mature, discipline of software engineering in which a development procedure involving a number of distinct tasks has been identified. Taking a simple example of a hydraulically controlled gangway, the analogy between modelling and software development is explored.

The result of this comparison is the division of model development into a set of analogous tasks, and the organisation of these tasks into a development procedure. This procedure highlights the need for a document detailing the model purpose, top-level design, equations derivation strategy and validation strategy. Validation is defined as the process of gaining confidence that the model fulfils its purpose, as distinct from verification, that the equations have been implemented correctly, and matching, fitting of simulated data to measured data.
Validation of helicopter mathematical models
Authors: Bradley R. , Padfield G.D. , Murray-Smith D.J. , Thomson D.G.
Published: November 2007

The validation of theoretical flight-mechanics models for helicopters is of considerable practical importance for the design of new rotorcraft. Conventional validation methods have involved comparisons of the responses of simulated and real helicopters to a simple input, such as a step or a pulse. The use of sufficiently small inputs allows the development and validation of linear models which can be used by the control system designer to endow the helicopter with acceptable stability characteristics and handling qualities over a limited operating envelope. For non-linear models, more suited to the investigation of large and rapid manoeuvres, one approach to model validation is to' use linearisation about a range of trim conditions and apply system identification and parameter identification techniques. Additionally, it is possible to transform the problem to the frequency domain in order to eliminate subsystems from the validation process. The large amplitudes of typical nap-of-the-earth manoeuvres demand a new approach to validation. Inverse simulation has demonstrated its value in this context.
Advantages of and developments in dual bluff-body vortex flowmeters
Authors: Bentley J.P. , Nichols A.R.
Published: November 2007

The paper begins by reviewing the main performance characteristics of vortex flowmeters - eg, signal stength, signal-to-noise ratio, frequency, repeatability, meter factor and blockage ratio. It then develops a performance equation which calculates the total time required to capture sufficient cycles to achieve a given overall repeatability. From this equation we see that for a typical single bluff-body vortex meter the time required to achieve an overall repeatability of 0.02% is 387min. This underlines the point that single bluff-body meters are in general not very useful for fiscal metering or custody-transfer applications.

The paper then reviews the general principles of vortex shedding from two bluff bodies in tandem, explaining that there are two distinct flow regimes, depending on whether the bluff-body separation is less than, or greater than, a critical value. A summary of results is presented for initial tests on 15 combinations of two rectangular bluff bodies in tandem, together with three single bluff bodies for comparison. These initial tests were carried out in a 300 mm diameter wind tunnel at a free-stream velocity of 6.5 mls and a turbulence intensity of 0.5%.

Seven combinations with optimum separations were then tested over a free-stream velocity range between 0.6 and 13.0 mls and at three turbulence levels. Detailed results showing the variation in RMS vortex velocity, signal-to-noise ratio, meter factor and percentage frequency standard deviation with free-stream velocity are presented. Certain of these combinations give a far more regular and repeatable vortex signal than single bluff bodies; the time required to achieve an overall repeatability of 0.02% is as low as 33 min.

All of the above dual combinations have a small separation, so that vortex shedding takes place behind the downstream bluff body only. Detailed maps of the vortex field around certain dual combinations are presented which show that, in certain cases, the oscillations of boundary layers in the gap are strongly correlated with the oscillations of boundary layers moving around the bluff bodies. Thus the vortex shedding from the downstream bluff body is reinforced by oscillating boundary layers moving through the gap.
Interconnected spatially distributed systems
Authors: Whalley R.
Published: November 2007

In this paper system models arising from process-plant installations are derived in the form of an interconnected series of mixed, distributed and lumped-parameter realisations. The terminal characteristics of these models is shown to be a rational, multidimensional function of a finite set of transformed discrete time-delay variables which may be used in feedback-control studies. By employing a linear mapping of the support of the model it is established that stability can be assessed using a corresponding algebraic function to that of the denominator of the system model. Simple worked examples are used to illustrate the procedure.
An adaptive time-of-flight anemometer
Authors: Tatnall M.L. , Sodhi C.
Published: November 2007

It is shown that the frequency of operation of self-oscillatory flowmeters fails to provide an absolute measure of fluid-flow velocity. A technique is described which makes use of the signals generated in a self-oscillatory system as adaptive markers for use in a time-of-flight method of flow measurement able to operate over a wide range of flow velocities. Experimental results are shown illustrating the operation of the device.
A laboratory sigma-delta modulator
Authors: Lewis C.P. , Hesketh T.G.
Published: November 2007

A simple method of analysing the limit-cycling behaviour of a sigma-delta modulator is introduced which is used to determine the performance of a system designed specifically for student use. The analysis is extended to predict the closed-loop performance of the modulator.
Lumped-parameter representation of fluid-system transients
Authors: Suwan K. , Anderson A.
Published: November 2007

Flow and pressure transients in closed pipes are described by non-linear hyperbolic partial differential equations. In many control applications a discrete-space lumped-parameter ordinary differential equation model is required. With such representations, care is needed to ensure that they retain essential physical characteristics of the phenomena described. Intentionally or otherwise, most of these fluid-system models are related to the numerical discretisation technique known as the Method of Lines. Aspects of implementing this are investigated, including the form of the basic equations and variables, representation of pipe friction, choice of interpolating polynomials in space and method of integration in time. These are compared with the standard Method of Characteristics solution for the original partial differential equations to eliminate any potential numerical instabilities, parasitic transient solutions or inconsistencies between steady and transient states which might influence adversely system control or stability studies. The Method of Lines is most appropriate for parabolic problems, and many existing applications to fluid transients are found to be satisfactory only where changes are gradual and continuous. The preferred formulation is free from this restriction, and applied to a stability investigation (prediction of compressor surging) is shown to perform reliably.
Materials analysis using laser-based spectroscopic techniques
Authors: Goddard B.J.
Published: November 2007

In this paper several laser-based spectroscopic methods capable of detecting low concentrations of a particular element are described, with particular emphasis on the contrasting techniques of Laser-Induced Breakdown Spectroscopy (LIBS), and Resonance Ionisation Mass Spectroscopy (RIMS). Simple mathematical treatments, based on thermodynamic considerations and rate equation models, are given for both systems, allowing semiquantitative analysis from the magnitudes of observed signals. Experimental results are presented for both methods. For LIBS these include the determination of the concentration of alloy constituents, the detection of surface contaminants and the use of measured line intensities to calculate electron temperatures in laser-produced plasmas. For RIMS, detection of the geologically important element rhenium (Re) was accomplished in the gas phase at a level of 4 x 10 8 atoms/cm3, and the relative proportions of the stable isotopes 185Re and 187Re were measured with the use of a quadrupole mass filter. In addition, an optogalvanic system is described, which was used to calibrate the wavelength of the RIMS resonance to an accuracy of 0.013 nm.
Flight control system design for VSTOL aircraft using switched H∞ controllers
Authors: Hyde R.A.
Published: November 2007

This is a design study on a Generic VSTOL Aircraft Model (GVAM) supplied by the Royal Aerospace Establishment, Bedford. Widely varying dynamics requires some form of gain scheduling or switching. The approach taken is to switch between linear controllers designed on linearisations of the non-linear model. The linear designs make use of an open-loop singular-value shaping technique developed by McFarlane and Glover (1988) and McFarlane, (1988) which optimises the system robustness to perturbations of the normalised c oprime factors of the plant. Switching between controllers is achieved using a technique proposed by Hanus, (1987) which permits smooth transition between controllers. A more detailed account of the design here can be found in Hyde, et al. (1990)..
A technique for measuring convective heat transfer at rough surfaces
Authors: Wang Z. , Ireland P.T. , Jones T.V.
Published: November 2007

A new method of measuring local heat transfer coefficients to rough surfaces has been developed. The technique was applied to an idealised section of a large-scaled model of a turbine blade cooling passage to assess the effect of surface irregularities which result from the blade manufacturing process. The experimental method is described in full, and the results are presented for tests on an isolated pin-fin situated in fully developed channel flow. The heat transfer coefficients measured to the rough surface of a plain passage were found to be in excellent agreement with that predicted from velocity measurements.
Twin-wire resistance-probe manometer for very low differential pressure measurement
Authors: Liu C.Y.
Published: November 2007

A precision twin-wire resistance-probe manometer has been developed for the purpose of measuring very low differential pressure. From the extensive performance tests conducted, it was found that the output voltage from the manometer is linearly proportional to the difference in pressure. Several ranges of calibration were made; the accuracy of the output depends upon the range and sensitivity setting of the manometer. For the range of 0-0.2 mm of water with a sensitivity setting of 1000 mVlmm, the accuracy of ±0.02 Pa (about ± 0. 002 mm of water) was achieved.
Embodiments of organisational fitness
Authors: Schwaninger Markus
Published: November 2007

In this contribution, a multi-level concept of organisational fitness is expounded and synthesised with the framework of the VSM, Stafford Beer's Viable System Model. The concept presented is based on recent progress made in the field of planning theory. The main proposition is that organisations must steer themselves on the grounds of orientators which pertain to different logical levels. These must be 'under control' simultaneously, despite contradictions between them. A set of orientators for an organisation to be viable is outlined. In this framework, the notion of 'viability beyond survival' is developed. The ideas expounded are illustrated by means of a real-life case.
Experimental intercomparison of Coriolis mass flowmeters
Authors: Cascetta F. , Cignolo G. , Goria R. , Martini G. , Rivetti A. , Vigo P.
Published: November 2007

This paper presents the first results of a systematic experimental intercomparison of the metrological performances of seven Coriolis mass flowmeters that are commercially available in Italy. Each of them was mounted and tested with similar operating conditions in the IMGC primary flow calibration facilities, Which enabled the authors to vary some of the most significantly influential factors. The test fluid was water at room temperature, and the maximum flow rates were ranged between 2.8 and 4.5 kg/s, according to each manufacturer's specifications.
The real-time application of VSS controllers: implementation on elements of a 'direct-drive' arm, a Syke robot and a PUMA robot
Authors: Richards R.J. , Reay D.S.
Published: November 2007

The results of the application of new controllers on three robot arms is described. The initial application of variable structure control on a two link direct-drive arm is followed by its implementation on two industrial arms, a Syke robot and a PUMA arm. To allow adequate computational power in the robot controller, a separate controller was built for the first arm which was demonstrated to be portable for use on both of the industrial arms.
Improved transient fault simulation on a laboratory model of a turbine-generator
Authors: Nouri H. , Colfer G.W.
Published: November 2007

In order to enable a simulated fault current in the region of 4000 A to produce a pulsating magnetisation in the stator coil, an arrangement of a parallel tuned-circuit was constructed. The performance characteristics of the tuned-circuit were assessed from an analytical solution (Transient response method) and modelling on an Apollo computer using the transient response package.

The inrush current which is associated with the starting of the tuned-circuit was controlled with a soft-start, which increased the input voltage across the coil from zero to full preset value in 50 cycles. The soft-start circuit consisted of two anti-parallel thyristors, current-limiting resistor, phase-angle trigger unit and its control circuitry.

Spurious triggering of the thyristor was greatly reduced by placing the current-limiting resistor in between the supply and the thyristor. The possible causes are discussed.

A detailed comparison of the measured flux for the fault current of 4000A at an air-gap of 75 mm, for conditions with and without the endbell, at the end of the rotor suggests that the conduction current is dependent on the contact resistance at the endbell and rotor interface.
Adaptive control of industrial processes
Authors: Smith L.S.P.S.
Published: November 2007

The paper reviews adaptive tuning techniques which have been implemented in commercial controllers, and successfully applied to a variety of industrial processes. Some characteristics of industrial processes which cause problems for adaptive tuners are discussed, together with solutions to these prablems.

Gain-scheduling is shown to be a useful alternative to continuously adaptive techniques where robustness is required with changing plant conditions. The closed-loop cycling method is discussed both as an independent auto-tuning technique, and as a pre-tune for parameterising continuously adaptive tuners. The strengths and weaknesses of waveform analysis techniques and model-based predictive controllers are highlighted.

A novel self-tuning output algorithm for driving motorised valves is proposed as a solution to problems encountered in controlling processes using these actuators.
On LQG self-tuning control: implementation and application
Authors: Forrest S.W. , Grimble M.J. , Johnson M.A.
Published: November 2007

The design and construction of a self-tuning controller software package intended for general industrial use as a single-loop controller is presented. An indirect self-tuning regulator is implemented with a Linear Quadratic Gaussian (LQG) control law, and a prediction error parameter estimation algorithm. The control law is derived using a polynomial equation approach. The software design is modular, avoids the use of global variables and includes provision for plant protection. A special feature of the work reported is the emphasis on jacketing software and the user interfaces necessary for routine industrial application. Experimental results demonstrate both the functionality and practicality of the device, and its fail-safe software mechanisms. The field test for the first industrial application is on a Main Boiler Feed Pump (MBFP) speed control sub-loop in a power station application. Some details of this application are given.
Metrological evaluation of several Coriolis mass flowmeters
Authors: Cascetta F. , Cignolo G. , Goria R. , Martini G. , Rivetti A. , Sardi M. , Vigo P.
Published: November 2007

This paper is the final report of an evaluation and research project on the metrological performances of six different mass flowmeters of the Coriolis type which were extensively tested, under identical operating conditions, at the IMGC flow measurement laboratory, making use of the Italian national standard calibration facilities. The first results of the evaluation project, already detailed in a previous paper, are also briefly reviewed.
Use of neural networks for parameter prediction and quality inspection in TIG welding
Authors: Zeng X.M. , Lucas J. , Fang M.T.C.
Published: November 2007

The potential of using neural networks in TIG welding has been investigated. It has been successfully demonstrated by using a commercial package, BRAIN-MA KER, on an IBM PC that the feed forward multilayer neural network, trained by the back-propagation algorithm with suitable structures, can give satisfactory predictions for both manual and mechanised TIG Welding. A neural network has been trained to predict the welding conditions (procedure) necessary to produce a good quality weld. The types of defect arising by the use of other welding conditions are also predicted. The feasibility of incorporating a neural network into a welding control system is also discussed.
Radiation attenuation of pulverised fuel in pneumatic conveying systems
Authors: Van Y. , Byrne B. , Coulthard J.
Published: November 2007

Following investigations into the characteristics of radiation attenuation of pulverised fuel in pneumatic conveying systems, practical considerations in designing a radiometric meter for the measurement of solids volumetric concentration are presented. Measurement errors due to variations in moisture content and chemical composition are discussed.
Multivariable multidimensional computer controlled systems
Authors: Whalley R. , Zeng Z.
Published: November 2007

Design and analysis procedures for multivariable multidimensional computer controlled systems are presented. An algorithm enabling relative stability to be assessed is derived and the stable portion of the gain space for a two-dimensional system is computed.
Self-tuning expert control for turbogenerator systems
Authors: Flynn D. , Hogg B.W. , Swidenbank E.
Published: November 2007

Practical application of adaptive controllers necessitates the incorporation of substantial monitoring or jacketing software. An expert system is proposed to perform such duties, allowing a distinction to be made between the control and identification algorithms, and the accompanying supervisory functions. The implications of employing expert systems for real-time environments are outlined, along with their consequences for control of a turbogenerator excitation system. An industry standard VME platform linked to a network of Inmos T800 transputers is used to establish the self-tuning expert controller. Illustrations are given of how the performance and robustness of the adaptive controller can be greatly improved through expert system intervention, both in simulation and on a laboratory micromachine system.
A practical optical force-feedback microphone
Authors: Karatzas L.S. , Keating D.A. , Usher M.J.
Published: November 2007

A novel technique of measuring diaphragm displacement in microphones using a laser-diode Fabry-Perot system is presented. The microphone diaphragm is held within an electrostatic force-feedback loop so as to improve the performance. A second loop operates around the laser, for noise minimisation purposes.

Following a brief introduction to the subject of optical detection in microphones, the modified Fabry-Perot interferometer is described, and the complete system with the two feedback loops presented. The characteristics of the laser driver and laser diode are examined. Theoretical responses are shown, for different cases, and noise calculations yield the dynamic ranges without feedback. The effect of feedback is then examined, both around the laser (electronic) and around the microphone capsule (electrostatic), and the dynamic ranges are recalculated to show the advantages of feedback. Intended directions for further research are also discussed.
Condition monitoring of automatic control systems using parameter and systems identification: a numerical investigation
Authors: Firoozian R. , Lee C.C.
Published: November 2007

The intense international competition for reducing manufacturing cost has forced many industrialists to implement total automatic control over a wide range of products and manufacturing processes. This, of course, results in substantial reduction of manpower on the factory floor and the task of condition/performance monitoring must be replaced by appropriate computer based software.

Many engineers have employed vibration analysis methods developed in recent years to monitor the condition of critical components such as gearboxes, bearings, belt-drives and rotating elements which are more susceptible to failure than other mechanical parts of machines. However, these methods are suitable for identifying faults that generate substantial increase in vibration level measured at a suitably selected point.

The authors argue that the parameter and system identification technique presented in this paper gives far more reliable information about imminent failure than the method mentioned above. The availability of high-quality feedback signals(s) removes the need and difficulty of selecting a suitable transducer. The method is based on the concept that the dynamic behaviour of automatic control systems can be modelled by identifiable linearised/ nonlinear transfer function with constant coefficients. The deviation of each parameter from the norm value indicates the failure/wear of respective elements in the system. The paper demonstrates that these parameters can be estimated relatively simply with efficient use of computer time and memory.

The method uses state variable filter (SVF) and recursive least square optimisation algorithm so that it may be implemented as an ON/OFF-line condition monitoring package. The numerical investigation from simulated data shows that the identified coefficients may be used to predict components failure. In addition, the algorithm is capable of identifying the relevant coefficients accurately if the noise level on the measured signal is less than 10% which is usually the case for most automatic control systems with high-performance feedback transducers. The procedure of designing a suitable filter capable of converging rapidly is discussed and the results show that a compromise has to be made between speed of conver-gence and the magnitude of noise in the feedback signal.
Nonlinear control of an autonomous tracked vehicle
Authors: Ping Lu  , Lin Kuo-Chi
Published: November 2007

The problem of motion control of an autonomous tracked vehicle is considered in this paper. While some well-known nonlinear control techniques are shown to be inapplicable to the problem, a recently developed nonlinear control approach is successfully applied. The performance of the controller in tracking desired trajectories is evaluated. The robustness of the controller is demonstrated by considering modelling uncertainties due to side slip of the vehicle.
An automatic trim recovery control system for engine-out take-off and initial climb of twin-engined light aircraft
Authors: McLean D. , Descombes C.
Published: November 2007

The problem of flying with one engine inoperative is a very difficult one for pilots of twin-engined general aviation (GA) aircraft, particularly at take-off and during initial climb. This paper presents an account of some of the effects which occur as a result of an engine failure during take-off and also the details of a proposed automatic control system design to recover the aircraft's heading and to make the aircraft climb to a suitable height at which the pilot can safely resume full control. A number of digital simulation results are presented to illustrate the nature of the problem and the performance which can be obtained from the proposed system.
A discrete characteristic locus design for a multichannel structural test system
Authors: Rossiter J.A. , Pratt R.W. , Smith K.J.
Published: November 2007

Structural tests are carried out in the automotive and aerospace industries to assess fatigue and vibration properties of engineering structures. Very often the multivariable nature of these tests is ignored and a sequential loop closure scheme is used with PID controllers in each loop. Earlier work has focused on the application of continuous-time Nyquist Array and Characteristic Locus methods to such tests. This paper extends that work by considering a discrete design approach to the Characteristic Locus method. The design process for a two-input two-output system and subsequent implementation on a beam and vibrator rig is described. With modest computational hardware, excellent results are obtained and shown to be superior to those obtained from the implementation of a discretised continuous-time Characteristic Locus controller.
Design of an electrostatic suspension system with minimum electric disturbing torque - for precision electrostatic gyroscopes
Authors: Yang W.Q.
Published: November 2007

An electrostatic gyroscope (ESG) requires an electrostatic suspension system (ESS) to keep its rotor suspended in a vacuum cavity. The conventional ESS operates with high standing voltage on opposing electrodes that causes a large electric disturbing torque (EDT) applied to the gyro rotor, with consequent loss of accuracy. In the newly-designed ESS the suspension voltage is applied to one electrode only, whilst the opposing electrode is kept at zero potential. With no standing voltage the EDT is kept to a minimum. The new system has an inherent square-root compensation. Theoretical analysis and computer simulations show that the new system meets the requirements for marine applications.
Image guided orthopaedic surgery design and analysis
Authors: Phillips R. , Viant W.J. , Mohsen A.M.M.A. , Griffiths J.G. , Bell M.A. , Cain T.J. , Sherman K.P. , Karpinski M.R.K.
Published: November 2007

Within the next few years it is envisaged that a number of computer assisted surgery products will become available. For many surgical procedures, outcome of surgery,, will rely on the accuracy and repeatability with which a computer assisted surgical toolperforms its task. This paper presents a Computer Assisted Orthopaedic System (CAOS) which takes an image guided approach to planning and implementing a trajectory, to assist an orthopaedic surgeon. Accurate delivery of this trajectory is achieved via an intelligent guide.

This paper details the design issues and identifies the registration and calibration techniques used by the CAOS intelligent guide. The paper also enumerates, and where possible quantifies, thefactors that influence the accuracy performance of the system. Accuracy trees are used to show the root source of inaccuracies and how they propagate and combine in a system.
Achieving benefits using traditional control technologies
Authors: Oglesby M.J.
Published: November 2007

The basic techniques of cascade and feedforward control are described together with the types of process problem to which they are suited. Their use is illustrated with simple examples. Among these are three-element level control, heat exchanger control and distillation control. The latter example quotes the magnitude of the benefits which can be achieved in practice.

Other areas where traditional techniques can be used are given. Amongst these are override controls with an illustration from distillation control, 'valve position control' with an example from a fired heater system and the use of calculated variables demonstrated by heat input control.
Computer aided system modelling using interactive computer graphics
Authors: Gonzalez-Altamirano G.R. , Owens T.J.
Published: November 2007

A program for computer aided system modelling is described. The program was developed to analyse step responses by identifying certain characteristics typical of systems of a given order. Graphical criteria are applied to responses to generate models in a simple interactive fashion. The results of experiments designed to evaluate the program graphically show the suitability of second-order-plus-time-delay models for processes with sigmoidal step responses. The program demonstrates the feasibility of using personal computers for graphical modelling.
Vehicle lateral control modelling for steering automation in the ADVANCE-F system
Authors: Chang Tang-Hsien
Published: November 2007

In order to set up a vehicle lateral controller for steering automation under the project ADVANCE-F, the frequency-shaped linear quadratic control theory is utilised to design the system for meeting requirements involved in tracking precision, robustness and ride quality by properly choosing the weighting factors. The final controller is composed of a full state feedback regulator with an observer. The simulation results reveal that the controller performs satisfactorily under a variety of situations including wind gust disturbance, transition curve and man-machine switching in a wide speed range from 0 kph to 120 kph.
Numerical and experimental analysis of laminar flow through square-edged orifice with variable thickness
Authors: Sahin B. , Ceyhan H.
Published: November 2007

In this work, axisymmetric, viscous, steady, incompressible and laminar flow through square-edged orifices has been studied. A numerical solution of the steady-state vorticity transport equation has been obtained from the two-dimensional Navier-Stokes equations. Finally, streamline patterns, vortex formations and separated flow regions have been predicted.

The effects of orifice plate thickness and Reynolds number on the flow characteristics have been investigated numerically and experimentally. The Navier-Stokes equations have also been integrated in order to compute the pressure distributions through the orifice. From these results, the orifice discharge coefficient has been computed and examined as the Reynolds number and the orifice plate thickness were varied. A comparison has been made between the experimental results, the numerical predictions and available experimental results. The predicted flow discharge coefficient values agreed closely with the experimental results.
Design of H∞ controller for precise positioning and comparison with PID control
Authors: Takahashi Yoshihiko , Hayase Minoru
Published: November 2007

A new control scheme based on H∞ control theory is proposed for precise positioning. In comparison with PID control, the validity of the proposed scheme has been confirmed by simulations at the micron scale. The effects of disturbances such as Coulomb friction and mechanical resonance mode are treated explicitly at the controller design stage. The proposed control scheme exhibits rapid response with good suppression of the effects of resonance vibration and Coulomb friction. Root locus simulation results for the closed-loop transfer function have shown that H∞ control is able to stabilise the mechanical resonance frequency mode, whereas PID control is not. Frequency response simulation results for the closed-loop transfer function of H∞ control have shown that the cut-off frequency increases and the mechanical resonance mode stabilises simultaneously when the H∞ norm condition, γ, is decreased.
PID controller tuning by an interactive multi-objective optimisation method
Authors: Wang Feng-Sheng , Yeh Chi-Liang , Wu Yieng-Chiang
Published: November 2007

An interactive multiobjective optimisation method was introduced in this study to tune satisfactory modes of a PID controller. An interval process was modelled by a set of transfer functions in this study. In general, such processes could not be handled by a PID controller which was tuned by a single-objective optimisation method. A trade-off tuning rule based on multi-objective optimisation methods was introduced to overcome this drawback. The robust stability for this multi-modelling control system performed by the multi-objective optimisation approach was automatically guaranteed. Extension to cascade control systems was also developed.
A vector-controlled doubly-fed induction generator for a variable-speed wind turbine application
Authors: Atkinson D.J. , Lakin R.A. , Jones R.
Published: November 2007

This paper examines the performance of a vector-controlled doubly-fed induction generator for wind turbine use. The scheme is considered for variable-speed-range applications to produce a greater wind energy capture from varying wind velocity. A major advantage of the doubly-fed scheme over the squirrel-cage generator is the reduced volt-ampere rating of the power converter used to control the rotor current. The singly-fed scheme requires that the power converter is able to carry the full generator output. In order to produce decoupled regulation of active and reactive output power, the rotor current is controlled using field orientation principles. The measurement of rotor position and the grid voltage vector position allows the rotor current to be controlled in a reference frame closely associated with the stator magnetising current. The stator active and reactive power are also measured and fed back into outer Ps and Qs control loops. The Ps and Qs controllers produce d and q axis rotor current demands for the inner rotor current vector controller. By control of the reactive power loop the generator can be made to produce power at unity power factor. The vector control of rotor current is carried out using a commercial PWM inverter equipped with vector control hardware as standard. The inverter also produces a unity power factor sinusoidal current interface to the grid network. The performance of the scheme is examined using both simulation and experimental results. The decoupling control of active and reactive power is demonstrated and shows the ability to generate power at unity power factor.
Control of an AUV in the vertical and horizontal planes: system design and tests at sea
Authors: Silvestre C. , Pascoal A.
Published: November 2007

The design, implementation and experimental testing of a control system for an autonomous underwater vehicle (AUV) are described. The paper introduces the nonlinear dynamic model of a prototype AUV named MARIUS and formulates a general problem of vehicle control for precise manoeuvring in the vertical and horizontal planes. The methodology adopted for control system design is nonlinear gain-scheduled control, whereby a set of finite H-infinity controllers is scheduled on the vehicle speed. The paper summarises the basic design steps and decribes a new method for the practical implementation of nonlinear gain-scheduled control systems that avoids some of the pitfalls described in the literature. Experimental results obtained during the sea trials with the vehicle in Sines, Portugal, are presented and discussed.
Measurement of temperature of a moving surface at a temperature below ambient
Authors: Fugang Li  , Wuyong Xia  , Biao Shen  , Fuqun Shao
Published: November 2007

The paper introduces the heat balance method of temperature measurement. It uses heat pump cooling to make a balance field of temperature between the object to be measured and the measuring head. The test was made in a stenter and a surface temperature of a moving fabric was measured and test results are given in the paper.