bluuebunny/crossref_metadata_2025 huggingface dataset:
Automatic shape analysis of crystal glasses
Authors: Nixon Mark
Published: November 2007

This paper presents an efficient algorithm as part of a programme of research in automatic shape inspection of quality crystal glasses. The shape of these glasses can vary since they are usually hand made and is important be cause they are often sold in matching sets. Shape analysis concerns the match of the outline of glass to a reference (or master) shape. An algorithm was developed to provide the offset by which the current outline needs to be translated and the factor by which it needs to be scaled, in order to register the outlines to provide the best least-squares match between the current outline and the master shape. Results are included which demonstrate the accuracy of the algorithm both in a simulated environment and when applied to real pictures. The difference data from the best match appears inadequate to grade glasses of the same type but can be used to sort different glasses reliably.

An efficient algorithm has therefore been developed to provide the best starting point from which shape comparison can ensue, and research is in progress to capitalise on this technique.
Model reference adaptive control of an electromechanical servo system
Authors: Figueredo K.R.A. , Edge K.A.
Published: November 2007

The tuning of classical, servo system controllers is often problematical, owing to the presence of system nonlinearities and unmeasured disturbances. Adaptive control schemes are of growing interest since the system is self-tuned, such that some pre-defined performance requirement is met, regardless of variations in system parameters.

This paper describes the design and implementation of a microprocessor-based model reference adaptive controller for a small electromechanical ,servo system. The control scheme is based on an implementation of hyperstability theory, and robustness is enhanced by the incorporation of certain 'safety-jacket'features.

Experimental studies demonstrate that the controlled process tracks the reference model to a consistently high standard, even in the presence of perturbations to the process dynamics. It is also shown that the design of the error filter plays an important part in the speed of adaptation, and guidelines for error filter design are proposed.
A general-purpose digital filter using the FAD integrated circuit
Authors: Coates Prof R. , Cheung K.Y. , Mathams R.F.
Published: November 2007

This paper describes the design and performance of a digital filter basfd upon the FAD (Filter And Detect) integrated circuit. Although the filter was initially devised to provide economical and flexible processing for low-and medium-frequency sonar system testing, simulation and signal processing, it may also be applied to a wide range of fixed-parameter or time-variable filtering tasks in the frequency band to 40 kHz.
Computer-aided optimisation of simplified discrete models for control systems
Authors: Al-Assadi Salem A. K. , Marouf Azzam A.
Published: November 2007

A computer-aided method for the computation of optimal discrete models with reduced orders for control systems is presented in this paper. The method used for simplification utilises a time-domain-optimisation technique to search for optimum values for the parameters of prespecified reduced-order discrete-time models for control systems. The measure of success of simplification is taken to be the minimum integral squared error between the step responses of the simplified discrete-time models and that of the actual system at sampling instants. Two examples are considered to illustrate the usefulness of the method in simplifying control systems given in various forms. One of the examples considered was to obtain reduced-order discrete-time models for a fourth-order Butterworth filter. The method proved to be powerful in finding the optimal discrete models with reduced orders for both short and long sampling periods.
A direct linear drive system with a laser interferometer and digital state-variable feedback control
Authors: Takahashi Yoshihiko , Takahashi Atsushi
Published: November 2007

A linear driving technique with a small degree of wobbling for an optical disc cutting machine is discussed. The track-pitch in the order of one micrometre causes low-velocity linear driving, by means of which the stage holding the exposure optics is carried in the disc radius direction, while the disc is rotating. In order to obtain low velocity, a calculating technique using the displacement output from a laser interferometer was adopted. A voice-coil motor drove the moving part directly as an actuator, and, for maintaining the accuracy of the calculated digital velocity, a digital state-variable feedback control was applied. This paper describes the main features of the mechanical system and its mathematical model in the form of a pulse transfer function, the low-velocity detection using a laser interferometer and the stability of the laser interferometer, the digital state-variable feedback control, and the simulation and experimental results. Finally, a small amount of wobbling, less than ± 0.13 μm with 80 μm/s velocity was achieved, and the validity of the proposed technique was confirmed.
A current overview of system dynamics
Authors: Wolstenholme Eric F.
Published: November 2007

The purpose of this paper is to present a state-of-the-art survey of the subject of system dynamics. This will include a brief historical review and an outline of the methodology, which is increasingly being recognised as having two separate phases. These are the qualitative diagram construction/analysis phase and the quantitative simulation phase. The purpose of the former is to develop a perspective on the system under study, covering its processes, information, organisational structure and strategies. Alternative types of system dynamics diagrams will be presented for this phase, the generic building blocks of these explored and some aspects of qualitative analysis discussed. The purpose of the simulation phase is to translate the system diagrams into behaviour over time. A summary of the steps of simulation analysis will be given and attention drawn to new thinking in sub-techniques and developments in simulation languages.
Guidance of an autonomous guided vehicle using low-level ultrasonic and odometry sensor systems
Authors: Pears N.E. , Bumby J.R.
Published: November 2007

A method of guidance is described for an autonomous guided vehicle (AGV) operating in a pre-defined and structured environment such as a warehouse or factory. The guidance system requires a series of data describing concatenated curved and straight-line segments to be passed to the vehicle as a representation of a planned path within its environment. The coordinate position of each line segment, the associated AGV direction, and the demand speed constitute a series of commands which are queued and then executed in sequence. In order to execute commands, the AGV is equipped with two-level sensor systems, ultrasonic transducers and odometry, which allow it to estimate and correct its global position continually. In addition to a queue of commands, the AGV also has a pre-programmed knowledge of the position of a number of correction boards within its environment. When the AGV passes such a correction board, it can measure its position relative to the board in the local frame of the board. This is then transformed into a global position correction. Position corrections appear as step disturbances to the control system. The control system is arranged so that it allows the vehicle to move back on to its planned trajectory after a position correction in a critically damped fashion.
Non-linear filtering to improve dexterity in spatial control
Authors: Bosman D. , Bakker W.
Published: November 2007

Task-dependent response - eg, in instrument calibration, spatial positioning and the like - is a long nursed requirement: transition to the end state very fast, albeit imprecise, followed by slower but very accurate final action. The realisation, of course, is a non-linear filter which can take many levels of refinement. In this paper the analysis is presented of the most simple continuous type and it is shown that signal-dependent overshoot (associated with fast response) can be obtained using networks with strictly low-pass (non-negative) impulse response.
Some new thoughts on dead-beat control in sampled-data systems
Authors: de Paor Annraoi M.
Published: November 2007

New approaches to the problem of dead-beat control in sampled-data systems, devised by the author for undergraduate instruction, are presented. Cascade control is discussed first; novel methods of computing control and output sequences in response to a step input are developed; and the problem of stability is highlighted. Stability problems are then resolved using a controller based on the theory of Observers, A very brief history of dead-beat control is given, in order to clarify the origin of Kalman's algorithm.
Sensitivity minimisation in computer control systems
Authors: Whalley R.
Published: November 2007

The sensitivity of linear, shift invariant system models to parameter variations is discussed. Conditions minimising the sensitivity of the system model to these variations are derived, enabling stability margins to be maintained.
Investigation of the enlarged least-square estimator combined with a classical PID controller
Authors: Teng F.C.
Published: November 2007

PID controllers of two degrees of freedom structure were implemented by Teng and Sirisena (1988). However, they may not be suitable in practice because their structure may not be understood easily by process engineers in industry. In this paper the enlarged least-square estimator in Teng and Sirisena (1988) is combined with the popular discretised classical PID controller. A Smith predictor is added to the controller for the control of dead-time process. The enlarged least-square estimator cope well with time-varying dead time owing to its adaptive nature. Simulation and experimental results verify that the new controller performs satisfactorily.
Double integrator processes with transient rate feedback: tutorial redesign using integral performance measures
Authors: de Paor Annraoi M.
Published: November 2007

Double integrator processes damped by transient velocity feedback are designed by minimising quadratic performance integrals involving error, error rate and error acceleration using step, ramp and step-plus-ramp testing functions. The approach is unified via the Liapunov matrix equation. Comparisons are drawn with earlier frequency-response and analytical-root-locus studies in instrument servomechanisms with inertial damping, which are characterised by the same overall transfer function. An adaptive control strategy is outlined.
Control and monitoring of a froth flotation column using a personal-computer
Authors: Pal R. , Masliyah J.
Published: November 2007

A computer-automated froth flotation circuit was designed and developed. Control and monitoring of the flotation column was carried out using a personal computer equipped with an inputloutput interface device. Process control strategy and analysis of the system are presented. The system hardware and software that were designed and developed are discussed.
A phase-sensitive optical heterodyne interferometer for surface height measurement
Authors: Offside M.J. , Somekh M.G.
Published: November 2007

A phase-sensitive scanning optical microscope is described which can measure surface height changes of less than 3 ångströms. The system is based on a heterodyne version of the Michelson interferometer, and has been designed to reject phase noise caused by vibration in the optics and the sample. A specially constructed objective lens is used to direct two laser beams on to the object surface. The first beam forms a tightly focused spot to probe the sample structure, and the second remains collimated, acting as a large-area on-sample reference beam.

The configuration allows the relative areas illuminated by the two beams to be varied both arbitrarily and independently, thus guaranteeing an accurate absolute phase measurement. This is an important advantage over existing techniques, in which the range of suitable samples is restricted by the limited size of the on-sample reference beam. The two beams reflected from the sample are interfered with a third, frequency-shifted, beam, so forming two heterodyne Michelson interferometers in parallel. The phase from each interferometer is then compared to provide the object-surface phase structure. Path-length fluctuations due to microphonics are common to both interferometers and are cancelled by this comparison.

Results from a bench-top version of the system are presented which demonstrate the principle of the technique, and the factors limiting the sensitivity are discussed.
Design of autopilots for wingless missiles
Authors: Counsell J.M.
Published: November 2007

A non-linear multi-input multi-output controller design technique is applied to control a wingless missile. It is readily demonstrated that this design is unique in the sense that it not only results in fast decoupled transient behaviour, but also that it can be extended simply to give safe control when one of the actuators is limited in rate or deflection.
Input-output decoupled linearisation of general non-linear systems
Authors: Xiaoping Yun  , Daizhan Cheng
Published: November 2007

The problem of input-output decoupled linearisation of a general non-linear system = f(x, u), y = h (x) is studied. By defining an affine approximation, the solution of this problem is related to the established results of affine non-linear systems. An algorithm is given to compute the non-linear feedback for input-output decoupled linearisation. Under the standard assumptions, a condition for feedback stabilisation is also obtained.
A loop-shaping approach to robust performance for SISO systems
Authors: Postlethwaite I. , Lin J.-L. , Gu D.-W.
Published: November 2007

This paper presents a procedure for solving a robust performance problem for SISO systems using a loop-shaping technique. We investigated first the relationship between a mixed-sensitivity H-infinity optimisation problem and classical loop shaping. It is shown how classical loop shaping can be used to minimise the H-infinity cost function. This then provides insight into a further development of loop shaping to minimise the structured singular value for robust performance. The approach is demonstrated by its application to the control of a robot arm whose moment of inertia varies considerably with angle.
LQG cost bounds in discrete-time H2/H-infinity control
Authors: Mustafa Denis , Bernstein Dennis S.
Published: November 2007

It is shown that a full-state feedback gain that was derived originally to satisfy a discrete-time closed-loop H-infinity norm bound, also minimises three distinct LQG cost bounds.
Management of complexity in problem solving
Authors: Espejo Raul
Published: November 2007

The Viable System Model (VSM) is a powerful tool to think about the complexity of human activities. However, in addition to models we need effective frameworks for action. This paper offers one such framework based on what is known as 'second-order cybernetics'. Second-order cybernetics put the emphasis in the observer and language as key aspects in order to develop explanations about our participation in human concerns. This emphasis permits us to develop a framework to discuss the complexity of human activities and with that it gives us a handle for problem solving in organisations; such a framework is introduced in this paper as the Cybernetic Methodology.
An intervention with the Cybernetic Methodology in Regent Engineering
Authors: Bowling Diane , Espejo Raul
Published: November 2007

This paper describes a practical application of Espejo's Cybernetic Methodology in Regent Engineering (Walsall) Ltd. This methodology makes explicit the need to consider organisational learning about problems in the structural context of the organisation concerned. The interplay between the operational, technical and human content of a problem with the organisational structure is illustrated through the example of 'delivery' in Regent Engineering. The Viable System Model (VSM) of Stafford Beer is used to examine the cybernetics of the organisation.
Stability of distribution-network governors
Authors: Favret Fabien , Jemmali Mohammed , Cornil Jean-Philippe , Deneuve Francis , Guiraud M. Jean-Pierre
Published: November 2007

Governors on distribution networks sometimes exhibit unstable operating characteristics which affect their operation adversely. In order to solve this problem it was necessary first to investigate pressure-regulator behaviour under various operating conditions and to highlight stability criteria. It was then possible to lay down selection criteria as well as to make installation and adjustment recommendations.

This study has made it possible to validate and to organise a comprehensive set of experimental data and is expected to help operators who face this type of difficulty with pressure regulators. Last, but not least, the study will have a major impact on governor-qualification testing which is mandatory for installation.
New concept for co-ordinated power-plant control
Authors: Klefenz G. , Krieger J.
Published: November 2007

Control schemes for boiler-turbine units have formerly given priority to the grid requirements by regulating steam extraction from the boiler with minimum delay. With boiler systems that are slow to respond, steam storage is exhausted before increased steam production begins, leading to temperature and pressure fluctuations, material stresses and shortened plant life. A system is described in which dynamic models of the fuel mills, boiler and turbine are used to delay change to the load set point of the turbine controller. This system optimises the rate of load change with stress-free operation. It has been in service in a 750 MW unit over a 2-year period.
A frequency-domain identification approach to the study of neuromuscular systems- a combined experimental and modelling study
Authors: Halliday D. , Murray-Smith D.J. , Rosenberg J.R.
Published: November 2007

Experimental investigation of the neuromuscular system involves not only analysis of continuous signals but also necessitates the study of sequences of action potentials recorded from individual neurones together with the interactions between several sequences. Trains of action potentials may be regarded as realisations of stochastic point processes and techniques for the identification of point process systems can provide valuable experimental tools for the investigation of neuromuscular systems. Computational methods are presented for estimating the finite Fourier transform of a point process, and the associated spectral estimation procedures are described. An example is presented to illustrate the application of linear point process model identification techniques to the muscle spindle receptor. Using this example, simulation techniques are applied to demonstrate that spectral estimates can provide valuable physiological insight.
Self-organising fuzzy logic control and the selection of its scaling factors
Authors: Linkens D.A. , Abbod M.F.
Published: November 2007

Fuzzy logic control has been applied successfully to many industrial processes. It is particularly appropriate when process models are either unknown, non-linear, or variable in structure. There are two problems in its usage. One is the obtaining of a suitable rule-base for the application, while the other is the selection of scale factors prior to fuzzification and after defuzzification. Self-organising fuzzy logic control obviates the first problem, and is demonstrated in this paper. The selection of the scale factors is more difficult, but heuristic rules are derived in this paper via experimentations on a wide range of processes. The rules have been elicited from single variable control of a liquid-level rig, an air-heating process, an electrical-drive controller, and an anaesthesia model. These heuristic rules are then generalised to the multi-variable case of a coupled-electric drives system and simultaneous control of muscle relaxation and unconsciousness in anaesthesia.
H-infinity-norm minimisation and the stabilisation of systems with repetitive dynamics
Authors: Owens D.H. , Rogers E.
Published: November 2007

Multi-pass or repetitive systems are 2-D systems evolving with respect to one discrete and one discrete or continuous variable. Physically, they are systems involving repetitive action with interaction between successive passes through the system dynamics. The paper describes the stability theory for such processes and demonstrates the relationship between stability criteria and the H-infinity-norm of an appropriate transfer-function matrix (TFM). Based upon feedback control structures, the problem of stabilisation is formulated as an H-infinity-norm optimisation problem with solution having a natural interpretation in terms of robustness margins. The role of high-gain feedback and control structure in stabilisation is illustrated by a number of simple examples. The presentation aims to define problems to stimulate research in the area rather than to provide complete solutions.
Russian and Soviet contributions to the development of control engineering: a celebration of the Lyapunov centenary
Authors: Bissell C.C.
Published: November 2007

Major aspects of Russian and Soviet control engineering over the last hundred years or so are reviewed in commemoration of the centenary of Lyapunov's doctoral thesis on the stability of motion. Work discussed includes: early contributions by Vyshnegradskii, Zhukovskii and Lyapunov; later developments in the theory of continuous and discrete linear systems by Mikhailov, Solodovnikov, Neimark, Kornilov and Tsypkin; and the non-linear techniques of Andronov, Lur'e, Aizerman, Gol'dfarb and others.
A high-speed image acquisition system for robotics
Authors: Smith J.S. , Tan C.M. , Lucas J.
Published: November 2007

There are many applications in industry for imaging systems. The majority of these use a video camera as the input device. The output from the camera is sampled and stored in memory and a computer used to analyse the image. Until recently, the time for the analysis of the image was relatively long in comparison with the acquisition time of the image. However, with the development of new high-speed microprocessors decreasing the processing time, the acquisition time of the image will become the limiting factor of the analysis rate. This paper describes the development of a prototype system to make possible the capture of a full frame image (256 lines), in under 15 ms, for analysis by a computer. With the use of programmable logic devices (PLDS) and hardware windowing techniques, the acquisition time for a part frame (40 lines) is 2.8 ms. Shorter acquisition times can be obtained, but with reduned resolution. An application of the imaging system is also presented.
Temperature control of industrial processes using a variable structure design philosophy
Authors: Spurgeon S.K.
Published: November 2007

This paper provides a tutorial review of the variable structure control system design philosophy. This method allows direct performance specification and exhibits inherent robustness properties. The problem of providing robust temperature control for an industrial furnace is formulated in terms of the variable structure system approach. Simulation results which are performed on different plant models generated from on-line identification are presented to illustrate the robustness of the approach.
Controller tuning via rule based identification
Authors: Wang H. , Daley S.
Published: November 2007

Based on the recently developed rule based identification algorithm of Wang and Jones (1991), this paper presents a new algorithm for controller tuning in unit feedback control systems. In the paper, the rule based identification algorithm is used directly to identify the model between the reference step input and the integral of the tracking error. Two stages of tuning are proposed. In the first stage, the correct structure of the controller is chosen by monitoring the integral of the tracking error. This enables the realisation of perfect steady-state tracking. In the second stage, the estimated model is used to tune the controller gains in order to provide an improved dynamic performance for the closed-loop response. The results of applying the algorithm to the stimulation of a real process are given.
Robust control design for nonlinear uncertain systems with incomplete matching conditions
Authors: Liqun Cong  , Landers P.H.
Published: November 2007

In this paper, the control problem of a class of nonlinear systems with uncertainties is investigated, and synthesis techniques are developed under the assumption of so-called incomplete matching conditions. Nonlinear state feedback, based on differential geometry, is utilised to linearise the nominal part of the system and guarantee that the nominal closed-loop system has the desired stability margin. Additional nonlinear feedback is introduced to compensate for uncertainties, and stability is guaranteed via the theory of Lyapunov. The technique is applied, for illustrative purposes, to two situations, a straightforward nonlinear case, and a linear unstable case.
Supervisory intelligent control using a fuzzy logic hierarchy
Authors: Linkens D.A. , Abbod M.F.
Published: November 2007

A generic architecture for supervisory intelligent control based on fuzzy logic is presented. The structure consists of a multi-layer controller which incorporates a rule-based fuzzy logic controller for direct control at the lower level. Higher-level supervisory control is used for supervising the operation of the direct controller. Typical tasks of the supervisory controller are monitoring the process and the controller for determining the operating modes, assignment of initial conditions for the local controller, adaptation schemes, and fault detection and diagnosis. The controller structure is described, followed by its implementation on a real-time process to illustrate the performance and applicability, of the proposed structure.
Genetic algorithms and applications in system engineering: a survey
Authors: Caponetto R. , Fortuna L. , Graziani S. , Xibilia M.G.
Published: November 2007

In this paper an overview on Genetic Algorithms (GAs) is reported. GAs are described from a theoretical point of view, important implementation problems are dealt with and a wide variety of GA applications reported in system engineering literature are described. The survey also includes some studies at present in progress in our laboratories, regarding the use of GAs in solving optimisation problems in the fields of neural networks and control theory.
The application of Poincaré maps, Lyapunov exponents and dimension techniques to engineering problems
Authors: Petrick M.H. , Wigdorowitz B.
Published: November 2007

Lyapunov exponents, Poincaré maps and fractal dimension techniques are discussed and applied to a nonlinear dynamic system model and to experimental time series data from a physical plant. The application and interpretation of the analysis results from the point of view of application to engineering problems is emphasised. It is shown that the techniques provide important additional tools for the nonlinear analysis of practical engineering problems.
Model reduction by an extended complex curve-fitting approach
Authors: Gong M. , Murray-Smith D.J.
Published: November 2007

A method of model reduction is presented which is based upon a complex curve-fitting technique and is applicable to multi-input multi-output models. This approach involves the minimisation of the weighted sum of the squares of differences between the frequency response of the known high-order system and the approximating reduced-order system. It represents an extension of techniques originally developed for the single-input single-output case.
A knowledge elicitation method for process control using expert system shells
Authors: Zeng X.M. , Powers A.R. , Lucas J.
Published: November 2007

The Liverpool University Knowledge Elicitation (LUKE) system is a software package which provides a methodfor the easy acquisition of expert knowledge for use in expert system shells. LUKE is based on a tree structured inference network showing the correlation of rules and data relevant to the chosen domain. The full LUKE system consists of a CAD package and a user interface package. The CAD package allows the goal, sub-goal, question and priorities for the chosen domain to be displayed. The user interface package is used to input text information and define the derived expressions used in the sub-goals. The knowledge engineer or expert can then review these rules, and update the rule tree if necessary, before adding weighting factors to indicate the relative importance. The full problem domain may be considered as a series of small scale activities, which are investigated separately.

The output file from a cross-compiler of the user interface package is the source file for the expert system shell, which has been chosen for the particular engineering application (eg, Savoir, BHRA). Detailed knowledge of this shell is not necessary. A run-time system provided by the expert system shell gives interim results. Repeated use of LUKE allows the knowledge engineer to adjust the weighting factors until the expected result is obtained. The complete expert system can be built by the knowledge engineer by linking each small scale expert system together to obtain the full solution.

An expert system for the prediction of cracking in a welded joint is given as an application of the LUKE system.
A describing function technique for sampling period selection and controller discretisation
Authors: de Paor Annraoi M. , O'Malley Mark
Published: November 2007

Most industrial processes that are to be controlled are continuous in nature. A very> extensive range of well tried methods for control systems analysis and design, together with the associated algorithms for implementation, are in continuous time form. Digital control algorithms can be produced by translation of the analogue designs or they can be developed using digital design techniques. Discretisation of analogue controllers can be done in many well known ways. In general the stability of the resulting system cannot be guaranteed, both because of inherent approximation and lack of guidance on choice of sampling period. The criticalfactor is the sampling period, too high a value and the system is unstable, too low and the controller is overdesigned.

A discretisation method for translation from analogue to digital is given here where, subject to certain constraints, the sampling period can be chosen so as to guarantee stability. Following on this, the Z transfer function of the controller is taken as the ratio of the zero order hold equivalent transfer function of the combined process and controller, to that of the process alone.
Robust observer based FDI and its application to the monitoring of a distillation column
Authors: Wang H. , Kropholler H. , Daley S.
Published: November 2007

Parametric design for observer gain matrices is utilised to formulate a fault detection and diagnosis algorithm for a class of dynamic systems. The systems considered are subject to both un-modelled dynamic uncertainties and unknown inputs. By making use of the free parameters available in the parametric design approach, a diagnostic vector is constructed which is shown to be capable of isolating faults. The remaining free parameters are then used to generate an optimally robust residual signal for fault detection. It is shown that this residual signal is insensitive to the model uncertainty and unknown inputs, but sensitive to system faults. The proposed FDI approach is demonstrated through its application to the monitoring of a simulated distillation column.
Performance of AC induction servo motors
Authors: Firoozian R.
Published: November 2007

Squirrel-cage induction motors have been the first choice for constant-speed drive systems because of their superb reliability, robustness and cost effectiveness. DC motors, on the other hand, with transistors/thryistors as the power amplifier have been used for speed and position control applications especially in high-performance manufacturing machines where the main requirements are fast response and high position accuracy. With the recent development of frequency inverters, it is now possible to control speed and position of AC motors at a competitive cost. This paper investigates the performance of three-phase squirrel-cage induction motors for position control. It is shown that by optimising the control parameters, an acceptable position accuracy can be achieved. The inherent nonlinearities and motor inductance limit the speed of response. However, utilising the speed-torque characteristics, the reliability of critical components can be improved significantly which makes A C motors an ideal choice for application where the speed of response is not as critical as the position accuracy and reliability. Three control techniques of on-off, multi-step and PID are reported and their performances are compared for an A C induction motor. The integral term of a PID controller ensures high position accuracy and stiffness at steady-state, whereas the derivative term provides some improvement on the transient response and prevents overshoot which is not acceptable for many industrial applications.
A novel direct adaptive control scheme for robotic manipulators
Authors: Leung T.P. , Su Chun-Yi
Published: November 2007

A novel direct adaptive controller is presented for robotic manipulators. The novelty of our results is due to the adaptive laws adjusting the control gains directly, rather than providing an explicit estimate of inertia parameters, which are then used in the control law. Furthermore, only four control gains should be adjusted adaptively, and that number is independent of the number of degrees-of-freedom of robotic manipulators. The regressor matrix used by the control law is calculated with respect to the desired trajectory. It is shown that the control strategies are globally stable in the presence of a class of state-dependent uncertainties, and the tracking error can be made arbitrarily small.
An analysis method for piecewise linear dynamical systems
Authors: Pettit Njal , Wellstead Peter E.
Published: November 2007

A wide range of nonlinear dynamical systems contain abrupt changes in system behaviour and are often controlled using some kind of logic such as a rule-base. These changes in the system dynamics or controller actions make such systems intractable to conventional methods of systems analysis. By assuming all system nonlinearities can be represented as piecewise linear functions, a graphical analysis technique reminiscent of a phase portrait is developed for this class of systems and controllers. The state space of the system model is mapped into a directed node graph that captures the possible dynamic paths through the system. The paths found are directly related to the piecewise linear system functions or logic rules that created them. This node graph provides a graphical representation of the system that, like the phase portrait, captures the global dynamics of the system. The major difference is that the node graph generalises the phase portrait idea to systems of arbitrary dimensions.
An investigation into Kalman filter target tracking algorithms and their real time parallel transputer implementation
Authors: El-Mahy Col Mohamed K. , White Brian A.
Published: November 2007

For target tracking applications, a Kalman filter is generally used to estimate the kinematic components of a manoeuvring target (position, velocity and acceleration) from noisy measurements. The tracking algorithm is selected according to a trade-off between its performance and real-time computational requirements when choosing the level of complexity of the model. According to the application, either a linear or a nonlinear Kalman filter algorithm can be used to track manoeuvring targets. However, although excellent accuracy estimates can be achieved with any chosen algorithm, it requires a huge amount of calculation thus making real-time processing impossible.

This paper investigates the parallel implementation of tracking Kalman filters (EKF, GRF, LDKF and MGEKF) in both 2- and 3-D frames onto a range of transputer topologies to enable practical realisations. The partitioning strategies are highlighted, real-time implementation results are presented, and the relative speedup and efficiency are calculated to evaluate the performance of each parallel implementation.
Robust tracking of elastic joint manipulators using sliding mode control
Authors: Wilson G.A. , Irwin G.W.
Published: November 2007

Tracking control of manipulators with joint flexibility is considered. Singular perturbation techniques are employed to decompose the system dynamics into reduced-order models in separate time-scales. Based on these reduced-order models, a two time-scale composite control strategy is adopted and three control laws developed: (i) Continuous Composite Control (CCC), (ii) Sliding Mode Composite Control (SMCC) and (iii) Extended Sliding Mode Composite Control (ESMCC). The SMCC controller enables accurate tracking to be maintained in the presence of payload variations which degrade the performance of the CCC controller, while the ESMCC controller also compensates for the effects of parameter variations on the fast system states, a problem which has not previously been addressed. Simulations of an RTX robot are employed to evaluate the relative performances of these control laws.
A parallel implementation of the Kalman filter with application to measurements on electrical drives
Authors: Bucci G. , Germano A. , Tofoni T.
Published: November 2007

In this paper a parallel implementation of the Kalman filter is proposed, to speed up computation using concurrent calculus techniques and factorisation methods, that help avoid numerical instability problems. The algorithm has been implemented on a measuring system based on the use of a transputer network and a data acquisition board, and applied to measurement on asynchronous motors. Some experimental results obtained with the proposed real system are also shown and the performance is reported.
Advances in multi-detector arrays for mass spectrometry - a LINK (JIMS) project to develop a new high-specification array
Authors: Birkinshaw Keith
Published: November 2007

Mass spectrometry is a powerful tool in molecular analysis and the study of molecular structure as well as in ionic physics and chemistry research. In mass spectrometers which spatially disperse the ions the traditional single slit ion detector results in a very low ion collection efficiency. Arrays of detectors overcome this problem but have been adopted only slowly because of their complexity, low resolution and high cost. All these problems have been addressed in the design of a new high-resolution array on a silicon chip supported by the LINK (JIMS) programme. This device consists of a one-dimensional array of ion detectors on a pitch of 25 microns giving 400 detectors per cm. It has been fully tested and combines many of the properties of the ideal array. This paper provides a background to this important area and considers advantages and limitations of arrays. The array developed at Aberystwyth is outlined.
The impact of system tribology on automatic control of cone crushers
Authors: Moshgbar M. , Parkin R. , Bearman R.A.
Published: November 2007

Cone crushers are a family of secondary and tertiary rock crushers used in the mineral processing and aggregate industries. The quarrying industry in the UK alone produces some 250 MTonnes of aggregates per annum for use in the construction industry.

Conventional cone crushers utilise on/of control which is based on personnel observation and manual off-line adjustment of the machine setting. The adjustment is effected mechanically or via a control panel and electrical means. This process involves long machine and plant down-time and can result in an inconsistent product due to drift in the machine setting caused by continuous wear of the liners used in the crushing chamber.

The impact of tribological parameters on the real-time control of cone crushers and a mechatronic solution to enhance and automate the control system is reported. The system employs a combination of intelligent sensors, predictive mathematical models and AI technology to provide real-time information on a number of system parameters. The information is utilised by a cascaded adaptive control system to maintain the correct cone crusher setting for optimum system performance. The improved control strategy is estimated to result in an annual saving of around £30 million in the UK alone.
Multiple-loop PID controller tuning by the goal attainment trade-off method
Authors: Wang Feng-Sheng , Wu Tzay-Yuan
Published: November 2007

An interactive multi-objective optimisation method has been introduced in this study for tuning multi-loop PID controllers. Several design specifications may be simultaneously considered in this optimisation problem. The multi-objective PID tuning, problem was then reformulated into the goal attainment framework. Minimisation of the attainment factor was used as a design index for checking the system whether it met the goals. A trade-off procedure should be performed to achieve the acceptable control effects if the goals were unsatisfied. The one-parameter tuning PID controller was introduced in this work so that the number of the tuning parameters of the multi-loop controllers was reduced. The interactive optimisation search was accordingly lightened. Two examples, a two-loop and a three-loop process, were given to illustrate the design concept.
An AFR estimator for spark-ignited engines
Authors: Gong C. , Thompson S.
Published: November 2007

In this article an air-fuel ratio (AFR) estimator, using torque measurements, for a spark-ignited engine is presented. Instead of estimating the in-cylinder AFR directly the estimator, which employs a stochastic linear filtering technique, generates an estimation of a predefined AFR effector (that is, it estimates a multi-valued function of the AFR). The AFR effector equation may be solved directly to give a rich and lean value for the AFR. Since only one of these values will be the required estimate, it is shown how, for a simple ratio AFR controller, that this can be found from throttle angle measurements. Simulation results on a validated engine model show that the estimator has good transient performance.
On the guaranteed stability based adaptive control of robotic manipulators: continuity and boundedness
Authors: Stepanenko Yury , Su Chun-Yi , Hashimoto Hideki
Published: November 2007

Based on the guaranteed stability approach, a modified adaptive controller is presented for robotic manipulators. The developed control strategy guarantees uniform ultimate boundedness of the tracking errors and parameter errors in the presence of a class of state-dependent uncertainties, and the tracking error can be made arbitrarily small. It is shown that with resettable design parameters and a low-pass-filter form of update equation the performance degradation and destabilisation of robotic systems can be prevented effectively in the practical situation.
Actuator fault diagnosis for nonlinear dynamic systems
Authors: Wang H.
Published: November 2007

In this paper a novel approach for the fault detection and diagnosis of the actuators in nonlinear systems is presented. The faults are assumed to be any unexpected changes of the parameters in the actuators, which include either abrupt changes or slowly drifting changes. Firstly a known nonlinear system is considered, where an adaptive diagnostic model incorporating the estimate of fault is constructed. The diagnostic algorithm is then developed which produces the estimate of the fault so that the error between the system output and that of the model is minimised. Unknown nonlinear systems are then studied using a feedforward neural network trained to estimate the system under healthy conditions. Taking the trained neural network as the neuro model of the system, similar detection and diagnostic algorithms to that of known systems are obtained which are still capable of producing a good estimate for the fault. The method is demonstrated using a simulated nonlinear system and good results are obtained.
Heat transfer models for boiler fouling monitoring
Authors: McGurn S. , Thompson S.
Published: November 2007

This paper uses heat transfer models to monitor fouling from ash in a coal-fired power generation boiler. In particular, a counterflow heat exchanger model for the economiser and a periodic flow model for the airheater are developed. Model inputs are local measurements of flow, temperature, etc, and the outputs are fouling indices in real time.

Results from tests on a transient-load full-scale power station are piesented for both models. Recurring fouling patterns are shown to suggest relationships with time, load and with changes in the in-service cleaning system.
Concept evaluation trials of teleoperation system for control of an underwater robotic arm by graphical simulation techniques
Authors: Boyle B.G. , McMaster R.S. , Nixon J.H.
Published: November 2007

In the main, the current control method for underwater manipulators involves a master-slave robot configuration combined with visual feedback provided by closed-circuit TV from a number of ROV mounted cameras. In order to overcome the various drawbacks of this system, a new method of both control and feedback, utilising simulation software developed for off-line programming, is currently under development at Cranfield. This paper describes these new methods, and summarises the need for them and their inherent advantages over current technology. It also includes a description of thefirst stages of their development and the evaluation experiments which were used to judge the feasibility of the continuance of the project.
An industrial review of advanced process control of continuous processes on refineries and petrochemical plants
Authors: Ogden-Swift A.
Published: November 2007

In many sectors of the process industries, advanced control and closed-loop optimisation is recognised as a mechanism for improving competitiveness. Projects are common with payback times of less than 1 year. For many companies the range of technologies is bewildering. This can be overcome by use of a reputable and experienced consultant. Increaslingly, the large control systems companies are providing these services and technologies. For many operating companies this will be the best path for ensuring they achieve the benefits they expect over the lifetime of a project.
An overview of multivariate statistical process control in continuous and batch process performance monitoring
Authors: Martin E.B. , Morris A.J.
Published: November 2007

Univariate SPC systems effectively only detect, or provide early warning of off-specification production, process disturbances and process malfunctions related to individual quality measurement sources. Consenquently, they provide litte information about the interactions between the variables which are so important in complex processes such as those now found in the process and manufacturing industries. These limitations can be addressed through the application of Multivariate Statistical Process Control (MSPC), The bases of MSPC are the projection techniques of Principal Components Analysis (PCA) and Projection to Latent Structures (PLS). Through the application of PCA or PLS, the process can be defined in terms of a much reduced set of latent variables (a linear combination of the original variables), which reflect the true dimensionality of the process This paper presents an overview of multivariate statistical process control for continuous and batch processes. The power of the methodology is demonstrated by application to two industrial processes.