bluuebunny/crossref_metadata_2025 huggingface dataset:
On the measurement of variations in the spin velocity of a wheel
Authors: Sharp R S , Allison D J
Published: October 2002

Research into the in-plane vibration properties of rotating tyre-wheel-hub assemblies involved the need to measure accurately small variations in the substantially larger angular velocity of an automotive wheel hub. Straightforward application of a tachogenerator to the task would have been subject to the classic measurement difficulty that the variable of interest was the small difference between two large quantities. The necessary accuracy would not have been achievable. The test wheel assembly was an automotive type, deriving from a vehicle fitted with anti-lock brakes. It was fitted with a toothed ring and variable reluctance proximity sensor in its standard form. A method for using this sensor's output to derive information on the wheel spin velocity variation was derived. The method used and its proof by simulation and by experimentation are described.
The discrete-time equivalent of an analogue controller by the parabolic approach
Authors: Chen C-M , Liu F-H
Published: October 2002

A new discretization method is proposed to convert an analogue controller to its corresponding counterpart for the discrete-time system. This method is suitable for the natural response curve and can be more effective for some digitally redesigned systems. From the mapping region of s domain to z domain, the paper shows that such an approach can generate a corresponding stable discrete-time controller for a stable continuous-time controller. The discrete-time controller via an approach of parabolic transformation shows a good performance for its originally continuous-time response and can tolerate a comparatively large sampling period of the discrete-time system. An illustrated example is simulated to demonstrate the effectiveness of these results.
Neural-network-based sensor validation for gas turbine test bed analysis
Authors: Zedda M , Singh R
Published: October 2002

This paper presents the use of neural networks for steady state sensor validation of gas turbines. The application is particularly suitable for test bed data analysis. Sensor failures are frequent in gas turbines and their effect on the accuracy and reliability of the performance analysis can be dramatic. Both test bed analysis and analysis of on-wing engines can be strongly affected by a measurement bias. The problem of isolation of faulty sensors can be complicated by the presence of actual engine faults that are still unknown at this stage of the analysis. Auto-associative neural networks have been used together with a minimization technique to perform multiple sensor failure detection and isolation of a low-bypass-ratio turbofan engine. Neural networks have been shown to be able to isolate faulty sensors successfully, even in the presence of unknown engine faults. Direct consequence of the application of neural networks is that the following estimation of the engine component performance parameters can be carried out separately, after rejection of biased measurements.
Physical model-based inversion in control systems design using bond graph representation Part 1: Theory
Authors: Ngwompo R F , Ngwompo R F , Scavarda S , Thomasset D
Published: October 2002

System inversion is a concept that often appears either implicitly or explicitly in the design of control systems (e. g. decoupling, feedback linearization or feedforward control). This paper presents an algorithm for the representation of an inverse systems model using bond graph techniques. Structural invertibility conditions are investigated graphically and the structure of the inverse model is discussed. This graphical inversion method is carried out in parallel with classical inversion algorithms using causality manipulations in bond graphs. The physical approach adopted here is enhanced with applications presented in Part 2 which follows.
The tracking of a manoeuvring object by using an adaptive Kalman filter
Authors: zou H-K , Lin Y-T
Published: October 2002

The aim of this paper is to improve the tracking performance of an aeronautical object with manoeuvring flight. The conventional Kalman filter may induce unsatisfactory tracking errors when applied to the manoeuvring object, since the parameters of the filter cannot adapt to the manoeuvring object. For this reason, two adaptive techniques are presented in this paper. The first is based on the covariance matching technique and the other on the Kumar adaptive Q theory. These tracking algorithms both give satisfactory performance from the simulation results. The comparison between the performance of these two tracking algorithms is also presented.
Non-linear control with Lyapunov stability applied to spacecraft with flexible structures
Authors: Lin Y-Y , Lin G-L
Published: October 2002

The method of input-output feedback linearization incorporating the Lyapunov stability analysis was applied in this study to design a stable control law for the problem of reorienting a spacecraft with flexible appendages. Only three mutually orthogonal torque actuators on the hub are required for the proposed control law to perform a desired simultaneous multi-axis reorientation. Mathematical modelling of the system gives a set of coupled ordinary and partial differential equations, which includes attitude dynamics of the spacecraft and dynamics of the flexible structures. To simplify the system equations for controller design, deformations of the flexible structures were assumed to be small and mode-shape functions were applied first. Furthermore, the set of non-linear equations governing the attitude motions was transformed into a Euler parameters representation. Through the method of feedback linearization and vector subtraction in the Euler parameters space, the dynamics of the attitude errors were formulated as a set of stable second-order ordinary differential equations with constant coefficients, which are the gains of the attitude feedback control law. Vibration control of the flexible structures in the form of adaptive damping was also derived from the procedure of Lyapunov stability analysis and becomes a part of the attitude feedback control law. The stability of the overall dynamic system can be achieved by tuning the selected control gains in the Lyapunov analysis. Attitude manoeuvre of a model spacecraft was tested using the proposed control law and the simulation results were compared for the cases with and without adaptive structural damping. This study also shows that, by selecting the adaptive damping coefficients, the optimal time and torque manoeuvre of the flexible spacecraft can be determined.
Observations on the controllability of motion of two-wheelers
Authors: Seffen K A , Parks G T , Clarkson P J
Published: October 2002

This paper presents an investigation into the motion of two-wheelers: everyday motorcycles and bicycles. The emphasis is on controllability of the system for small lateral deviations from straight running under idealized rider control. After introduction, a discussion of the kinematics, assumptions and geometry of a rider-vehicle system is presented, followed by a statement of the equations of motion. The control systems analogy is briefly reviewed, and state space methods formalize the concept of controllability. The difficulty in steered riding is quantified by the ratio of maximum to minimum singular values of the controllability Grammian and rideability is investigated for different designs of (a) a motorcycle from a well-known study and (b) a bicycle from a recent investigation. New insight into controlled two-wheeler behaviour is shown, compared with traditional methods, and can provide another means to design for a safety of vehicle performance.
Modelling and control of a disk file head-positioning system
Authors: Yamaguchi T
Published: October 2002

This paper overviews servo control technology in the field of motion control for disk file systems. In the hard disk drive (HDD) system, the head must be positioned on the desired track quickly and precisely, and this performance must be robust. Recent required positioning accuracy is about 50 nm (±3σ). To meet these requirements, many servo control methods have been proposed and applied to the system. Major research subjects for fast movement are a reference trajectory design and a track-seeking servo design. In particular, a two-degree-of-freedom (2 DOF) servo control with a multirate sampling period has been developed for the track-seeking servo. Two design methods of 2 DOF feedforward controller are proposed here.

While reading/writing data, very precise positioning on a target data track is required. One of the most effective methods for precise positioning under various disturbances is to increase the servo bandwidth. This paper examines the use of loop shaping, state feedback and a dual-stage actuator servo to increase the servo bandwidth with sufficiently robust stability. Feedforward methods to cancel disturbances are also applied under the condition that the disturbances are either detectable or can be estimated, such as repeatable runout error, which is synchronous to disk rotation.
Quantifying the robustness of flight control systems using Nichols exclusion regions and the structured singular value
Authors: Bates D G , Kureemun R , Postlethwaite I
Published: October 2002

This paper establishes some connections between classical stability metrics currently used in the aerospace industry for the certification of flight control laws and modern tools for the robustness analysis of uncertain multivariable systems. Multiloop simultaneous gain and phase margin robustness specifications are written as Nichols plane exclusion regions for the open-loop frequency response of each loop of the system. Satisfaction of these robustness specifications for uncertain multivariable systems is then shown to be exactly equivalent to satisfying a certain bound on the structured singular value μ of the closed-loop system. The proposed tools are applied to the problem of analysing the robustness of an integrated flight and propulsion control system for a future V/STOL aircraft concept subject to variations in aircraft mass and centre of gravity. In particular, the implications for the proposed method of difficulties in computing tight bounds on μ are considered.
Air-fuel ratio and speed control for low emission vehicles based on sliding mode techniques
Authors: Puleston P F , Monsees G , Spurgeon S K
Published: October 2002

This paper deals with the combined air-fuel ratio (AFR) and speed control of automotive engines. The robust controller is developed using dynamic sliding mode (SM) control design methods. The proposed controller set-up is tested under realistic operating conditions by means of computer simulation using a comprehensive non-linear model of a four-stroke engine, specifically provided by the automotive industry for these purposes. This accurate industrial model comprises extensive dynamics description and numerous look-up tables representing parameter characteristics obtained from experimental data. The SM controller set-up proves to be robust to model uncertainties and unknown disturbances, regulating effectively the engine speed for a wide range of set-points while maintaining the AFR at the stoichiometric value.
A method of designing a robust force controller of a water-hydraulic servo system
Authors: Sanada K
Published: October 2002

Robust force control of a water-hydraulic servo system is discussed. The system treated in this paper is a model of a moulding press used for a fabrication process of large-scale integration packages. The whole surface of a wafer is covered with a thin plastic layer by the press. The performance of force control is important to obtain sufficient quality. The press is driven by a ram cylinder and a water-hydraulic servo valve. Considering the uncertainty caused by the flow characteristics of the valve in the overlap region and the mechanical stiffness of the press, a method of designing a robust force controller is proposed by applying H∞ control theory. Qualitative evaluation of modelling error is the key to the design of the robust controller. The performance of the robust controller is examined using an experimental water-hydraulic servo system set-up. It is illustrated how the system responses are influenced by the weighting function parameters of H∞ control theory.
Modelling and non-linear discontinuous feedback control of crane lifter systems
Authors: Karkoub M A , Zribi M
Published: October 2002

In this paper, a non-linear dynamic model is derived for a crane lifter system. The derived model is underactuated since it has two inputs and four degrees of freedom. A non-linear control scheme is then proposed for the system. The objective of the control scheme is to drive the hoist and trolley positions to their desired values and to eliminate the oscillations of the cable and load as quickly as possible. The model and the control scheme are simulated on a digital computer and the results show that the theoretical developments work well.
Reduction of residual vibrations in a rotating flexible beam with a moving payload mass
Authors: Choura S
Published: October 2002

The reduction of residual vibrations for the position control of a flexible rotating beam carrying a payload mass is investigated. The common practice used to find the position control of a flexible multi-link arm is to assign a torque actuator to each joint while the payload mass is kept fixed relative to the end-link during the time of manoeuvre. This paper examines the stability of the system if either the payload is freed accidentally to move along the beam during the time of manoeuvre or is allowed to span the beam in a desired path for control purposes. A candidate Lyapunov function is constructed and its time rate of change is examined. It is shown that the use of a PD (proportional plus derivative) torque control yields a convergence of residual vibration to zero, an attainment of the rigid-body rotation to a prespecified desired angle of manoeuvre and a constant velocity of the payload mass as it moves relative to the beam. For manipulation purposes, an additional control force is added to the moving actuator in order to regulate its axial motion. It is shown that allowing the axial motion of the payload mass in a prescribed manner leads to a considerable reduction of its residual vibrations as compared to the case where the payload mass is fixed to the beam tip during the time of manoeuvre. Stability is also verified through simulations of rigid-body rotation and payload axial motion track prespecified reference trajectories.
Robust stability of uncertain linear systems with multiple time delays
Authors: Fang Y
Published: October 2002

In this paper, the robust stability of uncertain linear systems with multiple time delays is studied. Sufficient conditions for robust stability of linear time delay systems with convex perturbations are obtained. From these sufficient conditions, a few results on robust stability of systems with other perturbations are derived. Some previously known sufficient conditions are generalized.
Qualitative observer and its application to fault detection and isolation systems
Authors: Zhuang Z , Frank P M
Published: October 2002

Qualitative simulation is one of the main techniques in qualitative reasoning. It has the great potential to solve engineering problems, if only the difficulty of ambiguity can be overcome. On the other hand, in many applications measurements are often available. In this paper a qualitative observer is proposed, which is based on qualitative simulation and applied using a novel technique: observation filtering. This provides a framework in which the measured information can be utilized to reduce accumulated ambiguity and to avoid spurious solutions. Simulated results of qualitative simulation and qualitative observer are compared to show the effect of the new approach. As an application to fault detection and isolation, qualitative extensions of the dedicated observer scheme and the generalized observer scheme are presented.
Gain-scheduled flight control via two-degree-of-freedom H∞ optimization
Authors: Walker D J
Published: October 2002

The gain scheduling of a multivariable controller designed using H∞ optimization is presented. The design uses a two-degree-of-freedom H∞ optimization based on five linearizations taken from the non-linear rigid body equations of motion of a helicopter over the range 0–80 knots. The scheduled controller's parameters were computed on-line by linear interpolation with air speed of the design parameter sets. The resulting controller schedule was tested using a sophisticated and representative nonlinear simulation.
Eigenvalue placement and simultaneous stabilization using tabu search
Authors: Abdel-Magid Y L , Selim S Z
Published: October 2002

This paper considers the problem of designing controllers to place simultaneously the closed-loop eigenvalues of a finite number of plants, representing different operating conditions of a system, in a specific region in the left half of the complex s plane. The problem of selecting the controller gains is converted to a simple optimization problem with an eigenvalue-based performance criterion, which is solved by a tabu search. Various performance criteria are suggested and formulated, allowing the eigenvalue placement in distinctive locations in the complex s plane. Several examples are included to demonstrate the usefulness of the method.
Evolutionary Hinfin; design of an electromagnetic suspension control system for a maglev vehicle
Authors: Dakev N V , Whidborne J F , Chipperfield A J , Fleming P J
Published: October 2002

A multiobjective evolutionary algorithm approach is proposed for the H∞ design of an electromagnetic suspension (EMS) control system for a maglev vehicle. The evolutionary algorithm is used in conjunction with an H∞ loop-shaping design procedure to perform multiobjective search over a set of possible weighting function structures and parameter values in order to satisfy a number of conflicting design criteria. It is demonstrated that the proposed approach offers a number of potential benefits over other ‘mixed optimization’ techniques by allowing the control engineer to select from a number of satisfactory design solutions of differing complexity.
Robust fault detection of dynamic systems via genetic algorithms
Authors: Patton R J , Chen J , Liu G P
Published: October 2002

This paper presents a new approach to the design of robust fault detection systems via a genetic algorithm. To achieve robustness, a number of performance indices are introduced, which are expressed in the frequency domain to account for the frequency distributions of incipient faults, noise and modelling uncertainty. All objectives are then reformulated into a set of inequality constraints on performance indices. A genetic algorithm is thus used to search an optimal solution to satisfy these inequality constraints. The approach developed is applied to a flight control system example and results show that incipient sensor faults can be detected reliably in the presence of modelling uncertainty.
A genetic algorithm for affine invariant object shape recognition
Authors: Tsang P W M
Published: October 2002

In this paper, a novel technique for matching images of object shapes which have been subject to affine transformation caused by variations in the camera position is reported. The method is based on the genetic algorithm, and is more efficient and reliable than conventional approaches that rely on corresponding dominant point pairs to determine the best alignment between object boundaries. Experimental results are presented to demonstrate the feasibility of the approach and its capability in identifying object shapes that had been distorted with heavy noise contamination
Robust system identification using the Hough transform
Authors: Henderson M , Ingleby M , Ford D
Published: October 2002

The Hough transform provides a basis for robust extraction of shapes and continues to attract the interest of the image processing community. It has robustness properties desirable in many applications of pattern recognition, including parameter estimation. These properties are robustness to impulsive noise, insensitivity to partial occlusion of patterns, graceful degradation of performance in the presence of Gaussian and impulsive noise, as well as the ability to respond to concurrent patterns coexisting in the same data source. This technique has been applied to the problem of parameter estimation for linear and non-linear models. A critical comparison is made with the more traditional least-squares-based parameter estimators and it is argued that transform-based techniques are, in certain circumstances, more suitable for real-time intelligent control than those currently in use.
Finite difference and finite element approaches to dynamic modelling of a flexible manipulator
Authors: Tokhi M O , Mohamed Z , Azad A K M
Published: October 2002

This paper presents a comparative investigation of the dynamic characterization of flexible manipulators on the basis of accuracy, computational efficiency and computational requirements using finite difference (FD) and finite element (FE) methods. A constrained planar single-link flexible manipulator is considered. Finite-dimensional simulations of the manipulator are developed using FD and FE methods. The simulation algorithms thus developed are implemented on two computing domains and their performances, on the basis of accuracy in characterizing the behaviour of the manipulator and computational efficiency, are assessed.
Simulation of fluid power circuits using artificial network models: Part 2: Circuit simulation
Authors: Xue Y , Watton J
Published: October 2002

A variety of fluid power components, modelled by artificial networks, are brought together to form a motor speed control system. The dynamic behaviour of the system is predicted with the support of additional artificial networks to define the initial conditions. The effect of changing the volume between the pump and control valve is then considered using computer simulation and verified by experiment. A novel feature is the use of the pressure relief valve to determine supply pressure rather than fluid compressibility using the conventional computer simulation approach.
Fuzzy deadband compensator
Authors: Mustafa M M
Published: October 2002

The presence of deadband in actuators can cause unacceptable control performance such as steady state error in the system. This work is focused on type 1 systems with deadband in the actuators. Incorporating integral action in the controller can eliminate this static error, but at the expense of having overshoot or oscillatory response, which is unacceptable in many positioning systems. The fuzzy deadband compensator proposed here operates on top of the existing controller and does not require a priori knowledge of the size of the deadband. The fuzzy deadband compensator employs variable ‘waiting time’ before the deadband is taken out. An element of patience is introduced in the compensator to prevent overcompensation. The compensator was successfully tested to a hydraulic servomechanism.
Output feedback stabilization of hydraulic drives based on bilinear approximations and canonical observers
Authors: Schwarz H
Published: October 2002

This paper deals with the control of hydrostatic drives on the basis of bilinear models. It is shown that by using bilinear models a considerably better approximation of the non-linear behaviour of hydraulic drives can be achieved compared with common linear models. The bilinear model approach gives rise to control results valid not only for fixed operating points but also for the complete operation range of the drives. In particular, an output feedback using a canonical observer and quadratic state feedback is proposed. A separation theorem for this non-linear control scheme similar to that for linear systems is proved, i.e. the dynamics of the observer and of the controlled plant are adjustable separately.
Fault classification of fluid power systems using a dynamics feature extraction technique and neural networks
Authors: Le T T , Watton J , Pham D T
Published: October 2002

Multilayer perceptron (MLP) type neural networks and dynamic feature extraction techniques, namely linear prediction coding (LPC) and LPC cepstrum, are used to classify leakage type and to predict leakage flowrate magnitude in an electrohydraulic cylinder drive. Both single-leakage and multiple-leakage type faults are considered. A novel feature is that only pressure transient responses are employed as information. In addition, the feature extraction technique used to detect faults can result in a large data dimensionality reduction. The performance of two MLP models, namely serial and parallel, are studied to reflect the importance of the way data are presented to the MLP.
Control chart pattern recognition using a new type of self-organizing neural network
Authors: Pham D T , Chan A B
Published: October 2002

Control charts as used in statistical process control can exhibit six principal types of patterns: normal, cyclic, increasing trend, decreasing trend, upward shift and downward shift. Apart from normal patterns, all the other patterns indicate abnormalities in the process that must be corrected. Accurate and speedy detection of such patterns is important to achieving tight control of the process and ensuring good product quality. This paper describes a new type of neural network for control chart pattern recognition. The neural network is self-organizing and can learn to recognize new patterns in an on-line incremental manner. The key feature of the proposed neural network is the criterion employed to select the firing neuron, i.e. the neuron indicating the pattern class. The paper gives a comparison of the results obtained using the proposed network and those for other self-organizing networks employing a different firing criterion.
State of the art and trends in using smart materials and systems in transportation vehicles
Authors: Boller Chr
Published: October 2002

An overview is given on state-of-the-art development and future trends in integrating sensing, actuation and control functions into transportation vehicles. After categorizing the wide range of smart materials and systems various applications from the aerospace, automotive and railway sector are described, which are either already in use or very much considered for application. This includes systems for damage monitoring and situation awareness using smart sensors and antennae, autonomous driving based on smart cameras, thermal and electrical controlled actuation in engines and for comfort improvement, systems for vibration damping and noise cancellation and much more. Technology gaps to be closed in future research activities are described.
The long-term monitoring of civil engineering and building structures—developments in techniques for monitoring corrosion in reinforced and post-tensioned concrete
Authors: Hammersley G P , Dill M J
Published: October 2002

An important step in the progress towards smart structures is the development of reliable systems for the long-term monitoring of performance. Data obtained from monitoring can provide an early warning system to maximize the safe use of structures, contribute towards planned maintenance by giving advanced notice of durability or structural problems and provide information on actual performance, which can be fed back into the design process.

This paper sets out to describe some developments in permanent in situ monitoring systems which have achieved practical use on civil engineering and building structures constructed from concrete, concentrating on the key area of corrosion of reinforced and post-tensioned concrete. The techniques are illustrated with case histories.
Smart machine tools
Authors: Corbett J
Published: October 2002

Improved manufacturing methods have become crucial factors in retaining global competitiveness for a wide range of products. This has led to the development of new automatic supervision techniques for use in smart machine tools. These are necessary because it is not possible to design and manufacture machine tool structures and systems with work zone areas of sufficient accuracy and repeatability to meet the improved performance requirements demanded by many modern manufacturing companies. The principal areas for automatic supervision of the machine tool are the tooling, appropriate machine elements and the overall machine system.

Thermal effects have been shown to be the largest source of dimensional errors and apparent non-repeatability of machines. Therefore, for the highest precision machines on-line temperature monitoring and control is of paramount importance. This paper describes the application of automatic supervision techniques applied to the NION diamond turning and grinding machine, developed by Cranfield Precision Engineering Limited, which is the most accurate machine tool, of its size, currently available, as well as an ultra precision five-axis grinding machine, built in Japan by the Toyoda Machine Works Limited.

In addition, following a project at Cranfield University, the benefits of on-line measuring techniques are discussed in obtaining new cost effective manufacturing methods for producing aero-engine turbine blades. Further examples are given, including major projects at Liverpool John Moores University and Eindhoven University of Technology, where significant improvements in accuracy capabilities were obtained for a standard cylindrical grinding machine and a five-axis vertical milling machine.
New robust stability results for linear systems with structured non-linear perturbations
Authors: Fang Y
Published: October 2002

The robust stability of linear systems with unstructured, structured or non-linear perturbations is investigated in a unifying framework. New sufficient conditions in terms of matrix Riccati inequalities are obtained. Some previously known results are generalized.
Distributed rotor dynamics
Authors: Bartlett H , Whalley R
Published: October 2002

The modelling, simulation and analysis of powered rotors with ‘long’ thin shells is investigated. General results enabling the prediction of the torsional vibrational signature of high-speed assemblies under acceleration or braking conditions are outlined. It is demonstrated that simulated response characteristics can be easily obtained and the effect of varying the rotor geometry can be routinely accommodated. Finally, a rotor for a high-speed paper manufacturing unit is investigated and the torsional behaviour of the assembly is computed. The volatile transient conditions presented are commented upon.
Motion planning of redundant robot manipulators using constrained optimization: A parallel approach
Authors: Chen C-L , Lin C-J
Published: October 2002

A redundant manipulator can achieve a principal task and additional tasks by utilizing the degrees of redundancy. In the present paper, the redundancy resolution problem is formulated as a local equality constrained optimization problem. A motion planning solution corresponding to a design objective is then obtained using a new approach, called the perturbation method. In contrast to conventional approaches, the inverse of the Jacobian matrix is not required in the method proposed. Tracking errors can be bounded by a permissible zone, which is a function of normal tracking error and a safety factor. Positioning of the end effector within the permissible zone is satisfactory for the completion of any given step and signals the beginning of the next step. The position angle change of each joint is also bounded in each sampling interval as a function of robot maximum speed. Computer simulations written in the parallel processing language occam and computed on a transputer-based computation network are used to study the behaviour of the method proposed. Results validate the approach.
A robotic motion controller using a self-organizing fuzzy logic algorithm with grey prediction
Authors: Huang S-J , Lee J-S
Published: October 2002

It is well known that robotic manipulators are highly non-linear coupled dynamic systems. It is difficult to establish an appropriate mathematical model for the design of a model-based controller. Although fuzzy logic control has model-free features, it still needs time-consuming work for rule bank and fuzzy parameter adjustment. Hence the self-organizing fuzzy controller is proposed to manipulate the motion trajectory of robots with multiple degrees of freedom. This approach has learning ability for responding to the time-varying characteristic of a robot. Its control rule bank can be established and modified continuously by on-line learning with zero initial fuzzy rules. However, this control strategy has larger oscillatory behaviour during initial learning. Here a self-organizing fuzzy controller with grey prediction is proposed to improve this behaviour. The experimental results show that this intelligent controller can reduce significantly the oscillatory amplitude of the output trajectory and tracking error.
On optimizing performance indices with pole assignment constraints
Authors: Hu T , Lam J
Published: October 2002

In this paper, a unified gradient-based treatment for optimizing certain performance indices under the constraint of pole assignment is provided. By introducing a free optimization parameter and solving a special Sylvester matrix equation, compact gradient formulae are derived for general-purpose gradient descent numerical implementation. Special problems including robust stability pole assignment and H2 sensitivity reduction are employed to illustrate the technique. In particular, comparisons of different performance indices to maximize the complex stability radius are made.
Design of an input amplitude-constrained discrete-time control system
Authors: Zhu K Y , Krishnan S M
Published: October 2002

A discrete-time controller based on an augmented system is proposed. The controller globally stabilizes a class of type- m systems subject to an input amplitude constraint. It is shown that use of the augmented system model allows us to handle with ease the system with arbitrary zeros and especially time delay. Stability results for both regulation and tracking are established on the basis of Lyapunov function methods and simulations of the demonstration are also carried out.
A Tabu search method for the optimization of fluid power circuits
Authors: Connor A M , Tilley D G
Published: October 2002

This paper describes the development of an efficient algorithm for the optimization of fluid power circuits. The algorithm is based around the concepts of Tabu search, where different time-scale memory cycles are used as a metaheuristic to guide a hill climbing search method out of local optima and locate the globally optimum solution. Results are presented which illustrate the effectiveness of the method on mathematical test functions. In addition to these test functions, some results are presented for real problems in hydraulic circuit design by linking the method to the Bath fp dynamic simulation software. In one such example the solutions obtained are compared to those found using simple steady state calculations.
Self-tuning proportional, integral and derivative controller based on genetic algorithm least squares
Authors: Warwick K , Kang Y-H
Published: October 2002

A self-tuning proportional, integral and derivative control scheme based on genetic algorithms (GAs) is proposed and applied to the control of a real industrial plant. This paper explores the improvement in the parameter estimator, which is an essential part of an adaptive controller, through the hybridization of recursive least-squares algorithms by making use of GAs and the possibility of the application of GAs to the control of industrial processes. Both the simulation results and the experiments on a real plant show that the proposed scheme can be applied effectively.
Regional eigenvalue-clustering robustness analysis for singular systems with structured parameter perturbations
Authors: Chou J-H , Liao W-H
Published: October 2002

In this paper, under assumptions that the nominal linear singular system is regular and impulse-free and has all its finite eigenvalues lying inside certain specified regions, a sufficient condition is proposed to preserve the assumed properties when the structured parameter perturbations are added into the nominal singular system. No restriction is imposed on the shapes of the specified regions. The proposed method is applicable to both the continuous-time case and the discrete-time case. When all the finite eigenvalues are just required to locate in the stable region, the proposed criterion will become the stability robustness criterion. By mathematical analysis, the presented criterion is proved to be less conservative than the existing criterion reported recently.
A new robust non-linear self-tuning predictive control using neural networks
Authors: Zhu K Y , Qin X F , Chai T Y
Published: October 2002

An adaptive version of a novel robust predictive control for a class of non-linear systems is presented. The non-linear system is separated into linear and non-linear parts by Taylor series expansion and then the latter part is identified by a neural network, which is then compensated in the control algorithm such that feedback linearization can be achieved. Thus the influence of the non-linearity and model uncertainties may be eliminated or reduced. In the case of time-varying or unknown systems the linear part of the system model is estimated by an RLS (recursive least-squares) algorithm. Simulation results show that the proposed scheme may improve the system performance.
Modelling of transient flow in hydraulic pipelines
Authors: Taylor S E M , Johnston D N , Longmore D K
Published: October 2002

This paper describes a method of modelling time-varying flow in hydraulic pipelines which may be incorporated into time domain simulations of hydraulic systems operating with variable time steps. A previously reported finite element method is extended. New approximations to frequency-dependent friction for laminar and turbulent flow are presented. These are applicable to this finite element method as well as the method of characteristics and finite difference methods. Simulation results are compared against theory and excellent agreement is found.
Geometry-related constraints in the design of active noise control systems
Authors: Tokhi M O
Published: October 2002

This paper presents a coherent method of design of active noise control systems for compact and distributed sources of noise in a three-dimensional non-dispersive propagation medium. An analysis of single-input single-output, single-input multiple-output and multiple-input multiple-output control structures is provided. This focuses on systems in stationary (steady state) conditions. The conditions for the robust operation of such systems on the basis of optimum cancellation, in relation to the controller design, are determined. These conditions are interpreted as constraints on the geometric compositions of the system.
On the optimal control of flexible manipulators
Authors: Farid M , Lukasiewicz S A
Published: October 2002

This paper presents a simple technique based on numerical optimization to solve trajectory control and time optimal control of multiple-link robotic arms with flexible links and joints. The proposed technique finds the joint torques required to move the end-point from rest to rest through a specified path. In trajectory control problems the desired position of the payload is given versus time, while in time optimal control problems the path and the constraints on the joint torques are known. Inverse dynamics of flexible manipulators is non-causal because the point for which the prescribed motion is specified and the application points of control torques are connected by deformable bodies. Non-causality is taken into account via consideration of pre-actuation and post-actuation in the solution procedure.
Systematic approach to the control of hydrostatic drives
Authors: Murrenhoff H
Published: October 2002

Starting with a systematic of hydrostatic drives the paper shows which kinds of control are used today and how they can be divided to find a good analytical way of describing open and closed loops. Open loops can be distinguished by primary and secondary control. Closed loops are divided into force or torque control, speed control and position or angle control. Typical performances of linear and rotary drives are discussed using state-of-the-art controllers. The paper finishes with the controls necessary for the supply of hydrostatic drives, which is mainly a pressure control but can also be a flow or power control.
Control of an electropneumatic actuator: Comparison between some linear and non-linear control laws
Authors: Brun X , Belgharbi M , Sesmat S , Thomasset D , Scavarda S
Published: October 2002

The aim of this paper is to present and to compare some linear and non-linear control laws for an electropneumatic positioning system both for point-to-point control and for tracking control. The experimental results are presented in terms of repeatability for each control law implemented on the same device: an in-line electropneumatic servo-drive. Different kinds of model, namely a non-linear affine model, linearized tangent model and a reduced linearized tangent model, are presented to synthesize the different control laws. For this a new mathematical modelling of the servo-distributor flow stage is described.
Electric-hydrostatic drive—an innovative energy-saving power and motion control system
Authors: Helduser S
Published: October 2002

The paper describes investigations of an electric-hydrostatic drive system, its components and its application in the clamp of a plastics injection moulding machine. The aim of the research work was to reveal the potential advantages and challenges of the new direct pump control concept as well as the suitability of hydraulic pumps for variable-speed operation.

Measurements of component efficiency have proven that hydraulic components have very good efficiency compared with variable-speed electric motors. Therefore, the total efficiency of the electric-hydrostatic drive at a high load (close to corner power) cannot be expected to be noticeably better than the conventional drive system comprising an asynchronous electric motor and variable-displacement hydraulic pump, although fixed-displacement pumps can have better efficiency than variable-displacement pumps have. Improvements may be seen at part-load. The major advantages of the new motor-pump concept are reduction in power losses and noise during part-load and during idling. This was demonstrated in a test cycle.

The design of hydraulic pumps applied in an electric-hydrostatic drive has to be carefully evaluated for suitability. Some piston pumps and internal gear pumps without gap compensation seem to work well under the specific load conditions of variable-speed drives, but not all units worked sufficiently during endurance testing. Owing to the high overload capability of rare earth electric motors, the dynamic performance of the electric-hydrostatic drive can be compared with that of many standard variable-displacement pumps. This was evaluated with performance tests of the clamp unit of a plastics injection moulding machine. The dry cycle time (Euromap 6 standard) achieved (1.8 s for a machine with a 1600 kN clamping force) proved the excellent controllability of the electric-hydrostatic drive and the high dynamic performance capability.

The combination of a speed-controlled a. c. servomotor and fixed-displacement pump increases the number of direct pump control concepts that a hydraulic project engineer can apply to design competitive hydraulic systems for customer applications.
Parameter identification and trajectory following of a two-link rigid manipulator
Authors: Fotouhi-C R , Szyszkowski W , Nikiforuk P N , Gupta M M
Published: October 2002

An adaptive controller for rigid manipulators is discussed in this paper. The scheme presented is applied to a two-link rigid manipulator. It takes full advantage of the known parameters of the manipulator while estimating the unknown parameters. In deriving the dynamic equations of motion, all the physical parameters of the manipulator, including the distributed masses of the links, are taken into account. The overall control system maintains the structure of the computed torque system with an adaptive element. The convergence of the control is considered in detail. A method of selecting the best combination of the various gains is presented. Some simulation results of the manipulator with unknown payload masses following a desired trajectory are presented.
A note on order reduction by the discrete-time least-squares Padé method
Authors: Lucas T N
Published: October 2002

It is shown that reduced order models produced by the least-squares Padé method for discrete-time systems can sometimes produce misleading results for step and polynomial inputs. A more representative way of deriving such models is put forward and a numerical example is given to illustrate the points raised in the discussion.
Multigrid techniques: A fast and efficient method for the numerical simulation of elastohydrodynamically lubricated point contact problems
Authors: Venner C. H. , Lubrecht A. A.
Published: October 2002

The introduction and further development of algorithms based on multigrid (multilevel) techniques has resulted in fast and efficient solvers for elastohydrodynamically lubricated (EHL) point contact problems. As a result the capability to simulate steady state and transient point contact problems numerically has greatly increased in the past decade. This has led to an increased understanding of the mechanisms controlling film formation and pressure in the contact in relation to the operating conditions. In this article an overview is given of the essential ingredients of an efficient multigrid algorithm for an EHL point contact problem. Results are presented for some characteristic problems that illustrate today's numerical simulation capability.

It is concluded that, with respect to EHL, one of the main questions of the last part of the century has been answered, i.e. how to solve efficiently the modelling equations such that realistic and highly loaded situations can be simulated. The challenge that researchers and engineers now face is how to translate the new insights into simple rules for design and engineering, and to establish clearly the limits of validity of the models that are used in simulations both on the scale of the contact as a whole as well as on a subcontact scale.
Optimum initial axial compression due to preload in an arrangement of two tapered roller bearings Part 1: Analysis
Authors: Bercea I , Nélias D , Cretu S
Published: October 2002

This study is focused on a bearing arrangement made of two tapered roller bearings and a shaft, supporting a combination of axial and radial loads. The paper is divided in two parts. This part presents first a numerical procedure to obtain the internal load distribution within tapered roller bearings. The internal load distribution is required to estimate the bearing fatigue life. Afterwards, a numerical method and the related algorithm for a load support system constituted of a shaft and two tapered roller bearings are described. The effect of the initial axial preload (or total axial compression) is taken into account. In consequence the method proposed can be used to select an adequate axial preload in order to increase the system survivability. An example of model implementation, i.e. application to the transfer shaft of an automobile automatic transaxle, is presented in Part 2 of the paper.