Showing papers in "Transactions of the Institute of Measurement and Control in 1995"
TL;DR: In this article, a review of model-based fault diagnosis techniques is provided, starting from basic principles, the properties and limitations of different methods are discussed, and the problems encountered in both the residual generation and evaluation stages of fault diagnosis have been outlined.
Abstract: This paper provides a review of model-based fault diagnosis techniques. Starting from basic principles, the properties and limitations of different methods are discussed. The main aim is to give some guide-lines for the use of model-based methods. Accordingly, the problems encountered in both the residual generation and evaluation stages of fault diagnosis have been outlined. A comparison of quantitative and qualitative methods is also given. Finally, the limitation of model-based methods and the alternative and supplementary use of heuristic knowledge are discussed.
74 citations
TL;DR: A CAOS which takes an image guided approach to planning and implementing a trajectory, to assist an orthopaedic surgeon, and identifies the registration and calibration techniques used by the CAOS intelligent guide.
Abstract: Within the next few years it is envisaged that a number of computer assisted surgery products will become available. For many surgical procedures, outcome of surgery,, will rely on the accuracy and repeatability with which a computer assisted surgical toolperforms its task. This paper presents a Computer Assisted Orthopaedic System (CAOS) which takes an image guided approach to planning and implementing a trajectory, to assist an orthopaedic surgeon. Accurate delivery of this trajectory is achieved via an intelligent guide.This paper details the design issues and identifies the registration and calibration techniques used by the CAOS intelligent guide. The paper also enumerates, and where possible quantifies, thefactors that influence the accuracy performance of the system. Accuracy trees are used to show the root source of inaccuracies and how they propagate and combine in a system.
65 citations
TL;DR: An adaptive neural network controller is presented for flexible joint robots using Singular Perturbation techniques by modelling the elastic forces as the fast variables and link variables as slow variables to eliminate the tedious preliminary computation of the regressor matrix.
Abstract: In this paper, an adaptive neural network controller is presented for flexible joint robots using Singular Perturbation techniques by modelling the elastic forces as the fast variables and link variables as slow variables. The neural network controller is to control the slow dynamics in order to eliminate the tedious preliminary computation of the regressor matrix. Unlike many neural network (NN) controllers in the literature, inverse dynamical model evaluation is not required and no time-consuming training process is necessary except for initialising the NNs based on approximate function values at the initial posture at time t = 0. It can be shown that the controller can control the system successfully by intensive computer simulation tests.
34 citations
TL;DR: In this paper, the design of robust computer control systems for balancing and attitude control of double and triple inverted pendulums is considered, where a DC motor mounted at the upper hinge is used to balance and control attitude of the upper link.
Abstract: The design of robust computer control systems for balancing and attitude control of double and triple inverted pendulums is considered in this paper. For the double inverted pendulum, a DC motor mounted at the upper hinge is used to balance and control attitude of the upper link. For the triple inverted pendulum a DC motor mounted at the middle hinge is used to control the middle link, whereas proportional position control applied to a motor at the upper hinge is utilised to maintain the upper link in alignment with the middle link. In both cases the lower hinge is left free to rotate. The controller designs are based on linearised discrete-time models of the inverted pendulums. Each controller utilises state feedback implemented via reduced-order state observers. The relative stability properties of the control systems are evaluated using Nyquist plots of suitably defined functions. The controllers are designed using Matlab and implemented in a PC using C language. Experimental results showed satisfactor...
29 citations
TL;DR: In this paper, three feedback devices are described arising from research supported by the EPSRC and BRITE-EURAM, including a 2 ½-D programmable surface using shape-memory alloy wires, a surface with programmable compliance using electro-rheological fluids, and a robot-like device which provides force feedback to the user and is programmed to mimic the dynamic characteristics of the virtual object and its interaction both with the virtual environment and the operator.
Abstract: Virtual reality technology has great potential for design for assembly, disassembly and maintenance but such manipulation tasks by their very nature involve tactile and kinaesthetic interaction. Consequently, a new generation of tools needs to be developed to provide the appropriate tactilelkinaesthetic feedback to the user in order to complement the traditional visual technology. Three feedback devices will be described arising from research supported by the EPSRC and BRITE-EURAM.(1) A 2½-D programmable surface using shape-memory alloy wires.(2) A surface with programmable compliance using electro-rheological fluids. Haptic searching over the surface gives the illusion of the presence of an object.(3) The Reactabot™ , a robot-like device which provides force feedback to the user and is programmed to mimic the dynamic characteristics of the virtual object and its interaction both with the virtual environment and the operator.
11 citations
TL;DR: In this article, a dexterous 3-fingered 1-thumb hand driven by high power/weight performance pneumatic muscle actuators was designed for tele-presence control.
Abstract: Manipulators in one form or another have been in existence for many hundreds of years with the design (ranging from simple hooks or two-jaw systems to complex multi-articulated grippers) usually motivated by the particular class of task. When the problem domain includes a varied range of objects, one approach is to emulate those attributes of the human hand which make it such a versatile end-effector.This work considers the design of a dexterous (3-fingered 1-thumb) hand driven by newly developed high power/weight performance pneumatic muscle actuators (PMA). Although the manipulator can be used in conventional robotic applications the primary aim is for a high-performance tele-presence system with full manipulator input and tactile feedback. The robot manipulator closely replicates the skeletal layout of the human hand, making controlfrom a gloved input device (developed at Salford) feasible, thereby substantially reducing the control difficulties associated with decterous devices and making widevpread l...
10 citations
TL;DR: In this paper, a novel approach for the fault detection and diagnosis of the actuators in nonlinear systems is presented, where the faults are assumed to be any unexpected changes of the parameters in the actuator, which include either abrupt changes or slowly drifting changes.
Abstract: 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.
6 citations
TL;DR: 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 in this article, which employs a combination of intelligent sensors, predictive mathematical models and AI technology to provide realtime information on a number of system parameters.
Abstract: 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...
6 citations
TL;DR: In this article, an interactive multi-objective optimisation method has been introduced for tuning multi-loop PID controllers, where several design specifications may be simultaneously considered in this optimisation problem.
Abstract: 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.
6 citations
TL;DR: In this paper, a linear reduced-order control model is obtained from a nonlinear simulation model using novel data-based model reduction and linearisation techniques, which is then used to design two multivariable non-minimal state variable feedback (SVF) control systems.
Abstract: The paper discusses the multivariable modelling and control of a glasshouse micro-climate. A linear reduced-order control model is obtained from a nonlinear simulation model using novel data-based model reduction and linearisation techniques. This control model is then used to design two multivariable non-minimal state variable feedback (SVF) control systems. The first utilises an LQoptimal Proportional-Integral-Plus (PIP) design method incorporating multi-objective optimisation of the weighting matrices, achieving partial dynamic decoupling; while the second uses an algebraic approach to combined pole-assignment and full dynamic decoupling. These controllers are evaluated, to ensure robustness, using the nonlinear simulation model, prior to implementation and evaluation on the real glasshouse during the 1993-94 winter growing season. Control results are excellent with very tight control to the desired setpoints in all three climate variables. For example, air temperature is controlled to within 0.5°C of the setpoint for 85% of the validation period, and is shown to be very robust to model uncertainty and extreme weather conditions.
6 citations
TL;DR: Questions about computer assisted orthopaedic surgical systems, cost effective, necessary, desirable or indeed indicated in current cost containment in the NHS, and points which are conducive to a positive response from the end user (surgeons, and hospital management) are discussed.
Abstract: Orthopaedic implants are manufactured to the highest degree of precision by some of the most precise machines known to man and inserted into patients by some of the most imprecise methods known. Computer assisted systems aim to overcome this dichotomy by improving the planning and implementation of orthopaedic surgery. This can be achieved by providing the surgeon with better information for planning and a more precise means of implementing the surgery.This surgical advancement will change current orthopaedic practice significantly if the appropriate surgical issues are considered during their development. Safety is obviously paramount and is being addressed, as is registration between the real (patient) and the virtual computer world.The more subtle, but nevertheless important, surgical issues have as yet not been fully identified or addressed satisfactorily. The following questions serve to highlight them. Is there an optimal system size, shape, reach, control and positioning in surgery? What are the sa...
TL;DR: A method of measuring the variance of a noisy process on-line, enabling the application of adaptive Statistical Process Control to supervise a continuous process loop, and produces an uncorrected sequence from potentially correlated data.
Abstract: This paper describes a method of measuring the variance of a noisy process on-line, enabling the application of adaptive Statistical Process Control (SPC) to supervise a continuous process loop. A fundamental requirement of SPC techniques is that the data are independent. Process control loops typically generate autocorrelated data, and this tends to create an increase in the false alarm rate when attempting to apply SPC techniques. The method presented here produces an uncorrected sequence from potentially correlated data, overcoming this problem. The SPC supervisory unit acts externally to the control loop preventing any lags in feedback. When these SPC charts are used in a supervisory role with a conventional PID controller, application of individual PID terms achieves a much quieter control with little reduction in performance and without the need for prior off-line noise tests. The results of tests in simulation and on a steam-water heat exchanger are presented.
TL;DR: In this article, the authors used heat transfer models to monitor fouling from ash in a coal-fired power generation boiler and found that recurring fouling patterns suggest relationships with time, load and with changes in the in-service cleaning system.
Abstract: 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.
TL;DR: A new method of both control and feedback, utilising simulation software developed for off-line programming, is currently under development at Cranfield, and the need for them and their inherent advantages over current technology are described.
Abstract: 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.
TL;DR: Using experimental frequency response data, the Ziegler-Nichols tuning method for PID design is demonstrated to yield an unstable closed-loop system and a strategy which specifically aims to counter the adverse phase characteristics of the plant at resonance is adopted.
Abstract: Efficient operation of a distributed solar collector field requires effective regulation of the outlet temperature. Control schemes utilising PI-based controllers, whether adaptive or fixed paramet...
TL;DR: In this paper, a tuning technique based on sensitivity functions is proposed for a DC motor generator pilot plant, where the output responses to certain input signals, in our case step signals, must be available.
Abstract: At control system implementation some trial-and-error on-line tuning of the controller is often necessary for performance improvement. This procedure is unfortunately difficult to pursue in some cases due to a high degree of controller complexity and therefore a large number of possible tuning parameters. The problem can be obviated through the implementation of a tuning technique based on sensitivity functions. Systematic adjustments are made on the basis of responses obtained from measurements on the system being tuned. No plant model is needed, in fact only the output responses to certain input signals, in our case step signals, must be available. The approach is illustrated by the aid of the DC motor generator pilot plant.
TL;DR: In this article, the capacitance variable area flowmeter or rotameter for gas measurements is developed, which uses the change of the annular gap between the float and the tapered bore at different positions to measure the corresponding change in capacitance in the form of voltage.
Abstract: The principle of the capacitance variable area flowmeter or rotameter for gas measurements is developed. This method utilised the change of the annular gap between the float and the tapered bore at different positions to measure the corresponding change in capacitance in the form of voltage. From performance tests conducted for air on both a simulated rotameter and an actual rotameter constructed based on the principle described, good agreement was obtained between analytical and experimental results. It was found that the output voltage from this rotameter depended upon the relative sizes of the diameters of the tapered bore and the float, and the angle of the tapered tube.
TL;DR: In this article, the authors use a method for calculating the uncertainties in indirect measurements of both relative humidity and humidity ratio and therefore for comparing the performances of different sensors, starting from the manufacturer's specification for the more common air humidity sensors.
Abstract: To compare different methods of measuring humidity can be somewhat complicated because of both the high number of measurable hygrometric parameters and their lack of homogeneity. Given that there are measurement uncertainties, this comparison is possible through the law of propagation of measurement uncertainties. In this paper the authors use a method for calculating the uncertainties in indirect measurements of both relative humidity and humidity ratio and therefore for comparing the performances of different sensors. This comparison is developed, starting from the manufacturer's specification for the more common air humidity sensors. The indirect measurement uncertainties at different dry bulbs are presented using diagrams for each sensor family. The results provide useful information both for analysing the humidity measurement uncertainty of a specific sensor, and for choosing the most suitable sensor for given measurement conditions.
TL;DR: In this paper, a PI state feedback controller for multivariable discrete systems is proposed and the issue of robust controller design is addressed and the resulting design structure, in contrast to other schemes, is always controllable and observable and can thus lend itself for the developing of control algorithms using standard methods such as eigenvalue assignment.
Abstract: A PI state feedback controller for multivariable discrete systems is proposed and the issue of robust controller design is addressed. The resulting design structure, in contrast to other schemes, is always controllable and observable and can thus lend itself for the developing of control algorithms using standard methods such as eigenvalue assignment. Robust performance is achieved through a minimum norm design using a matrix pseudo inverse. Simulation example shows the effectiveness of the resulting controller.
TL;DR: In this article, the authors compare a range of multivariable design strategies using a commercial multi-ivariable coupled tank experimental rig as the uncompensated plant, and compare their results with those of those of the same authors who only require minimal system information.
Abstract: A large number of design strategies exist for multivariable control situations. Many of' the methods require a linear time-invariant process characterisation in the form of a state space model or transfer function matrix description. Quite often this is not available and could be evpensive to realise. If this latter route is pursued there needs to be considerable benefits in the quality of the resulting closed-loop performance, especially when compared to those methods which only require minimal system information. The main aim of this paper is to compare a range of multivariable design strategies using a commercial multivariable coupled tank experimental rig as the uncompensated plant,
TL;DR: In this paper, the suspension voltage is applied to one electrode only, whilst the opposing electrode is kept at zero potential, and with no standing voltage the electric disturbing torque (EDT) is kept to a minimum.
Abstract: An electrostatic gyroscope (ESG) requires an electrostatic suspension system (ESS) to keep its rotor suspended in a vacuum cavity. The conventional ESS operates with high standing voltage on opposing electrodes that causes a large electric disturbing torque (EDT) applied to the gyro rotor, with consequent loss of accuracy. In the newly-designed ESS the suspension voltage is applied to one electrode only, whilst the opposing electrode is kept at zero potential. With no standing voltage the EDT is kept to a minimum. The new system has an inherent square-root compensation. Theoretical analysis and computer simulations show that the new system meets the requirements for marine applications.
TL;DR: A strategy for the use of sensor information in a general purpose teleoperation system for rehabilitation using human models of reaching and grasping tasks as the basis for the development of sensor-based strategies for interaction with the environment.
Abstract: This paper presents a strategy for the use of sensor information in a general purpose teleoperation system for rehabilitation. Current research in teleoperation and mobile robotics is reviewed and its relationship to the design of a rehabilitation manipulation system is discussed. Human models of reaching and grasping tasks are used as the basis for the development of sensor-based strategies for interaction with the environment. Integration of the strategies with the Cambridge University Robot Language is discussed, and quantitative results of experimental trials are presented.
TL;DR: The paper addresses discrete systems with a finite number of states which can be modelled by the state equations of a finite automaton based on arithmetic representations of Boolean functions appearing on the right-hand side of the underlying finite state equations.
Abstract: The paper addresses discrete systems with a finite number of states which can be modelled by the state equations of a finite automaton. In contrast to traditional work, the paper is based on arithm...
TL;DR: In this paper, the effect of step and pulsating increases in gas flow through a vehicle exhaust system was investigated for an automotive application, and simulation results portraying the effect and effect of these increases were presented.
Abstract: Analytical procedures enabling the modelling of variable geometry exhaust gas systems are considered. An automotive application is investigated. Simulation results portraying the effect of step and pulsating increases in gas flow through a vehicle exhaust system are presented.
TL;DR: In this paper, methods for assessing band-limited image data interpolator speed and accuracy have been addressed, and techniques for the measurement of interpolation performance and an interpolator accuracy test have been developed.
Abstract: Methods for assessing band-limited image data interpolator speed and accuracy are addressed. Techniques for the measurement of interpolation performance and an interpolator accuracy test have been developed. Application to synthetic aperture radar image interpolators show that adequate accuracy can be achieved with as low as 4-point interpolation, and that fairly coarse spatial approximation can be used in many practical instances in order to gain a significant improvement in interpolation speed.
TL;DR: In this paper, a modified adaptive controller for robotic manipulators is presented, which guarantees uniform ultimate boundedness of the tracking errors and parameter errors in the presence of a class of state-dependent uncertainties.
Abstract: 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.
TL;DR: This paper presents a method for the numerical determination of the z- transform and the modified z-transform of a proper rational function expressed in the Laplace transform complex variables that is equally applicable to single-loop and multi-loop systems.
Abstract: This paper presents a method for the numerical determination of the z-transform and the modified z-transform of a proper rational function expressed in the Laplace transform complex variables. The method is easy to implement on a computer using any high-level language and does not necessarily require the poles of the s-domain function to be found. The method is equally applicable to single-loop and multi-loop systems.
TL;DR: In this paper, an air-fuel ratio estimator, using torque measurements, for a spark-ignited engine is presented, instead of estimating the in-cylinder AFR directly.
Abstract: 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 employ...
TL;DR: In this paper, the authors presented a numerical model for the conical entrance orifice plate flow sensor, which is essentially used as a low Reynolds number flow measuring device, based on the Lam and Bremhorst model.
Abstract: This paper presents a numerical model for the conical entrance orifice plate flow sensor, which is essentially used as a low Reynolds number flow measuring device. The model was developed using a low Reynolds number k-ɛ model of turbulence – the Lam and Bremhorst model. Numerical results were obtained for diameter ratios of 0.1, 0.2 and 0.3, and for pipe Reynolds numbers of between 80 and 60000. The computed discharge coefficients are compared with available experimental data and with the value stated in BS 1042. Results show that the model developed can predict the discharge coefficient to within ±3% for the range of diameter ratios and Reynolds numbers investigated.
TL;DR: The AMST 1994 Symposium on the Application of Multivariable System Techniques (AMST 94) as discussed by the authors attracted both research and industrial contributions reflecting current trends in system dynamics, modelling and control.
Abstract: In March 1994 the fifth symposium on the ’Application of Multivariable System Techniques (AMST 94)’ was held at the University of Bradford, UK. The symposium, which was jointly organised by the Institute of Measurement and Control and the University of Bradford, attracted both research and industrial contributions reflecting current trends in system dynamics, modelling and control. Papers which were accepted for presentation were published by Mechanical Engineering Publications Limited (Whalley, 1994) and within a short space of time moved onto the MEP’s best seller list. Given the success of the symposium, a number of independent reviewers identified papers of general interest which had the potential for ~ ~cz~zsc~ctio~.~ publication and additionally reflected the flavour of