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New Publications are available now online for this publication.
Please follow the links to view the publication.Optimal control of electromagnetic actuator considering energy loss minimisation in electric circuit
http://dl-live.theiet.org/content/conferences/10.1049/cp_20080217
A finite element - based simulation of the single - phase electromagnetic actuator control including 3D electromagnetic field, circuit and movement model coupling to optimal control is presented. The subject of this paper is to study an optimal control technique that minimises quadratic energy function in the electric circuit. As a new contribution an algorithm based on Linear Quadratic Problem coupled with electromagnetic actuator model in a closed - loop control system is proposed.Reliability in electromagnetic systems: the role of electrical contact resistance in maintaining automobile speed control system integrity
http://dl-live.theiet.org/content/conferences/10.1049/ic_20070027
Electromagnetic systems depend upon the integrity of electrical connections. An intermittent speed sensor connection is shown to generate a false speed signal that may allow an automobile speed control system to engage at low speed and cause a sudden acceleration. Preventive measures are discussed. The current approach to controlling uncommanded sudden accelerations seems to rely upon the driver braking against full engine power to bring the vehicle to a halt. More effective and safer control would be achieved by cutting off the fuel supply the moment that an uncommanded wide open throttle condition was detected, thereby preventing the sudden acceleration. (6 pages)The maximum-gain, minimum-integral principle applied to materials testing
http://dl-live.theiet.org/content/conferences/10.1049/ic_19961462
The maximum-gain, minimum-integral principle is a method of tuning PID controllers proposed by E.C. Hind (1978, 1980) who first expressed this approach in terms of frequency response and then later (1981) in the time domain using set-point changes. This paper describes the application of the time-domain method for tuning PID controllers for servo-hydraulic and electromechanical materials-testing machines. Good tuning is essential to ensure that applied loads and strains are faithfully replicated. The tuning method is simple to use and an automated version of it is now commercially available for materials-testing machines. Two improvements to Hind's method have been proposed: first, a better final response is obtained if the undershoot is monitored during the maximum-gain phase rather than overshoot. Second, the minimum-integral phase is easier to apply if the servo error is monitored with the demand set to a triangular waveform shape. For systems which have a lightly damped resonance, derivative compensation reduces the stability margin. For such systems, it is better to augment PID with a series lag filter and use lag instead of derivative compensation. (6 pages)Design and construction of a micromechanical optical actuator
http://dl-live.theiet.org/content/conferences/10.1049/ic_19950573
Optically powered fluid actuators are under development for use in `control-by-light' systems including one based on photothermal effects inside a closed cell. The miniaturisation of the converter has been shown to improve the speed of operation of this device substantially, with time constants of the order of tens of milliseconds. Further integration of the various device components in silicon allows for performance improvements which are discussed. This paper focuses on the production and assembly of the multiple-wafer device using a combination of simple micromachining techniques. Some typical experimental results are presented and future developments are discussed. (3 pages)Uncertainty modelling and structured singular-value computation applied to an electromechanical system
http://dl-live.theiet.org/content/journals/10.1049/ip-d.1992.0041
The investigation of closed-loop systems subject to model perturbations is an important issue to assure stability robustness of a control design. A large variety of model perturbations can be described by norm-bounded uncertainty models. A general approach for modelling structured complex and real-valued parametric perturbations is presented. The resulting robustness analysis problem is solved nonconservatively using real and complex-structured singular-value calculations. The uncertainty modelling and robustness analysis are shown for a high-accuracy 5D electromechanical positioning device to be used in optical (Compact Disc) recording.Employing chaos tools and methods in magnetic levitation
http://dl-live.theiet.org/content/journals/10.1049/ip-smt_19990002
Magnetic levitation by tuned circuits is a known method for freely suspending ferromagnetic objects. Though the method yields a relatively simple system which includes a surprisingly small number of components, it exhibits complicated dynamics. As a result, stabilisation of these levitators is a complex task. It is shown that, by employing chaos theory and by applying methods of control developed in association with chaotic systems, the stabilisation of the present levitator is made simpler, and can be achieved at lower source frequencies. This reduction of source frequency is shown to be of practical value. Furthermore, a measure known among chaos researchers (the correlation dimension) for assessing the complexity of chaotic systems has been found to be valuable for evaluating and developing the novel stabilisation method.Dynamic analysis of a bistable actuator for digital hydraulics
http://dl-live.theiet.org/content/journals/10.1049/iet-smt_20080124
A fast and small electromagnetic actuator, which requires a small amount of work to switch between two stable positions, for the use in digital hydraulics, is presented. A dynamic study of the bistable actuator as part of a new kind of hydraulic on/off valve is carried out. A prototype is built and measured to verify the analysis. The results show that with careful elaboration the design is feasible. Furthermore, the response times depend on driving frequencies and an optimal current density for minimal energy consumption in cyclic action can be found. A single on/off valve is a critical part of a digital hydraulic system.Diagnostic system to determine the in-service life of dry vacuum pumps
http://dl-live.theiet.org/content/journals/10.1049/ip-smt_19990654
A diagnostic system for dry pumps is proposed. It predicts future pump motor current from time-series in-situ measurements. The prediction system has been constructed using a data acquisition system with an online system identification software algorithm. A field test on a low pressure chemical vapour deposition (LPCVD) system for the silicon nitride process predicted large values of motor current, some of which correlated well with actual motor currents as the pump became clogged. The combined use of the predicted motor current and the stability criteria shows promise in predicting the actual service life of a dry pump.Magnetic momentum management for a geostationary satellite platform
http://dl-live.theiet.org/content/journals/10.1049/iet-cta.2008.0327
The attitude control system of three-axis stabilised geostationary platforms is usually based on a set of reaction wheels, the operation of which requires periodic desaturation manoeuvres in order to dump the angular momentum accumulated because of external secular disturbance torques. The need for such manoeuvres can be minimised by careful design of the satellite platform. In this paper, the control issues associated with the adoption of a magnetic actuator for (partial) momentum dumping on a geostationary platform are discussed, with specific reference to the robustness issues arising due to the highly uncertain space environment at geostationary earth orbit altitude.