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No description available.

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The only commercially operating magnetically levitated (maglev) transport system in the world is the link between Birmingham International Airport and the National Exhibition Centre. Comparative financial analysis for this route showed that the construction costs for both wheeled and maglev systems were similar and that the cost of the guideway accounted for over 70% of the total. In part this was because the guideway was elevated; a likely requirement for any future urban system. A substantial reduction in installation costs for a system of this nature can only be achieved by the use of cheap, lightweight and flexible guideways. The British Rail Research maglev vehicle was designed for use on a rigid guideway and it was known that excessive flexibility would make the suspension control system unstable. The aim of the study was to develop a maglev suspension control strategy that was insensitive to guideway flexibility. Vibration measurements were carried out on the Birmingham guideway to establish its modal properties. It was found to be sufficiently rigid to allow the existing controller to work without problems .Measurements were also made on the guideway of a Swiss cablecar transit system. This was felt to represent the extremes of both lightness and flexibility and established the range of guideway dynamics that were likely to be encountered. For the initial experimental work, a section of the British Rail maglev test track was modified to incorporate three sections of flexible track. A personal computer was installed on board the vehicle and software was written to aid frequency response testing and dynamic system modelling. Tests were carried out to establish the dynamic parameters of the new sections of guideway. The existing rigid guideway controller separated magnet control from suspension control. Guideway flexibility destroys this separation and induces additional feedback terms that degrade system stability. Theoretical studies of an improved controller took advantage of the fact that that the suspension magnets act directly onto the guideway and affect the position of both vehicle and guideway. As the guideway is lightly damped it is only flexible over a narrow bandwidth and the new suspension controller is able to use vehicle inertia to react forces that control the guideway at its natural frequency. Theory suggested that this would restore the separation of magnet and suspension control even with a flexible guideway. For a variety of reasons, experimental implementation of the new controller proved to be difficult. Suspension performance on the flexible portions of the guideway was never adequately demonstrated. The work did however enable a very accurate theoretical model of the system to be developed. This model contrasted with earlier predictions because, on rigid guideways, it predicted substantially smaller phase margins than the earlier models had suggested. It showed that the new controller had only modest benefits relative to the original rigid guideway suspension controller. This led to the development of an improved controller, a "lumped" controller where magnet and suspension control are not separated. Modelling for a single degree of freedom vehicle on a single mode guideway showed that large improvements in suspension performance could be made. Further modelling of a three degree of freedom vehicle and a five mode three degree of freedom flexible guideway used parameters that represent the production vehicles at Birmingham. This work defined limits for guideway flexibility and vehicle dynamic performance and showed that maglev guideways for production scale vehicles, with the "lumped" controller, can be very flexible indeed. The major aim of the project was achieved. A suspension controller was developed that will allow a maglev vehicle to work on a guideway that is far lighter, more flexible and far cheaper than the guideway required for a conventional wheeled vehicle.

This thesis describes the development of a microprocessor based control system for a parallel hybrid petrol/electric vehicle. All the fundamental systems needed to produce an operational vehicle have been developed and tested using a full sized experimental rig in the laboratory. The work begins with a review of the history of hybrid vehicles, placing emphasis on the ability of the petrol electric design to considerably reduce the consumption of oil based fuels, by transferring some of the load to the broad base of fuels used to generate electricity. Efficient operation of a hybrid depends on the correct scheduling of load between engine and motor, and correct choice of gear ratio. To make this possible torque control systems using indirect measurements provided by cheap sensors, have been developed. Design of the control systems is based on a theoretical analysis of both the engine and the motor. Prior to final controller design, using the pole placement method, the transfer functions arising from the theory are identified using a digital model reference technique. The resulting closed loop systems exhibit well tuned behaviour which agrees well with simulation. To complete the component control structure, a pneumatic actuation system was added to a 'manual gearbox' bringing it under complete computer control. All aspects of component control have been brought together so that an operator can drive the system through simulated cycles. Transitions between modes of operation during a cycle are presently based on speed, but the software is structured so that efficiency based strategies may be readily incorporated in future. Consistent control over cycles has been ensured by the development of a computer speed controller, which takes the place of an operator. This system demonstrates satisfactory transition between all operating modes.

The aim of the research described in this thesis is to assess the technical feasibility of pneumatic tyres for passenger cars which have no directional reinforcement in their carcasses. Conventional tyres are constructed from composites of twisted textile or steel cords in a rubber matrix, a process which is both labour intensive and costly. If it were possible to injection mould or cast tyre carcasses in a single operation, and if the performance of the resulting tyres matched that of modern radial ply tyres, then the implications for the tyre industry would be of major proportions. After reviewing the history of pneumatic tyres and summarising their principal attributes, the design of unreinforced or fabricless tyres is investigated and methods developed for defining their meridional profiles. Materials suitable for their carcasses and treads are then considered, prior to describing the manufacture of two series of tyres designed to have section height to width ratios, or aspect ratios, of 0.9 and 0.7 respectively. To facilitate experimental work, two sizes of tyres were employed: half scale models for which testing procQdures had been developed previously; and a size suitable for small saloon cars. The results obtained on a range of tyre properties are presented and analysed to give a number of empirical relationships between the properties and the design variables: carcass material Young's modulus, carcass wall thickness and the inflation pressure. For the important property of radial stiffness which affects other tyre characteristics, an improved method of analysis is developed to allow the structural and pneumatic components to be quantified. Using the relationships established experimentally, consideration is given to optimising the design of a fabricless tyre. It is concluded that to approach the performance of a conventional tyre, a design with a low aspect ratio is preferred but, to restrict growth with inflation'pressure, limited directional reinforcement must be included as a circumferential-belt beneath the tread. Nevertheless, the discussion concludes that there are fundamental reasons why even the optimised tyre would be unacceptable for use on modern passenger cars, although less demanding applications may be identified.