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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

Measuring the effects of crosswinds on cars

Macklin, Adrian Roger January 1996 (has links)
The crosswind sensitivity of a car is described as the sensitivity of a driver-vehicle system to vehicle movements provoked by wind influences. Research has shown that it is a contributory factor in accidents and that it is adversely affected by certain body shapes and by reductions in weight. Future legislation calling for a reduction in the amount of Carbon Dioxide produced by cars may well lead to this reduction in weight. Tests have been carried out on llth scale car models to compare the different results produced by static and dynamic tests. Although static tests are easier to perform, dynamic tests, in which the model is propelled across the wind tunnel, offer the advantage of an improved simulation of the skewed profile that the vehicle encounters at full scale. In these experiments a number of different skew profiles, turbulence profiles and model configurations including estates, hatchbacks and saloons, were tested at Reynolds numbers above 4x10⁵. The results showed that data from the more simple static tests were generally more conservative than those from the dynamic tests in a skewed profile up to approximately 30° of yaw. However, the static tests were unable to predict the peak yawing moment that occurs as a result of the transient flow over the model as it enters the gust. The dynamic tests also indicated oscillations in the flow over the rear end of the models in the hatchbacks with backlight angles of 22° and 36°, although less so in the latter. Other results suggested that there was an improved correlation between lift coefficients from different skew profiles, if the mean local velocity integrated over the height of the model was used to non-dimensionalise the data. Quality Function Deployment is not an appropriate framework to be used in the development of a complete vehicle but would prove useful if applied to the issue of crosswind sensitivity as a sub-component.
62

The simulation of transient cross winds on passenger vehicles

Docton, Mark K. R. January 1996 (has links)
No description available.
63

Theoretical and experimental aerodynamic analysis for high-speed ground vehicles

Farhan, Ismail Haider January 1991 (has links)
An improved understanding of the aerodynamics of high-speed ground vehicles can lead to significant reductions in the energy consumption required for propulsion, an increase of vehicle cruising speed, and an increase in the safety and comfort of passengers. To contribute to these goals, this thesis employs theoretical and experimental techniques to investigate the air flow around a proposed geometry for a high-speed electromagnetic suspension (EMS) train. Train motion at normal cruising speed in still air and in crosswind conditions are studied, considering aerodynamic forces and moments, the wake in the lee side of the train and the turbulent boundary layer development. The theoretical prediction work may be conveniently divided into two parts, for inviscid flow, and with viscous effects included. In the first, a numerical technique called the panel method has been applied to the representation of the body shape and the prediction of the potential flow and pressure distribution. Two computer programmes have been written, one for a single vehicle in the presence of the ground at different yaw angles, and the second for application to two body problems, e.g. a train passing a railway station or a train passing the central part of another train. Both programmes have been developed in fully three-dimensional form, but are currently based purely on the source distribution method. This limits the applicability of the method, in particular to small angles of yaw, but useful results are still obtainable. In the second part of the theoretical prediction work, two methods based on the momentum integral equations for three-dimensional boundary layer flow have been developed for use with the aforementioned potential flow analysis; these predict the development of the three-dimensional turbulent boundary layer (i) on the central section (for the analysis of crosswind conditions) and (ii) on the nose of the train. The primary interest of the experimental programme was to provide qualitative and quantitative results for comparison with the theoretical predictions as well as to give insight into the flow behaviour around the train. The experimental tests also provided the first results for the influence of both stationary and moving ground planes on the EMS train. Extensive wind tunnel tests were performed on four purpose-made models of the high-speed train to measure aerodynamic forces, moments and pressures to establish ground effect characteristics. The experimental results demonstrated the importance of ground clearance. Flow visualisation showed that the wake vortices were both stronger and larger in the presence of a ground. At small yaw angles ground clearance had little effect, but as yaw increased, larger ground clearance led for example to substantial increase in lift and side force coefficients. The wind tunnel tests also identified the differences between a moving and a fixed ground plane. The measured data showed that the type of ground simulation was significant only in the separated region. A comparison of the results predicted using potential flow theory for an EMS train model and the corresponding results from wind tunnel tests indicated good agreement in regions where the flow is attached. For small yaw angles, not more than 15°, predicted pressure distributions reproduced measured behaviour. For greater angles, the shed vorticity (associated with flow separation) has a strong effect on the surface pressure field and this would have to be introduced into the panel method to improve prediction. The turbulent boundary layer calculations for the train in a crosswind condition showed that the momentum thickness along the crosswind surface distance co-ordinate increased slowly at the beginning of the development of the boundary layer but then increased sharply at the side top roof on the lee side. The sharp increase is believed to indicate a tendency for flow separation as the solution procedure exhibits signs of failure in this region. Suggestions are made in the thesis for ways of improving both this and other aspects of the theoretical approach.
64

Optimisation of engine-transmission systems in heavy commercial vehicles

Deal, Michael Henri January 1980 (has links)
This thesis examines various control strategies aimed at optimising the steady-state operation of engine-transmission systems for heavy commercial vehicles in order to achieve minimum fuel consumption. The work includes three stages: i) the analysis and synthesis of the problems associated with the control of propulsion plants, ii) the mathematical optimisation of multi-variable systems and iii) the optimisation of an engine shunt-transmission system. The control of propulsion plants for heavy commercial vehicles is examined by reviewing the prime movers and transmissions in use or likely to be used in the near future. The parameters specially highlighted include the external controls and the alterations which can be made to improve component matching. The problem of optimising multi-variable systems is set out. The mathematical optimisation of multi-variable systems involves techniques for the maximization of a n-variable function specific to propulsion plants. The function maximized is not known analytically and can only be evaluated at discrete points. A large number of searching procedures are reviewed and developed to minimize the number of evaluations. The engine transmission system optimised comprises a diesel engine driving a hydro-mechanical transmission of the shunt type. The hydrostatic drive is made up of two variable-displacement units. The external controls are the fuel rack position and the two unit swash displacements. The characteristics of the system are investigated theoretically. Various optimisers, scheduled and on-line, are proposed and one has been fitted on a test rig and will be tested shortly.
65

An object-oriented railway system and power network simulator

Siu, Lok Kee January 1995 (has links)
The increasing application of systems engineering to the design of modern railways has placed a heavy demand on high quality software-based railway system simulators. Very often, a simulator of this kind is not only expensive to build but also to maintain. Modifications and extensions of an existing simulator are always necessary. This leads to the need for investigation into the use of advanced modelling and software engineering techniques to improve the simulation programs such that they are robust yet easy to change. The work described in this thesis, divided into two parts, investigates a) software design using object-oriented technology; b) algorithms for the efficient solution of power network in the DC railway system simulation context. Regarding the software design, an adaptable simulation framework design based on a subsystem-manager-database structured concept has been built using Borland C++. A class library consisting of 66 classes has also been developed. The simulator developed to date, working on any IBM compatible PCs, is able to produce system performance including substation loads, train voltage and current profiles, rail potentials and train diagrams. The simulator models have been verified by means of comparing the results generated by the Birmingham University Fortran multi-train simulator. On the efficient power network solution algorithms, an extensive investigation into the sparse matrix and iterative numerical methods has been conducted. Several representative algorithms have been coded for a comprehensive dynamic speed trial. According to the results, the variable bandwidth preordering is by far the most efficient algorithm for small to medium scale simulations, whilst the minimum degree ordering is the fastest algorithm for simulations including rail potential calculations in which the system usually has several hundred nodes.
66

Extending the range of electric vehicles

Tempest, Andrew S. January 1990 (has links)
The objective of the research project was to evaluate the effectiveness of auxiliary energy storage systems, used in addition to a battery, for extending the range of an electric vehicle. Initially, the work focused around the use of a high speed flywheel to complement the electric vehicle battery. The work was then extended to cover auxiliary energy storage in general. Practical work was carried out using a Bedford/Chloride CF Van, which was equipped with various sensors by Bristol Polytechnic. Using measurements carried out on milk rounds in the local area, a driving cycle was derived, and used to characterise the CF van. This was in turn used to create a pro-forma for a typical battery current demand profile experienced during the driving cycle. Laboratory testing was carried out by repeatedly putting the battery through this basic current cycle. Further cycles were then derived from the basic cycle. These were designed to show the effect of various amounts of auxiliary storage on battery current demand, and hence overall energy output. These were used with the battery in the same way as the basic cycle, allowing a comparison of the battery with and without energy storage. At the same time as the laboratory work was being done, a computer simulation of the Bedford CF was written. Having validated the model against both laboratory results and road test data, it was used to extend the results derived in the laboratory more generally. This was done by running simulated driving cycles for different battery conditions, by varying the performance of the simulated vehicle transmission, and by using different driving cycles. Flywheel auxiliary storage was also simulated, and its efficiency varied. Results from the project establish criteria by which auxiliary storage systems may be judged, by comparing them with the battery alone, and also for comparing regenerative and non-regenerative battery current cycles. This framework is then used to create general criteria which auxiliary energy storage systems must meet if they are to be effective. Possible avenues for future work are also put forward.
67

Artificial intelligence techniques in the scheduling and routing of automated guided vehicle systems

Wing, Michael Antony January 1990 (has links)
This dissertation examines the problems of scheduling and routing automated guided vehicles (AGVs). AGVs are unmanned vehicles following a network of guide paths controlled by a supervisory controller. They represent a highly flexible material moving system well suited to the developing technologies of advanced manufacturing. The research in this area is motivated by the importance of AGVs in modern factories and the inadequacies of current methods of control. These inadequacies include the lack of adequate temporal reasoning, production of vehicle schedules that support automated guided vehicle system (AGVS) rather than global manufacturing objectives, the inability to produce quickest routes for vehicles and the lack of dynamic replanning. Unlike conventional controllers of AGVs the AGV scheduler presented in this dissertation (PRISMM - Planner for Reactive Intelligent Scheduling of Material Movement) considers global manufacturing objectives as well as local AGVS objectives when generating AGV schedules. It exploits novel techniques for routing vehicles that uniquely allow the integration of the shortest or the quickest routes into a timetable of vehicle movements. The techniques guarantee to find a route if one exists and will allow the imposition of deadlines. Algorithms to find a fast route through large or extremely busy route networks have also been derived. These methods will guarantee to find a route between two points as long as the vehicle begins its journey from a reserved parking space. A replanning technique has been proposed for dealing with most common errors of AGV schedule execution. A new method for the most commonly encountered problem requires no reordering of plan steps.
68

The steady state forces and moments on a railway wheelset including flange contact conditions

Brickle, Barrie Vaughan January 1973 (has links)
Railway vehicles are fitted with coned wheels to provide a measure of stability, but it can be shown that since the forces between wheel and track are non-conservative, dynamic instability occurs at a certain critical speed. Under these conditions the wheelsets sway from side-to-side of the, track with the flanges of the wheels contacting the rails. This can lead to derailment when the wheel climbs up the rail and eventually jumps off. The forces which exist between wheel and rail are due to the phenomenon known as "creepage", and various theories exist which predict these forces in the plane of the contact area. An investigation has been carried out into these theories with the railway wheelset problem in view, particularly the flange contact case. It is possible, by assuming small displacements which avoid flange contact, to carry out a linearised study of the lateral dynamics of a wheelset, but the presence of the wheel flanges introduces a nonlinearity into the problem. A mathematical model of a wheelset and track has been defined based on real wheels with a "worn" tyre profile and real track. Computer programs have been written which calculate the contact points when the wheelset is displaced laterally and yawed by various amounts, including flange ,contact conditions. Up to three contact points can exist between the wheelset, and track. Forces in the contact areas have been calculated using the various theories assuming the wheelset to be rolling along the track a ta constant velocity in a displaced position. These forces have been manipulated to give the total forces and, moments on the wheelset and are presented for various vertical load distributions and for various angular and lateral displacements of the wheelset from its central position. Although theories exist which predict the forces for flange type contact, i. e. very elongated contact ellipse with a large amount of spin present, it became apparent during the course of the investigation that very little experimental evidence was available for such conditions. As a result a roller rig was built to provide this data, and measurements were made of the lateral force due to various amounts of lateral creep and spin on elongated contact ellipses. Results from these tests have been compared with the available theories and show reasonable agreement.
69

Biodegradation of oil on railway tracks

Smith, A. D. January 1981 (has links)
No description available.
70

Neural network identification and control of electrical power steering systems

Ouyang, Xiaohong January 2000 (has links)
No description available.

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