Global Navigation Satellite Systems (GNSS) have an endless number of applications in industry, science, military, transportation and recreation & sports. Two systems are currently in operation namely GPS (the USA Global Positioning System) and GLONASS (the Russian GLObal NAvigation Satellite System), and a third is planned, the European satellite navigation system GALILEO. The potential performance improvements achievable through combining these systems could be significant and expectations are high. Computer software can be used to simulate the overall process of GNSS (signal transmission and reception) and produce realistic simulated GNSS measurements. Using such simulated measurements, current and future GNSS systems and possible new applications of GNSS can be investigated. Thus data simulation is the perfect research tool in GNSS fields. Oceanography, is one application of GNSS, which requires position determination with a high accuracy. LEO satellites are used to measure the precise height of the sea surface for studying the dynamics of the world's oceans. Achieving maximum benefit from the altimetric data collected by LEO satellites requires a radial orbit accuracy of 10 cm, or better. It is in determining this orbit where GNSS may be utilised. GPS already delivers high quality position information for LEO satellite orbits such as Topex/Poseidon (1992- present). However LEO satellite orbits determination can still benefit from using GPS combined with GALILEO as there will be more visible satellites and a higher quality of measurements. Investigation of LEO satellite orbit determination using GPS or GALILEO or both systems requires GPS and GALILEO measurements. Due to the lack of real GALILEO measurements, as the system is still in development, the simulation of GPS and GALILEO measurements is required. In order to generate realistic simulated GPS and GALILEO data, the errors, which predominate in GNSS measurements, must be accurately modelled. During this research, it has been shown that it is possible to generate realistic simulated GPS data through the more realistic simulation of the ionospheric, tropospheric and multipath delays. Models with a high spatial resolution have been implemented to simulate the real behaviour of the ionosphere and troposphere. The behaviour of the resulting simulated GPS data is shown to follow the behaviour of real GPS data with a strong agreement. It has also been possible to generate GALILEO simulated data through modifying the simulation software using the GALELEO Design technical specifications. The potential impact of using GPS and GALILEO on LEO satellite orbit determination could be investigated on Topex/Poseidon mission which real GPS data was available from the beginning of this study. The performance of GPS, GALILEO, combined GPS/GALILEO and combined GPS-modernised/GALELEO constellations have been investigated in relation to the reduced dynamic orbit determination of the LEO satellite Topex/Poseidon. It can be concluded that the GALILEO constellation will provide high quality real time LEO satellite orbits compared with GPS. GALELEO constellation will provide slightly better quality real time LEO satellite orbits over the combined GPS-present/GALELEO constellation. However the best quality real time LEO satellite orbits will result from the combined GPS-modernised/GALILEO constellation.

The NAVSTAR Global Positioning System (GPS) has been under development by the US Department of Defense since 1973. Although GPS was developed for precise instantaneous position and velocity determination, it can be used for high precision relative positioning, with numerous applications for both surveyors and geodesists. The high resolution of the satellite's carrier phase has enabled relative positioning accuracies of the order of one part per million to be routinely obtained, from only one or two hours of data. These accuracies are obtained using the broadcast ephemeris, which is the orbit data that is broadcast in the satellite's radio transmission. However, the broadcast ephemeris is estimated to be in error by up to twenty five metres and this error is one of the principle limitations for precise relative positioning with GPS. An alternative to the broadcast ephemeris, is to determine the satellite orbits using the carrier phase measurements, obtained from a network of GPS tracking stations. This thesis describes the algorithms and processing techniques used for the determination of GPS satellite orbits using double differenced carrier phase measurements. The data from three different GPS campaigns have been analysed, which demonstrate a GPS orbital accuracy of between two and four metres, giving baseline accuracies of the order of one or two parts in ten million.

The Global Positioning System (GPS) has been an undoubted success and a great many applications have benefited from it. It does however have limitations, which make its use in certain environments, and for certain tasks, difficult or indeed impossible.In recent years a second satellite based navigation system, the Global'naya Navigatsionnaya Sputnikov Sistema (GLONASS) has become increasingly available. A great deal of interest has been expressed in combining both these systems, in the hope that combined GPS/GLONASS technology will present significant benefits under conditions where GPS alone has struggled. The research described in this thesis was undertaken to examine the potential benefits and problems of such a combination. This has been primarily achieved through the modification of the existing GPS processing software of the Institute of Engineering Surveying and Space Geodesy (IESSG) to accept GLONASS observations. The analysis of data collected under controlled conditions and processed through this software has highlighted biases in the pseudorange measurements from the GLONASS satellites. This is due to the fact that each GLONASS satellite broadcasts on a different frequency, which is then delayed by slightly different amounts through the Radio Frequency (R/F) section of the receiver. If these R/F sections were identical in each receiver, this error source would cancel, but this has not been found to be the case with the receivers used in this research. Interestingly, no such biases have found to be present in the GLONASS carrier phase observations. Various tests have been performed and the data processed through both IESSG and commercially available software. These have highlighted that there are undoubted potential benefits of using combined GPS/GLONASS receivers in environments where visibility is restricted. Under ideal conditions however, the effect of any benefit is reduced, and indeed the biases present in the GLONASS pseudoranges may slightly degrade the accuracy of differential positioning. The software developed has already been used in other research projects within the IESSG. Although the future of the GLONASS system is somewhat uncertain, any future changes to it should be easily accounted for within the code. There is however a real need to further develop and incorporate cycle slip detection software, especially for GLONASS observations, and to investigate the possibility of solving for the biases in the GLONASS pseudoranges.

In recent years, the market served by satellite positioning systems has expanded exponentially. It is stimulated by the needs of an ever increasing number and variety of scientific, business and leisure applications. The dominant system is the USA's GPS, or Global Positioning System. However, GPS is not a panacea for all positioning tasks, in any environmental situation. For example, two of the fastest growing applications, vehicle tracking and personal location, operate in an often harsh signal reception environment. This can be so severe that even with the current 29 working satellites, GPS may struggle to perform. In exceptional circumstances it can fail to provide a positioning service at all. The simplest way to improve the situation when signal reception is poor, is to add similar signals from alternative satellite systems. This has already been achieved by combining GPS with the Russian satellite positioning system, Global'naya Navigatsionnaya Sputnikova Sistema, abbreviated to GLONASS. The combination of GPS with GLONASS is referred to here as Hybrid. But how good is Hybrid relative to GPS, and how can performance be evaluated objectively? The research project presented here set out to answer this question, and to understand the situations in which Hybrid failed, and ask what solutions were then available to fulfil a positioning task. The problems associated with integrating one satellite positioning system with another, their potential inconsistencies and their impact on positioning errors were also examined. This field of research is relevant to Hybrid as defined here, and also to other mixed systems, for example GPS with EGNOS, a European geostationary satellite system, and GPS with Galileo, a proposed global system controlled by the Europeans. The issues were addressed from the viewpoint of practical usage of the positioning systems. Hence the many and varied experiments to quantify positioning performance using both static receivers, and a variety of platforms with wide ranging levels of vehicle dynamics. The capability of satellite positioning systems to work in the harshest environments, was tested in the proposed Olympic sport of bob skeleton. This involved the development of the acquisition system, and a number of programs. The latter were equally applicable to the ensuing work with road vehicles, and the quantitative assessment of positioning performance relative to a truth. The processes established to manipulate, import, and merge satellite based vehicle tracking data with Ordnance Survey digital mapping products, have already been used in four other projects within the School of Civil Engineering. The software to regularise positioning interval, smoothing processes, and to compare tracking data with a truth, have been similarly provided. Without major funding the outlook for GLONASS and hence Hybrid looks bleak, and it is predicted that without replenishment the constellation may fall to six satellites by the end of 2001. However as mentioned above, the issues identified, and ideas and software developed in this research, will be directly applicable to any future hybridisation of GPS with Galileo.

Environmental pressures are driving automotive manufacturers towards light weight cost efficient structures. Composite materials have been shown to display high specific energy absorption levels thus offering opportunities for mass reduction over conventional steel structures. Whilst composites display these specific advantages, the mechanisms by which energy is absorbed are more complex and are preventing widespread acceptance of composite structures. This work aims to further scientific understanding of the crushing process and provide realistic data for a wide range of processing conditions and commonly used materials. The main objectives of this study were to quantify the effect of industrial manufacturing conditions on the crush performance of composite structures, and to correlate the performance to a number of in-plane laminate properties. The manufacturing parameters considered are constituent material related (mould temperature, post-cure time and resin composition), interlaminar toughness related and process related (amount of binder and voidage). The work presented in the thesis reports the results of axial crushing experiments, in-plane and inter-laminar testing performed on composite parts made from glass reinforced polyester and vinylester resins. The preforms were made from 2 fabrics; a continuous filament random mat and a 0/90° non crimp fabric. All parts were produced by resin transfer moulding (RTM) under conditions which were representative of medium volume industrial processing. Constituent material results demonstrate clear advantages associated with the use of vinylester resin and that while relationships between all in-plane properties and the crush performance can be observed, the ultimate compressive stress is the most reliable indicator of this performance. Interlaminar toughness enhancement shows great promise for tailoring of the crush curve and increase in energy absorption of non-crimp fabrics. Results for the processing work are directly applicable to existing manufacturing and demonstrate the potential for real reductions in cycle time and increase in properties.

GPS and Inertial Navigation Systems (INS) are increasingly used for positioning and attitude determination in a wide range of applications. Until recently, the very high cost of the INS components limited their use to high accuracy navigation and geo-referencing applications. Over the last few years, a number of low cost inertial sensors have come on the market. Although they exhibit large errors, GPS measurements can be used to correct the INS and sensor errors to provide high accuracy real-time navigation. The integration of GPS and INS is usually achieved using a Kalman filter which is a sophisticated mathematical algorithm used to optimise the balance between the measurements from each sensor. The measurement and process noise matrices used in the Kalman filter represent the stochastic properties of each system. Traditionally they are defined a priori and remain constant throughout a processing run. In reality, they depend on factors such as vehicle dynamics and environmental conditions. In this research, three different algorithms are investigated which are able to adapt the stochastic information on-line. These are termed adaptive Kalman filtering algorithms due to their ability to automatically adapt the filter in real time to correspond to the temporal variation of the errors involved. The algorithms used in this research have been tested with the IESSG's GPS and inertial data simulation software. Field trials using a Crossbow AHRS-DMU-HDX sensor have also been completed in a marine environment and in land based vehicle trials. The use of adaptive Kalman filtering shows a clear improvement in the on-line estimation of the stochastic properties of the inertial system. It significantly enhances the speed of the dynamic alignment and offers an improvement in navigation accuracy. The use of the low cost IMU in a marine environment demonstrates that a low cost sensor can potentially meet the requirements of navigation and multi-beam sonar geo-referencing applications.

A surface shedding discrete vortex method has been developed for stimulating incompressible flows around pitching aerofoils. The method is able to predict both attached and separated flows, the latter typified by the formation and transport of large vortices. The structures of dynamic stall flow are well captured without the need for other means to predetermine the separation points. In contrast to most other vortex methods, the method presented herein can perform quantitative analysis. Throughout a wide range of incidence, the pressure distributions are smooth and the normal force and pitching moment are in good agreement with experimental data. The method is also able to predict the flow with external constraints for simulating the effects of wind tunnel blockage. In this regard quantitative results and flow structures have been obtained which are consistent with those expected. Following the review of previous work presented in the introduction, the mathematical formulation of the method is expounded. A velocity expression is theoretically derived for flows with both a moving inner boundary (aerofoil) and fixed external constraints (wind tunnel walls). To maintain both no penetration and no slip conditions, it is concluded that an external constraint parallel to the free stream can be modelled by placement of a constant vortex sheet along the boundary, and the introduction of distributed vortices next to the constraint to represent the boundary layer. The vortex sheet strength is equivalent to the free stream velocity while the strength of the vortices can be calculated in the same manner as for the internal boundary. This conclusion avoids the necessity of employing mirror vortices and iteration techniques in traditional models. The aerodynamic loads are computed from the pressure distribution. For the computation of surface pressures, the relationship between the pressure gradient and the rate of vorticity creation on the surface has been developed for a moving boundary.

Open cavity flow is that of most interest to researchers. The flow is typical to that found to exist in the bomb bay of the F-111 and is characterised by intense acoustic levels. A review of the work of previous experimental researchers is included for comparison with the findings of the present thesis. The flow physics indicate that a series of vortices travel downstream in the cavity and are driven by vorticity generated at the upstream lip of the cavity. When strengthened the downstream moving vortex influences the mass addition and expulsion at the trailing edge initiating a pressure wave which propagates upstream and sustains the process of completing the feedback lopp. These features are elucidated upon in the present thesis. The flow at Mach 0.85 and Mach 1.19 is analysed with only differences in the external stream being apparent for the higher Mach number case. The suppression of the acoustic environment is investigated by sloping the aft wall of the cavity. The results of the CFD study are used to examine why sloping of the aft cavity wall is successful. It is shown that the flow tends towards a steady state and the results are compared to the hypothesis of Heller and Bliss. This hypothesis is substantiated by the present simulations and in doing so the work demonstrates the ability of CFD to be used as a tool in conjunction with experimental methods to enhance the understanding of cavity flows. An area of cavity flows for which information is sparse is for the transitional cavity flows. A review of the literature shows that the 4 types of cavity flow exist at supersonic speeds and these are identified by the CFD. The results of the computational study are used to examine when the impingement and exit shocks, characteristic of closed cavity flow, collapse to form a single shock wave. This point is defined as L/Dcrit and occurs when the vertices of the separation and recompression wakes merge. It represents the boundary between transitional-closed flow and closed flow and the CFD predictions are compared to Prandtl-Meyer theory when investigating the position of L/Dcrit.

This research project is about product development strategy and practice in the automobile industry. Specifically, it concerns the transformation of Rover Group body and tool development capability over four years from 1993 to 1997. A single Rover Body and Pressings organisation was created in 1991. It encompassed the functions of Body Engineering, Press Tool Engineering, and Press Tool Manufacturing. As Engineering Director the Author had the opportunity to directly influence a significant portion of the body product creation process. At the start of the research period the product development performance of Rover Body and Pressings was weak. Major investments in new press equipment could not depend on in-house die technology. Quality and cost delivery incurred customer dissatisfaction. Resulting from the research are three innovations: The Engineering Quality Assurance Procedure was implemented as a disciplined stage/gate quality management system. A focused manufacturing strategy was implemented for die manufacturing based on die size. A new engineering design methodology was established utilising the scientific principles of metal forming technology as an integrated element in the design process. These innovations were applied within the strategic framework of a new model describing a system view of the product creation process for body, at enterprise level. The new product development process strategy was partially applied to two new vehicle programmes. One vehicle has since been initiated and delivered from within the new framework. Strategic targets were defined for product development at Rover Body and Pressings covering product quality, development lead time, press tool cost and programme financial budget. The targets for quality and lead time were met during the research period. Although substantial progress is evident in physical performance the targets for press tool cost and programme budget were not met. The major elements of the product development strategy applied in this research remain in place. The transfer of the strategic model of concurrent engineering to a wider context was demonstrated by applying it as part of the Rover Group product development reengineering project.

In this thesis the author presents two areas of work; exploring the integration of Computational Fluid Dynamics (CFD) into engine design for Jaguar Cars Ltd and developing a novel 'mesh construction' method for making mesh generation both easy and fast. It is concluded that Jaguar can use CFD in the evaluation stage of the engine design process, although not in the concept stage of design. The CFD predictions are shown to be useful for detecting flow related faults and determining the general flow trends, but they should not be used as an absolute measure of the flow variables. The author has determined an efficient method for obtaining good quality meshes using commercial modelling and mesh generation software which requires a skilled CFD analyst. Steady flow analysis of an engine port and cylinder design could currently be completed in about six weeks using a high-powered workstation. The author recommends dedicated workstations for CFD analysis and training Jaguar's draughtsmen to create CAD models with computer analysis requirements in mind. The author's mesh construction program automatically joins two overlapping meshes or cuts one mesh from another. Whilst the program works well on the test cases considered, it is not at a stage for commercial exploitation. Further development is therefore recommended.