Rover Group had began to address product quality in the 1980's, by collaborating with the Honda Motor Company, and commencing a "Total Quality Improvement - TQI" initiative. Whilst delivering initial improvement, it was not considered to be sufficient to sustain an organisational culture of ongoing improvement activity within the business. A five year quality strategy was created, which identified improvement milestones for each of the key business processes that drive Rover Group. A significant deployment of the quality strategy is represented by Rover's new product introduction process, which led to the creation of Project Management Policy (PMP), and a series of processes constructed as a framework known as Common Business Environment (CBE). Implementation of PMP is achieved by the mandatory requirement for new product teams to conform to the "six quality and reliability prescriptives", which are measured by adoption of a team-based self assessment process and senior management review. The Rover Group Quality Strategy demonstrates innovation in the conceptual model designed for its initial creation, and the deployment process by application of Group Judgement Theory, and the Japanese technique of "Hoshin Kanri" policy deployment. This represents a significant contribution towards the achievement of improved business results by Rover Group in aspects of product development lead time and quality.

Minimisation of the mass of aerospace structures has been investigated by researchers and designers for many years. It is an efficient means to reduce the manufacturing costs, fuel consumption and environmental impact. To achieve this objective, high performance composite materials and optimised configurations are utilised in modern aircraft design. Additionally, use of the postbuckling reserve of strength has been considered during the preliminary design stage to obtain more efficient structures. The exact strip analysis and optimum design software VICONOPT has been developed and used in postbuckling analysis. VICONOPT is able to give a good initial evaluation of load versus end shortening when compared with experimental and finite element results. However it provides poor predictions of the stress and strain distributions in the postbuckling range. This is due to its assumptions concerning the longitudinal invariance of stress and the sinusoidal variation of buckling modes in the longitudinal direction. These assumptions are appropriate for initial buckling analysis but they limit the accuracy of subsequent postbuckling analysis. This thesis outlines some developments which improve the existing exact strip postbuckling analysis by improving the accuracy of mode shape prediction and stress and strain distributions. Based on previous research by Von Karman, improved governing equations are derived and solved for general anisotropic plates with different in- plane edge conditions. Implementation of the improved analysis in VICONOPT enhances the accuracy of mode shapes and stress and strain distributions in the postbuckling analysis.

The exploitation of computational fluid dynamics for non linear aeroelastic simulations is mainly based on time domain simulations of the Euler and Navier-Stokes equations coupled with structural models. Current industrial practice relies heavily on linear methods which can lead to conservative design and flight envelope restrictions. The significant aeroelastic effects caused by nonlinear aerodynamics include the transonic flutter dip and limit cycle oscillations. An intensive research effort is underway to account for aerodynamic nonlinearity at a practical computational cost.To achieve this a large reduction in the numbers of degrees of freedoms is required and leads to the construction of reduced order models which provide compared with CFD simulations an accurate description of the dynamical system at much lower cost. In this thesis we consider limit cycle oscillations as local bifurcations of equilibria which are associated with degenerate behaviour of a system of linearised aeroelastic equations. This extra information can be used to formulate a method for the augmented solve of the onset point of instability - the flutter point. This method contains all the fidelity of the original aeroelastic equations at much lower cost as the stability calculation has been reduced from multiple unsteady computations to a single steady state one. Once the flutter point has been found, the centre manifold theory is used to reduce the full order system to two degrees of freedom. The thesis describes three methods for finding stability boundaries, the calculation of a reduced order models for damping and for limit cycle oscillations predictions. Results are shown for aerofoils, and the AGARD, Goland, and a supercritical transport wing. It is shown that the methods presented allow results comparable to the full order system predictions to be obtained with CPU time reductions of between one and three orders of magnitude.

published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

The chemical and physical limits of cycle-to-cycle combustion variability and engine out emissions of a gasoline port fuelled spark ignition engine have been investigated. The experimental investigations were carried out on a V8 engine with port fuel injection and variable intake valve timing. The chemical limits of stable combustion have been shown to be a function of burned gas, fuel and air mixture. The widest limit, gas fuel ratio of <24, burned gas fraction <0.27 and AFR >9 was found at maximum brake torque spark timing. Retarding the spark timing by 10oCA caused a small reduction in the stable area, 20oCA retard reduced the stable combustion area significantly, whereby stable combustion occurred within an area of gas fuel ratio of <19, burned gas fraction <0.2 and AFR >10. Burn rate analysis indicated increased variability in both the flame development and rapid burn period. The increase in variability in the rapid burn period is greater than that associated with the flame development. The variability is magnified from flame development through the rapid burn phase. This finding was consistent for unstable combustion caused by exceeding chemical and physical limits. Engine out emissions were investigated and characterised using engine global state parameters, for example AFR, burned gas fraction, for both stable and unstable combustion conditions. Carbon monoxide and oxides of nitrogen emissions correlations were unaffected by the presence of unstable combustion events whereas hydrocarbon emissions showed a significant increase. The incorporation of these findings were implemented into an engine simulation (Nu-SIM V8) investigating the impact for the New European Drive Cycle condition.

This PhD investigates driver behavioural adaptation to in-vehicle navigation systems (IVNS). Behavioural adaptation is receiving an increasing amount of research attention in traffic psychology, but few studies have directly considered the concept in relation to IVNS. The thesis aims were addressed using a range of quantitative and qualitative methodologies. Using two online surveys, over 1300 drivers (including over 1000 IVNS users) were sampled, to identify a range of positive, neutral and negative aspects of end-user behavioural adaptation to IVNS in terms of both safety and navigational efficiency. The first survey (N=450) aimed at drivers in general, showed that IVNS users believe they commit some common driving errors (e.g. misreading signs when leaving a roundabout) significantly less frequently than ordinary drivers who do not use these systems, but that they also feel they drive without fully attending to the road ahead significantly more frequently. The second survey (N=872) was aimed at IVNS users only, and further explored distracted driving. This survey found that the majority of IVNS users have interacted with their system while driving (e.g. to enter a destination), and that some do so frequently. It also showed that system reliability is a key issue affecting most current IVNS users, revealing that some drivers have followed inaccurate as well as illegal and potentially dangerous, system-generated route guidance information in a range of different contexts. A longitudinal diary study (N=20) then collected rich qualitative data from a sample of worker drivers who regularly used their IVNS in unfamiliar areas. The data collected illustrated the diverse contexts in which drivers experience aspects of behavioural adaptation to IVNS identified in the surveys. Both the IVNS user-survey and diary study also identified key demographic individual difference variables (most notably age and computing skill) that were associated with the extent to which driver’s experienced different manifestations of behavioural adaptation to IVNS. Moreover, other individual difference variables (e.g. complacency potential, system-trust, confidence) were found to be associated with more specific behavioural adaptations. Two simulator studies investigated system interaction while driving. The first (N=24) demonstrated the poor degree of correspondence between drivers’ perceptions of driving performance when entering destinations while driving (relative to normal driving) and objective performance differences between these conditions. The second simulator study (N=24) showed that safety and training based interventions designed to reduce the extent to which drivers use IVNS while driving or to improve their performance if they do had only a modest effect on dependent measures. This thesis represents the first attempt in the literature to bring together research from diverse areas of human factors and traffic psychology to consider behavioural adaptation to in-vehicle navigation systems. By associating a range of these issues with behavioural adaptation to IVNS, it has indirectly increased the scope of several salient, previous research findings. Moreover, by investigating many of these issues in depth, using both quantitative and qualitative methodological approaches, it has set the foundation for future work. Such work should aim to explore many of the issues raised, and develop effective remediating or mitigating intervention strategies for negative behavioural adaptations that could adversely affect driving safety, as well as to encourage and support those which may be considered more positive.

When helicopters operate close to the ground in desert conditions, the rotor wake can entrain large amounts of dust into the flow field surrounding the aircraft. This entrainment of dust can result in the potentially dangerous condition known as brownout where the pilot loses situational awareness. Understanding the physics that governs the entrainment of dust from the ground may eventually allow the condition of brownout to be avoided completely. To enable the formation of dust clouds around helicopters to be investigated, Brown's Vorticity Transport Model~(VTM) has been enhanced to include the ability to model the entrainment of dust from the ground and the transport of this dust once in the flow field. Comparison of the predictions of the VTM with experimental results has shown the VTM to be capable of capturing the general characteristics of the dust clouds. Close examination of the formation of the dust clouds revealed that the general physics that governs the entrainment process is the same for different rotors and a universal model of this process is described. Differences in the size and density of the dust clouds that form around different rotors result from differences in the overall behaviour of the wakes that are generated. The design of a rotor can have a significant effect on the size and density of the dust cloud that is produced. The tip vortices have been identified as the main cause of the changes to the dust cloud. However, the behaviour of these tip vortices, when the rotor is operating in ground effect, is dependent on the rotor design and also on the advance ratio of the rotor. Thus, to determine the size and density of the dust cloud that would form around any particular rotor, the behaviour of the wake of that rotor must first be known.

This purpose of this dissertation is to ascertain whether solar sublimation is a viable method for the deflection of a Near Earth Asteroid. From a research view point, the methods and analysis are applicable to proximal motion around a celestial body, in particular one with a non-Keplerian or irregular orbit as in the case here with the orbit being constantly altered by the deflection action and subject to perturbations, such as solar radiation pressure. Two concepts, and the corresponding dynamics and control, are presented based on previous trade-off and optimisation studies. The first uses a paraboloidic reflector to concentrate the solar radiation onto a solar-pumped laser, which is then directed onto a specific spot on the NEO by a small directional mirror. The spacecraft orbits are designed to fly in formation with the asteroid around the Sun, and are based on the orbital element differences. The formation orbits were optimised based on a number of single and multiple objective functions. A feedback control law is presented for the orbital maintenance required to counteract the solar radiation pressure (due primarily to the large surface area of the primary reflector), and the third-body effects due to the gravitational field of the asteroid. The second option takes advantage of the balance between the gravity attraction of the NEO and solar pressure acting on the collector. The mirror focuses the light directly onto the asteroid surface, controlling the beam by adjusting the focal point of the primary reflector. By altering the shape of the mirror surface, both the focal point and the vector of the solar radiation pressure can be manipulated. An interesting navigation strategy is proposed based on the attitude measurements, the inertial position of each spacecraft, the intersatellite position and velocity measurements, and a 2D image from a rotating onboard camera. The navigational data is used for both the orbital control of the spacecraft and for the beam pointing. The results of simulations of a hypothetical deflection mission of the asteroid Apophis are presented for the dynamics, control, attitude and navigation, accounting for solar radiation pressure, the gravity field of the asteroid, and the deviation of the NEO orbit. The results show that both concepts provide the required deflection with a feasible mass at launch, solving most of the issues related to the solar sublimation method. One of the critical aspects of this deflection concept is properly placing the concentrators in the proximity of the asteroid in order to avoid the plume impingement and the occultation from the asteroid itself. Issues regarding the contamination of the mirrors are addressed and compared with the simulated deflections predicted considering no contamination. Lastly, initial system mass budgets are presented.

Multiple gravity assist (MGA) trajectories represent a particular class of space trajectories in which a spacecraft exploits the encounter with one or more celestial bodies to change its velocity vector; they have been essential to reach high Delta-v targets with low propellant consumption. The search for optimal transfer trajectories can be formulated as a mixed combinatorial-continuous global optimisation problem; however, it is known that the problem is difficult to solve, especially if deep space manoeuvres (DSM) are considered. This thesis addresses the automatic design of MGA trajectories through global search techniques, in answer to the requirements of having a large number of mission options in a short time, during the preliminary design phase. Two different approaches are presented. The first is a two-level approach: a number of feasible planetary sequences are initially generated; then, for each one, families of the MGA trajectories are built incrementally. The whole transfer is decomposed into sub-problems of smaller dimension and complexity, and the trajectory is progressively composed by solving one problem after the other. At each incremental step, a stochastic search identifies sets of feasible solutions: this region is preserved, while the rest of the search space is pruned out. The process iterates by adding one planet-to-planet leg at a time and pruning the unfeasible portion of the solution space. Therefore, when another leg is added to the trajectory, only the feasible set for the previous leg is considered and the search space is reduced. It is shown, through comparative tests, how the proposed incremental search performs an effective pruning of the search space, providing families of optimal solutions with a lower computational cost than a non-incremental approach. Known deterministic and stochastic methods are used for the comparison. The algorithm is applied to real MGA case studies, including the ESA missions BepiColombo and Laplace. The second approach performs an integrated search for the planetary sequence and the associated trajectories. The complete design of an MGA trajectory is formulated as an autonomous planning and scheduling problem. The resulting scheduled plan provides the planetary sequence for a MGA trajectory and a good estimation of the optimality of the associated trajectories. For each departure date, a full tree of possible transfers from departure to destination is generated. An algorithm inspired by Ant Colony Optimization (ACO) is devised to explore the space of possible plans. The ants explore the tree from departure to destination, adding one node at a time, using a probability function to select one of the feasible directions. Unlike standard ACO, a taboo-based heuristics prevents ants from re-exploring the same solutions. This approach is applied to the design of optimal transfers to Saturn (inspired by Cassini) and to Mercury, and it demonstrated to be very competitive against known traditional stochastic population-based techniques.

Despite the amount of research into the cavity flow problem the prediction of the flow patterns, associated forces and acoustic phenomena remains an unsolved problem. The coupling of the shear layer dynamics, the internal vortical structures and the acoustics of the cavity make it a very complex flow despite the simple geometry. Once doors, stores and release mechanism are added the problem is compounded, thus accurate prediction methods are a necessity. The cavity has been shown to oscillate in different modes depending on the flow conditions and the geometry of the cavity. Two modes of oscillation were examined in detail, these being the wake and shear layer mode, using computational fluid dynamics and experimental data where available. The flow code used is the in-house CFD solver PMB and the experimental data has been provided by DERA. The cavity geometry was for a 1VD=5 cavity with a W/D ratio of 1 for the 3D investigation. For the wake mode the Reynolds number has been varied from 5,000 to 100,000 and the Mach number has been varied from 0.3 to 1.0 in order to examine the effect of changing conditions on this mode of oscillation. The characteristics of this mode of oscillation have been identified and a stable region within the varying Mach and Reynolds numbers has been shown. Outside of this stable region a blended flow has been identified. For the shear layer mode of oscillation the open cavity environment has been examined. This cavity is of great interest as examples of it can be found in current airframes, the H- 111 for example. This flow type is characterised by intense acoustic noise at distinct frequencies which could cause structural fatigue and damage sensitive electronics. However, this cavity type also has a relatively benign pressure distribution along the length of the cavity making it ideal for store separation. The flow cycle predicted shows that the separated shear layer impact on the rear wall generates strong acoustic waves. These waves are further enhanced by the interaction of the wave with the vortices and upstream wall of the cavity. The flow conditions of interest for this case are M=0.85 and Re=6.783 million. A study of the effect of time step, grid refinement and turbulence model has been performed. It has been seen that the density of the grid and the turbulence model chosen must be considered as a pair; if the grid is too fine it may resolve scales being modelled by the turbulence model and result in a double counting of energy resulting in spurious results. One area of cavity studies that has received only sparse investigation is the effect of 3-Dimensionality on the flow. One objective of this work was to try and rectify this. However, it was found that the choice of solver could play a significant role in the accurate prediction of the 3D cavity flow. For cases where the acoustic spectrum is broad, typical URANS codes may have difficulty in predicting these flows. Under such conditions DES or LES would be more appropriate choices. However, when the frequency spectrum is not as spread out URANS can provide good results. This can be seen in the 3D cavity case where doors are present and aligned vertically. The wake mode, while identified in 2D. has received little attention in 3D. It is generally thought that the effect of the third dimension would be to trip the wake mode to shift to another mode of oscillation. This study has shown that this is indeed the case. The flow cycle shown is more reminiscent of the blended flows shown in some 2D cases.