This thesis presents a new finite element analysis (FEA) method for calculating the critical stress in an aircraft wheel’s lock-ring. The lock-ring is used on many modern designs in place of the bolts that join the two main sections of the wheel. The lock-ring is a safety critical component of the wheel as a failure could lead to an explosive release of tyre pressure. The stress field in this wheel forms a fatigue cycle as the wheel rotates when the aircraft manoeuvres on the ground. The stress field at the critical location on the lock-ring is strongly dependent on the contacting surfaces of three structural components of the wheel: the main hub, the lock-ring and the freeflange. Until completion of this work no method existed to calculate the fatigue stress cycle at this design critical location. Modern wheel designs, to minimise aircraft weight and therefore fuel use, are of minimum weight designs. This means that the aluminium material in the latest wheel designs is subjected to greater stress than in previous designs, therefore the ‘margin of safety’ for the wheels is reduced. It is important that methods are developed to calculate the stress in all regions of the wheel, including the lock-ring. Lock-ring wheel designs were originally used on military aircraft and more recently they have become common on business jet aircraft. Very recently the feasibility of their use on large commercial aircraft that carry upwards of 100 passengers is being considered. The operating environment on large commercial aircraft is very harsh for wheels and the methodology developed in this work is required to correctly assess the use of these wheels in this harsh and safety critical environment. The calculation method is compared against physical test data measured on two wheels using strain gauges. The wheels, with tyres installed, were loaded and rolled on a road wheel dynamometer to simulate aircraft ground manoeuvres. Measuring the critical location is difficult as access to it is limited; it had not been measured before. The measured data are used to verify the new FEA method. The new FEA method was developed with the potential for use by both a nonspecialist engineer and use in a modern Concurrent Engineering environment as requirements. The FEA is linked directly to the CATIA 3D computer aided design (CAD) model, using CADNexus software. This link is made in such a way that a modification to the design, once included in the CAD model, can be easily and automatically followed by an update to the FEA. The FEA requires solution of a non-linear model because contact between three structural components is critical and therefore must be modelled in detail. The general perception in industry is that non-linear FEA is a complex subject and must be undertaken by an experienced FEA specialist – this work provides strong supportive evidence to contradict this general perception. The FEA itself is implemented using ANSYS® Workbench software. The new analysis method, including the model set-up parameters is stored in an analysis template. This analysis template effectively captures the knowledge of a specialist FEA engineer so that it can be used, for design purposes, by a non-special engineer. The final FEA method is useful not only to non-specialist engineers but also, because the specialist knowledge is contained within the ANSYS® Workbench template, for outsourcing this structural analysis work to lower cost economies. The works creates a new FEA method of specific use to manufactures and designers of weight optimised aerospace wheels. Furthermore, in a more general context, it demonstrates that even complex non-linear FEA can be defined within knowledge capturing templates. This makes it accessible to engineers without specialist expertise with FEA. Empowering the design engineer to structurally optimise their own designs will lead to leaner design teams, which will consequently reduce development costs. The new method can be competed as part of a Concurrent Engineering process. This is advantageous as it can expedite the design process, therefore allowing FEA results to be available early enough in the programme to be made use of.

This thesis reports the analysis and design of a hovering rotor equipped with both slotted and blended trailing-edge flaps. This was accomplished by combining a simple blade element method with 3D inviscid and RANS CFD that allowed for a robust sequence of design specification, analysis, and verification. Most modern helicopters have high levels of blade twist and various tip shape designs to help improve hover performance. However, such blade designs face problems due to compressibility effects on the advancing blade in forward flight. The twisted blade gives rise to negative incidence at the blade tip, which accelerates shock formation on the lower surface. The current work looks to evaluate the implementation of a low twist rotor for improved forward flight performance and recovering any potential losses in hover performance by deflecting fixed, trailing-edge flaps.

This thesis investigated the management of electric vehicle battery charging in distribution networks. Different electric vehicle fleet sizes and network locations were considered. The energy storage capacity and backup generator’s energy requirements were calculated to achieve daily energy balance in a low voltage distribution network with micro-generation. The effect of the electric vehicle battery demand as controllable loads on the backup generator energy requirements was assessed. It was found that the use of electric vehicles as controllable loads reduced the energy requirements from the backup generator or made it unnecessary to achieve energy balance. Two control algorithms for the battery charging management of electric vehicles clustered in battery charging facilities were designed and developed. One algorithm calculates electric vehicle battery charging profiles for vehicles located in a parking space. Different charging policies were investigated, showing the ability of the control algorithm to define the electricity profile of the parking space according to network constraints and the policies’ objectives. The second algorithm calculates the number of batteries and chargers that are required to satisfy the battery demand of electric vehicle battery swapping stations. The impact of the number of chargers and batteries on the swapping station’s electricity load profile were evaluated. An agent-based control system was designed and developed for the battery charging management of electric vehicles dispersed in distribution networks. The electric vehicle battery charging schedules are calculated according to electricity prices and distribution network technical constraints. The real-time operation of the agent-based control system was demonstrated in the laboratory of TECNALIA’s research centre in Bilbao, Spain. A series of experiments showed the ability of the control system to operate and manage the electric vehicle battery charging when the distribution network is operated within its loading capacity and when the network technical limits are violated.

In the early phase of the design of a space mission it is generally desirable to investigate as many feasible alternative solutions as possible. Traditionally a system margin approach is used in order to estimate the correct value of subsystem budgets. While this is a consolidated and robust approach, it does not give a measure of the reliability of any of the investigated solutions. In addition the mass budget is typically overdimensioned, where a more accurate design could lead to improvements in payload mass. This study will address two principal issues typically associated with the design of a space mission: (i) the effective and efficient generation of preliminary solutions by properly treating their inherent multi-disciplinary elements and (ii) the minimisation of the impact of uncertainties on the overall design, which in turn will lead to an increase in the reliability of the produced results. The representation and treatment of the uncertainties are key aspects of reliable design. An insufficient consideration of uncertainty or an unadapted mathematical representation leads to misunderstanding of the real issues of a design, to delay in the future development of the project or even potentially to its failure. The most common way to deal with uncertainty is the probabilistic approach. However, this theory is not suitable to represent epistemic uncertainties, arising from lack of knowledge. Alternative theories have been recently developed, amongst which we find Evidence Theory which is implemented in this work. Developed by Shafer from Dempster's original work, it is regarded by many as a suitable paradigm to accurately represent uncertainties. Evidence Theory is presented and discussed from an engineering point of view and special attention given to the implementation of this approach. Once mathematically represented, the uncertainties can be taken into account in the design optimisation problem. However, the computational complexity of Evidence Theory can be overwhelming and therefore more efficient ways to solve the reliable design problem are required. Existing methods are considered and improvements developed by the author, to increase the efficiency of the algorithm by making the most of the available data, are proposed and tested. Additionally, a new sample-based approximation technique to tackle large scale problems, is introduced in this thesis. Assuming that the uncertainties are modelled by means of intervals, the cluster approximation method, and especially implemented as a Binary Space Partition, appears to be very well-suited to the task. The performance of the various considered methods to solve the reliable design optimisation problem in the frame of Evidence Theory is tested and analysed. The dependency on the problem characteristics, such as dimensionality, complexity, or multitude of local solutions are carefully scrutinised. The conclusions of these tests enables the author to propose guidelines on how to tackle the problem depending on its specificity. Finally, two examples of preliminary space mission design are used to illustrate how the proposed methodology can be applied. Using realistic and current mission designs, the results show the benefits that could be achieved during the preliminary analyses and feasibility studies of space exploration.

This document is the executive summary of the author's Engineering Doctorate portfolio. It is entitled "Key Challenges in the Development of Automotive Software-based Electronic Control Systems", and presents the main results from two distinct but interrelated projects, each of which addresses a different challenge. It begins with an introduction to automotive software-based electronic control systems, and emphasises the problems associated with the use of software. The first project was concerned with using software in a safety-related control system, and addressed the issue of how to demonstrate that it was sufficiently safe, i.e. that there was sufficient confidence that the software would behave as expected, even under fault conditions. The second project was concerned with the investigation and introduction of a new simulation technology for developing electronic control systems. It sought to address the challenge presented by the need to develop ever more complex systems, whilst at the same time reducing dependence on prototype testing, and reducing the time available for development. The projects ran concurrently throughout, and both were perfonned within the ElectricallElectronic Engineering department at Jaguar Cars, who are responsible for the development of all the control systems within Jaguar's products. This summary concludes with a section which hypothesises on the future direction for automotive software-based electronic control system technology, against a context of the business environment in which the industry operates.

Signals broadcast by the Global Navigation Satellite Systems (GNSS) enable global, autonomous, geo-spatial positioning exploited in the areas such as geodesy, surveying, transportation and agriculture. The propagation of these signals is affected as they propagate through the Earth's upper atmosphere, the ionosphere, due to the ionic and electronic structure of the ionosphere. The ionosphere, a highly dynamic and spatially and temporally variable medium, can be the largest error source in Global Navigation Satellite System (Klobuchar 1991) in the absence of the Selective Availability. Propagation effects due to the ionosphere lead to errors in the range measurements, impact on receiver signal tracking performance and influence the GNSS positioning solution. The range error can vary from 1 to 100m depending on time of day, season, receiver location, conditions of the earth's magnetic field and solar activity (Hofmann-Wellenhof et al. 2001). This thesis focuses on modelling, monitoring and mitigating the ionospheric effects in GNSS within the scope of GNSS modernization, which introduces new signals, satellites and constellations. The ionosphere and its effects on GNSS signals, impact of the ionospheric effects at the receiver end, predicted error bounds of these effects under different solar, geomagnetic and ionospheric conditions, how these effects can be modelled and monitored with current and new (possible with GNSS modernization) correction approaches, degradation in the GNSS positioning solution and mitigation techniques to counter such degradation are investigated in this thesis. Field recorded and simulated data are considered for studying the refractive and diffractive effects of the ionosphere on GNSS signals, signal tracking performance and position solution. Data from mid-to-high latitudes is investigated for the refractive effects, which are due to dispersive nature of the ionosphere. With the use of multi-frequency, multi-constellation receivers, modelling of the refractive effects is discussed through elimination and estimation of these effects on the basis of dual and triple frequency approaches, concentrating on the benefit of the new GNSS signals. Data from the low latitudes is considered for studying the diffractive effects of the ionosphere, scintillation in particular, in GNSS positioning, and possible mitigation techniques to counter them. Scintillation can have a considerable impact on the performance of GNSS positioning by, for instance, increasing the probability of losing phase lock with a signal and reducing the accuracy of pseudoranges and phase measurements. In this sense, the impact of scintillation on signal tracking performance and position solution is discussed, where a novel approach is proposed for assessing the variance of the signal tracking error during scintillation. The proposed approach also contributes to the work related with scintillation mitigation, as discussed in this thesis. The timeliness of this PhD due to the recent and increasingly active period of the next Solar Cycle (predicted to reach a peak around 2013) and to the ongoing GNSS modernization give this research an opportunity to enhance the ionospheric knowledge, expertise and data archive at NGI, which is rewarding not only for this PhD but also for future research in this area.

The automotive industry is becoming more global and cosmopolitan, while the markets are becoming fragmented and differentiated because of the sophistication of the customer. This requires the automotive manufacturers to have a product well suited to these factors more quickly and cheaply, which necessitates the accurate definition of the product. Two European automotive manufacturers NPI processes were studied and this showed that poor performance in the product definition phase was deemed to be a major reason for sub-optimal performance in both companies, even though the approaches were very different. It was therefore decided to develop and apply tools to assist in the development of petrol engines to overcome these deficiencies. When these shortcomings are considered in the context of petrol engine development it can be seen through examination of the literature and industry that: • There is no method for the translation of the values of the company or product into tangible engineering terms and in the context of this project, with focus on vehicle and engine performance. This can result in the poor positioning of a vehicle in the market due to inappropriate characteristics • Having defined the required vehicle performance, it is not possible to demonstrate the feel of the vehicle until the hardware is physically available. This means that often there is a long lead-time between the setting of a target and the concept ratification through driving the new vehicle. This often results in a point of no (or very costly) return very early during the programme. • Fuel economy is becoming an increasingly significant issue with the introduction of fiscal penalties for poor fuel consumption vehicles. There are currently no processes available for the calculation of steady state or drive cycle fuel economy which allow for the accurate modelling to include combustion, pumping and friction losses, and the control of the engine with the engine management system To overcome these limitations three main groups of innovative tools/techniques have been developed and applied on new engine and vehicle programmes. • Marque engineering: a proposal to translate the brand objectives into engineering terms has been developed to a level where the engine torque output can be linked to the product position • Engine and vehicle performance simulation: a vehicle has been built to demonstrate how a new vehicle/engine will feel to drive by controlling the original engine performance to allow the simulation of the concept engine performance in the concept vehicle. This means it is possible to demonstrate and ratify a given engine/vehicle performance based on experience of the simulated product and to conduct sensitivity studies to discreet aspects of the performance feel of the vehicle • Steady state and drive cycle fuel economy: simulation programs have been written that take the basic engine efficiency relationships and through manipulation it is possible to determine the exact operating point of the engine, steady state or transient, and then determine the fuel economy. In order to determine the exact operating point it is necessary to consider detailed component data and key calibration data. Therefore it is possible to understand the effects of small changes to engine geometry, components or calibration on the fuel used. These developed techniques have been compared with traditional methods to determine the benefits in the concept confirmation phase of a new programme. This investigation showed that the reductions in phase duration, resource requirements and cost could be achieved in the order of 49, 27 and 17% respectively. This is coupled with the ability to obtain a more accurate product positioning through the capacity precisely to predict the product attributes. To conclude, the ability to define the product well is paramount to the success of an automotive manufacturer, and in support of this my project has developed tools and techniques that will greatly assist the development of petrol engines.

When an articulated tipper unit is being loaded or is tipping, it is unlikely to be standing on perfectly level ground. Also, the centre of gravity of the load is unlikely to be in the centre of the body. Hence the loads carried by the suspension and tyres on one side of the tipper will be greater than those on the other side. This uneven loading will cause the tyres and suspension on one side of the tipper unit to deform more than those on the other side. It will also cause the chassis to deform; the twisting about its longitudinal axis being the most significant mode of deformation. As a result of these deformations caused by the uneven loading, the position of the centre of gravity will be shifted even further towards the more heavily loaded side. This will cause even more uneven loading and further deformations. Under stable conditions a situation will exist at which the position of the centre of gravity, the deformations and the forces transmitted through the system are compatible. Instability, resulting in roll-over would occur if the overall centre of gravity of the load, body, chassis etc. were to fall outside the area bounded by the contact of the wheel with the ground, before a stable condition was reached. Many factors influence the roll stability. To increase stability, an understanding of the influence of components of the lorry on the stability is required. In order to achieve this, a theoretical model of an articulated tipper was developed which will allow roll-over predictions to be made for a given lorry in likely attitudes. In this model dimensions and stiffness of the lorry components can be altered to assess their influence on roll stability. The previous theoretical roll-over models were based on lumped mass systems, representing various parts of the lorry inter-connected by compliant elements. Certain flexibilities such as the tyres, suspension units, etc. could be obtained from the respective components manufacturers but the tractor and trailer chassis flexibilities are unknown. To overcome this problem the flexibilities were obtained from full scale static tilt tests. This is a very expensive undertaking, providing a limited means in which to assess those elements of trailer design which are important in improving stability, without further recourse to more tilt tests. It was decided that the finite element method should be used to model the tractor and trailer, in order to determine the important deformations. Once the finite element model is created it is relatively straight forward to make changes to the structure. Hence an assessment of component contribution to roll stability can be undertaken relatively inexpensively. Whilst a vehicle operator should always endeavour to discharge the payload with the vehicle standing on level ground, practical situations arise where this is not possible. This may be due to the absence of level ground or poor judgement by the operator, which may result in the vehicle being tipped on a lateral ground slope. As a result of this, the maximum ground slope angle considered for the theoretical model is limited to eight degrees, as this position is at least twice the severity of ground slope on which a vehicle should normally be tipped. For each trailer design, the magnitude of the load, position of the load, ram length and ground slope can be varied in any combination. Four payloads and up to nine payload positions are considered, varying the ground slope from 0 to 8 degrees and varying the ram length from 2 to 8 meters. Also, three further chassis configurations, based on the reference chassis were modelled to investigate the contribution of important component flexibilities on roll stability.

Air Traffic Controllers (ATCOs) are responsible for the safety and efficiency of all air traffic. It is essential that controllers maintain a consistently high standard of human performance in order to maintain flight safety. Knowledge of human factor influences on controller performance is critical to understand and mitigate threats to performance. Previous research has largely focused on the association between single factors and performance, which has resulted in a comprehensive understanding of single factor influences. In current control environments however, the residual threats for incidents often result from the interaction of multiple human factors and the resulting cumulative impact on performance. This thesis describes a set of studies that investigate the relationship between multiple, co-occurring factors, and the association with human performance. Findings contribute further understanding of multifactor combinations and associations with human performance, and provide novel and practical recommendations for the mitigation of multifactor influences on controller performance. A literature review, incident report analysis and survey of air traffic professionals confirmed that a majority of research approaches were fundamentally single-factor in nature, which is out of step with real air traffic management (ATM) contexts. In addition, findings confirmed that multiple factors co-occur in an air traffic control (ATC) environment, and are associated with controller performance. An off-line experiment using students as participants investigated the relationship between a set of human factors and the association with performance. Results indicate that several factors known to be associated with controller performance do co-vary and factors may interact to produce a cumulative Influence on performance. An interview study with en-route controllers contributed to an understanding of mitigation strategies of multifactor influences. The research presented in this thesis has contributed findings that have both theoretical and practical implications. This research has addressed long-standing gaps within human performance literature and contributed new understanding to the complex field of human performance in air traffic control. Findings suggest that factors do co-occur in ATC, and interact to negatively influence performance, pushing controllers to the edge of performance. This research argues for a more ecologically valid investigation of real-world systems using multiple factors rather than the traditional one or two-factor paradigms. In addition, this research investigation has contributed novel understanding of mechanisms which may mitigate multifactor influences and has developed practical recommendations for aviation personnel that may be used to support performance, thereby preventing performance decline, with important implications for maintaining and improving safety within the ATC domain.

Space missions have evolved considerably in the last fifty years in both complexity and ambition. In order to enable this continued improvement in the scientific and commercial return of space missions new control systems are needed that can manage complex combinations of state of the art hardware with a minimum of human interaction. Distributed multi-agent systems are one approach to controlling complex multisatellite space missions. A distributed system is not enough on its own however,the spacecraft must be able to carry out complex tasks such as planning,negotiation and close proximity formation flying autonomously. It is the coupling of distributed control with autonomy that is the focus of this thesis. Three contributions to the state of the art are described herein. They all involve the innovative use of multi-agent systems in space missions. The first is the development of a multi-agent architecture, HASA, specifically for space missions. The second is to use embedded agents to autonomously control an interferometric type space telescope. The third is based on software agents that coordinate multiple Earth observation missions coupled with a global optimisation technique for data extraction. The HASA architecture was developed in reaction to the over generality of most multi-agent architectures in the computer science and robotics literature and the ad-hoc, case-by-case approach, to multi-agent architectures when developed and deployed for space missions. The HASA architecture has a recursive nature which allows for the multi-agent system to be completely described throughout its development process as the design evolves and more sub-systems are implemented. It also inherits a focus on the robust generation of a product and safe operation from architectures in use in the manufacturing industry. A multi-agent system was designed using the HASA architecture for an interferometric space telescope type mission. This type of mission puts high requirements on formation flying and cooperation between agents. The formation flying agents were then implemented using a Java framework and tested on a multi-platform distributed simulation suite developed especially for this thesis. Three different control methods were incorporated into the agents and the multi-agent system was shown to be able to acquire and change formation and avoid collisions autonomously. A second multi-agent system was designed for the GMES mission in collaboration with GMV, the industrial partner in this project. This basic MAS design was transferred to the HASA architecture. A novel image selection algorithm was developed to work alongside the GMES multi-agent system. This algorithm uses global optimisation techniques to suggest image parameters to users based on the output of the multi-agent system.