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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.

Computer simulation models are increasingly necessary as a design tool for modern vehicles, for which a subcategory relates to motorcycles. Simulation models can be employed for a variety of applications, an important area of which relates to the motorcycle's dynamic responses. The response of a motorcycle is heavily dependent on the rider's control actions, and consequently a means of replicating the rider's actions provides an important extension to this area. The application of mathematical control techniques for replicating the motorcycle rider's control actions is presented in this thesis, detailing specifically the techniques of optimal control and model predictive control. The work begins with modelling the dynamics of the motorcycle using standard procedures. The application of optimal control to a motorcycle rider is not new, but the available results have been extended significantly over those previously available, allowing further insights into the behaviour and therefore applicability of this strategy to modelling a motorcycle rider. Use of the model predictive control approach is new in the field of motorcycle rider modelling, and a similarly extensive parametric study is conducted to evaluate the suitability of this approach, and to highlight the similarities and differences between this and the optimal control approach. Both controller models were simulated over a standard single lane-change manoeuvre. Comparison of the relative performances of the two control approaches confirmed strong similarities between the techniques, particularly when the modelled rider is permitted an extensive knowledge of the approaching road path to follow. When this knowledge is restricted, differences were apparent between the two, suggesting the predictive control approach is capable of better performance here, and therefore represents a more robust control strategy. An option of the predictive control approach allows more elaborate target paths for the rider to follow to be set. However, defining the target path for the rider model to follow as the road centreline, and then permitting the controller itself to select the most appropriate course to take, has also been shown to be the more suitable option. The predictive control technique for motorcycle rider modelling is shown to be a theoretically suitable application. Further work is suggested to validate the results presented here. If it can be confirmed that the model accurately captures a motorcycle rider's actions, this will prove a very useful tool for the understanding of a motorcycle rider's control actions, with potential benefits towards rider safety and furthermore as a design tool for the motorcycle industry.

This thesis addresses problems associated with surface quality measurement and residual volatile organic compounds for composite laminates intended for use as cosmetic body parts based on unsaturated polyester resin containing shrinkage control additives. Surface quality measurement techniques were compared for composite laminates allowing for rapid characterisation and benchmarked to industrial standards. Thermal desorption and solvent elution techniques were used for the detection of residual volatiles with styrene and benzaldehyde being the main focus. The degree of conversion and residual volatiles were monitored for three peroxide initiators via a series of statistically developed experiments. This work highlighted the need for alternative shrinkage control methods. A novel approach was studied through the use of nano-scale silicates. An exfoliation process was developed with subsequent characterisation of thermal and mechanical properties for the nanocomposite. Finally, a series of hybrid matrices consisting of nanocomposite and low profile additive blends were monitored for effects on surface roughness, residual volatile levels and mechanical performance.