The crash of the Boeing 737-400 G-OBME at Kegworth on the 8th January 1989 provided an opportunity to investigate how the passengers were injured during the crash. A computer simulation was subsequently set up to assess the kinematics of the passengers and to establish the likely forces which they would have experienced during the crash. Two computer models were created using the crash victim simulation program, MADYMO. The models were used to study the brace and upright positions and to establish any correlation with body injuries and forces predicted by the models. A parametric study was, subsequently, undertaken with the objective of improving seat design. Further studies were undertaken to evaluate the effects of body posture and impact pulses upon 5th percentile female, 50th percentile male and 95th percentile male occupants. The objective of the research was to establish the severity of injuries for various occupant statures when seated in accordance with the dynamic seat requirements of Aerospace Standard 8049. The research was used to establish the loads sustained on the head, thorax, lumbar spine, pelvis and lower limbs. A three dimensional computer model was created with the objective of studying the effect of lateral acceleration components as specified in Aerospace Standard 8049. Furthermore, the model was used to establish the injuries which might be sustained in other types of aircraft accidents. Using the data of the same aircraft, this was further utilised to investigate different seat orientations and restraint systems. Finally, a spine model was created which examined the detailed loading of the spine using the 16G dynamic test pulse. This showed that the spine of a lap belted occupant is heavily loaded during the impact. Thus, the computer modelling of the brace for impact position led to the recommendation for a new improved brace position which could reduce the likelihood of lower limb flail. In addition, it has been found not to increase spinal loading.

No description available.

No description available.

Autonomous systems are becoming increasingly commonplace, with applications either existing or suggested in many different industries. As levels of autonomy increase, the need for these systems to interpret with environments in which they operating and make decisions about their own future actions following internal failures or external threats. In the past, reliability analysis methods have been suggested as having the potential to provide information that could be used in a real-time decision support tool for autonomous systems in changing environments. Real-time support is particularly important in systems such as unmanned aerial vehicles (UAV), where any delay in making a decision following a failure occurrence or the emergence of a threat could be catastrophic. Reliability Analysis can be used to calculate the failure probability of a mission such as that performed by a UAV by modelling the mission as a sequence of tasks known as a phased mission. Binary Decision Diagram models have shown great potential for analysing phased mission systems since they can produce accurate mission and phase failure probabilities in reasonably short time frames. Although research to date has shown that Binary Decision Diagrams appear to have the most promise for performing the real-time analysis that would be required as an input to a decision making tool for phased mission systems, the analysis as it stands still falls some way short of being near-instant, as it must be for decisions to be made quickly when required. In common with many systems, phased mission systems can contain components that fail in multiple failure modes. It is therefore important that multiple failure modes are modelled while developing the Binary Decision Diagram tools and techniques considered in this research. The research presented in this thesis aims to address the deficiencies seen in previous methods by investigating the Binary Decision Diagram techniques and suggesting how the techniques can be developed for use within a decision support tool where fast, accurate decision making is required. The novelty of the research is as follows: 1. Different Binary Decision Diagram models for phased mission systems are reviewed and three new Binary Decision Diagram models are proposed to improve the efficiency and accuracy of analysis for phased mission systems containing multiple failure mode components. 2. Since the size of a Binary Decision Diagram has a significant effect on the time required to quantify it and the Binary Decision Diagram size is influenced by variable ordering, nine different variable ordering schemes are investigated for phased mission systems. Eight of them are extended from fault tree analysis of single phase systems containing single failure mode components and one is newly-developed specially for use within a decision support tool. 3. Due to the potential time limitation for decision making, approximation methods are investigated to evaluate the failure probabilities in phased mission systems while trading off between accuracy and analysis efficiency. Three new approximation models are developed and their analysis efficiency advantage over the exact analysis is demonstrated testing on a large number of sample phased mission systems. A performance indicator is developed in order to facilitate the choice of approximation method taking into account accuracy and efficiency requirements. The benefits of the developed methods are demonstrated through the consideration of a case study.

This Thesis describes techniques used in the analysis of aerospace adhesively bonded sandwich joints using radially polarised shear wave EMATs, together with an analysis of the general performance of the EMAT systems used in the investigation. It is generally accepted that to date there is no satisfactory technique for the detection of defect types commonly encountered in adhesively bonded aerospace samples. This has limited the use of adhesives for joining components on critical parts, where no additional fixing techniques are used. Consequently, if a test procedure could be developed to accurately monitor post production defects and in-service degradation then there would be great benefits in terms of weight saving and strength in joined components which were held together by adhesive bonds alone. Ultrasonics is a technique commonly applied to the assessment of bond quality and readily lends itself to the probing of media which support the propagation of acoustic waves. The principal is that the propagation of sound through a medium gives some indication of the mechanical properties of that medium, and in terms of an adhesive layer could measure the strength of the adhesive bulk itself- cohesion. The efficiency of propagation of sound from one medium to another depends on the physical properties of each medium, and possibly on how well the surfaces of each medium are joined together - adhesion. Adhesion is the more difficult property to monitor as it is not just a case of mechanically keying one medium to another on a nanometre scale, but other interactions occur between the media similar to a Van der Walls type force that also contribute to adhesion. It has been extensively reported in the literature that the most sensitive ultrasonic wave to use would be ashearwave at normal incidence to the adherent-adhesive interface. Radially polarised shear wave EMATs have been used to generate the shear waves that induce a shear stress at an adherent-adhesive interface. Some of the work involved in this project has concentrated on the design, construction and characterisation of these EMATs and the supporting hardware such as current pulser circuits and the necessary low noise-high bandwidth preamplifiers. The experimental work is presented in chapters 3-7. Chapter 3 covers the performance of the EMAT systems, chapter 4 discusses the EMAT operation on birefringent aluminium plates, chapters 5 and 6 cover the results and analysis used in the adhesive bonds and chapter 7 describes a technique to monitor adhesive cure using EMATs which monitor changes at an adherent-adhesive interface and within the adhesive bulk itself.

This thesis deals with safety verification analysis of collision avoidance systems for unmanned vehicles. The safety of the vehicle is dependent on collision avoidance algorithms and associated control laws, and it must be proven that the collision avoidance algorithms and controllers are functioning correctly in all nominal conditions, various failure conditions and in the presence of possible variations in the vehicle and operational environment. The current widely used exhaustive search based approaches are not suitable for safety analysis of autonomous vehicles due to the large number of possible variations and the complexity of algorithms and the systems. To address this topic, a new optimisation-based verification method is developed to verify the safety of collision avoidance systems. The proposed verification method formulates the worst case analysis problem arising the verification of collision avoidance systems into an optimisation problem and employs optimisation algorithms to automatically search the worst cases. Minimum distance to the obstacle during the collision avoidance manoeuvre is defined as the objective function of the optimisation problem, and realistic simulation consisting of the detailed vehicle dynamics, the operational environment, the collision avoidance algorithm and low level control laws is embedded in the optimisation process. This enables the verification process to take into account the parameters variations in the vehicle, the change of the environment, the uncertainties in sensors, and in particular the mismatching between model used for developing the collision avoidance algorithms and the real vehicle. It is shown that the resultant simulation based optimisation problem is non-convex and there might be many local optima. To illustrate and investigate the proposed optimisation based verification process, the potential field method and decision making collision avoidance method are chosen as an obstacle avoidance candidate technique for verification study. Five benchmark case studies are investigated in this thesis: static obstacle avoidance system of a simple unicycle robot, moving obstacle avoidance system for a Pioneer 3DX robot, and a 6 Degrees of Freedom fixed wing Unmanned Aerial Vehicle with static and moving collision avoidance algorithms. It is proven that although a local optimisation method for nonlinear optimisation is quite efficient, it is not able to find the most dangerous situation. Results in this thesis show that, among all the global optimisation methods that have been investigated, the DIviding RECTangle method provides most promising performance for verification of collision avoidance functions in terms of guaranteed capability in searching worst scenarios.

he digital revolution in the latter part of the twentieth century has resulted in the increased use and development of Cyber-Physical Systems. Two of which are Unmanned Aerial Systems (UAS) and Integrated Vehicle Health Management (IVHM). Both are relatively new areas of interest to academia, military, and commercial organisations. Designing IVHM for a UAS is no easy task – the complexity inherent in UAS, with projects involving multiple partners/organisations; multiple stakeholders are also interested in the IVHM. IVHM needs to justify itself throughout the life of the UAS, and the lack of established knowledge makes it hard to know where to start. The establishment and analysis of requirements for IVHM on UAS is known to be important and costly – and for IVHM a complex one. There are multiple stakeholders to satisfy and ultimately the needs of the customer, all demanding different things from the IVHM, and with limited resources they need to be prioritised. There are also many hindrances to this: differences in language between stakeholders, customers failing to see the benefits, scheduling conflicts, no operational data. The contribution to knowledge in this thesis is the IVHM Requirements Deployment (IVHM-RD) – a method for a designer of UAS IVHM to build a tool which can consolidate and evaluate the various stakeholder’s requirements. When the tool is subsequently populated with knowledge from individual Subject Matter Experts (SMEs), it provides a prioritised set of IVHM requirements. The IVHM-RD has been tested on two design cases and generalised for the use with other designs. Analysis of the process has been conducted and in addition the results of the design cases have been analysed in three ways: how the results relate to each design case, comparison between the two cases, and how much the relationships between requirements are understood. A validation exercise has also been conducted to establish the legitimacy of the IVHM-RD process. This research is likely to have an impact on the elicitation and analysis of IVHM requirements for UAS – and the wider design process of IVHM. The IVHM-RD process should also prove of use to designers of IVHM on other assets. The populations of the design cases also provide information which could be useful to other designer and future research.

No description available.

No description available.

During wind tunnel testing of jet-lift, short take-off and vertical landing (STOVL) aircraft it is usual to simulate the jet efflux but not the intake flows. The intakes, which are commonly faired over or are unpowered, are generally tested in separate wind tunnel experiments. The forces acting on the wind tunnel model are determined by the linear addition of the forces obtained from the two separate tests. There is some doubt as to whether this is a valid approach. A systematic experimental investigation was, therefore, conducted to determine the magnitude of any jet/intake interference effects on a generic jet-lift STOVL aircraft in transitional flight, out of ground effect. Comparisons made between separate and simultaneous jet and intake testing concluded that a mutual jet/intake interference effect does exist. The existence of this interference means that the aerodynamic wing lift loss in transitional flight deduced from isolated jet and intake testing is less than the lift loss obtained from simultaneous jet and intake testing. The experimental research was supplemented by some simplified computational fluid dynamics (CFD) studies of elements of the flow-field about the aircraft using the k-e turbulence model. The numerical modelling enabled aspects of the flow-field around the aircraft to be visualised which could not easily be done using the experimental apparatus. It is a requirement of the Eng]) programme that part of this thesis must address a management topic linked to the research. In this case the management aspects of wind tunnel project work were examined. A scenario was developed which established a requirement for a large-scale, low-speed wind tunnel with a Reynolds number capability of 20 million. A study was performed on the decision-making process and investment appraisal methods used in the procurement of such a wind tunnel.