PhD and Masters by research theses (SoE)
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Browsing PhD and Masters by research theses (SoE) by Supervisor "Allerton, David J."
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Item Open Access Assessment of the autonomous air traffic control resolution tool for free flight(Cranfield University, 2004-07) Juman, M. A.; Allerton, David J.In order to improve air traffic coordination and planning, future ATMs need to allow various users of a particular airspace, timely access to the same data. Already, advances in technology, in the form of enhanced tools assisting airspace controllers and users, have enabled the sharing of high fidelity data across systems and improving standards in air traffic safety and throughput. To-date most of these tools are human- centered. The thesis presents a set of human-centered tools which use a common data structure for: detecting and resolving air traffic congestion, conflict detection and resolution and limiting the search space, in a ‘free-flight environment’. The chosen data-structure represents sets of discretized and indexed volumes of airspace, called ‘bins’, which store all the information necessary for operation in different airspace sectors. An algorithm using these bins has been proposed in the thesis. A large number of experiments carried out on a single purpose simulator, developed as a part of the thesis, have resulted in a set of optimized conflict free routes, which amply illustrate both medium and short-term detection of congestion and conflicts and provide solutions for their avoidance, across a large airspace volume that contains several airspace sectors, efficiently. In addition, a limited set of experiments, carried out with qualified ATCs in the loop, highlights the fact that the proposed ATM tool does assist them in better visualizing traffic flow and encounter geometry(ies).Item Open Access Data fusion methodologies for multisensor aircraft navigation systems(Cranfield University, 2004-04) Jia, Huamin; Allerton, David J.The thesis covers data fusion for aircraft navigation systems in distributed sensor systems. Data fusion methodologies are developed for the design, development, analysis and simulation of multisensor aircraft navigation systems. The problems of sensor failure detection and isolation (FDI), distributed data fusion algorithms and inertial state integrity monitoring in inertial network systems are studied. Various existing integrated navigation systems and Kalman filter architectures are reviewed and a new generalised multisensor data fusion model is presented for the design and development of multisensor navigation systems. Normalised navigation algorithms are described for data fusion filter design of inertial network systems. A normalised measurement model of skewed redundant inertial measurement units (SRIMU) is presented and performance criteria are developed to evaluate optimal configurations of SRIMUs in terms of the measurement accuracy and FDI capability. Novel sensor error compensation filters are designed for the correction of SRIMU measurement errors. Generalised likelihood ratio test (GLRT) methods are improved to detect various failure modes, including short time and sequential moving-window GLRT algorithms. State-identical and state-associated fusion algorithms are developed for two forms of distributed sensor network systems. In particular, innovative inertial network sensing models and inertial network fusion algorithms are developed to provide estimates of inertial vector states and similar node states. Fusion filter-based integrity monitoring algorithms are also presented to detect network sensor failures and to examine the consistency of node state estimates in the inertial network system. The FDI and data fusion algorithms developed in this thesis are tested and their performance is evaluated using a multisensor software simulation system developed during this study programme. The moving-window GLRT algorithms for optimal SRIMU configurations are shown to perform well and are also able to detect jump and drift failures in an inertial network system. It is concluded that the inertial network fusion algorithms could be used in a low-cost inertial network system and are capable of correctly estimating the inertial vector states and the node states.Item Open Access Design of data structures for terrain reference navigation(Cranfield University, 1994-05) Gia, M. C.; Allerton, David J.This thesis describes the design of a data structure for use with Digitised Terrain Elevation Data (DTED) in Terrain Reference Navigation (TRN) systems. The data structure is based on a variant of quad-tree and oct-tree data structures to provide an efficient representation of terrain in terms of storage requirements and acccss operations. These data structure are applied to flight path planning operations in mission management applications. The algorithms developed for flight path planning have becri implemented in the C programming language for a standard PC. Current research in TRN systems is reviewed and attention is given to the use of hierarchical data structures to cope with the potentially large data base needed for DTED files. Data structure combining quad-trees and oct-trees are developed with an emphasis on data reduction using pointerless trees and the use of locational codes to provide straightforward mapping between quad-trees and oct-trees, in other words, between two-dimensional co-ordinates and three-dimensional co-ordinates. Analysis of these algorithms is described for two DTED files to illustrate storage improvements and to verify a set of database access operations. These data structures are applied to problems of flight path planning where the navigation space comprises objects above a specific altitude and this three-dimensional space is searched for a flight path which avoids the obstacles and satisfies specific operational criteria. Algorithms are developed to extract a visibility graph from the terrain database and to determine the preferred flight path from a set of paths which satisfy defined constraints. Several search techniques are developed which exploit the efficiency of the quad-tree and oct-tree data structures. These methods are extended to real-time flight-path planning where predicted times for access operations are used to direct flight path extraction by varying the tree resolution during computation of the flight path. A comprehensive set of results are provided to illustrate: the storage efficiency of quad-tree and oct-tree data structures the application of pyramid structures to represent navigation space analysis of the time to compute the visibility graph and to extract flight paths integration of these methods with a real-time mission management simulation on a PC The thesis draws conclusions on the efficiency of these techniques for the represcntation of DTEDs and to access objects in TRN systems. It is observed that the use of hierarchical data structures in the form of quad-trees and oct-trees offers significant improvement in accessing DTEDS, for future use in TRN systems. The thesis concludes by outlining areas of further work where the techniques can be further &N, cloped for applications in mission management and navigation using DTED files.