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No description available.

No description available.

The research was instigated by the Civil Aviation Authority (CAA) to examine the implications for air traffic controllers' (ATCO) job satisfaction of the possible introduction of systems incorporating computer-assisted decision making. Additional research objectives were to assess the possible costs of reductions in ATCO job satisfaction, and to recommend appropriate task allocation between ATCOs and computer for future systems design (Chapter 1). Following a review of the literature (Chapter 2) it is argued that existing approaches to systems and job design do not allow for a sufficiently early consideration of employee needs and satisfactions in the design of complex systems. The present research develops a methodology for assessing affective reactions to an existing system as a basis for making reommendations for future systems design (Chapter 3). The method required analysis of job content using two techniques: (a) task analysis (Chapter 4.1) and (b) the Job Diagnostic Survey (JDS). ATCOs' affective reactions to the several operational positions on which they work were investigated at three levels of detail: (a) Reactions to positions, obtained by ranking techniques (Chapter 4.2); (b) Reactions to job characteristics, obtained by use of JDS (Chapter 4.3); and (c) Reactions to tasks, obtained by use of Repertory Grid technique (Chapter 4.4). The conclusion is drawn that ATCOs' motivation and satisfaction is greatly dependent on the presence of challenge, often through tasks requiring the use of decision making and other cognitive skills. Results suggest that the introduction of systems incorporating computer-assisted decision making might result in financial penalties for the CAA and significant reductions in job satisfaction for ATCOs. General recommendations are made for allocation of tasks in future systems design (Chapter 5).

Prior to the development of a production standard control system for ML Aviation's plan-symmetric remotely piloted helicopter system, SPRITE, optimum solutions to technical requirements had yet to be found for some aspects of the work. This thesis describes an industrial project where solutions to real problems have been provided within strict timescale constraints. Use has been made of published material wherever appropriate, new solutions have been contributed where none existed previously. A lack of clearly defined user requirements from potential Remotely Piloted Air Vehicle (RPAV) system users is identified, A simulation package is defined to enable the RPAV designer to progress with air vehicle and control system design, development and evaluation studies and to assist the user to investigate his applications. The theoretical basis of this simulation package is developed including Co-axial Contra-rotating Twin Rotor (CCTR), six degrees of freedom motion, fuselage aerodynamics and sensor and control system models. A compatible system of equations is derived for modelling a miniature plan-symmetric helicopter. Rigorous searches revealed a lack of CCTR models, based on closed form expressions to obviate integration along the rotor blade, for stabilisation and navigation studies through simulation. An economic CCTR simulation model is developed and validated by comparison with published work and practical tests. Confusion in published work between attitude and Euler angles is clarified. The implementation of package is discussed. dynamic adjustment of assessment. the theory into a high integrity software Use is made of a novel technique basing the integration time step size on error Simulation output for control system stability verification, cross coupling of motion between control channels and air vehicle response to demands and horizontal wind gusts studies are presented. Contra-Rotating Twin Rotor Flight Control System Remotely Piloted Plan-Symmetric Helicopter Simulation Six Degrees of Freedom Motion

The rapid economic growth of Taiwan has been paralleled by an increase in marine. traffic in the port of Keelung. The increase has been evolutionary and, prior to this study, has lacked the benefit of supporting research necessary to ensure no loss in navigational efficiency. The study uses eclectic methodologies to: identify the nature of marine traffic at Keelung; assess the associated risks; and identify measures needed to reduce risk and increase navigational efficiency. For contextual purposes the study reviews current marine traffic operations at Keelung against the background of geographical constraint and environmental conditions. Radar survey and extensive sampling of professional opinion indicate that existent traffic control measures are both inadequate and open to contravention. Casualty analysis further identifies areas of concern where navigation risk has been shown to exist In particular the traffic separation scheme, introduced in 1990; has been found inadequate and lack of movement control reduces navigational efficiency. Use of visual simulators, at Taiwan Ocean University and University of Plymouth, provided a unique opportunity to compare present marine traffic operations against a modified model. The modified model incorporated limited vessel traffic service functions and channel markers, neither of which exist at present in the live situation. Most significantly the experiment has enabled evaluation of the difference between Taiwanese and foreign ship masters when handling ships in the port approaches. Analysis of ship's tracks, and subjects' perceptions, concludes that provision of channel markers and sequence control greatly simplifies the operation and reduces risk. The need to widen the traffic lanes by reducing the separation zone between inward and outward lanes is identified. The study shows that navigational safety and efficiency at Keelung can be improved through the introduction of small changes to operation and working practices, The study provides the basis for a programme of continuing work necessary to maintain or further improve standards once the recommendations of the study have been implemented.

The project has been directed towards improving the accuracy and safety of marine navigation and ship handling, whilst contributing to reduced manning and improved fuel costs. Thus, the aim of the work was to investigate, design and develop an adaptable mathematical model that could be used in an integrated navigation system (INS) and an automatic collision avoidance system (ACAS) for use in marine vehicles. A general overview of automatic navigation is undertaken and consideration is given to the use of microprocessors on the bridge. Many of these systems now require the use of mathematical models to predict the vessels' manoeuvring characteristics: The different types and forms of models have been investigated and the derivation of their hydrodynamic coefficients is discussed in detail. The model required for an ACAS should be both accurate and adaptable, hence, extensive simulations were undertaken to evaluate the suitability of each model type. The modular model was found to have the most adaptable structure. All the modular components of this model were considered in detail to improve its adaptability, the number of non-linear terms in the hull module being reduced. A novel application, using the circulation theory to model the propeller forces and moments, allows the model to be more flexible compared to using traditional B-series four-quadrant propeller design charts. A new formula has been derived for predicting the sway and yaw components due to the propeller paddle wheel effect which gives a good degree of accuracy when comparing simulated and actual ship data, resulting in a mean positional error of less than 7%. As a consequence of this work, it is now possible for an ACAS to incorporate a ship mathematical model which produces realistic manoeuvring characteristics. Thus, the study will help to contribute to safety at sea.

Part one of the thesis contains analysis of the methods of computation in navigation. We start with loxodromic navigation and, although this subject is well documented, we make a positive attempt to analyse the subject matter using the methods of differential geometry. We then turn to the problem of shortest path curves and set out an alternative method of solving the problem of navigating along the arc of a great circle on the surface of a sphere which can be generalised to other surfaces. In particular, a contribution made by the thesis is an analysis of the problem of navigating along shortest path geodesic arcs on the surface of a spheroid which introduces an algebraic representation of the geodesic curve by solving Clairaut' s equation using a cylindrical transformation. We are therefore able to compute the the coordinates of the positions of points along the path of the geodesic and the length of arc along the path of the. geodesic curve can then be computed step by step between these points by a numerical method - the Direct Cubic Spline method which was first introduced by this author in the Bachelor of Philosophy thesis in 1982 and is developed further in part 2 of this thesis. We apply this method also to the special problem of computing the distance along the shortest path between nearly antipodean points on the surface of a spheroid. We analyse the problem of computing an observer's position on the surface of the Earth using astronomical observations and show how a position locus is distorted when it is transferred over the surface. We offer a method of computing the observer's position by a series of observations of a single astronomical body taken over a comparitively short period of time and which does not necessarily include an observation at the tide of meridian passage of the body. In part two of the thesis we discuss the Direct Spline approximation to integrals and give some error bounds. The Direct Cubic Spline is a step by step method of fitting a cubic spline to the integral of a function directly which computes the value of the integral of the function step by step between the data points which need not be evenly spaced. We extend the idea to splines of higher order and give the formula from which they may be obtained but we show that, except for a particular special form of the direct quartic spline. the higher order direct splines do not yield algorithm for computing integrals which are as efficient as the Direct Cubic Spline.

Heading measurement is required on board light aircraft, surface ships and underwater vessels. It is also used for the position navigation of commercial cars and military vehicles.

Radio waves in the Very Low Frequency (VLF) band (3-30kHz) are reflected from the lowest part of the ionosphere, the D-region. Due to their relative stability and low attenuation they are utilized for navigation, timing and frequency comparisons. Any changes in D-region electron density structure are known to influence the phase velocity of VLF waves. Both regular diurnal and irregular behaviour have been extensively reported. A comparison of theoretical techniques is presented, demonstrating the influence of changes in radio frequency, ground conductivity, geomagnetic path azimuth and latitude. Described in this thesis is an analysis of the experimentally determined performance, within the U.K., of the VLF navigation system 'Omega'. The system relies on the stability of the phase velocity of the transmitted signals to provide a navigation fix. Both diurnal and seasonal variations in signal phase are investigated while the effects of modal interference and ionospheric disturbances are noted. In order to reduce errors resulting from regular variations in phase velocity, a prediction technique has been developed by the Omega Navigation System Operations Detail (ONSOD). An assessement of the validity of ONSOD predictions within the U.K. is presented and it is apparent that a number of differences exist between them and the experimental data. Major errors are evident at dawn over certain near north-south paths and marked differences may occur between data collected at particular sites. The relevance of these differences to Differential Omega is noted and an investigation into the performance of an Omega/Satellite combined system is conducted. The variations within the U.K. are not completly accounted for by changes in propagation path length although theoretical investigations indicate the importance of changes in electron density structure along the whole path. It is evident that the sunrise schedules of the ONSOD prediction program require modification.