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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

An optimum visual sensor configuration for terrestrial locomotion

Daniels, Geoffrey Philip January 2015 (has links)
Human technological advancement has continually created new opportunities for machinery to automate intensive tasks. However, these machines still need to be delivered and often controlled by humans. Autonomous Ground Vehicles (AGVs) can completely remove the locomotion dependency of these systems on humans, enabling a robotic revolution. The locomotive performance of AGVs is dependent on the quantity and quality of information received about the terrain ahead; for this purpose, vision is by far the most effective sense. Contextual machine vision is a new area of research where fundamental questions such as how to optimise a visual system specification for a locomotive platform to enable fast locomotion are yet to be addressed. In this thesis, abstract mathematical models of a generic vision sensor and generic locomotor platform were developed to investigate the relationship between sensor specification and locomotor performance with respect to a single key parameter, the maximum ground speed. Initially a static AGV model was investigated, before being expanded to include forward motion, thus enabling the maximum dynamic performance of an AGV to be evaluated. The vision sensor model was designed with interchangeable sensor geometries so that the performance of multiple sensor geometries could be compared. Two of the sensor geometries were designed to approximate a digital camera and human eye, while the third removed non-linearities associated with the detector. The optimum specification to enable maximum speed was defined by the geometry of the sensor. The achievable proximity to the optimum is restricted by system resolution. Generally the sensor geometries analogous to a digital camera and human eye outperformed the linearised model, however, this model can be made insensitive to sensor angle which can be advantageous. Optical flow algorithm performance was not directly effected by detector geometry. Although the resolution variation of the non-linearised detectors and locomotion context reduced tracking performance. Simulating pose error on the model with a random or systemic error resulted in the outcome that vision was a requirement for motion estimation, leading to the development of an AGV vision system for human AGVs. The performance of a visually limited, controlled, human AGV, in a virtual reality environment showed a minimum of 500 features was required for good performance at a foot placement task.

The investigation of neutral beams for space research

Jones, T. V. January 1966 (has links)
No description available.

On the design of a high-subsonic jet transport aircraft with particular reference to thrust-vectoring

Saeedipour, Hamid R. January 1998 (has links)
The conceptual design of a jet civil transport aircraft with and without thrust- vectoring is considered. The project studies thrust-vectoring effects using externally adjustable exhaust nozzles on the design of a high-subsonic civil jet transport aircraft with twin wing-mounted turbofan engines. The status, importance and classifications of thrust- vectoring technology are presented and some examples of thrust vectored civil and military aircraft are given. A literature survey, a discussion of the theoretical, computational and experimental work along with an outline for future work are given. In order to achieve these goals, a convergent iterative computer program (ICP) was written in FORTRAN-77 for the UNIX computer operating system. It is for the preliminary design of a high-subsonic jet transport aircraft and airworthiness regulations were adhered to throughout the design. By using a series of subroutines, the program is structured so that the effects of any change in the design parameters can be readily evaluated and future improvements and expansions can easily be made. The ICP uses a step-by-step method to integrate along the flight path and the output is presented after several iterations when there are no further changes. An experimental study has been conducted, using the Goldstein Laboratory's open-return Project Wind-Tunnel with a closed working-section. This experimental work produced the aerodynamic force coefficients and the induced-drag factors of different combinations of six wings and two jets with circular and rectangular' nozzle exits.The experimental wing-jet-flap configurations with jet deflections were modelled by the Vortex Lattice Method (VLM) using a NASA code, slightly modified for this project. Experimental and VLM results are presented for the thrust-vectoring effects on the force coefficients for the wing-jet-flap combinations at different jet velocities, wing angles of attack, nozzle pitch, yaw angles and nozzle exit shapes. The pressure and velocity distributions, predicted by the VLM code, for the six wings in the vicinity of the jet engines were also displayed. Different circular and rectangular nozzles at various angles have been used to provide these jet deflections. Estimates have been obtained for the resulting modification to the induced drag and extra-circulation. Only the preliminary design stage of a civil jet transport aircraft is considered and no detailed study of the dynamic stability, the structure or the economics of the aircraft is given in this thesis.

Modelling the behaviour of composite structures under impact and crush loading

Tan, Wei January 2016 (has links)
Composite materials are finding increasing utilisation in a number of transportation industries concerned with making structures lighter to reduce environmental impact and improve efficiency. Nevertheless, composite structures are susceptible to damage from low-velocity impact events leading to a significant reduction in compression- after-impact residual strength. Another major challenge is to ensure a prescribed level of crashworthiness of fibre-reinforced composite vehicles. The accurate assessment of the effect of impact damage and the performance of structures under crush loading for composite aerostructures, for example, currently requires costly and highly inefficient experimental testing to meet certification requirements. The aim of this project is to develop and validate a reliable, predictive material damage model for capturing impact damage, residual strength and energy absorption capacity of thermoset and thermoplastic composites for crashworthiness assessments. A mesoscale intralaminar damage model, which combines a range of novel techniques to accurately capture the material response under damaging loads, was developed. This physically-based model makes a significant contribution to composite modelling capability by accounting for the intralaminar nonlinear material response, unloading/reloading and load reversal behaviour, fibre-dominated and matrix-dominated damage mode interactions and robust characteristic length calculation. A cohesive zone model, with mixed-mode softening law, was used to model the interlaminar damage. The presented model requires only physically measureable parameters, such as geometry, ply-level material properties and loading conditions, to achieve an accurate predictive solution of impact and crush behaviour of composite structures. A series of tests have been conducted for the measurement of interlaminar and intralaminar fracture toughness as well as the non-linear shear behaviour of AS4/PEKK thermoplastic composite laminates. The measured intrinsic ply-level values were then used as input material parameters for the finite element analysis. The effectiveness of the composite damage model was validated using experimental data obtained from in-house experimental testing as well as from the literature. Results showed that the model can accurately predict the intralaminar damage features, delamination damage area of composite structures under low-velocity impact as well as compressive behaviour and residual strength in compression after impact. Both the qualitative and quantitative aspects of intralaminar and interlaminar damage for wedge-shape and corrugated-shaped composite structures under crush loading were accurately captured. The predicted crush morphologies, force displacement response and dissipated energy were in a good agreement with experimental results, which demonstrates the reliability of this model in predicting impact and crush response of composite structures. The proposed model can be exploited by industry to reduce time and cost in the development of composite structures.

The design and operation of high pressure injectors as gas jet boosters

Hoggarth, Malcolm Leslie January 1968 (has links)
No description available.

Off-line programming, verification and optimisation of industrial control systems

Danielsson, Fredrik K. J. January 2002 (has links)
No description available.

Nonlinear control engineering with application to robotic and machinery control systems

Mohamedy, Alaa Eldien Shawky January 2003 (has links)
No description available.

Air jet vortex generator flow control applied to the rear multi element high downforce wing of a Formula One racing car

Akanni, Saïf-Deen January 2002 (has links)
No description available.

Aircraft routing using nonlinear global optimization

Wilson, Simon Paul January 2003 (has links)
No description available.

The microbial biochemistry of slow sand filters

Law, Samantha P. January 2003 (has links)
No description available.

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