Publikationen 2005 der Eberhard-Karls-Universität Tübingen aus der Fakultät für Biologie

Bibliographie von Publikationen, die von Angehörigen der Fakultät für Biologie der Universität Tübingen im Jahr 2005 erstellt wurden, u.a. Dissertationen, Diplomarbeiten, Aufsätze, Monographien

A Study of Planar and Nonplanar Membrane Wing Planforms for the Design of a Flapping-Wing Micro Air Vehicle

Flapping wings may have potential for success in the realm of micro air vehicles (MAVs). The goal of this thesis was to investigate a variety of flapping wing planforms, including nonplanar effects, to create an optimum planform for an MAV design. Test stand and model prototype experiments were conducted to measure the lift and propulsive thrust generated by flapping wing planforms with a variety of nonplanar tips. The polynomial planform with 20º tip anhedral was selected for the flapping-wing MAV designed herein because of its enhanced performance, reaching over 15 g of lift. A propulsive thrust analysis was performed on the selected wing, indicating sufficient levels of thrust production. Instantaneous lift and strobe photography analyses were performed to investigate the underlying physical effects of nonplanar tips, particularly their ability to reduce negative upstroke lift

Investigation and Characterization of a Cycloidal Rotor for Application to a Micro-Air Vehicle

In recent years, interest has been growing in a new class of very small flight vehicles called micro air vehicles (MAVs). The use of cycloidal propulsion for such a vehicle has some advantages over other configurations that make it an attractive alternative to fixed-wing and rotary-wing vehicles. In a cycloidal blade system, a series of blades rotate around an axis of rotation oriented parallel to both the blades and the horizon. As the blades rotate about the axis, their pitch angle is varied periodically. This paper investigates a small scale cycloidal rotor to determine its viability for use on a micro air vehicle. An analytical model, using a combination of wind turbine theory and an indicial solution for the aerodynamic response was developed in an attempt to predict rotor performance. A small experimental rotor was constructed and tested to determine the effects of blade number, blade pitch angle, and rotational speed on thrust output, power requirements, and efficiency. While a six-bladed configuration demonstrated more thrust production than a three-bladed one, results showed lower efficiency than that predicted and may suffer from blade-wake interference. High blade pitch angles of $30^{\circ}$ to $40^{\circ}$ are necessary to meet thrust requirements for an MAV. Experimental results are compared with predictions as well as to results from a conventional rotor to ascertain the effectiveness of the cycloidal configuration. A maximum figure of merit of approximately 0.55 is achieved during testing, comparable with the conventional rotor. However, figure of merit for the cycloidal rotor declines as rotational speed increases, severely limiting its usefulness if high efficiency is necessary. An investigation of the flow field around the rotor is conducted to achieve an acceptable quantitative picture of the rotor downwash. Results demonstrate that outflow is directed approximately $15^{\circ}$ from the vertical. Although it appears that flow may expand upon exiting the rotor, results are inconclusive at this time. An MAV utilizing cycloidal propulsion is modeled in CATIA to determine its viability. The cyclo-MAV utilizes two cycloidal rotors, providing thrust, propulsion, and control. Complete vehicle weight is 240 grams. Based on the experimental results, it is feasible to construct a micro air vehicle using cycloidal propulsion

Omnidirectional vision with frontal stereo

This study describes a novel imaging system that can be used as a front end for a vision system for guidance of unmanned aerial vehicles. A single camera and a combination of three specially designed reflecting surfaces axe used to provide (a) complete onmidirectional vision with no frontal blind zone and (b) stereo range within a frontal field. Important features are (i) the use of a single camera, which, apart from minimising cost, eliminates the need for alignment and calibration of multiple cameras; and (ii) a novel approach to stereoscopic range computation that uses a single camera and a circular baseline to overcome potential aperture problems

Omnidirectional vision with frontal stereo

This study describes a novel imaging system that can be used as a front end for a vision system for guidance of unmanned aerial vehicles. A single camera and a combination of three specially designed reflecting surfaces are used to provide (a) complete omnidirectional vision with no frontal blind zone and (b) stereo range within a frontal field. Important features are (i) the use of a single camera, which, apart from minimising cost, eliminates the need for alignment and calibration of multiple cameras; and (ii) a novel approach to stereoscopic range computation that uses a single camera and a circular baseline to overcome potential aperture problems