Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (p. 83-85). Also available in print.

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

With increasing focus on climate change more research for net-zero emission are being made in the aviation industry.This project focuses on electric propulsion on a unmanned aerial vehicle (UAV) with a blended wing body (BWB) design. More specifically finding a solution for a propulsion system using electric ducted fan (EDF) engines for a scaled version of the KTH Aerospace project Green Raven. The system consists of a powerplant and power supply i.e engine(s) and a sufficient battery package. The goal is to find a solution to power this 7 kg aerial vehicle for 60 minutes with a consistent cruising speed of 30 m/s. To accomplish this an understanding of thrust and drag profile is essential in order to determine the requirements for the EDFs. Understanding the limitations of the scaled Green Raven is also necessary in order to provide a feasible solution for power supply. The result is to use 2x 50 mm EDF engines providing a total thrust of 16.7 Newtons that is integrated in the main body. To supply these engines two battery sets (one per EDF) composed of three different battery types have been chosen, giving a total capacity of 24 000 mAh for one hour flight time. This propulsion setup fulfils the requirements, though not without flaws because of the choice of integrating the EDFs. An alternative solution would be having the engines externally mounted in order to free up the space in the body for more efficient batteries.

Technology advances each day, with every advancement new and improved products are accompanied. Robots come in various shapes and sizes, from the size of a fly to the size of a human being. The purpose of this project is to further our understanding in how to build a robot, more specifically, a mono wheeled robot and design control systems enabling it to balance by itself. The robot is a one-wheeler with ducted fans on top. It is to balance with the help of the wheel in one direction and with ducted fans in the perpendicular direction.The robot succeeded in balancing with the wheel. However with help of the fans the robot only managed to balance for approximately 20 seconds. Analysing the frequency content from figures 5.2, 5.4, 5.3 resulted in finding frequencies under 1Hz being dominant in the output signals from the control system, observing this a clear oscillation frequency was only determined for the ducted fan system while the wheel system was non periodic. The study concluded that one cannot stabilize the control systems individually because that can lead to disturbances for the other. The results showed that even though the wheel’s control system was stable, it was affected by the second control system, causing disturbances. / För varje dag som går tar tekniken ett steg frammåt, hela tiden med nya och förbättrade produkter. Robotar kommer i olika former och storlekar, från storleken av en insekt till storleken av en människa. Syftet med detta projekt är att utvidga förståelsen över hur man bygger en robot, mer specifikt, en enhjulig robot samt hur man konstruerar ett reglersystem för att få roboten att balansera på egen hand. Roboten är en enhjuling med fläktar. Syftet är att bygga och programmera den till att balansera på egen hand, i ena riktningen med hjulet och i andra riktningen med fläktarna. Roboten lyckades balansera med hjälp av hjulet, men med fläktsystemet balancerade roboten endast i cirka 20 sekunder. Med hjäp av frekvenspspekrumen i figurer 5.2, 5.4, 5.3 försöktes en oscillationsfrekvens och periodtid tas fram, detta erhölls endast för fläktsystemet då hjulsystemet inte gav en tydlig oscillationsfrekvens. Slutsatsen som drogs var att det inte går att stabilisera de individuella systemen separat och sedan kombinera dem. Detta på grund av att det leder till att det ena systemet riskerar att agera som en störsignal till det andra systemet.