From "Flying Forever" by Ben Coughlan:
The Australian National University
College of Engineering & Computer Science
Solar Enrygy Series
Solar Unmanned Aircraft
Ben Coughlan (College of Engineering and Computer Science)DATE: 2012-01-19
TIME: 15:00:00 - 16:00:00
LOCATION: Ian Ross Seminar Room
Unmanned aircraft are becoming increasingly popular for use in defence, law enforcement and civilian applications. Many of these emerging applications require the aircraft to remain airborne for many hours, even days at a time. Such endurance usually requires very large and expensive aircraft. While battery and fuel cell technologies are improving and becoming more common on smaller aircraft, solar is the most promising energy that can be harvested from the environment while airborne. In combination with behavioural algorithms designed to optimise the energy usage of the aircraft and gain energy from air movement, solar energy is a required step on the path to persistent flight. Unmanned aircraft present unique challenges for deploying photovoltaic technologies and require some unconventional solutions.
The albatross can travel great distances
with very little energy using a technique
known as dynamic soaring. Unmanned Aerial Vehicles (UAVs) are used for things like aerial mapping, surveillance, atmo-
spheric observation, communication relays as well as various military applications. Many of these tasks could benefit from the ongoing or even persistent presence of a UAV or one with
a practically limitless range.
Aircraft have the ability to harvest solar and wind energy during flight to give them more speed, altitude or electrical energy. By managing these energies and balancing resources against mission objectives, aircraft can benefit from substantially increased performance and the possibility of persistent flight.
This project will focus primarily on producing a frame-work for developing, assessing and deploying small scale fixed wing aircraft capable of managing their own energy resources in balance with their given mission objectives. ...
Modelling Energy Flow
Like any physical system, an Aerial Vehicle is comprised of a number of energy sources, stores and sinks, and has methods for transforming this energy over various states. An energy source is external to the aircraft itself and supplies energy that can be harnessed and used to achieve various goals. This includes the sun which provides electrical energy harvested by photo-voltaic cells on the
surface of the aircraft and air movement in the forms of wind and rising warm air known as thermals, which can provide speed and/or altitude via techniques known as dynamic soaring and thermalling.
The energy flow within an aircraft system can be modelled as a directed graph. Each node represents either an energy source, transitional device (like a motor), or an energy sink. The edges of the graph can be annotated with the efficiency of the energy transition.
Experiments are performed on a commercially available airframe, the Alex F5B. The Alex F5B is constructed of and is made of composite materials to provide a very strong and stiff airframe. This airframe provides a very wide speed envelope allowing various techniques to be tested in various conditions.
The motor is capable of pulling the aircraft vertically at 100 km/h, however this is only used in short bursts to gain altitude. While gliding, the propeller folds flat against the fuselage to minimise drag.
The current payload is an EagleTree inertial data recorder and transmitter allowing the state of the aircraft to be viewed live on a base-station. The data recorded includes GPS, air-speed, accelerations, barometric altitude, servo positions and current draw from the battery. ...