For those of you not familiar with the project we are a university team competing in the 2008 UAV Outback Rescue Challenge, for more information about our team visit our site: www.aessuav.org
On May 10th we attempted our first bottle drop from 400 feet. The bottle had an aluminum tab attached to it which was held by small servo at the center of gravity of the UAV. We took off under manual control and gained altitude, as the UAV flew it’s oval path autonomously, the bottle was released over the field. The first bottle we dropped was a 500mL Nalgene bottle, which failed miserably (see picture below).
With the water bottle attached, the flight characteristics were not affected, although takeoff distance was increased, the autopilot’s ability to control the UAV was not affected noticably. During these flights the winds were relatively high, ranging from 10 to 15 MPH, which made navigation for the UAV difficult, but the autopilot performed admirably. Though at times it was blown off the path, it returned quickly to the intended flight path. Several autonomous test flights were performed in the windy conditions, further demonstrating the robustness of our UAV platform.
Three more test flights were performed on May 15th, all of which included water bottle drops with different bottle designs that took into account lessons learned from the first test. Enclosures were developed for subsequent bottles that allowed them to survive the 400-foot drop. Data was also gathered about where the bottles landed and at what point they were released. With this data the theoretical and actual horizontal distance traveled were compared. After analysis it turned out that the horizontal distance traveled from two of the drops was consistent, this allowed a simple model to be developed for the trajectory of the bottle. During the final flight, aerial video of the bottle being released was also obtained from the onboard digital camera (see the video below).
These test flights provided valuable data about how the bottle’s trajectory is affected by the wind resistance, as well as about how the UAV platform handles moderate winds. The next crucial step will be to integrate the onboard computer along with the camera into the aircraft to allow testing of the system as a whole.