Design of UAV for photogrammetric mission in Antarctic area
The history of UAVs is relatively long and many such vehicles are in service for different tasks. They can be used even in environment, which is inhospitable for a human, e.g. in case of extreme temperature. Moreover, they can perform a task that is difficult or impossible for manned aircraft because of its size and usually relatively high airspeed. The photogrammetric tasks belong to this group, especially if we need to make the high resolution pictures during low level flight. The advantages of a small UAV for such missions are more evident if we want to investigate the natural environment, where there are wild animals. The paper presents the small UAV designed for special task, which is the counting of penguins in Antarctica. Inhabited area, extreme weather conditions, the fearfulness of penguins and the goal of the mission put up certain requirements for the UAV. It had to be a reliable, stable platform, which is able to take photogrammetric equipment and to perform precise flight to cover the whole investigated area. Design evolution A decade ago in Warsaw University of Technology a project of simple training glider (PW- USZATEK) was developed. The glider had wings placed on the high pylon, just to be able to operate in rough terrain where there are often no prepared landing strips or runways (like the hang-gliders taking-off from the mountain slopes). In order to investigate dynamic properties of such configuration and compare them with the results of calculations a scaled model of this glider was built. This model was later redesigned as the UAV platform for testing different propulsion systems. The skills gained during realization of this project became very helpful for the current project devoted to designing the UAV for photogrammetric missions, which has to operate from the area with many obstacles on the landing fields. The basic aim of photogrammetric mission is the orthophotomap, which consists of the set of orthophotos. There are several requirements for successful result of photogrammetric work: The optical axis of the camera should be vertical, The photo-shots should be in the same scale, which means that the flight level should be constant, The photo-shots frame should be overlapped in both – longitudinal and lateral directions, The flight trajectory should exactly follow a planned grid, and this requirement is not so easy to fulfil. Aerodynamic design The initial configuration was designed as glider with relatively small wing loading. For windy conditions in Arctic area such configuration could be very sensitive to gusts. Therefore, the span of main wing was reduced to obtain lower wing loading and also span of horizontal tail was reduced respectively to save similar stability margin. The airfoils for main wing were selected based on computation of basic performance and taking into account small Reynolds number (Re=500 000). Finally Eppler 205 airfoil was selected. The complex aerodynamic calculation for the modified configuration was made using panel code (PANUKL package). All characteristics, including stability derivatives were computed. Some damping derivatives with respect to acceleration (with respect to ) were computed using ESDU reports and handbook methods. Flying qualities The requirement of strong stable flight causes, that very good flying qualities are necessary. Therefore stability analysis was made in early stage of design using SDSA package. First static stability analysis was done. The results were satisfying and static margin was in range 15-35% of MAC. The dynamic analysis proved that, all modes of motion are stable in almost whole airspeed range and only phugoid can be unstable in small airspeed regime. First test flight confirmed good stability and correct flying qualities. Current state of the project and close future Currently two built UAVs called “PW-ZOOM” are on the trip to Antarctica. They will be used to investigate areas inhabited by penguins, starting from November 2014. First results are expected in the beginning of 2015.