Cracking nuts with a sledgehammer

 As part of the EndeAR research project, small UAVs shall be able to estimate the wind vector in their vicinity based on their flight attitude. To do this, you need not only the direction of movement in space, which is provided by an inertial measurement unit, but also the speed and direction of the inflow. That is why each UAV is equipped with two small multi-hole probes under the wings.
 Before use, the probes must undergo calibration. Unfortunately, due to ongoing construction work, the small calibration facility is currently not available, so that the probes have to be calibrated in the large wind tunnel. The set-up is actually a bit of an overkill and reminds of the proverbial sledgehammer for cracking nuts.
 Due to the use on the UAV, both the dimensions of the probes and the number of available pressure measurement channels are limited. For this reason, a rather unusual design with only four holes was used. The preliminary evaluation shows that there are no difficulties in approximating the calibration by polynomial functions. Before the free flight, a further calibration should be carried out in place, i.e. in the flow field of the aircraft and therefore again in the large wind tunnel.

© J. Frey