Simultaneous Wind Field Measurement with a swarm of multicopter UAV

Abstract:

Measuring wind on a wide range of scales is a key point for the understanding of dynamics in the in the atmospheric boundary layer (ABL). There are several systems and methods for measuring the wind velocity, e.g. remote sensing (i.e. lidar, sodar and radar), meteorological masts with cup or sonic anemometers, or aircraft systems (manned and unmanned). They all lack the possibility to measure simultaneously at multiple, flexible measurement points in space. In our approach, multicopter UAVs are used as measurement systems. For measuring wind flow fields on small scales, a swarm of multicopters is proposed. Predefined flight paths and hover positions can be programmed for all single instances of the swarm and commanded to each system through a common controller. The sensors of the flight controller are used for obtaining the wind velocity. Different approaches are discussed to measure the wind. The UAVs are additionally equipped with temperature and humidity sensors.

To evaluate the performance of the chosen UAV hardware, tests were performed in a wind tunnel at the University of Oldenburg, the wind energy test site Risoe of the Danish Technical University (DTU) and the meteorological observatory Lindenberg of the German Meteorological Service (DWD).

The wind tunnel tests revealed that in laminar wind tunnel flow, the UAVs can easily withstand wind speeds up to 16 m/s. These findings were confirmed through test flights at the DTU test site in a turbulent ABL and in comparison to sonic anemometers on a 70-m mast. More extensive test flights with a swarm of 10 systems were conducted in July 2020 at MOL-RAO with several flight patterns. A vertical array of drones close to the 99 m meteorological mast was used to compare wind, temperature and humidity levels at multiple levels. To evaluate the differences between the measurements of the individual UAVs, all systems were flown at same height and compared with sonic anemometer data at that same height. Additionally, a 2-D field of 3x3 UAVs was flown. This pattern was placed to coincide with the measurement plane of a vertically scanning Doppler wind lidar, and thus allows comparing the flow structures measured with this system. We will present preliminary results of the measurement campaign as well as lessons-learned for the setup and deployment of a UAV swarm for atmospheric sciences.