Wind Sensor Stability for Atmospheric Measurements using Unmanned Aircraft

In recent years, interest in collecting high resolution measurements within the atmospheric boundary layer (ABL) has greatly increased. There is a general lack of these measurements and current data models are not able to accurately resolve key ABL structures. Obtaining high resolutions measurements within the ABL, especially in urban areas, can greatly improve the forecasting of low-level winds. Recent works have explored the use of small unmanned aircraft systems (sUAS) that have different on-board sensors. These sensors can record various atmospheric properties, such as wind speed, temperature, pressure, and relative humidity. Depending on the design, sUAS can reach altitudes of several thousand feet, making them ideal for taking vertical profiles of the ABL. At Oklahoma State University (OSU), many of these vehicles are being built and tested for collecting ABL measurements. The Skateboard-1000 (SKB), a custom-built quadcopter, has an on-board wind sensor called the Trisonica Mini 2D Ultrasonic Anemometer. Ultrasonic anemometers utilize ultrasonic sound waves to measure wind speed and direction as the wind passes through a precise array of speakers and microphones. Since the propeller inflow velocity negatively impacts the reliability of the measurements, The vehicle has a gimbal for stability and is on a stand to put the sensor above. Keeping the vehicle steady is important for accurate data gathering but can be problematic during higher wind conditions. In conditions where high gusts or wind shear are present, the SKB can struggle to react quickly to the changes, thus leading to the anemometer to be at an unsteady attitude. In literature, hexacopter and octocopter configurations are inherently more stable than quadcopters and can react quicker in extreme wind conditions. This increased stability could allow for more accurate wind measurements from a gimbal-mounted anemometer in higher wind conditions that could be encountered at higher altitudes. To test this theory, the same anemometer set up was mounted on another aircraft, the Adaptive Remote-Controlled Hexacopter for Engineering Research (ARCHER), which is built in a hexacopter configuration. With a weight of 10.7 kg and a propeller diameter of 22 in, ARCHER is slightly larger than the SKB. These aircraft are flown to compare the wind data from two identical sensor systems on different aircraft configurations. The aircraft in these tests were flown at various altitudes alongside a Vaisala Windcube, which is a ground based. The recorded anemometer wind data, along with inertial measurement unit data from each vehicle will be gathered, along with the recorded wind speeds from the ground-based sensors. The collected data will be analyzed to evaluate vehicle performance under identical conditions and to investigate potential correlations between aircraft configurations and the accuracy of vehicle-derived data, considering the aircraft's overall stability in various wind conditions.