Measuring the Wind Vector Using the Autonomous Mini Aerial Vehicle M2AV

TLDR

Wind is defined as the vector difference between aircraft inertial velocity and true airspeed, and the meteorological mini unmanned aerial vehicle (M2AV) was employed to measure this vector. True airspeed was derived from five‑hole probe pressure data and calibration polynomials, while inertial velocity, position, and attitude were estimated by a Kalman filter fusing GPS and INS data, and an in‑flight wind calibration corrected heading, pitch offset, and airspeed biases. The M2AV achieved remarkably fine temporal and spatial resolution, capturing turbulence up to 40 Hz, and after in‑flight calibration its mean horizontal and vertical wind estimates agreed well with simultaneous sodar and tower measurements.

Abstract

Abstract The meteorological mini unmanned aerial vehicle (M2AV) was used for measuring the meteorological wind. The wind is the vector difference between the aircraft speed relative to the earth (inertial velocity) and relative to the airflow (true airspeed). The latter was computed from five-hole-probe pressure measurements in combination with calibration–coefficient polynomials obtained during wind tunnel calibration. The aircraft inertial velocity, position, and attitude were calculated using a Kalman filter that combined data from a global positioning system (GPS) and an inertial navigation system (INS). The temporal (and spatial) resolution of the M2AV wind measurement is remarkably fine. An inertial subrange of locally isotropic turbulence can be measured up to 40 Hz (or 0.55 m at 22 m s−1 airspeed). The first M2AV wind estimation showed some systematic deviations compared to the expected values (like a constant mean wind in every flight direction). Therefore, an in-flight wind calibration technique was developed that corrects for the inaccuracy of the true heading, the constant offset of the pitch angle, and the underestimation of the true airspeed. The final adjusted wind measurements were verified during a field experiment at the measurement field of the German Meteorological Service, southeast of Berlin. The mean horizontal and vertical wind measured by the M2AV agreed well with simultaneous sodar and tower measurements.