Abstract
Traditional configurations for mounting Temperature–Humidity (TH) sensors on multirotor Unmanned Aerial Systems (UASs) often suffer from insufficient radiation shielding, exposure to mixed and turbulent air from propellers, and inconsistent aspiration while situated in the wake of the UAS. Descent profiles using traditional methods are unreliable (when compared to an ascent profile) due to the turbulent mixing of air by the UAS while descending into that flow field. Consequently, atmospheric boundary layer profiles that rely on such configurations are bias-prone and unreliable in certain flight patterns (such as descent). This article describes and evaluates a novel sensor housing designed to shield airborne sensors from artificial heat sources and artificial wet-bulbing while pulling air from outside the rotor wash influence. The housing is mounted above the propellers to exploit the rotor-induced pressure deficits that passively induce a high-speed laminar airflow to aspirate the sensor consistently. Our design is modular, accommodates a variety of other sensors, and would be compatible with a wide range of commercially available multirotors. Extensive flight tests conducted at altitudes up to 500 m Above Ground Level (AGL) show that the housing facilitates reliable measurements of the boundary layer phenomena and is invariant in orientation to the ambient wind, even at high vertical/horizontal speeds (up to 5 m/s) for the UAS. A low standard deviation of errors shows a good agreement between the ascent and descent profiles and proves our unique design is reliable for various UAS missions.
Highlights
High-resolution profiles of the Atmospheric Boundary Layer (ABL) are critical for obtaining measurements important for a range of microscale and mesoscale phenomena
Our evaluations focus on three fundamental contributions of the design: (1) reliable temperature–humidity sensor readings during both ascent and descent in vertical profiling missions at varying speeds; (2) invariance of the orientation of the housed sensors to ambient wind; and (3) the ability to accurately capture atmospheric phenomena when compared to a radiosonde
Filtering could wash out the difference in post-processing depending upon the details available in the observation
Summary
High-resolution profiles of the Atmospheric Boundary Layer (ABL) are critical for obtaining measurements important for a range of microscale and mesoscale phenomena. Recent technological advancements have enabled the use of Unmanned Aerial Systems (UASs) to perform targeted, controlled, and frequent profiles using fixed wings [4] and multirotors [5,6] Both fixed-wing and multirotor UASs offer distinct advantages over passive balloon and parachute systems in terms of the ease, frequency, and spatiotemporal resolution of observations. Sensors 2019, 19, 2481 a geometry that offers convenient placement for a variety of sensors, and a payload capacity that even permits heavier sensors (ultrasonic anemometer, particle counter, aerosol sensor, etc.) to be airborne Their relatively small launch/land footprint makes them suitable for use in remote locations without the need for runways [7]. Their use for a variety of profiling applications such as the measurement of Temperature–Humidity (TH) data [8,9], wind-estimation [10,11,12,13], air quality measurements [14,15], etc. has increased significantly in recent years
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