Considerations for temperature sensor placement on rotary-wing unmanned aircraft systems

Abstract

Integrating sensors with a rotary-wing unmanned aircraft system (rwUAS) can introduce several sources of biases and uncertainties if not properly accounted for. To maximize the potential for rwUAS to provide reliable observations, it is imperative to have an understanding of their strengths and limitations under varying environmental conditions. This study focuses on the quality of measurements relative to sensor locations on board rwUAS. Typically, thermistors require aspiration and proper siting free of heat sources to make representative measurements of the atmosphere. In an effort to characterize ideal locations for sensor placement, a series of experiments were conducted in the homogeneous environment of an indoor chamber with a pedestal-mounted rwUAS. A suite of thermistors along with a wind probe were mounted inside of a solar shield, which was affixed to a linear actuator arm. The actuator arm was configured such that the sensors within the solar shield would travel underneath the platform into and out of the propeller wash. The actuator arm was displaced horizontally underneath the platform while the motors were throttled to 50 %, yielding a time series of temperature and wind speed that could be compared to temperatures being collected in the ambient environment. Results indicate that temperatures may be biased in the order of 0.5–1.0 ∘C and vary appreciably without aspiration, sensors placed close to the tips of the rotors may experience biases due to frictional and compressional heating as a result of turbulent fluctuations, and sensors in proximity to motors may experience biases approaching 1 ∘C. From these trials, it has been determined that sensor placement underneath a propeller on an rwUAS a distance of one quarter the length of the propeller from the tip is most likely to be minimally impacted from influences of turbulence and motor, compressional, and frictional heating while still maintaining adequate airflow. When opting to use rotor wash as a means for sensor aspiration, the user must be cognizant of these potential sources of platform-induced heating when determining sensor location.

Publication
Atmospheric Measurement Techniques, 11, 5519–5530
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Brian Greene
Brian Greene
Ph.D. Student

My research focuses on developing and utilizing uncrewed aircraft systems (UAS) to collect observations in the planetary boundary layer. This application includes instrumentation, electronics, flight mechanics, thermodynamics, fluid mechanics, and signal processing. I also model the stable boundary layer using large-eddy simulations to better understand how observations from UAS can best represent turbulence across the simulated domain.

Antonio R. Segales
Antonio R. Segales
PhD Candidate

My research centers around developing small unmanned aircraft systems for adaptive atmospheric sampling which involves CAD modeling, systems optimization, hardware and software integration, and control theory. I have led the design of the CopterSonde series of vehicles, which is used to perfrom controlled and targeted weather sampling at high temporal and spatial resolutions. I am also advising other projects in which sensor integration or new UAS are required.