Fast-response hot-wire flow sensors for wind and gust estimation on UAVs

Abstract

Due to limitations in available sensor technology, unmanned aerial vehicles (UAVs) lack an active sensing capability to measure turbulence, gusts, or other unsteady aerodynamic phenomena. Conventional in situ anemometry techniques fail to deliver in the harsh and dynamic multirotor environment due to form factor, resolution, or robustness requirements. To address this capability gap, a novel, fast-response sensor system to measure a wind vector in two dimensions is introduced and evaluated. This system, known as `MAST' (for MEMS Anemometry Sensing Tower), leverages advances in microelectromechanical (MEMS) hot-wire devices to produce a solid-state, lightweight, and robust flow sensor suitable for real-time wind estimation onboard a UAV. The MAST uses five pentagonally-arranged microscale hot-wires to determine the wind vector's direction and magnitude. The MAST's performance was evaluated in a wind tunnel at speeds up to 5 m/s and orientations of 0°-360°. A neural network sensor model was trained from the wind tunnel data to estimate the wind vector from sensor signals. The average error of the sensor is 0.14 m/s for speed and 1.6° for direction. Furthermore, 95% of measurements are within 0.36 m/s for speed and 5.0° for direction. With a bandwidth of 570 Hz determined from square-wave testing, the MAST stands to greatly enhance UAV wind estimation capabilities and enable capturing relevant high-frequency phenomena in flow conditions.

FlowDrone: Wind Estimation and Gust Rejection on UAVs Using Fast-Response Hot-Wire Flow Sensors

“…In this section, we summarize our previous work [1] on designing the MAST: an omnidirectional flow sensor suitable for integration on multirotor UAVs. The MAST in this paper uses five hot-wire sensing elements arranged in a pentagonal configuration (Fig.…”

“…First, they are small (on the order of a few millimeters) and lightweight (on the order of a few grams). Second, they have very low latency (< 2ms) [1] and can operate at rates commensurate with typical drone control rates (> 500Hz). Third, they allow accurate realtime estimation of wind magnitude and direction [1].…”

“…Second, they have very low latency (< 2ms) [1] and can operate at rates commensurate with typical drone control rates (> 500Hz). Third, they allow accurate realtime estimation of wind magnitude and direction [1]. As such, we believe that MEMS-based airflow sensors can fill an important gap in sensing technology for multirotor drones.…”

Bio-inspired, sensitivity-enhanced, bi-directional airflow sensor for turbulence detection

“…Current airflow sensors are primarily designed to detect slow changes in steady airflow from a single direction using active methods such as thermal, 5,6 torque, 7 and drag force sensing. 8 However, these sensors are limited in identifying complex aerodynamic environments.…”

“…Another approach involves adding commercial sensor arrays to detect airflow information from multiple directions. 6,[19][20][21] However, these sensors are bulky, heavy, and consume excessive power. They are difficult to install on modern, multi-functional lightweight quadrotors that are increasingly miniaturized.…”