A Lightweight, Compliant, Contact-Resistance-Based Airflow Sensor for Quadcopter Ground Effect Sensing

Sensors to measure quadcopter ground effect are often relatively large, heavy, and require significant power, which restricts their applicability when it comes to small quadcopters and other aircraft that require lightweight and non-obstructive solutions. This paper presents the design of an elastomeric contact-resistance-based airflow sensor to measure ground effect with a mass of approximately 0.04 g and a power draw of 42 μW when in operation. It uses a rigid flap attached to the top of a flexible conductive pillar (CNT/PDMS), which deflects with varying winds speeds. A simple model is presented to describe expected trends between air flow speeds and sensor deflection and is compared with a wind tunnel characterization of the sensor for varying airflows. The sensor is characterized in a wind tunnel to identify a minimum airflow necessary for sensor functionality. Finally, sensors are attached to a Crazyflie 2.0 (Bitcraze) quadcopter and tested for performance in detecting ground effect, where there is a clear trend between sensor output and the intensity of the turbulent flow, related to proximity to ground and thrust level.