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Description
Propeller imbalance is one of the most frequent causes of excessive vibration in multicopter UAVs. It often occurs after a crash, a hard landing, or when the propeller clips an obstacle during flight, and the resulting vibration can reduce the maneuverability of the drone. Instead of using an accelerometer on each arm, which increases airframe mass and adds extra data channels that the flight controller must sample and process, this work aims to develop an arm structure that can sense its own vibration condition as part of the airframe. A 3D-printed insert is designed to fit inside the carbon tube arm, carrying a strip of carbon-based conductive PLA as the sensing element. The conductivity of this filament comes from a network of carbon nanofillers dispersed in the polymer. When the arm flexes under vibration, the filler network changes its configuration and causes a measurable resistance change. The insert is placed near the arm-to-center-plate joint, where bending strain from propeller-induced vibration is expected to concentrate. The main part is produced using standard FDM 3D printing, followed by surface finishing and electrode preparation on the sensing element. The sensor output is passed through a signal conditioning circuit before being read by a microcontroller, and the signal is analyzed in the time domain (RMS amplitude) and frequency domain (FFT, focusing on the 1× rotational frequency component) to distinguish balanced from imbalanced propeller conditions. This concept can be developed further for multicopter arms that monitor their own mechanical condition during flight, as a lightweight and low-cost option for in-flight structural health monitoring.
