Maple Samara-Inspired Monocopter: An Autorotative Study on Powered Descent

Abstract

Samara-inspired monocopters offer low disc loading and the prospect of stable descent with minimal actuation, yet the role of autorotative geometry in powered descent has received little direct attention. This thesis isolates that role by characterizing how an autorotative monocopter's descent behavior changes across a motor-input sweep under two initial conditions: released with pre-spin near its autorotative equilibrium, and released from rest far from it. A PLA wing was iteratively developed from a Norway maple CT scan into a stiffened, reliably autorotating wing and fitted with a brushed-motor circuit built around a Seeed XIAO NRF52840. The wing was tethered to restrict motion to the vertical axis and released from approximately 3.5 m inside a Vicon motion-capture volume. Five motor levels from 0% to 100% throttle were tested, each repeated five times per initial condition. A Python pipeline processed the Vicon trajectories, using an adaptive analysis window to exclude the release transient and tether arrest, and extracted descent rate, RPM, and coning angle over a consistent interval for every trial. The pipeline resolved three distinct dynamical regimes in both conditions: a low-throttle regime (near-autorotative behavior with pre-spin; sub-threshold behavior without), a thrust-modulated regime in which descent rate drops sharply while RPM rises modestly, and a thrust-dominated regime at full throttle where the two conditions converge on descent rate, RPM, and coning angle. The regime sequence shifts by one throttle step between conditions: the pre-spin wing enters thrust-modulated descent at 55% throttle, while the no pre-spin wing does not reach a comparable state until 70%. The core finding is that releasing the wing near its autorotative equilibrium has clear aerodynamic advantages at low motor inputs within the drop window tested. Pre-spin releases the wing near its autorotative equilibrium, giving the motor meaningful descent authority at low throttle settings where the no pre-spin wing has none, extending the usable control band and positioning the autorotative equilibrium as an active design parameter for lightweight, energy-constrained monocopters.