Aerodynamic Force Characterization of a Novel Variable Amplitude Flapping Wing Robot

Flapping-wing aerial vehicles (FWAVs) have long been inspired by the efficiency and maneuverability of bird flight. However, most existing FWAVs rely on fixed-amplitude geared flapping mechanisms, limiting their ability to adapt across flight regimes such as takeoff, cruising, and landing. To address this limitation, a novel Field-Oriented Control (FOC) cable-driven variable amplitude flapping mechanism has been developed, enabling dynamic control over both flapping frequency and amplitude. This study presents the first experimental evaluation of the aerodynamic forces generated by this biomimetic system at varying flapping amplitudes and frequencies. To quantify the aerodynamic performance of the flapping mechanism, a two-degree-of-freedom (2DOF) load cell measurement is taken capable of measuring cycle-averaged lift and thrust forces. A range of flapping amplitudes and frequencies is tested to assess how these parameters influence force production. The collected force data are processed to generate time-averaged lift and thrust plots as a function of stroke amplitude and frequency, providing critical insight into optimal operating conditions for flight. The results are compared with theoretical modeling for ideal amplitude and frequency in FWAV design and this study will inform future work flight testing the FWAV named K1 that utilizes the novel drive mechanism. The proposed and tested flapping methodology here aims to provide a robust framework for future ornithopter flapping mechanisms, pushing the field closer to achieving fully articulated, multi-modal flight akin to biological birds.