Aerodynamic Effect of Wrist Folding on Passerines in Hovering Flight with a Multi-articulated Flapping-wing Robot

Abstract

　　In this study a novel multiarticulate flapping-wing robot with five degrees of freedom on each wing was designed and fabricated to replicate hovering motion of passerines for force measurement and PIV experiments Recent years several researchers have focused on exploring the aerodynamic characteristics of insects and also some simplified model of birds However birds like passerines perform much more complicated wing kinematics which are rarely tested The detailed aerodynamic effect of wings with higher degrees of freedom still remains to be further investigated Two modified wing trajectories from previous observed wing kinematics of passerines were experimented in this research to investigate the aerodynamic differences one with a larger folding amplitude similar to that of real passerines and one with only half the amplitude Kinematics of the robot was verified utilizing direct linear transformation (DLT) which confirmed that the wing trajectories had high correlation with the desired motion According to the lift force measurements 4 phases of the wingbeat cycle were characterized and elaborated through camera images and flow visualization results We found that although less folding caused higher negative lift during upstrokes it also induced greater lift at the initial downstroke through ‘wake capture’ which ended up producing higher cycle-averaged lift However this does not imply that less folding benefits flight performance Further investigation such as the horizontal force or power requirement could be a helping hand to more thoroughly understand the pros and cons of folding on passerines during hovering flight

Date of Award	2020
Original language	English
Supervisor	Szu-I Yeh (Supervisor)