Kinematics and Dynamics of Autorotating Samara Seeds Using High-Speed Imaging and Image Recognition Techniques
Nandeesh Hiremath, Shashwat Sparsh, Kai A. Ponting · 2024
Samaras belong to a class of fruit produced globally by various trees, most famously of the genus \textit{Acer} commonly known as Maples. They have evolved with a single auto-rotating wing, enabling them to spend more time suspended in the air, allowing the wind to carry them farther. Samaras have been studied extensively for decades for their naturally evolved wing structures and high aerodynamic performance. The auto-rotating characteristics of these seeds have been the subject of biological and aerodynamic studies. Biological studies have focused on using statistical studies of the distribution of fruit at the base of the seeds to quantify the effectiveness of auto-rotation. Aerodynamic studies have focused on utilizing rotorcraft design concepts to the falling motion of Samaras to quantify their performance. The general narrative provided by biologists and ecologists is that the single-bladed seeds enhance the flight characteristics, resulting in seed dispersal. However, such a claim is far from reality when the majority of the fallen seeds are found within a 20-foot radius of the mother tree. This begs the question, \textit{``a) Do the single-bladed seeds undergoing auto-rotation truly support the widely accepted claim of seed dispersal? b) Is there any peculiar morphological or flight characteristics that make a minority number of seeds fly far distances?"} These questions are the premise of this research, and we explore the kinematic and dynamic characteristics of a statistically large number of seed samples subjected to free fall. The flight characteristics of this naturally occurring phenomenon would be beneficial for modeling robotic systems for aerial delivery, large-scale seed dispersal, and even to the extent of terraforming Mars. The current work is limited to studying a statistically large number of seed samples to gauge the distributions of aerodynamic parameters like wing loading, aspect ratio, geometric twist, force, and moment coefficients. The work emphasizes using a single high-speed camera with mirror arrangements in order to capture frontal and bottom views of the falling Samara seeds. The paper comprises the image processing schemes implemented for uniquely identifying the position and orientation of the falling samaras.