This work presents an exploration of autorotational behavior, observing naturally occurring structures to provide insight into the stability and design of autorotative mechanisms. A rotor is said to be in autorotation when, in the presence of airflow, a natural rotation generates lift to either suspend or slow the descent of a rotor. This phenomenon is observed in nature in the form of samaras, a seed pod morphology evolved in parallel by maple trees and many other organisms around the world. Simulation and experimental observation of samara vertical descent behavior provides insight into the stability of naturally evolved autorotative structures. A control-oriented model is presented to simulate the steady-state and dynamic behavior of single-winged samaras. The model is validated through experimentation and comparison to previous experimental data in the literature. This effort yields a compact model which allows for analytical exploration of design parameter bounds and stability. Autorotation provides a platform for development of unmanned aerial vehicles which can perform agile maneuvers and stable hovering in a power-efficient manner. The concept of tethered autogyros applies well to versatile surveillance platforms and high-altitude power generation; however, minimal prior literature exists on the tethered autogyro configuration. A generalized model is presented to explore the aerodynamic equilibrium space of autogyros in response to regenerative braking. Comparison with experimental data from the literature provides validation and visualizes the effects of varying inputs such as braking torque, wind speed, etc. This model is expanded to include the balancing forces of a catenary tether as well as the coupled aerodynamic and tether contributions within a wind field that varies with altitude in a physically accurate manner. Numerical methods are presented for solving aerodynamic equilibrium conditions and tether response coupling to explore the viability and practicality of high-altitude deployment for power generation as well as lower altitude extended and efficient flight of a smaller surveillance craft.
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Doctor of Philosophy (Ph.D.)
College of Engineering and Computer Science
Mechanical and Aerospace Engineering
Length of Campus-only Access
Doctoral Dissertation (Open Access)
McConnell, Jonathan, "A Study of Autorotation: Samara Seed Pods and Tethered Autogyros" (2022). Electronic Theses and Dissertations, 2020-. 1411.