A Study of Autorotation: Samara Seed Pods and Tethered Autogyros

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

Design and Modeling of Smartphone Controlled Vehicle

While many have worked on the transition phases of more popular hybrid aerial vehicle configurations, In this paper, we explore a novel multi-mode hybrid Unmanned Aerial Vehicle (UAV). Due to its expanded flying range and adaptability, hybrid aerial vehicles—which integrates two or more operating configurations—have become more and more widespread. The stages of transition between these modes are reasonably important whether there are two or more flight forms present. Whereas numerous have worked on the early stages of more widely used hybrid aerial vehicle types, in this paper a brand-new multi-mode hybrid UAV will be investigated. In order to fully exploit the vehicle's propulsion equipment and aerodynamic surfaces in both a horizontal cruising configuration and a vertical hovering configuration, we combine a tailless fixed-wing with a four-wing monocopter. By increasing construction integrity over the whole operational range, this lowers drag and wasteful mass when the aircraft is in motion in both modes. The transformation between the two flight states can be carried out in midair with just its current flying actuators and sensors. Through a ground controller, this vehicle may be operated by an Android device

An Analytical Investigation of Flapping Wing Structures for Micro Air Vehicles

An analytical model of flapping wing structures for bio-inspired micro air vehicles is presented in this dissertation. Bio-inspired micro air vehicles (MAVs) are based on insects and hummingbirds. These animals have lightweight, flexible wings that undergo large deformations while flapping. Engineering studies have confirmed that deformations can increase the lift of flapping wings. Wing flexibility has been studied through experimental construction-and-evaluation methods and through computational numerical models. Between experimental and numerical methods there is a need for a simple method to model and evaluate the structural dynamics of flexible flapping wings. This dissertation's analytical model addresses this need. A time-periodic assumed-modes beam analysis of a flapping, flexible wing undergoing linear deformations is developed from a beam analysis of a helicopter blade. The resultant structural model includes bending and torsion degrees of freedom. The model is non-dimensionalized. The ratio of the system's structural natural frequency to wingbeat frequency characterizes its constant stiffness, and the amplitude of flapping motion characterizes its time-periodic stiffness. Current flapping mechanisms and MAVs are compared to biological fliers on the basis of the characteristic parameters. The beam analysis is extended to develop an plate model of a flapping wing. The time-periodic stability of the flapping wing model is assessed with Floquet analysis. A flapping-wing stability diagram is developed as a function of the characteristic parameters. The analysis indicates that time-periodic instabilities are more likely for large-amplitude, high-frequency flapping motion. Instabilities associated with the first bending mode dominate the stability diagram. Due to current limitations of flapping mechanisms, instabilities are not likely in current experiments but become more likely at the operating conditions of biological fliers. The effect of structural design parameters, including wing planform and material stiffness, are assessed with an assumed-modes aeroelastic model. Wing planforms are developed from an empirical model of biological planforms. Non-linearities are described in the effect of membrane thickness on lift generation. Structural couplings due to time-periodic stiffness are identified that can decrease lift generation at certain wingbeat frequencies

Aeronautical Engineering: A cumulative index to the 1984 issues of the continuing bibliography

This bibliography is a cumulative index to the abstracts contained in NASA SP-7037(171) through NASA SP-7037(182) of Aeronautical Engineering: A Continuing Bibliography. NASA SP-7037 and its supplements have been compiled through the cooperative efforts of the American Institute of Aeronautics and Astronautics (AIAA) and the National Aeronautics and Space Administration (NASA). This cumulative index includes subject, personal author, corporate source, foreign technology, contract, report number, and accession number indexes