Engineering Commons^™

Aerothermodynamic Analysis Of A Mars Sample Return Earth-Entry Vehicle, Daniel A. Boyd

Mechanical & Aerospace Engineering Theses & Dissertations

Because of the severe quarantine constraints that must be imposed on any returned extraterrestrial samples, the Mars sample return Earth-entry vehicle must remain intact through sample recovery. Vehicles returning on a Mars-Earth trajectory will attain velocities exceeding any that have been experienced by prior space exploration missions, with velocities approaching 14 km/s. Velocities as high as these will encounter significant heating during atmospheric re-entry to Earth.

The purpose of this study has been to systematically investigate the aerothermodynamic challenges that will result from a Mars sample return, Earth-entry vehicle design. The goal was to enable efficient estimation of maximum stagnation …

Effects Of Automated Fiber Placement On High Strain Rate Compressive Response Of Advanced Composites, Alexander Trochez

Mechanical & Aerospace Engineering Theses & Dissertations

Automated Fiber Placement (AFP) technology shows great promise in manufacturing carbon fiber composite structures. However, intermittent defects occur in the process that can affect the overall mechanical performance of the structure. The aim of this work is to investigate the effects of deliberately placed principal defects (Gap, Overlap, and Fold) on the compressive response under quasistatic (strain rate ~10^-3 s^-1) and dynamic (strain rate ~10³ s-1) loading conditions. The controlled defects were placed at the laminate level in different orientations and depths. High strain rate compression experiments were conducted using a split Hopkinson pressure bar (SHPB) …

A Cost Effective Design For A Propeller Thrust/Torque Balance, Nicholas Barrett Sadowski

Mechanical & Aerospace Engineering Theses & Dissertations

Wind tunnel balances are used with aircraft models, propellers, and components to measure applied forces and moments. The design and manufacture of a balance is often for a specific test, test article and conditions. This paper discusses the theory, design, calibration, and testing of a new small propeller balance for use in a low-speed wind tunnel. The new balance is named the ODU15X15.

Theory discussed herein covers how the two measurement components, thrust and torque, affect the balance design. These loads generate strains which are in turn read by strain gages arranged in Wheatstone bridges. The design follows well known …

Volterra Series Approximation For Multi-Degree Of Freedom, Multi-Input, Multi-Output, Aircraft Dynamics, Alexander J. Chen

Mechanical & Aerospace Engineering Theses & Dissertations

An analytical model of a second order system is extended from a single-axis framework, to a multi-axis, multi-degree of freedom framework for a multiple input, multiple output system. This mathematical model is built from the variational approach of the Volterra series representation of nonlinear systems. The new representation describes the second order, oscillatory natural modes of a system, and shows how to organize the Volterra terms in intuitive ways. The constructed mathematical model aims to establish an organization of the Volterra kernels to allow for analytical cause and effect type analysis on system behavior.

To demonstrate the accuracy of the …

Learn-To-Fly Control System Design, Alexander Brent Streit

Electrical & Computer Engineering Theses & Dissertations

In order to improve aircraft flight control system development life cycle, new flight control techniques are being explored to allow the system to ``learn-to-fly" with limited a priori information of the aircraft's aerodynamic characteristics. One approach is to have a system identification process operating on-the-fly to generate mathematical models which can be used to update control laws. In this thesis, a wind tunnel experiment was conducted with a model aircraft set up to be free-to-roll, so system identification and control methods could be explored for a one-degree-of-freedom case. In particular this thesis covers the design of a novel control system …

Distributed Sensing And System Identification Of Cantilever Beams And Plates In The Presence Of Weak Nonlinearities, Patrick Sean Heaney

Mechanical & Aerospace Engineering Theses & Dissertations

While the mathematical foundation for modal analysis of continuous systems has long been established, flexible structures have become increasingly widespread and developing tools for understanding their mechanics has become increasingly important. Cantilever beams and plates, in particular, have been extensively studied due to their practical importance as approximations of more complex structures. The focus of this thesis is on understanding the dynamics of vibrating cantilever beams and plates through analytical and experimental investigation. Various models for the mechanics of these structures, of varying physical fidelity, are described and compared. A fiber optic sensing system is utilized to experimentally acquire distributed …

Design And Implementation Of An Artificial Neural Network Controller For Quadrotor Flight In Confined Environment, Ahmed Mekky

Mechanical & Aerospace Engineering Theses & Dissertations

Quadrotors offer practical solutions for many applications, such as emergency rescue, surveillance, military operations, videography and many more. For this reason, they have recently attracted the attention of research and industry. Even though they have been intensively studied, quadrotors still suffer from some challenges that limit their use, such as trajectory measurement, attitude estimation, obstacle avoidance, safety precautions, and land cybersecurity. One major problem is flying in a confined environment, such as closed buildings and tunnels, where the aerodynamics around the quadrotor are affected by close proximity objects, which result in tracking performance deterioration, and sometimes instability. To address this …

Human-Robot Collaborative Force-Controlled Micro-Drilling For Advanced Manufacturing And Medical Applications, Parimal Mahesh Prajapati

Mechanical & Aerospace Engineering Theses & Dissertations

Robotic drilling finds applications in diverse fields ranging from advanced manufacturing to the medical industry. Recent advances in low-cost, and human-safe, collaborative robots (e.g., Sawyer) are enabling us to rethink the possibilities in which robots can be deployed for such tedious and time-consuming tasks. This thesis presents a robotic drilling methodology with features of force-control enabled micro-drilling and human-robot collaboration to reduce programming efforts and enhance drilling performance. A Sawyer robot from Rethink Robotics, which offers safe physical interactions with a human co-worker, kinesthetic teaching, and force control, is used as the test bed. The robot’s end-effector was equipped with …

A Monolithic Internal Strain-Gage Balance Design Based On Design For Manufacturability, Thomas Ladson Webb Iii

Mechanical & Aerospace Engineering Theses & Dissertations

This paper proposes an alternative approach to internal strain-gage balance design driven by Design for Manufacturability (DFM) principles. The objective of this research was a reduction in fabrication time and, subsequently, cost of a balance by simplifying its design while maintaining basic stiffness and sensitivity. Traditionally, the National Aeronautics and Space Administration (NASA) Langley Research Center (LaRC) balance designs have relied on Electro-Discharge Machining (EDM), which is a precise but slow and, therefore, expensive process. EDM is chosen due to several factors, including material hardness, surface finish, and complex geometry, including blind cuts. The new balance design objectives require no …

Gust Alleviation System For General Aviation Aircraft, Lucas Coleman Mills

Mechanical & Aerospace Engineering Theses & Dissertations

A designed control motion scheme to improve passenger comfort in general aviation aircraft by reducing normal acceleration and pitch rate due to turbulence is investigated. An aerodynamic math model is created for ViGYAN’s Active Ride Improvement System flight article, a one-eighth scale Pilatus Porter PC-6 with conventional forward main wing, aft horizontal and vertical tails, and a single engine with tractor configuration. The test article incorporates a full-span gust flap and forward mounted gust sensor to mechanize the gust alleviation control system, and these features are present in the dynamic model. The model is a two degree of freedom linear …