Engineering Commons^™

A Multi-Regulator Sliding Mode Control Strategy For Output-Constrained Systems, Hanz Richter

Mechanical Engineering Faculty Publications

This paper proposes a multi-regulator control scheme for single-input systems, where the setpoint of a regulated output must be changed under the constraint that a set of minimum-phase outputs remain within prescribed bounds. The strategy is based on a max–min selector system frequently used in the aerospace field. The regulators used for the regulated and limited outputs are of the sliding mode type, where the sliding variable is defined as the difference between an output and its allowable limit. The paper establishes overall asymptotic stability, as well as invariance properties leading to limit protection. The design methodology is illustrated with …

An Automated Test Station Design Used To Verify Aircraft Communication Protocols, Joshua Berrian

Master's Theses

Requirements verification is typically the costliest part of the systems engineering design process. In the commercial aircraft industry, as the software and hardware design evolves, it must be verified to conform to requirements. In addition, when new design releases are made, regression analysis must be performed which usually requires repeat testing. To streamline verification, a suite of automated verification tools is described in this document which can reduce the test effort. This test suite can be qualified to be used to verify systems at any DO-178B design assurance level. Some of the software tools are briefly described below.

There are …

Experimental Investigation And Cfd Simulation Of Active Damping Mechanism For Propellant Slosh In Spacecraft Launch Systems, Dhawal Leuva

Doctoral Dissertations and Master's Theses

Motion of propellant in the liquid propellant tanks due to inertial forces transferred from actions like stage separation and trajectory correction of the launch vehicle is known as propellant slosh. If unchecked, propellant slosh can reach resonance and lead to complete loss of the spacecraft stability, it can change the trajectory of the vehicle or increase consumption of propellant from the calculated requirements, thereby causing starvation of the latter stages of the vehicle. Predicting the magnitude of such slosh events is not trivial. Several passive mechanisms with limited operating range are currently used to mitigate the effects of slosh. An …

Integration Of Unmanned Aerial Systems In Class E Airspace: The Effect On Air Traffic Controller Workload, Jeeja S. Vengal

Doctoral Dissertations and Master's Theses

As technology rapidly advances and our imagination is no longer fantasy but instead reality, the aviation community needs to concentrate on the harsh truth of airspace safety. In the situation of integrating unmanned aerial systems (UASs) into the National airspace, UASs outside of terminal areas would generally be permitted to fly their preferred routes, and self-separate, with minimal intervention from air traffic control. From an air traffic control perspective, the integration could raise a number of human performance problems including workload extremes and passive-monitoring demands. One fundamental requirement for operation in the National Air Space is to preserve the safety …

Development Of A Higher-Order Navier-Stokes Solver For Transient Compressible Flows, Arjun Vijayanarayanan

Doctoral Dissertations and Master's Theses

A higher‐order density based Navier‐Stokes solver was developed for 2‐Dimensional flows using the finite volume approach. The Van leer flux‐splitting technique was used to calculate the fluxes. The second‐order spatial accuracy was achieved using the variable extrapolation method developed by Van leer called the Montone Upstream Centered Scheme for Conservation Laws (MUSCL) approach. The code development was done using Matlab. The code was verified using two validation cases. Firstly, subsonic, transonic, and supersonic flows over the 2‐D bump were simulated, and the results of the code were compared to the results from Fluent. Secondly, the shock‐tube problem was chosen, and …

Effective Approach For Estimating Turbulence-Chemistry Interaction In Hypersonic Turbulent Boundary Layers, L. (Lian) Duan, M. P. Martín

Mechanical and Aerospace Engineering Faculty Research & Creative Works

An effective approach for estimating turbulence-chemistry interaction in hypersonic turbulent boundary layers is proposed, based on "laminar- chemistry" Reynolds-averaged Navier-Stokes mean flow solutions. The approach combines an assumed probability density function with a temperature fluctuation scaling, which provides the second moment for specifying the shape of the probability density function. As a result, the effects of temperature fluctuation on chemical production rates can be estimated without solving an additional moment evolution equation. The validity of this method is demonstrated using direct-numerical-simulation data. This approach can be used to identify regions with potentially significant turbulence-chemistry interaction in hypersonic boundary layers and …

State Of The Art Of Piloted Electric Airplanes, Nasa's Centennial Challenge Data And Fundamental Design Implications, Lori Anne Costello

Doctoral Dissertations and Master's Theses

The purpose of this study was to determine the current state of the electric airplane as primarily defined by results from NASA's Green Flight Challenge Competition. New equations must be derived in order to determine the endurance and range for electric airplanes since the standard equations depend upon weight change over a flight and the weight of an electric airplane does not change. These new equations could then be solved for the optimal velocity and altitude which were the two driving factors that could change range and endurance for a given airplane configuration. The best velocity for range and endurance …

Innovative Double Bypass Engine For Increased Performance, Sanjivan Manoharan

Doctoral Dissertations and Master's Theses

Engines continue to grow in size to meet the current thrust requirements of the civil aerospace industry. Large engines pose significant transportation problems and require them to be split in order to be shipped. Thus, large amounts of time have been spent in researching methods to increase thrust capabilities while maintaining a reasonable engine size. Unfortunately, much of this research has been focused on increasing the performance and efficiencies of individual components while limited research has been done on innovative engine configurations. This thesis focuses on an innovative engine configuration, the High Double Bypass Engine, aimed at increasing fuel efficiency …

The Propulsive Design Aspects On The World’S First Direct Drive Hybrid Airplane, Ankit Nanda

Doctoral Dissertations and Master's Theses

The purpose of this thesis is to design a safe technology demonstrator by implementing a direct drive propulsion system for a gas-electric hybrid aircraft. This system was integrated on the Embry-Riddle Eco-Eagle for the Green Flight Challenge 2011. The aim of the system is to allow the pilot to use the electric motor as an independent power source to fly the aircraft once at cruise altitude, while having a gas engine to allow for higher power capability.

The system was designed to incorporate the motor and the motor control unit provided by Flight Design and Drivetek AG alongside a Rotax …

Numerical Analysis Of Gun Barrel Pressure Blast Using Dynamic Mesh Adaption, Sathish Xavier

Doctoral Dissertations and Master's Theses

A Computational Fluid Dynamics (CFD) method has been applied to simulate the pressure blast of the projectile which is launched from a barrel and to investigate the pressure distribution and sound pressure level (dB) along different positions away from the gun axis and towards the fuselage of the aircraft. Fluent was employed to simulate the unsteady flow using dynamic mesh with moving boundary. Most CFD based ballistics-model requires additional thermodynamic functions which must be derived from the Noble-Abel equation of state. The unsteady, axisymmetric Navier Stokes equation systems were numerically solved using the Advection Upstream Splitting Method (AUSM) scheme; with …

Aviation Wildlife Hazard - Uk Flight Safety Committee, Paul F. Eschenfelder

Paul F. Eschenfelder

No abstract provided.

Design And Control Of Flapping Wing Micro Air Vehicles, Michael L. Anderson

Theses and Dissertations

Flapping wing Micro Air Vehicles (MAVs) continues to be a growing field, with ongoing research into unsteady, low Re aerodynamics, micro-fabrication, and fluid-structure interaction. However, research into flapping wing control of such MAVs continues to lag. Existing research uniformly consists of proposed control laws that are validated by computer simulations of quasi-steady blade-element formulae. Such simulations use numerous assumptions and cannot be trusted to fully describe the flow physics. Instead, such control laws must be validated on hardware. Here, a novel control technique is proposed called Bi-harmonic Amplitude and Bias Modulation (BABM) which can generate forces and moments in 5 …

Evaluation Of Nanocomposites For Shielding Electromagnetic Interference, Kenneth Y. Chong

Theses and Dissertations

Numerous efforts are ongoing to research and develop nanocomposite materials for space applications. Current composite spacecraft materials are nonconductive and require costly shielding materials to be applied in order to protect spacecraft from the harmful effects caused by electromagnetic interference (EMI), which is a by-product of exposure to the space environment. Conductive fillers (nanofibers) are being employed in composites to produce nanocomposites to reduce the dry weight of space vehicles while providing sufficient protection against EMI. This eliminates the need to apply secondary shielding materials to spacecraft. This thesis studied a nanocomposite consisting of Cycom 5575-2 glass with multi-walled carbon …

Two-Dimensional, Time-Dependent Plasma Structures Of A Hall Effect Thruster, David Liu

Theses and Dissertations

The Hall thruster is a type of electric propulsion utilized by satellites to perform a wide variety of missions ranging from station keeping, orbital maneuvers, and even deep space propulsion. In order to accommodate the multitude of missions it also has a wide assortment of sizes and power configurations which can range from approximately an inch in diameter at 20 W to a couple of feet in diameter at 1.5 kW. Additionally, this electro-static device provides high specific impulse without the added weight penalty associated with conventional chemical thrusters. It supplies this high specific impulse by ionizing a gas such …

Stochastic Real-Time Optimal Control: A Pseudospectral Approach For Bearing-Only Trajectory Optimization, Steven M. Ross

Theses and Dissertations

A method is presented to couple and solve the optimal control and the optimal estimation problems simultaneously, allowing systems with bearing-only sensors to maneuver to obtain observability for relative navigation without unnecessarily detracting from a primary mission. A fundamentally new approach to trajectory optimization and the dual control problem is developed, constraining polynomial approximations of the Fisher Information Matrix to provide an information gradient and allow prescription of the level of future estimation certainty required for mission accomplishment. Disturbances, modeling deficiencies, and corrupted measurements are addressed with recursive updating of the target estimate with an Unscented Kalman Filter and the …

Increasing The Performance Of A Sliding Discharge Actuator Through The Application Of Multiple Potentials, Steven D. Seney Jr.

Theses and Dissertations

This work encompasses a comparison between a sliding discharge DBD actuator with grounded and AC biased sliding electrode driven at kHz frequency. The induced velocity in the bulk flow was recorded with PIV and compared for multiple potential splits between two test configurations and a baseline sliding discharge actuator over three test phases. In the first test phase, varying potential splits were examined between the primary and secondary electrode with the sliding electrode grounded. The potential splits induced a thicker induced jet than the baseline case with similar peak velocities on the order of 1.25 m/s at the 61 mm …

Vortex Shedding From Elongated Bluff Bodies, Zachary J. Taylor

Electronic Thesis and Dissertation Repository

As the spans of suspension bridges increase, the structures become inherently flexible. The flexibility of these structures, combined with the wind and particular aerodynamics, can lead to significant motions. From the collapse due to flutter of the Tacoma Narrows Bridge to the case of vortex-induced vibrations (VIV) of the Storebælt Bridge, it is evident that a better understanding of the aerodynamics of these geometries is necessary. The work herein is motivated by these two problems and is presented in two parts.

In the first part, the focus is on the physical mechanisms of vortex shedding. It is shown that the …

Effect Of The Thickness Of Undoped Gan Interlayers Between Multiple Quantum Wells And The P-Doped Layer On The Performance Of Gan Light-Emitting Diodes, T. Lu, S. Li, K. Zhang, C. Liu, Y. Yin, L. Wu, H. Wang, Xiaodong Yang, G. Xiao, Y. Zhou

Mechanical and Aerospace Engineering Faculty Research & Creative Works

InGaN based light-emitting diodes (LEDs) with undoped GaN interlayer of variant thicknesses grown by metal-organic chemical vapor deposition technique have been investigated. It was found that the thickness of undoped GaN interlayers affected LEDs' performance greatly. The LED with 50 nm undoped GaN interlayer showed higher light output power and lower reverse-leakage current compared with the others at 20 mA. Based on electrical and optical characteristics analysis and numerical simulation, these improvements are mainly attributed to the improvement of the quality of depletion region by inserting an undoped GaN layer, as well as reduction of the Shockley-Read-Hall recombination in InGaN/GaN …

Flow Characteristics Of The Renovated Cal Poly 3 X 4 Ft Subsonic Wind Tunnel, Mathew L. Thomas, Dorian V. Pandey, Jason N. Nguyen

Aerospace Engineering

This paper investigates the flow characteristics of the renovated Cal Poly 3 x 4 ft subsonic wind tunnel. The IFA 300 constant-temperature anemometer along with a cross-plane X-wire dual-sensor probe was used to measure the mean velocity and turbulence intensity of the tunnel flow and part of the turbulent boundary layer at one section of the tunnel. Because of the malfunction of one channel of the IFA 300, only one wire of the dual sensor probe was calibrated for the measurements. The probe was then placed in a streamlined probe holder mounting on the traverse inside the wind tunnel. The …

Mission Performance Considered As Point Performance In Aircraft Design, Robert A. Mcdonald

Aerospace Engineering

The cruise or loiter performance of an aircraft is intimately tied to its wing loading and its thrust-to-weight ratio. Paradoxically, mission performance is often not considered when these fundamental aircraft parameters are determined in conceptual design. In this paper, the traditional constraint diagram is extended to include contours of range or endurance parameter. These performance metrics represent the mission-performance capability of the aircraft without sizing the aircraft to a particular mission. This gives the designer an immediate and intuitive understanding of the tradeoff between the point and mission performance of the aircraft. The potential freedom for the designer to choose …

Dual Operation Human-Machine Interface, Petr Krupansky, Jiri Vasek, Claudia Keinrath, Michael C. Dorneich, Larry Ball

Michael C. Dorneich

The paper describes a Dual Operation concept and one example of its design. The amount of information the pilot must process, already high in current Air Traffic Management (ATM) operation, will increase dramatically in the envisioned future ATM environment. New pilot functions will require new levels of automation. Thus cockpit displays must be modified in order to facilitate the pilot's future tasks and to manage the increased information available. One approach to these challenges is to adaptively modify the displays depending on current pilot tasks and situation. Simply adding functionality to current day displays has the potential to reach an …

Mission Performance Considered As Point Performance In Aircraft Design, Robert A. Mcdonald

Robert A. McDonald

The cruise or loiter performance of an aircraft is intimately tied to its wing loading and its thrust-to-weight ratio. Paradoxically, mission performance is often not considered when these fundamental aircraft parameters are determined in conceptual design. In this paper, the traditional constraint diagram is extended to include contours of range or endurance parameter. These performance metrics represent the mission-performance capability of the aircraft without sizing the aircraft to a particular mission. This gives the designer an immediate and intuitive understanding of the tradeoff between the point and mission performance of the aircraft. The potential freedom for the designer to choose …

Vibration-Based Health Monitoring Of Multiple-Stage Gear Train And Differential Planetary Transmission Involving Teeth Damage And Backlash Nonlinearity, Andrew Patrick Sommer

Master's Theses

The objective of this thesis is to develop vibration-based fault detection strategies for on-line condition monitoring of gear transmission systems. The study divides the thesis into three sections. First of all, the local stresses created by a root fatigue crack on a pinion spur gear are analyzed using a quasi-static finite element model and non-linear contact mechanics simulation. Backlash between gear teeth which is essential to provide better lubrication on tooth surfaces and to eliminate interference is included as a defect and a necessary part of transmission design. The second section is dedicated to fixed axis power trains. Torsional vibration …

Designing Propulsion Systems For Future Aerospace Applications, Nihad E. Daidzic

Aviation Department Publications

No abstract provided.

Stoichiometric H2ice With Water Injection And Exhaust And Coolant Heat Recovery Through Organic Rankine Cycles, Alberto Boretti

Mechanical and Aerospace Engineering Faculty Research & Creative Works

High power density, stoichiometric, turbocharged, directly injected engines with water injection and a three-way catalytic converter after treatment have been proposed as one of the most promising H2ICE [1]. These throttle-controlled engines have top brake efficiencies exceeding 40%, but large penalties in efficiency reducing the load with 1 bar BMEP values approaching 10%. Recovery of the large amount of fuel energy lost in the coolant especially at low loads as well as the fuel energy lost in the exhaust that is significant at high loads and speeds may push not only the top brake efficiencies to exceed the 45% mark, …

Advances In Hydrogen Compression Ignition Internal Combustion Engines, Alberto Boretti

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The turbocharged direct injection lean burn Diesel engine is the most efficient engine now in production for transport applications within heavy duty trucks applications full load brake engine thermal efficiencies up to 45% and reduced penalties in brake engine thermal efficiencies reducing the load by the quantity of fuel injected. the secrets of this engine's performances are the high compression ratio and the lean bulk combustion mostly diffusion controlled in addition to the partial recovery of the exhaust energy to boost the charging efficiency. the major downfalls of this engine are the carbon dioxide emissions and the depletion of natural …

Femtosecond Laser Fabricated All-Optical Fiber Sensors With Ultrahigh Refractive Index Sensitivity: Modeling And Experiment, Lan Jiang, Longjiang Zhao, Sumei Wang, Jinpeng Yang, Hai Xiao

Mechanical and Aerospace Engineering Faculty Research & Creative Works

All-optical fiber sensors based on ultracompact fiber inline Mach-Zehnder interferometer (MZI) are fabricated by side-ablating a Ushape microcavity in a single-mode optical fiber with the fiber core partially removed using femtosecond (fs) laser pulses, in which the two light paths are accordingly formed in the remaining D-type fiber core and the U-shape microcavity. Beam propagation method (BPM) analysis is utilized to illustrate the dependences of good transmission spectra on parameters including the ablation depth, ablation length and the refractive index of Ushape microcavity, which gives some guidelines to optimize parameters for fs laser micromachining and predicts RI (refractive index) sensitivities …

Challenges For The Accurate Determination Of The Surface Thermal Condition Via In-Depth Sensor Data, Bryan Scott Elkins

Doctoral Dissertations

The overall goal of this work is to provide a systematic methodology by which the difficulties associated with the inverse heat conduction problem (IHCP) can be resolved. To this end, two inverse heat conduction methods are presented. First, a space-marching IHCP method (discrete space, discrete time) utilizing a Gaussian low-pass filter for regularization is studied. The stability and accuracy of this inverse prediction is demonstrated to be more sensitive to the temporal mesh than the spatial mesh. The second inverse heat conduction method presented aims to eliminate this feature by employing a global time, discrete space inverse solution methodology. The …

Sitting In The Pilot's Seat: Optimizing Human-Systems Interfaces For Unmanned Aerial Vehicles, Steven Michael Queen, Kurt Sanner

STAR Program Research Presentations

One of the pilot-machine interfaces (the forward viewing camera display) for an Unmanned Aerial Vehicle called the DROID (Dryden Remotely Operated Integrated Drone) will be analyzed for optimization. The goal is to create a visual display for the pilot that as closely resembles an out-the-window view as possible. There are currently no standard guidlines for designing pilot-machine interfaces for UAVs. Typically, UAV camera views have a narrow field, which limits the situational awareness (SA) of the pilot. Also, at this time, pilot-UAV interfaces often use displays that have a diagonal length of about 20". Using a small display may result …

The Biglobal Instability Of The Bidirectional Vortex, Joshua Will Batterson

Doctoral Dissertations

State of the art research in hydrodynamic stability analysis has moved from classic one-dimensional methods such as the local nonparallel approach and the parabolized stability equations to two-dimensional, biglobal, methods. The paradigm shift toward two dimensional techniques with the ability to accommodate fully three-dimensional base flows is a necessary step toward modeling complex, multidimensional flowfields in modern propulsive applications. Here, we employ a two-dimensional spatial waveform with sinusoidal temporal dependence to reduce the three-dimensional linearized Navier-Stokes equations to their biglobal form. Addressing hydrodynamic stability in this way circumvents the restrictive parallel-flow assumption and admits boundary conditions in the streamwise direction. …