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Flightlines, Vol. 11, No. 1, Jeffrey A. Johnson

Flightlines Newsletter

No abstract provided.

Utilization Of A Piezoelectric Polymer To Sense Harmonics Of Electromagnetic Torque, Jason Neely, Steven Pekarek, Daniel S. Stutts, Philip Beccue

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, the use of a piezoelectric polymer material to measure the harmonics of electromagnetic torque produced by a permanent magnet synchronous machine is described. The advantages of the polymer include low cost, durability, and flexibility. In addition, wide-bandwidth sensors are relatively easy to design and couple to drive system hardware for harmonic evaluation or to use in feedback-based control. To illustrate the use of the polymer, the electrical and mechanical properties of three sensors are described. The results of time-domain simulation and hardware experiments are used to validate that the voltage obtained from the sensors is linearly related …

Fifty Years Of Hypersonics: Where We've Been, Where We're Going, John J. Bertin, Russell M. Cummings

Aerospace Engineering

Hypersonic flight has been with us since 22 September 1963, when Robert M. White flew the North American X-15 at 4520 mph at an altitude of 354,200 ft—a Mach number of 6.7! This remarkable achievement was accomplished over six decades due to intensive research and development by a large number of scientists and engineers. In spite of that momentous achievement, designers have found the hypersonic environment to be harsh and non-forgiving. New programs since the 1960s have often uncovered the unknown unknowns, usually the hard way—early flights of new systems have often revealed problems of which the designers were …

Design And Development Of A Low-Cost High Range Resolution X-Band Radar, Paul C. Cantu

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

Synthetic Aperture Radar (SAR) is one of the main tools for microwave remote sensing because of its multi-dimensional high resolution characteristics and the capability to operate in nearly all weather conditions, day and night. The University of Nebraska-Lincoln (UNL) initiated the design and development of a low-cost airborne SAR in January 2001 to support our Airborne Remote Sensing Program. The objectives of this project are separated into various evolutionary stages. This thesis will focus on the initial phase of design and construction of an X-band high range resolution radar (HRR) using basic RF /microwave and digital components. The following stages …

Computational Challenges In High Angle Of Attack Flow Prediction, Russell M. Cummings, James R. Forsythe, Scott A. Morton, Kyle D. Squires

Aerospace Engineering

Aircraft aerodynamics have been predicted using computational fluid dynamics for a number of years. While viscous flow computations for cruise conditions have become commonplace, the non-linear effects that take place at high angles of attack are much more difficult to predict. A variety of difficulties arise when performing these computations, including challenges in properly modeling turbulence and transition for vortical and massively separated flows, the need to use appropriate numerical algorithms if flow asymmetry is possible, and the difficulties in creating grids that allow for accurate simulation of the flowfield. These issues are addressed and recommendations are made for further …

Multidisciplinary Applications Of Detached-Eddy Simulation To Separated Flows At High Reynolds Numbers, Scott A. Morton, Matt Steenman, Russell M. Cummings, James R. Forsythe, Kenneth E. Wurtzler, Kyle D. Squires, Shawn H. Woodson, Phillippe R. Spalart

Aerospace Engineering

We focus on multidisciplinary applications of detached-eddy simulation (DES), principally flight mechanics and aeroelasticity. Specifically, the lateral instability (known as abrupt wing stall) of the preproduction F/A-18E is reproduced using DES, including the unsteady shock motion. The presence of low frequency pressure oscillations due to shock motion in the current simulations and the experiments motivated a full aircraft calculation, which showed low frequency high-magnitude rolling moments that could be a significant contributor to the abrupt wing stall phenomenon. DES is also applied to the F-18 high angle of attack research vehicle (HARV) at a moderate angle of attack to reproduce …

Flightlines, Vol. 10, No. 2, Jeffrey A. Johnson

Flightlines Newsletter

No abstract provided.

Microstructural Study Of Nanoprecipitates In Rra Treated Al-7075 T6 Using Afm/Ufm/Stem, Samuel J.M. Kuhr, Margaret Pinnell, Daniel Eylon

Mechanical and Aerospace Engineering Faculty Publications

7075 T651 aluminum alloy is frequently used in aircraft applications for its high strength to weight ratio. However, aircraft parts made of this alloy have been plagued by stress corrosion cracking (SCC). Retrogression and re-aging (RRA) is a post T651 two-stage heat treatment that provides improved SCC resistance with minimal loss in tensile strength. In this study, various forms of microscopy and mechanical testing are used to investigate how the RRA process affects the microstructure.

The microscopic observations in this paper show that the precipitates in the aluminum alloy coarsen and that the grain boundary regions are depleted of copper …

Computational Simulation And Piv Measurements Of The Laminar Vortical Flowfield For A Delta Wing At High Angle Of Attack, Russell M. Cummings, Scott A. Morton, Stefan G. Siegel

Aerospace Engineering

The low-speed, laminar flowfield for a 70°-sweep delta wing is investigated. Solutions to the unsteady, three-dimensional, compressible Navier-Stokes equations were obtained on an unstructured grid to match results from an experiment performed in a water tunnel. The experiment was conducted with the delta wing at an angle of attack of 35° and the freestream flow at a root-chord Reynolds number of 40,700. The computational results are analyzed and compared with the experimental results in order to show how computations and experiments can be conducted in a synergistic fashion. Details about the primary vortex location, vortex burst, secondary vortex, and shear …

Des Grid Resolution Issues For Vortical Flows On A Delta Wing And An F-18c, Scott A. Morton, Mathew B. Steenman, Russell M. Cummings, James R. Forsythe

Aerospace Engineering

An assessment of unstructured grids for use in Detached-Eddy Simulations (DES) of vortical flowfields over two configurations, a 70 degree delta wing and an F-18C are presented. The role of the grid in detached eddy simulations of vortical flowfields, including complex features such as vortex breakdown, is assessed on a delta wing with comparison to wind tunnel data. Adaptive mesh refinement is applied to the delta wing grid to improve the focus region aft of the vortex breakdown where massively separated flow exists and unsteady pressures are generated that could impact the loads on vertical tails of more complex configurations. …

A Multifaceted Approach To The Aiaa Foundation Undergraduate Team Aircraft Design Competition, Russell M. Cummings, Aaron R. Byerley

Aerospace Engineering

A multifaceted, novel approach was used to help students create entries for the AIAA Foundation Undergraduate Team Aircraft Design Competition. Each entry involved the design, analysis, construction, and testing of the aircraft. Three groups were involved for each airplane: the first group was responsible for the airframe, the second group was responsible for the engine, and the third group was responsible for the construction and flight testing of a radio-controlled flying model. There was an overall Chief Executive Officer who insured that engine-airframe integration issues were addressed. Students from a variety of majors, both technical and non-technical, participated in various …

From Learning To Talk To Learning Engineering; Drawing Connections Across The Disciplines, Nikos J. Mourtos

Faculty Publications

This paper introduces eight so-called conditions of learning (immersion, demonstration, engagement, expectations, responsibility, approximation, employment and response), which have been previously established for the learning of literacy. It is stipulated that these conditions are universal in nature; in other words, they must be present for any learning to occur. When these conditions are met, students learn more efficiently and are able to enjoy and appreciate their subject matter. The article discusses briefly how these conditions were established and their relevance in the study of engineering. More importantly, the article also presents examples of how these conditions can be satisfied in …

Aspects Of Control For A Parafoil And Payload System, Nathan Slegers, Mark Costello

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

A parafoil controlled by parafoil brake deflection offers a lightweight and space-efficient control mechanism for autonomous placement of air-dropped payloads to specified ground coordinates. The work reported here investigates control issues for a parafoil and payload system with left and right parafoil brakes used as the control mechanism. It is shown that parafoil and payload systems can exhibit two basic modes of lateral control, namely,roll and skid steering. These two modes of lateral steering generate lateral response in opposite directions. For example, a roll steer configuration turns left when the right parafoil brake is activated, whereas a skid steer configuration …

Comparison Of Measured And Simulated Motion Of A Controllable Parafoil And Payload System, Nathan Slegers, Mark Costello

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

For parafoil and payload aircraft, control is affected by changing the length of several rigging lines connected to the outboard side and rear of the parafoil leading to complex changes in the shape and orientation of the lifting surface. Flight mechanics of parafoil and payload aircraft most often employ a 6 or 9 DOF representation with the canopy modeled as a rigid body during flight. The effect of control inputs is idealized by the deflection of parafoil brakes on the left and right side of the parafoil. Using a small parafoil and payload aircraft, glide rates and turn performance were …

On The Use Of Rigging Angle And Canopy Tilt For Control Of A Parafoil And Payload System, Nathan Slegers, Mark Costello

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

Controllable parafoil and payload aircraft are controlled with downward deflection of left and right parafoil brakes. Lateral control is obtained by differential deflection while longitudinal control is created by collective deflection of the left and right side parafoil brakes. The work reported considers an alternative method to control parafoil and payload air vehicles by tilting the parafoil canopy for lateral control and changing rigging angle for longitudinal control. Using a nonlinear 9 degree of freedom simulation model, it is shown that canopy tilt provides a powerful lateral control mechanism and rigging angle provides a viable longitudinal control mechanism.

Cool Flames In Propane-Oxygen Premixtures At Low And Intermediate Temperatures At Reduced-Gravity, Howard Pearlman, Michael R. Foster, Devrez Karabacak

Faculty Publications - Biomedical, Mechanical, and Civil Engineering

No abstract provided.

Hierarchical Optimal Control Of A Turning Process - Linearization Approach, Anand Dasgupta, B. Pandurangan, Robert G. Landers, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Machining process control technologies are currently not well integrated into machine tool controllers and, thus, servomechanism dynamics are often ignored when designing and implementing process controllers. In this paper, a hierarchical controller is developed that simultaneously regulates the servomechanism positions and cutting forces in a lathing operation. The force process and servomechanism system are separated into high and low levels, respectively, in the hierarchy. The high level goal is to maintain a constant cutting force to maximize productivity while not violating a spindle power constraint. This goal is systematically propagated to the lower level and combined with the low level …

Output Feedback Force Control For A Parallel Turning Operation, Raghusimha Sudhakara, Robert G. Landers

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Parallel machine tools (i.e., machine tools capable of cutting a part with multiple tools simultaneously but independently) are being utilized more and more to increase operation productivity, decrease setups, and reduce floor space. Process control is the utilization of real-time process sensor information to automatically adjust process parameters (e.g., feed, spindle speed) to increase operation productivity and quality. To date, however, these two technologies have not been combined. This paper describes the design of an output feedback controller for a parallel turning operation that accounts for the inherent nonlinearities in the force process. An analysis of the process equilibriums explains …

Stochastic Game Approach To Air Operations, Ben G. Fitzpatrick, William M. Mceneaney, Istvan G. Lauko

Mathematics Faculty Works

A Command and Control (C²) problem for Military Air Operations is addressed. Specifically, we consider C² problems for air vehicles against ground based targets and defensive systems. The problem is viewed as a stochastic game. In this paper, we restrict our attention to the C² level where the problem may consist of a few UCAVs or aircraft (or possibly teams of vehicles); less than say, a half-dozen enemy SAMs; a few enemy assets (viewed as targets from our standpoint); and some enemy decoys (assumed to mimic SAM radar signatures). At this low level, some targets are …

Simultaneous Observations Of Mesospheric Gravity Waves And Sprites Generated By A Midwestern Thunderstorm, D. D. Sentman, E. M. Wescott, R. H. Picard, J. R. Winick, H. C. Stenbaek-Nielsen, E. M. Dewan, D. R. Moudry, F. T. São Sabbas, M. J. Heavner, J. Morrill

U.S. Air Force Research

The present report investigates using simultaneous observations of coincident gravity waves and sprites to establish an upper limit on sprite-associated thermal energy deposition in the mesosphere. The University of Alaska operated a variety of optical imagers and photometers at two ground sites in support of the NASA Sprites99 balloon campaign. One site was atop a US Forest Service lookout tower on Bear Mt. in the Black Hills, in western South Dakota. On the night of 18 August 1999 we obtained from this site simultaneous images of sprites and OH airglow modulated by gravity waves emanating from a very active sprite …

Intelligent Strain Sensing On A Smart Composite Wing Using Extrinsic Fabry-Perot Interferometric Sensors And Neural Networks, Kakkattukuzhy M. Isaac, Donald C. Wunsch, Steve Eugene Watkins, Rohit Dua, V. M. Eller

Electrical and Computer Engineering Faculty Research & Creative Works

Strain prediction at various locations on a smart composite wing can provide useful information on its aerodynamic condition. The smart wing consisted of a glass/epoxy composite beam with three extrinsic Fabry-Perot interferometric (EFPI) sensors mounted at three different locations near the wing root. Strain acting on the three sensors at different air speeds and angles-of-attack were experimentally obtained in a closed circuit wind tunnel under normal conditions of operation. A function mapping the angle of attack and air speed to the strains on the three sensors was simulated using feedforward neural networks trained using a backpropagation training algorithm. This mapping …

Comparison Of 3-, 5-, And 6-Phase Machines For Automotive Charging Applications, B. Zhang, Hua Bai, Walter Eversman, Ronald J. Krefta, Duane J. Buening, Steven Pekarek, Gregory R. Holbrook

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, the performance of a 5-phase claw-pole machine/converter system is compared with those of 3-phase and 6-phase systems of the same volume. It is shown that the acoustic output of the 5-phase machine compares favorably with that of the 6-phase machine and is much lower than that of the 3-phase machine over a majority of the operating range. In addition, the output current produced by the 5-phase machine Is, in general, 6-8% higher than those of the 3-phase and 6-phase machines. These results suggest that for maximizing power density while minimizing cost and acoustic noise, 5-phase machines provide …

Missile Longitudinal Autopilot Design Using A New Suboptimal Nonlinear Control Method, Ming Xin, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A missile longitudinal autopilot is designed using a new nonlinear control synthesis technique called the θ-D approximation. The particular θ-D methodology used is referred to as the θ-D H2 design. The technique can achieve suboptimal closed-form solutions to a class of nonlinear optimal control problems in the sense that it solves the Hamilton-Jacobi-Bellman equation approximately by adding perturbations to the cost function. An interesting feature of this method is that the expansion terms in the expression for suboptimal control are nothing but solutions to the state-dependent Riccati equations associated with this class of problems. The θ-D H2 design has the …

Nonlinear H Infinity Missile Longitudinal Autopilot Design With Θ-D Method, Ming Xin, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper, a new nonlinear control synthesis technique, the theta- D method, is employed to design a missile longitudinal autopilot. The θ-D technique yields suboptimal solutions to nonlinear optimal control problems in the sense that it provides approximate solution to the Hamilton-Jacobi-Bellman (HJB) equation. Semi-global asymptotic stability can be achieved by manipulating the perturbation terms which are added to the cost function in developing a series solution. Furthermore, this method can be used to provide an approximate closed-form solution to the state dependent Riccati equation. The particular θ-D methodology adopted in this paper is referred to as θ-D H …

A Single-Element Tuning Fork Piezoelectric Linear Actuator, J. Satonobu, K. Nakamura, S. Ueha, Daniel S. Stutts, James R. Friend

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper describes the design of a piezoelectric tuning-fork, dual-mode motor. The motor uses a single multilayer piezoelectric element in combination with tuning fork and shearing motion to form an actuator using a single drive signal. Finite-element analysis was used in the design of the motor, and the process is described along with the selection of the device's materials and its performance. Swaging was used to mount the multilayer piezoelectric element within the stator. Prototypes of the 25-mm long bidirectional actuator achieved a maximum linear no-load speed of 16.5 cm/s, a maximum linear force of 1.86 N, and maximum efficiency …

Approximate Dynamic Programming Based Optimal Neurocontrol Synthesis Of A Chemical Reactor Process Using Proper Orthogonal Decomposition, Radhakant Padhi, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The concept of approximate dynamic programming and adaptive critic neural network based optimal controller is extended in this study to include systems governed by partial differential equations. An optimal controller is synthesized for a dispersion type tubular chemical reactor, which is governed by two coupled nonlinear partial differential equations. It consists of three steps: First, empirical basis functions are designed using the "Proper Orthogonal Decomposition" technique and a low-order lumped parameter system to represent the infinite-dimensional system is obtained by carrying out a Galerkin projection. Second, approximate dynamic programming technique is applied in a discrete time framework, followed by the …

A Product Architecture-Based Conceptual Dfa Technique, Robert B. Stone, Daniel A. Mcadams, Varghese J. Kayyalethekkel

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A conceptual design for assembly (DFA) method is introduced in this paper. The method incorporates DFA analysis into the conceptual design phase. Current DFA methods, essentially all of which are post-design DFA analyses, are reviewed with emphasis on the popular Boothroyd and Dewhurst method. The product architecture-based conceptual DFA method developed and presented in this article uses two relatively new concepts: the functional basis and the method of module heuristics. The functional basis is used to derive a functional model of a product in a standard language and the module heuristics are applied to the functional model to identify a …

Proper Orthogonal Decomposition Based Modeling And Experimental Implementation Of A Neurocontroller For A Heat Diffusion System, Prashant Prabhat, S. N. Balakrishnan, Dwight C. Look, Radhakant Padhi

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Experimental implementation of a dual neural network based optimal controller for a heat diffusion system is presented. Using the technique of proper orthogonal decomposition (POD), a set of problem-oriented basis functions are designed taking the experimental data as snap shot solutions. Using these basis functions in Galerkin projection, a reduced-order analogous lumped parameter model of the distributed parameter system is developed. This model is then used in an analogous lumped parameter problem. A dual neural network structure called adaptive critics is used to obtain optimal neurocontrollers for this system. In this structure, one set of neural networks captures the relationship …