Restoration of the National Aerothermochemistry Laboratory Plasma Facility

REU Student: Alexander A. Soderlund, University of Texas

Faculty Mentor: Dr. Rodney Bowersox

This report details the redesign, reconstruction, and calibration of the Decaying Mesh Turbulence (DMT) Plasma Facility at the National Aerothermochemistry Laboratory. The integral parts of the old tunnel were combined with new parts to give the facility a smaller frame, thus making it more accessible and easier to perform various flow visualization tests such as Particle Image Velocimetry (PIV), Schlieren photography, and most importantly vibrational non-equilibrium tests via plasma electrodes, which is the main focus of the facility. The previous DMT plasma facility attempted to associate the rate at which turbulence decays with the rate at which an excited molecule approaches relaxation. Preliminary tests run on the new plasma facility show distinctive velocity, pressure, and boundary layer variations that correlate with theoretical plotlines derived from Bernoulli’s principle and the Law of Conservation of Mass. Eventually, the DMT plasma facility is planned to incorporate the Vibrationally Excited Nitric Oxide Monitoring technique, which will allow further research into the 3-D modeling of the velocity and temperature vectors of an excited NO molecule.


Analysis of Nonlinear Dynamical Systems using Markovian Representations

REU Student: Christopher L. Bertagne, Texas A&M University

Faculty Mentor: Dr. Raktim Bhattacharya

This paper presents a framework for understanding the behavior of nonlinear dynamical systems in N-dimensional state space. The basis of this approach is the generation of a stochastic matrix using techniques from the field of statistical physics. Though it contains the nonlinear nature of the system, the matrix itself is a linear operator, allowing easy and straightforward computation of the long-term behavior of the system via its stationary probability vector. Such a technique can be applied to situations where knowledge of the stability of highly nonlinear dynamical systems is of critical importance, such as in the design flight control laws.

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Stochastic Optimal Control-based Framework for Robot Motion Planning

REU Student: Ammar Mohamed Nasher Abbas, University of Michigan, Ann Arbor

Faculty Mentor: Dr. Suman Chakravorty

We looked at the problem of motion planning under uncertainty as an example of the stochastic optimal control problem under the process and sensing uncertainties. The four major blocks involved in generating control in the stochastic optimal control process were discussed, explained and illustrated with some real-world examples. In future, we are planning to implement a basic stochastic control scheme, such as Linear Quadratic Gaussian (LQG) controller and test it on simple robot model motion planning.

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Investigating Ideal Flow Parameters for an Autonomous Air Swimmer

REU Student: Bridig M. Flood, Texas A&M University

Faculty Mentor: Dr. Sharath Girimaji

Air Swimmers are helium-filled fish balloons that “swim” through the air via a remote that controls tail flapping and pitch. The aerospace industry is currently exploring different ways to design newer, better satellites and high altitude balloons. One option is to use balloons that run on turbofan technology, but balloons that utilize the tail flap configuration have the potential to be lighter, more cost effective, and more efficient. In order to translate the Air Swimmer toy into a useful engineering tool, it is necessary to investigate the functionality of the balloon, especially the tail, and how we can manipulate it (along with flow parameters) to maximize thrust produced. An experiment was designed to test several different fish tail shapes in a wind tunnel at varying flap frequencies and amplitudes. Two different methods to obtain thrust can be employed in conjunction with this experimental setup: first, a wake rake mounted with Pitot probes downstream of the model; second, a force balance attached to the tail calibrated to record thrust measurements. The tools necessary for each of these techniques have been constructed and mounted in the test section. In addition, tests have been performed on several tail models using the force balance, and some preliminary analysis has been completed. Finally, a smoke-wire tool for flow visualization was designed and manufactured. Ultimately, as this project continues, our team aims to work more closely with the theory team so that computational and experimental hypotheses can be correlated and analyzed.

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Maximizing the Thrust on the Tail Fin of an Autonomous Air Swimmer

REU Student: Allen Nicholas Mehrafshan

Faculty Mentor: Dr. Sharath Girimaji

This study utilizes wind tunnel testing to determine the best shape, size, frequency, and amplitude of the tail fin of an autonomous, neutrally buoyant air swimmer in order to maximize its thrust. The long term application goal of this study is to equip neutrally buoyant balloons, which are intended to replace satellites, with fins instead of motor fans previously proposed by NASA. Five different fin shapes are crafted out of balsa wood and tested in a closed circuit wind tunnel. Different methods, which are described in detail in the study, are attempted to determine thrust produced by each fin. These results are analyzed and interpreted to investigate the affects of size, shape, frequency, and amplitude on the thrust produced by each fin. Detailed explanations of the methods of modeling experimental methods, including 3D design software, are included.

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Gyroscopic Stabilization of Unstable Dynamical Systems

REU Student: Peter J. Jorgensen

Faculty Mentor: Dr. John E. Hurtado

The use of gyroscopically-induced moments for stabilization has been known about for over a century; Louis Brennan, in 1905, submitted a patent describing the use of gyroscopes to enable a monorail train or other two-wheeled vehicle to operate in a stable manner. Since then, gyroscopes have been adapted to stabilizing and actuating monorails, large oceangoing ships, as well as spacecraft and satellites. However, despite its prolific use in large-scale vehicles, very little has been done to realize gyroscopic stabilization for smaller applications such as robotics. Drawing on previous work applied to monorail-type vehicles, the principles of gyroscopic stability are applied to a similar small vehicle to show the feasibility of the technology on the smaller scale. Through dynamical analysis and simulation, stability and controllability of the system are predicted. Finally, through a prototype, the predictions and analysis are compared to actual system response. Thus, gyroscopic stabilization of small-scale vehicles is proven feasible. The implication of this work is to extend the use of gyroscopes to stabilize more complex dynamical systems, such as bipedal and humanoid robots.

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Gyroscopic Stabilization of Unstable Vehicles

REU Student: Kyle D. Chapkin

Faculty Mentor: Dr. John E. Hurtado

The purpose of this project is to design and build a rapid prototype control moment gyro (CMG) stabilized vehicle to demonstrate a proof of concept and help advance further research into the idea of terrestrial robotic stabilization with CMGs. In the constructed first generation prototype, a single CMG was mounted onto an unstable 2 degrees of freedom (DOF) vehicle, currently only capable of a rolling motion, and balanced said vehicle by countering external disturbances through use of the precession effect. An external torque applied to the vehicle causes the CMG react by turning on an axis that is perpendicular to both the spin axis and torque axis and creates a restoring torque on the vehicle, returning it to its desired position. The active control of the gimbal rate angle, and the resulting torque, forms the basis of the actuating mechanics. The vehicle created does successfully demonstrate the ability to self-stabilize and return to equilibrium when disturbed, showing a successful implementation of hardware and principles. Future models will see a vehicle with no umbilical tether to allow for further range of movements, a 4 DOF model capable of pitch and yaw in addition to roll, and eventually a robot with two mounted CMGs to allow for stable self-propelled motion.

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Increasing the Actively Controlled Expansion Wind Tunnel's Mach and Reynolds Number Operating Ranges

REU Student: Richard E. Kennedy

Faculty Mentor: Dr. Rodney Bowersox

One of the major issues currently faced by the Actively Controlled Expansion (ACE) high speed wind tunnel is liquefaction of the air in the tunnel test section during certain testing conditions. A ubiquitous problem in high speed wind tunnel testing, liquefaction refers to the condensation of oxygen out of air at certain thermodynamic gas states determined by flow conditions. The formation of this condensate can lead to error in pressure fluctuation readings, hence rendering the flow data unreliable. One way to combat this issue is to strategically increase the thermal capacity of the tunnel infrastructure. As can be proven by the basic isentropic flow relations, increasing the temperature of the air which reaches the test section increases the testing envelope of Reynolds and Mach numbers, thus opening the door for a plethora of novel high speed flow experiments. In addition, greater thermal capacity of the tunnel will reduce preheat running times which will save valuable compressed air needed to run the tunnels. Using commercially available heaters in conjunction with several PID controllers, a setup was designed and installed which successfully heated key ACE tunnel sections.

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Shape Memory Alloy Rotor Blade Deicing

REU Student: Daniel B. Sullivan, University of Maryland

Faculty Mentor: Dr. Jonathan Rogers

Because of power, space, and weight limitations, most modern rotorcraft lack deicing capabilities, thus reducing their operational capacity. The use of shape memory alloy (SMA) materials is an attractive solution for this problem due to their low weight and high deflection properties. This paper details a multi-stage feasibility study of a SMA-based rotor blade deicing concept. In the evaluated design, a thin aluminum sheet shaped as the leading edge of a NACA 0012 airfoil is connected to thin NiTi SMA wires. When the wires are actuated, they contract, deforming the aluminum sheet and fracturing the ice on its surface. First, the motivation for such a design is presented along with a brief overview of existing research into rotor blade deicing. The basic design is then described in more detail. The software analysis performed on the design is discussed. The design and construction of the prototype is also presented. When tested, the prototype successfully fractured a solid sheet of ice on its surface.

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