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Description
Advancements in the field of design and control of lower extremity robotics requires a comprehensive understanding of the underlying mechanics of the human ankle. The ankle joint acts as an essential interface between the neuromuscular system of the body and the physical world, especially during locomotion. This paper investigates how the modulation of ankle stiffness is altered throughout the stance phase of the gait cycle depending on the environment the ankle is interacting with. Ten young healthy subjects with no neurological impairments or history of ankle injury were tested by walking over a robotic platform which collected torque and position data. The platform performed a perturbation on the ankle at 20%, 40%, and 60% of their stance phase in order to estimate ankle stiffness and evaluate if the environment plays a role on its modulation. The platform provided either a rigid environment or a compliant environment in which it was compliant and deflected according to the torque applied to the platform. Subjects adapted in different ways to achieve balance in the different environments. When comparing the environments, subjects modulated their stiffness to either increase, decrease, or remain the same. Notably, stiffness as well as the subjects’ center of pressure was found to increase with time as they transitioned from late loading to terminal stance (heel strike to toe-off) regardless of environmental conditions. This allowed for a model of ankle stiffness to be developed as a function of center of pressure, independent of whether a subject is walking on the rigid or compliant environment. The modulation of stiffness parameters characterized in this study can be used in the design and control of lower extremity robotics which focus on accurate biomimicry of the healthy human ankle. The stiffness characteristics can also be used to help identify particular ankle impairments and to design proper treatment for individuals such as those who have suffered from a stroke or MS. Changing environments is where a majority of tripping incidents occur, which can lead to significant injuries. For this reason, studying healthy ankle behavior in a variety of environments is of particular interest.
ContributorsBliss, Clayton F (Author) / Lee, Hyunglae (Thesis director) / Marvi, Hamid (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
The ASU Compact X-ray Free Electron Laser (CXFEL) is a first of its kind instrument that will illuminate the processes of life and allow scientists to create more effective treatments for disease. The dimensions of the linear accelerator (LINAC) cavities must remain stable during operation, for a change in the geometry alters the standing wave microwave energy resonance within the cavities and leads to reflected rather than coupled and useful microwave energy to electric field coupling. This disturbs the electron bunch acceleration dynamics critical to the ultimate generation of x-ray pulses. Cooling water must be supplied to the electron generating RF-GUN, and linear accelerator (LINAC) structures at unique flowrate and temperature setpoints that are specific to the operating mode of the CXFEL. Design specifications for the water supply to the RF-GUN and three LINACs and were made for the nominal operating mode, which adds a 3 kW heat load to the water. To maintain steady cavity dimensions, water must be supplied to each device under test at 30.0 ºC ± 0.06 ºC. The flowrate of water must be 3.5 GPM to the RF-GUN and 2.5 GPM to each of the three LINACs with ± 0.01 GPM flowrate resolution. The primary function of the Dedicated-Precision Thermal Trim Unit (D-PTTU) is to control the flowrate and temperature of water supply to each device under test. A simplified model of the system was developed to select valves that would meet our design specifications for flowrate and temperature control. After using this model for valve selection, a detailed system model was created to simulate relevant coupled-domain physics of the integrated system. The detailed system model was used to determine the critical sensitivities of the system and will be used to optimize the performance of the system in the future. Before the detailed system model can be verified and tuned with experiments, the sensors were calibrated in an ice-bath to ensure the sensors measure accurate and precise values. During initial testing, the D-PTTU was able to achieve ± 0.02 ºC temperature resolution, which exceeds the design specification by a factor of three.
ContributorsGardeck, Alex John (Author) / Holl, Mark (Thesis director) / Smith, Dean (Committee member) / Department of Physics (Contributor) / Mechanical and Aerospace Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
The objective of this project is to design an indraft supersonic wind tunnel that is safe and comparatively simple to construct. The processes and methodology of design are discussed. As with every supersonic wind tunnel, the critical components are the nozzle, diffuser, and the means of achieving the pressure differential which drives the flow. The nozzle was designed using method of characteristics (MOC) and a boundary layer analysis experimental proven on supersonic wind tunnels [5]. The diffuser was designed using the unique design features of this wind tunnel in combination with equations from Pope [7]. The pressure differential is achieved via a vacuum chamber behind the diffuser creating a pressure differential between the ambient air and the low pressure in the tank. The run time of the wind tunnel depends on the initial pressure of the vacuum tank and the volume. However, the volume of the tank has a greater influence on the run time. The volume of the tank is not specified as the largest tank feasible should be used to allow the longest run time. The run time for different volumes is given. Another method of extending the run duration is added vacuum pumps to the vacuum chamber. If these pumps can move a sufficient mass out of the vacuum chamber, the run time can be significantly extended. The mounting design addresses the loading requirements which is closely related to the accuracy of the data. The mounting mechanism is attached to the rear of the model to minimize shockwave interference and maximize the structural integrity along the direction with the highest loading. This mechanism is then mounted to the bottom of the wind tunnel for structural rigidity and ease of access.
ContributorsWall, Isaiah Edward (Author) / Wells, Valana (Thesis director) / Kshitij, Abhinav (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
This project aims to study the relationship between model input parameters and model output accuracy of the Tool for Automation of Computational Aerodynamics of Airfoils (TACAA). The input parameters of study are Mach number and Reynolds number, and inputs are tested through three flight speed regimes and from laminar to turbulent flow. Each of these input parameters are tested for the NACA 0012 and SC-1095 airfoils to ensure that the accuracy is similar regardless of geometric complexity. The TACAA program was used to run all simulation testing, and its overall functionality is discussed. The results gathered from the preliminary testing showed that the spread of variable input data points caused data gaps in the transonic regime results, which provided motivation to conduct further testing within the transonic region for both airfoils. After collecting all TACAA results, data from wind tunnel testing was compiled to compare. The comparison showed that (1) additional testing would be necessary to fully assess the accuracy of the results for the SC-1095 airfoil and (2) TACAA is generally accurate for compressible, turbulent flows.
ContributorsKuang, Joyce (Co-author) / Stickel, Hannah (Co-author) / Wells, Valana (Thesis director) / Duque, Earl (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
The temperature of exhaust pipes can be dangerous in dry areas where there is a lot of brush. The temperatures of exhaust pipes can reach a high enough temperature to start a fire if touching the dry brush, which ignites around 300°C. The goal of this project was to explore different techniques to limit the possibility of these brush fires. Specifically, different methods were explored to reduce the temperature of the pipe that would be contacting the brush. Fires can begin within seconds of contacting the hot exhaust pipes [10]. This experiment found that of the three options tested: exhaust wrap, heat sink with thermoelectric devices, and high temperature paint, adding a heat shield/sink is the best way to limit the high temperatures from igniting the brush. There was a cooling difference of nearly 100°C when a heat shield/sink was added to the bare pipe. The additional thermal mass as well as the finned heat sinks attached to the heat sink helped dissipate the heat from the pipe and release the waste heat into the surroundings. The increase in surface area in correspondence with forced convection from the surrounding air lowered the temperature of the metal in contact with the dry brush.
ContributorsHodges, Andrew (Author) / Benson, David (Thesis director) / Bocanegra, Luis (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
This thesis project examines the stability margin for different rotor configurations for a quadcopter and compares them against each other to determine the most stable flight configuration possible. The first configuration develops a “standard” for quadcopters with each motor in a corner of a cube at a 60-degree angle from the Y-Axis. The remaining tests increase the angle five degrees per configuration, allowing the motors to get incrementally closer to each other until no longer viable. Five different tests are outlined below depicting the microscopic changes in the pitch and roll of the device. The on-board controller in the quad-copter tracks both the acceleration and gyroscopic movements of the device to obtain the stability margin of each test. Computational analysis is then used to calculate and compare the values found to determine the most stable configuration.
ContributorsCorino, Tyler Michael (Author) / Kuo, Chen-Yuan (Thesis director) / Lynch, John (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
This study explores the relationship between three physics-based predictive models defined by Castruccio et al. (2013), and four different distinct experimental morphologies of lava flows produced in a series of laboratory simulations where polyethylene glycol 600 (PEG) was pumped into an inclined chilled bath of water. The length of the experimental flow was recorded over time to create an experimental model to later be compared to the physics-based predictive models. The experimental morphologies are pillowed, rifted, folded, and leveed flows which can be characterized by a dimensionless parameter 𝛹, which scales natural lava flows to experimental lava flows and is a ratio of timescales, the characteristic timescale of thermal flux from the vent and the characteristic timescale of crust formation caused by surface cooling (Fink and Griffiths 1990). The three physics-based models are presented such that the downslope gravitational acceleration drives the flow, while either the Newtonian viscosity of the flow, the Yield Strength of the core (YS), or the Yield Strength of the growing crust (YSC) is the primary retarding factor in flow propagation. This study concluded that low 𝛹-value flows (low flux, low temperature, extensive crust formation) are better captured by the YSC model. And although the Newtonian model did not perfectly capture the behavior of any experimental flows in this study, high 𝛹-value flows (high flux, high temperature, little crust formation) that formed levees exhibited the most Newtonian behavior.
ContributorsCourtney, Cara Alexandra (Author) / Clarke, Amanda B. (Thesis director) / Huang, Huei-Ping (Committee member) / Williams, David A. (Committee member) / School of Sustainability (Contributor) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
This thesis will cover the basics of 2-dimensional motion of a parafoil system to determine and
design an altitude controller that will result in the parafoil starting at a location and landing within the
accepted bounds of a target location. It will go over the equations of motion, picking out the key
formulas that map out how a parafoil moves, and determine the key inputs in order to get the desired
outcome of a controlled trajectory. The physics found in the equations of motion will be turned into
state space representations that organize it into differential equations that coding software can make
use of to make trajectory calculations. MATLAB is the software used throughout the paper, and all code
used in the thesis paper will be written out for others to check and modify to their desires. Important
aspects of parafoil gliding motion will be discussed and tested with variables such as the natural glide
angle and velocity and the utilization of checkpoints in trajectory controller design. Lastly, the region of
attraction for the controller designed in this thesis paper will be discussed and plotted in order to show
the relationship between the four input variables, x position, y position, velocity, and theta.
The controller utilized in this thesis paper was able to plot a successful flight trajectory from
10m in the air to a target location 50m away. This plot is found in figure 18. The parafoil undershot the
target location by about 9 centimeters (0.18% error). This is an acceptable amount of error and shows
that the controller was a success in controlling the system to reach its target destination. When
compared to the uncontrolled flight in figure 17, the target will only be reached when a controller is
applied to the system.
design an altitude controller that will result in the parafoil starting at a location and landing within the
accepted bounds of a target location. It will go over the equations of motion, picking out the key
formulas that map out how a parafoil moves, and determine the key inputs in order to get the desired
outcome of a controlled trajectory. The physics found in the equations of motion will be turned into
state space representations that organize it into differential equations that coding software can make
use of to make trajectory calculations. MATLAB is the software used throughout the paper, and all code
used in the thesis paper will be written out for others to check and modify to their desires. Important
aspects of parafoil gliding motion will be discussed and tested with variables such as the natural glide
angle and velocity and the utilization of checkpoints in trajectory controller design. Lastly, the region of
attraction for the controller designed in this thesis paper will be discussed and plotted in order to show
the relationship between the four input variables, x position, y position, velocity, and theta.
The controller utilized in this thesis paper was able to plot a successful flight trajectory from
10m in the air to a target location 50m away. This plot is found in figure 18. The parafoil undershot the
target location by about 9 centimeters (0.18% error). This is an acceptable amount of error and shows
that the controller was a success in controlling the system to reach its target destination. When
compared to the uncontrolled flight in figure 17, the target will only be reached when a controller is
applied to the system.
ContributorsTeoharevic, Filip (Author) / Grewal, Anoop (Thesis director) / Lee, Hyunglae (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
While golf has been around for centuries, the technology associated with the game has evolved significantly in an attempt to improve golfers’ scores. Specifically, researchers at Arizona State University (ASU) have looked at the dimple patterns on golf balls. They found that various dimple shapes, sizes, and patterns can have a serious impact on the flight of the ball, thus drastically improving the golfer’s game. This patented technology is the basis of the founding of Dimple Tech, a golf ball technology startup. Dimple Tech was founded by three ASU students in an effort to license the patent to the major golf ball manufacturers (Callaway, Titleist, TaylorMade, etc.). The ultimate goal of this startup was to build traction in any way possible, so the team made a video pitch that was sent to the aforementioned manufacturers. Although no traction came out of it, the project was a success as a market for this product was established and the company has a competitive advantage over other golf companies.
ContributorsStarostecki, Cameron (Co-author) / Kendall, William (Co-author) / Redmond, Michael (Co-author) / Byrne, Jared (Thesis director) / Sebold, Brent (Committee member) / Mechanical and Aerospace Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
This paper analyzes Burkina Faso’s Souro Sanou University Hospital Center’s energy needs and discusses whether or not solar panels are a good investment. This paper also discusses a way to limit the damage caused by power outages. The hospital has a history of problems with power outages; in the summer they have power outages every other day lasting between one to four hours, and in the rainy season they have outages once every other week lasting the same amount of time.
The first step in this analysis was collecting relevant data which includes: location, electricity rates, energy consumption, and existing assets. The data was entered into a program called HOMER. HOMER is a program which analyzes an electrical system and determines the best configuration and usage of assets to get the lowest levelized cost of energy (LCOE). In HOMER, five different analyses were performed. They reviewed the hospital’s energy usage over 25 years: the current situation, one of the current situation with added solar panels, and another where the solar panels have single axis tracking. The other two analyses created incentives to have more solar panels, one situation with net metering, and one with a sellback rate of 0.03 $/kWh. The result of the analysis concluded that the ideal situation would have solar panels with a capacity of 300 kW, and the LCOE in this situation will be 0.153 $/kWh. The analysis shows that investing in solar panels will save the hospital approximately $65,500 per year, but the initial investment of $910,000 only allows for a total savings of $61,253 over the life of the project. The analysis also shows that if the electricity company, Sonabel, eventually buys back electricity then net metering would be more profitable than reselling electricity for the hospital.
Solar panels will help the hospital save money over time, but they will not stop power outages from happening at the hospital. For the outages to stop affecting the hospital’s operations they will have to invest in an uninterrupted power supply (UPS). The UPS will power the hospital for the time between when the power goes out and when their generators are turning on which makes it an essential investment. This will stop outages from affecting the hospital, and if the power goes out during the day then the solar panels can help supplement the energy production which will take some of the strain from their generators.
The results of this study will be sent to officials at the hospital and they can decide if the large initial investment justifies the savings. If the solar panels and UPS can save one life, then maybe the large initial investment is worth it.
The first step in this analysis was collecting relevant data which includes: location, electricity rates, energy consumption, and existing assets. The data was entered into a program called HOMER. HOMER is a program which analyzes an electrical system and determines the best configuration and usage of assets to get the lowest levelized cost of energy (LCOE). In HOMER, five different analyses were performed. They reviewed the hospital’s energy usage over 25 years: the current situation, one of the current situation with added solar panels, and another where the solar panels have single axis tracking. The other two analyses created incentives to have more solar panels, one situation with net metering, and one with a sellback rate of 0.03 $/kWh. The result of the analysis concluded that the ideal situation would have solar panels with a capacity of 300 kW, and the LCOE in this situation will be 0.153 $/kWh. The analysis shows that investing in solar panels will save the hospital approximately $65,500 per year, but the initial investment of $910,000 only allows for a total savings of $61,253 over the life of the project. The analysis also shows that if the electricity company, Sonabel, eventually buys back electricity then net metering would be more profitable than reselling electricity for the hospital.
Solar panels will help the hospital save money over time, but they will not stop power outages from happening at the hospital. For the outages to stop affecting the hospital’s operations they will have to invest in an uninterrupted power supply (UPS). The UPS will power the hospital for the time between when the power goes out and when their generators are turning on which makes it an essential investment. This will stop outages from affecting the hospital, and if the power goes out during the day then the solar panels can help supplement the energy production which will take some of the strain from their generators.
The results of this study will be sent to officials at the hospital and they can decide if the large initial investment justifies the savings. If the solar panels and UPS can save one life, then maybe the large initial investment is worth it.
ContributorsSchmidt, Evin Khalil (Author) / Johnson, Nathan (Thesis director) / Miner, Mark (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05