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Description
In recent years, a new type of ionic salt based solid propellant, considered inert until the application of an electric current induces an electro-chemical reaction, has been under investigation due to its broad range of possible uses. However, while many electric propellant formulations and applications have been explored over the

In recent years, a new type of ionic salt based solid propellant, considered inert until the application of an electric current induces an electro-chemical reaction, has been under investigation due to its broad range of possible uses. However, while many electric propellant formulations and applications have been explored over the years, a fundamental understanding of the operational mechanisms of this propellant is necessary in order to move forward with development and implementation of this technology. It has been suggested that the metallic additive included in the formulation studied during this investigation may be playing an additional, currently unknown role in the operation and performance of the propellant. This study was designed to examine variations of an electric propellant formulation with the purpose of investigating propellant bulk volume electrical resistivity in order to attempt to determine information regarding the fundamental science behind the operation of this material. Within a set of fractional factorial experiments, variations of the propellant material made with tungsten, copper, carbon black, and no additive were manufactured using three different particle size ranges and three different volume percentage particle loadings. Each of these formulations (a total of 21 samples and 189 specimens) were tested for quantitative electrical resistivity values at three different pulse generator input voltage values. The data gathered from these experiments suggests that this electric propellant formulation’s resistivity value does change based upon the included additive. The resulting data has also revealed a parabolic response behavior noticeable in the 2D and 3D additive loading percentage versus additive particle size visualizations, the lowest point of which, occurring at an approximately 2.3% additive loading percentage value, could be indicative of the effects of the percolation phenomena on this material. Finally, the investigation results have been loosely correlated to power consumption testing results from previous work that may indicate that it is possible to relate propellant electrical resistivity and operating requirements. Throughout this study, however, it is obvious based on the data gathered that more information is required to be certain of these conclusions and in order to fully understand how this technology can be controlled for future use.
ContributorsBrunacini, Lauren (Author) / Middleton, James (Thesis advisor) / Dai, Lenore (Committee member) / Langhenry, Mark T (Committee member) / Arizona State University (Publisher)
Created2019
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Description
Many industries require workers in warehouse and stockroom environments to perform frequent lifting tasks. Over time these repeated tasks can lead to excess strain on the worker's body and reduced productivity. This project seeks to develop an exoskeletal wrist fixture to be used in conjunction with a powered exoskeleton arm

Many industries require workers in warehouse and stockroom environments to perform frequent lifting tasks. Over time these repeated tasks can lead to excess strain on the worker's body and reduced productivity. This project seeks to develop an exoskeletal wrist fixture to be used in conjunction with a powered exoskeleton arm to aid workers performing box lifting types of tasks. Existing products aimed at improving worker comfort and productivity typically employ either fully powered exoskeleton suits or utilize minimally powered spring arms and/or fixtures. These designs either reduce stress to the user's body through powered arms and grippers operated via handheld controls which have limited functionality, or they use a more minimal setup that reduces some load, but exposes the user's hands and wrists to injury by directing support to the forearm. The design proposed here seeks to strike a balance between size, weight, and power requirements and also proposes a novel wrist exoskeleton design which minimizes stress on the user's wrists by directly interfacing with the object to be picked up. The design of the wrist exoskeleton was approached through initially selecting degrees of freedom and a ROM (range of motion) to accommodate. Feel and functionality were improved through an iterative prototyping process which yielded two primary designs. A novel "clip-in" method was proposed to allow the user to easily attach and detach from the exoskeleton. Designs utilized a contact surface intended to be used with dry fibrillary adhesives to maximize exoskeleton grip. Two final designs, which used two pivots in opposite kinematic order, were constructed and tested to determine the best kinematic layout. The best design had two prototypes created to be worn with passive test arms that attached to the user though a specially designed belt.
ContributorsGreason, Kenneth Berend (Author) / Sugar, Thomas (Thesis director) / Holgate, Matthew (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
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Description
For the past two decades, advanced Limb Gait Simulators and Exoskeletons have been developed to improve walking rehabilitation. A Limb Gait Simulator is used to analyze the human step cycle and/or assist a user walking on a treadmill. Most modern limb gait simulators, such as ALEX, have proven themselves effective

For the past two decades, advanced Limb Gait Simulators and Exoskeletons have been developed to improve walking rehabilitation. A Limb Gait Simulator is used to analyze the human step cycle and/or assist a user walking on a treadmill. Most modern limb gait simulators, such as ALEX, have proven themselves effective and reliable through their usage of motors, springs, cables, elastics, pneumatics and reaction loads. These mechanisms apply internal forces and reaction loads to the body. On the other hand, external forces are those caused by an external agent outside the system such as air, water, or magnets. A design for an exoskeleton using external forces has seldom been attempted by researchers. This thesis project focuses on the development of a Limb Gait Simulator based on a Pure External Force and has proven its effectiveness in generating torque on the human leg. The external force is generated through air propulsion using an Electric Ducted Fan (EDF) motor. Such a motor is typically used for remote control airplanes, but their applications can go beyond this. The objective of this research is to generate torque on the human leg through the control of the EDF engines thrust and the opening/closing of the reverse thruster flaps. This device qualifies as "assist as needed"; the user is entirely in control of how much assistance he or she may want. Static thrust values for the EDF engine are recorded using a thrust test stand. The product of the thrust (N) and the distance on the thigh (m) is the resulting torque. With the motor running at maximum RPM, the highest torque value reached was that of 3.93 (Nm). The motor EDF motor is powered by a 6S 5000 mAh LiPo battery. This torque value could be increased with the usage of a second battery connected in series, but this comes at a price. The designed limb gait simulator demonstrates that external forces, such as air, could have potential in the development of future rehabilitation devices.
ContributorsToulouse, Tanguy Nathan (Author) / Sugar, Thomas (Thesis director) / Artemiadis, Panagiotis (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12