Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 11 of 11
Full-Text Articles in Engineering
Mechanistic Undrestanding Of Amorphization In Iron-Based Soft Magnetic Materials, Taban Larimian
Mechanistic Undrestanding Of Amorphization In Iron-Based Soft Magnetic Materials, Taban Larimian
ETD Archive
Iron-based magnetic alloys possess very good magnetic and mechanical properties. Among these alloys Fe-Si-B-based alloys show outstanding saturation magnetization and coercivity which makes them great candidates for many industrial applications. Addition of certain elements to the Fe-Si-B base is proven to improve the homogeneity and fineness of microstructure as well as enhance the magnetic behavior of these alloys. In this research work, we have studied the effect of adding copper and niobium to the Fe-Si-B base alloy. Previous studies have shown that magnetic alloys show better magnetic properties when their microstructure consists of nanocrystals embedded in an amorphous matrix. In …
Viability And Accessibility Of Urban Heat Island And Lake Microclimate Data Over Current Tmy Weather Data For Accurate Energy Demand Predictions., Irena A. Weclawiak
Viability And Accessibility Of Urban Heat Island And Lake Microclimate Data Over Current Tmy Weather Data For Accurate Energy Demand Predictions., Irena A. Weclawiak
ETD Archive
Building Energy Simulations (BES) are necessary for designing energy-efficient systems. Open-source simulation software developed by the Department of Energy (DOE), EnergyPlus (EP) provides Typical Meteorological Year (TMY) weather data that consists of a 15-year average. Two major concerns about this data are the inability to detect extreme conditions and limited data locations. There is a greater number of Microclimate (MC) stations that can be used for simulations, but it involves time-consuming data preparation to match the EP format. This study investigated the effects of Urban Heat Island (UHI) and the MC of Lake Erie. A comparison of the MC data …
An Evaluation And Economic Analysis Of A Water Main Geothermal System In A Residential Space, Brian L. Kohut
An Evaluation And Economic Analysis Of A Water Main Geothermal System In A Residential Space, Brian L. Kohut
ETD Archive
Iron-based magnetic alloys possess very good magnetic and mechanical properties. Among these alloys Fe-Si-B-based alloys show outstanding saturation magnetization and coercivity which makes them great candidates for many industrial applications. Addition of certain elements to the Fe-Si-B base is proven to improve the homogeneity and fineness of microstructure as well as enhance the magnetic behavior of these alloys. In this research work, we have studied the effect of adding copper and niobium to the Fe-Si-B base alloy. Previous studies have shown that magnetic alloys show better magnetic properties when their microstructure consists of nanocrystals embedded in an amorphous matrix. In …
Design, Control, And Optimization Of Robots With Advanced Energy Regenerative Drive Systems, Poya Khalaf
Design, Control, And Optimization Of Robots With Advanced Energy Regenerative Drive Systems, Poya Khalaf
ETD Archive
We investigate the control and optimization of robots with ultracapacitor based regenerative drive systems. A subset of the robot joints are conventional, in the sense that external power is used for actuation. Other joints are energetically self-contained passive systems that use ultracapacitors for energy storage. An electrical interconnection known as the star configuration is considered for the regenerative drives that allows for direct electric energy redistribution among joints, and enables higher energy utilization efficiencies. A semi-active virtual control strategy is used to achieve control objectives. We find closed-form expressions for the optimal robot and actuator parameters (link lengths, gear ratios, …
Robust Impedance Control Of A Four Degree Of Freedom Exercise Robot, Santino Joseph Bianco
Robust Impedance Control Of A Four Degree Of Freedom Exercise Robot, Santino Joseph Bianco
ETD Archive
The CSU 4OptimX exercise robot provides a platform for future research into advanced exercise and rehabilitation. The robot and its control system will autonomously modify reference trajectories and impedances on the basis of an optimization criterion and physiological feedback. To achieve this goal, a robust impedance control system with trajectory tracking must be implemented as the foundational control scheme. Two control laws will be compared, sliding mode and H-infinity control. The above robust control laws are combined with underlying impedance control laws to overcome uncertain plant model parameters and disturbance anomalies affecting the input signal. The sliding mode control law …
Neuromuscular Reflex Control For Prostheses And Exoskeletons, Sandra K. Hnat
Neuromuscular Reflex Control For Prostheses And Exoskeletons, Sandra K. Hnat
ETD Archive
Recent powered lower-limb prosthetic and orthotic (P/O) devices aim to restore legged mobility for persons with an amputation or spinal cord injury. Though various control strategies have been proposed for these devices, specifically finite-state impedance controllers, natural gait mechanics are not usually achieved. The goal of this project was to invent a biologically-inspired controller for powered P/O devices. We hypothesize that a more muscle-like actuation system, including spinal reflexes and vestibular feedback, can achieve able-bodied walking and also respond to outside perturbations. The outputs of the Virtual Muscle Reflex (VMR) controller are joint torque commands, sent to the electric motors …
Non-Intrusive Optical Measurement Of Electron Temperature In Near Field Plume Of Hall Thruster, Peter J. Urban
Non-Intrusive Optical Measurement Of Electron Temperature In Near Field Plume Of Hall Thruster, Peter J. Urban
ETD Archive
Currently there is a large interest in the use of more efficient means of propulsion in long term missions due to the costs and difficulties associated with placing and maintaining the needed fuel for conventional chemical systems in orbit. Mass reduction of upper stages will return large returns due to the great reduction in required lower stage fuel. Due to these factors, alternatives are undergoing active research, though this paper is concerned with the area of electrical propulsion. Electric propulsion is broadly defined as propulsion where the energization of the exhaust occurs via application of electromagnetic fields as opposed to …
Design And Control Of A Powered Rowing Machine With Programmable Impedance, Jose Humberto De La Casas Zolezzi
Design And Control Of A Powered Rowing Machine With Programmable Impedance, Jose Humberto De La Casas Zolezzi
ETD Archive
Due to the rise of obesity, diabetes and cardiovascular disease, research in human performance and physical activity has received increased attention. Rowing machines are used for performance improvements through concentric exercises, however a combination of concentric and eccentric actions is known to improve the effectiveness of training. In this work, a conventional rowing machine was modified to include an electric motor and a robust impedance control system, enabling programmable impedance with concentric and eccentric capabilities. Eccentric exercises are known to contribute significantly to the efficacy of training and to diminish the detrimental effects of humans operating in microgravity for long …
Investigation Of Extremum Seeking Control For Adaptive Exercise Machines, Brahm T. Powell
Investigation Of Extremum Seeking Control For Adaptive Exercise Machines, Brahm T. Powell
ETD Archive
Many muscle rehabilitation regimens are non-adaptive and recommended subjectively by physicians. While there are advantages to having the feedback of a qualified physician, utilizing real-time muscle performance feedback could be beneficial. An extremum seeking control design is proposed to fulfill the need for an automated, load-varying exercise machine that can optimize muscle performance.
Several steps are outlined to contribute to the realization of this goal. First, the extremum seeking control scheme is discussed. Second, the Hill muscle model will be described. Theoretical muscle effort extrema will be derived for selected optimization cases, namely maximizing average squared power by varying load …
Numerical Investigation Of Boiling In A Sealed Tank In Microgravity, Sonya Lynn Hylton
Numerical Investigation Of Boiling In A Sealed Tank In Microgravity, Sonya Lynn Hylton
ETD Archive
NASA's missions in space depend on the storage of cryogenic fluids for fuel and for life support. During long-term storage, heat can leak into the cryogenic fluid tanks. Heat leaks can cause evaporation of the liquid, which pressurizes the tank. However, when the tanks are in a microgravity environment, with reduced natural convection, heat leaks can also create superheated regions in the liquid. This may lead to boiling, resulting in much greater pressure rises than evaporation at the interface between the liquid and vapor phases. Models for predicting the pressure rise are needed to aid in developing methods to control …
Modeling Of Transient Thrust Of A Two Phase Propellant Tank, Karthik Mellechervu
Modeling Of Transient Thrust Of A Two Phase Propellant Tank, Karthik Mellechervu
ETD Archive
This thesis develops a model to predict various time-varying quantities associated with the evacuation of a pressurized container through a nozzle. The container is part of a satellite propulsion prototype used to study attitude control. Variables of interest include the thrust and mass of fluid in the tank as functions of time. A mathematical model based on transient expressions for mass and energy conservation is derived for a two-phase system representative of the conditions of the fluid inside the tank