Innovative Thermal Management Systems for Autonomous Vehicles — Design, Model, and Test

Emphasis on reducing fossil fuel consumption and greenhouse gas emissions, besides the demand for autonomy in vehicles, made governments and automotive industries move towards electrification. The integration of an electric motor with battery packs and on-board electronics has created new thermal challenges due to the heat loads\u27 operating conditions, design configurations, and heat generation rates. This paradigm shift necessitates an innovative thermal management system that can accommodate low, moderate, and high heat dissipations with minimal electrical or mechanical power requirements. This dissertation proposes an advanced hybrid cooling system featuring passive and active cooling solutions in a thermal bus configuration. The main purpose is to maintain the heat loads’ operating temperatures with zero to minimum power requirements and improved packaging, durability, and reliability. In many operating instances, a passive approach may be adequate to remove heat from the thermal source (e.g., electric motor) while a heavy load would demand both the passive and active cooling systems operate together for reduced electric power consumption. Further, in the event of a failure (e.g., coolant hose leak, radiator tube leak) in the conventional system, the passive system offers a redundant operating mode for continued operation at reduced loads. Besides, the minimization of required convective heat transfer (e.g., ram air effect) about the components for supplemental cooling enables creative vehicle component placement options and optimizations. Throughout this research, several cooling system architectures are introduced for electric vehicle thermal management. Each design is followed by a mathematical model that evaluates the steady-state and transient thermal responses of the integrated heat load(s) and the developed cooling system. The designs and the mathematical models are then validated through a series of thermal tests for a variety of driving cycles. Then, the cooling system design configuration is optimized using the validated mathematical model for a particular application. The nonlinear optimization study demonstrates that a 50\% mass reduction could be achieved for a continuous 12kW heat-dissipating demand while the electric motor operating temperature has remained below 65 centigrade degrees. Next, several real-time controllers are designed to engage the active cooling system for precise, stable, and predictable temperature regulation of the electric motor and reduced power consumption. A complete experimental setup compares the controllers in the laboratory’s environment. The experimental results indicate that the nonlinear model predictive control reduces the fan power consumption by 73% for a 5% increase in the pump power usage compared to classical control for a specific 60-minute driving cycle. In conclusion, the conducted experimental and numerical studies demonstrate that the proposed hybrid cooling strategy is an effective solution for the next generation of electrified civilian and combat ground vehicles. It significantly reduces the reliance on fossil fuels and increases vehicle range and safety while offering a silent mode of operation. Future work is to implement the developed hybrid cooling system on an actual electric vehicle, validate the design, and identify challenges on the road

PROBING TEMPORAL CHANGES IN MITOCHONDRIAL MEMBRANE POTENTIAL WITH IMPEDANCE SPECTROSCOPY

The electrical properties of mitochondria provide fundamental insights into metabolic processes in health and disease. This research studies electrical impedance spectroscopy as a non-invasive, sensitive, and relatively low cost technique to monitor biological processes, such as those involving changes in mitochondrial membrane potential. Our experimental strategy first involves treating suspensions of live mitochondria with the substrate succinate to stimulate activity of succinate dehydrogenase, or more simply Complex II. This triggers electron flux through Complex II and the remaining complexes of the electron transport chain, enabling them to pump protons across the inner membrane and build up a membrane potential. Subsequent variability is introduced by adding various concentrations of the uncoupler trifluorocarbonylcyanide phenylhydrazone (FCCP) and the neurotransmitter dopamine (DA) to mitochondrial suspensions, and measuring changes in impedance. Our results show that adding succinate decreases impedance, consistent with an increase in dielectric response and membrane potential. Overall, our investigation establishes real-time impedance spectroscopy as a non-destructive, potentially powerful method for membrane potential studies of mitochondria.Physics, Department o

Multiscale Mechanics of Failure in Extreme Environments

Over the past five decades there has been an intense effort to understand and control the thermomechanical response of materials in extreme environments. A number of technologies and applications critical to our safety and well-being stand to benefit from such understanding, including inertial confinement fusion, nuclear stockpile reliability, defense systems, spacecraft and hypersonic aircraft shielding, as well as vehicular crashworthiness. Materials in such extreme environments often exhibit complex, somewhat non-intuitive behavior that is difficult to predict with empirical or phenomenological models. As such, there has been an increasing effort to understand the microscale processes that govern the macroscale response. Here we provide a contribution to this effort through the development of a number of multiscale mechanism-based models that explore the fundamental nature of various microscale processes governing the macroscale thermomechanical response of materials in extreme environments. The extreme environments of interest here may include pressures on the order of the bulk modulus, shear stresses near the ideal strength, temperatures approaching melting, and timescales ranging from nanoseconds to the age of our Solar System (~5 billion years). We focus on materials in two particular extreme environments in this thesis. First and foremost, we explore the behavior of metals subject to very high rate deformation. Second, we study the behavior of planetary materials subject to the extreme thermomechanical environments in our Solar System. One of the main themes presented in the thesis is that the time-dependent failure of materials is governed, in part, by the kinetics of a hierarchy of microscopic material defects. Furthermore, the kinetics of one particular defect are often governed by lower length-scale defects. Examples of this are provided for twin boundary propagation at high loading rates, dynamic void growth in ductile materials, and fatigue crack growth in quasi-brittle asteroidal materials. A second theme is that simple mechanism-based models are powerful and instructive, particularly when it comes to building an intuition for dynamic failure processes. We make use of such simple scaling laws to help establish a deeper understanding of dynamic ductile failure of metals. We particularly focus on understanding how the rate-sensitivity of spall strength depends on a competition between the pre-existing material microstructure (e.g. second-phase particles and grain boundaries) and the shock-induced microstructure

Evolution of Subglacial Overdeepenings in Response to Sediment Redistribution and Glaciohydraulic Supercooling

Glaciers erode bedrock rapidly, but evacuation of sediments requires efficient subglacial drainage networks. If glaciers erode more rapidly than evacuation proceeds, a protective subglacial till layer can form to armor the bed. Where glaciers cross overdeepenings, local closed depressions, the bed slope opposes the ice surface and lowers the hydraulic potential gradient that drives water flow. Here, we present results of a dynamic, distributed model of coupled basal water flow and sediment transport to show how overdeepenings evolve over the course of a melt season. We use steady-state calculations as well as numerical simulations to understand how alluvial bed erosion alters overdeepenings. Numerical results from a modified form of the Spring-Hutter equations show behaviors that cannot be inferred from either local or steady-state calculations. In general, opposition of surface and bed slopes lessens sediment transport regardless of ice accretion from glaciohydraulic supercooling. Drainage efficiency strongly affects erosion and deposition rates. Results show characteristic behaviors of flow through overdeepenings such as overpressured water systems and accretion rates compatible with field measurements. Simulations that start with overdeepened glacier configurations progress out of a freezing regime where glaciohydraulic supercooling occurs. This progression indicates that glacier hydrology is more strongly affected by erosion and deposition than by freezing from glaciohydraulic supercooling. We discuss how this outcome affects glacier erosion and sediment transport under modern and past ice sheets

A Multicarrier Technique for Monte Carlo Simulation of Electrothermal Transport in Nanoelectronics

The field of microelectronics plays an important role in many areas of engineering and science, being ubiquitous in aerospace, industrial manufacturing, biotechnology, and many other fields. Today, many micro- and nanoscale electronic devices are integrated into one package. e capacity to simulate new devices accurately is critical to the engineering design process, as device engineers use simulations to predict performance characteristics and identify potential issues before fabrication. A problem of particular interest is the simulation of devices which exhibit exotic behaviors due to non-equilibrium thermodynamics and thermal effects such as self-heating. Frequently, it is desirable to predict the level of heat generation, the maximum temperature and its location, and the impact of these thermal effects on the current-voltage (IV) characteristic of a device. is problem is furthermore complicated by nanoscale device dimensions. As the ratio of surface area to volume increases, boundary effects tend to dominate the transfer of energy through a device. Effects such as quantum confinement begin to play a role for nanoscale devices as geometric feature sizes approach the wavelength of the particles involved. Classical approaches to charge transport and heat transfer simulation such as the drift-diffusion approach and Fourier’s law, respectively, do not provide accurate results at these length scales. Instead, the transport processes are governed by the semi-classical Boltzmann transport equation (BTE) with quantum corrections derived from the Schrodinger equation ̈ (SE). In this work, a technique is presented for coupling a 3D phonon Monte Carlo (MC) simulation to an electron multi-subband Monte Carlo (MSBMC) simulation. Both carrier species are first examined separately. An electron MC simulation of bulk silicon, a silicon n-i-n diode, and an intrinsic-channel fin-field effect transistor (FinFET) structure are also presented. A 3D phonon MC algorithm is demonstrated in bulk silicon, a silicon thin film, and a silicon nanoconstriction. These tests verify the correctness of the MC framework. Finally, a novel carrier scattering system which directly accounts for the interaction be- tween the two particle populations inside a nanoscale device is shown. e tool developed supports quantum size effects and is shown to be capable of modeling the exchange of energy between thermal and electronic particle systems in a silicon FinFET

Textile-Based Sensors and Smart Clothing System for Respiratory Monitoring

Long-term respiratory monitoring provides valuable information for diagnostic and clinical treatment. Traditional measures of respiration require a mouthpiece or a mask, neither of which can be used as ubiquitous healthcare equipment. Using a smart clothing system seems to be a better alternative. Researchers in the field of smart textiles have focused on the development of health-related products since the 1990s, and textile-based sensors used for respiratory measurements have been discussed in several projects. Although the soft and flexible characteristics of textile-based sensors make them attractive, the flexibility of the materials also affects the signal quality. In a laboratory situation, where each sensor is tested as a single element, this is not as critical as in a user situation, where the sensor is integrated into the clothing and worn by different users engaging in different activities. The principal objective of this thesis was to explore the possibility of performing reliable respiratory monitoring using a clothing platform. The research began by investigating the possible methods and materials that can be used to produce textile-based sensors for respiratory monitoring applications. The aim was to determine the most suitable method for integrating the sensing function into the clothing system. Study results have shown that sensors made with a conductive coating demonstrated superior performance in terms of sensitivity, stability, and reliability. Therefore, five prototype systems based on conductive coating technique were developed. Sensor placement, signal collection techniques, and the clothing system configuration were the main concerns, while issues related to the sensor wearability, maintenance, and aesthetic appearance, as well as the environment and health, were also discussed. Knitting was found to be the most economical method for producing the textile-based sensors; however, sensors made of knit fabric do not perform as well as the coated ones. Therefore, elastic-conductive hybrid yarns have been created to improve the electro-mechanical properties of knitted-based sensors, and eventually, a prototype with two sensors and a built-in data-bus was made by fully-fashion knitting technique. Two smart clothing system prototypes, based on conductive coating technique, were tested systematically by ten subjects. The first prototype consisted of one sensing element, and the results show that the smart clothing system could successfully monitor the subjects’ breathing patterns during sitting, standing, and different forms of running. The system has also proven to be useful in the observation of sleep apnea disorder symptoms. The second prototype consisted of two sensing elements. Apart from all the characteristics of the first prototype system, a system with two sensing elements can be used to determine the relationship between the rib cage and abdomen compartments, which provides information for certain diseases, e.g., cardiac arrhythmias. The second smart clothing system prototype was compared with a conventional respiratory belt for validation. Signals from the clothing system and the respiratory belt were collected simultaneously with a self-designed LabVIEW program, and further processed with MATLAB. Quantitative analyses were conducted based upon different comparison techniques, such as Pearson’s correlation, ANOVA and Fast Fourier Transform analysis. The results demonstrate that the smart clothing system can provide reliable respiratory measurements, with signals of comparable quality to the conventional respiratory belt. In addition, the wearability and user acceptance were studied by means of a survey. The survey results indicate that users were more comfortable with the smart clothing system and that most believe that using a smart clothing system will improve both health condition and quality of life

Textile-Based Sensors and Smart Clothing System for Respiratory Monitoring

Long-term respiratory monitoring provides valuable information for diagnostic and clinical treatment. Traditional measures of respiration require a mouthpiece or a mask, neither of which can be used as ubiquitous healthcare equipment. Using a smart clothing system seems to be a better alternative. Researchers in the field of smart textiles have focused on the development of health-related products since the 1990s, and textile-based sensors used for respiratory measurements have been discussed in several projects. Although the soft and flexible characteristics of textile-based sensors make them attractive, the flexibility of the materials also affects the signal quality. In a laboratory situation, where each sensor is tested as a single element, this is not as critical as in a user situation, where the sensor is integrated into the clothing and worn by different users engaging in different activities. The principal objective of this thesis was to explore the possibility of performing reliable respiratory monitoring using a clothing platform. The research began by investigating the possible methods and materials that can be used to produce textile-based sensors for respiratory monitoring applications. The aim was to determine the most suitable method for integrating the sensing function into the clothing system. Study results have shown that sensors made with a conductive coating demonstrated superior performance in terms of sensitivity, stability, and reliability. Therefore, five prototype systems based on conductive coating technique were developed. Sensor placement, signal collection techniques, and the clothing system configuration were the main concerns, while issues related to the sensor wearability, maintenance, and aesthetic appearance, as well as the environment and health, were also discussed. Knitting was found to be the most economical method for producing the textile-based sensors; however, sensors made of knit fabric do not perform as well as the coated ones. Therefore, elastic-conductive hybrid yarns have been created to improve the electro-mechanical properties of knitted-based sensors, and eventually, a prototype with two sensors and a built-in data-bus was made by fully-fashion knitting technique. Two smart clothing system prototypes, based on conductive coating technique, were tested systematically by ten subjects. The first prototype consisted of one sensing element, and the results show that the smart clothing system could successfully monitor the subjects’ breathing patterns during sitting, standing, and different forms of running. The system has also proven to be useful in the observation of sleep apnea disorder symptoms. The second prototype consisted of two sensing elements. Apart from all the characteristics of the first prototype system, a system with two sensing elements can be used to determine the relationship between the rib cage and abdomen compartments, which provides information for certain diseases, e.g., cardiac arrhythmias. The second smart clothing system prototype was compared with a conventional respiratory belt for validation. Signals from the clothing system and the respiratory belt were collected simultaneously with a self-designed LabVIEW program, and further processed with MATLAB. Quantitative analyses were conducted based upon different comparison techniques, such as Pearson’s correlation, ANOVA and Fast Fourier Transform analysis. The results demonstrate that the smart clothing system can provide reliable respiratory measurements, with signals of comparable quality to the conventional respiratory belt. In addition, the wearability and user acceptance were studied by means of a survey. The survey results indicate that users were more comfortable with the smart clothing system and that most believe that using a smart clothing system will improve both health condition and quality of life