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Virginia Tech
1.
Todaria, Prakhar.
Design, Modelling, and Test of an Electromagnetic Speed Bump Energy Harvester.
Degree: MS, Mechanical Engineering, 2016, Virginia Tech
URL: http://hdl.handle.net/10919/73795 
► Speed bump energy harvester, which aims to harvest energy from the passing by vehicles by absorbing their kinetic and potential energy, is designed, fabricated, simulated,…
(more)
▼ Speed bump energy harvester, which aims to harvest energy from the passing by vehicles by absorbing their kinetic and potential energy, is designed, fabricated, simulated, and tested in this research. The proposed design is analyzed with a theoretical modelling which has then been validated with a ground test. Result reveals that the prototype has been able to produce up to 600 watts of peak power and around 150 watts of RMS power which is significant number. Further analysis has been done which theoretically suggests that the numbers could be increased up to 1 KW by optimizing the speed bump design and varying the system parameters such as electrical damping, mechanical damping, velocity and weight of the vehicles. Overall, system is able to increase the overall energy density by using Mechanical Motion Rectification (MMR) technology which would allow the increase in the power generation almost by double. Furthermore, different vehicle models have been used to analyze the effectiveness and accuracy of the harvester and also, the effect of harvester on the dynamics of the vehicle has been studied and analyzed in detail.
Advisors/Committee Members: Zuo, Lei (committeechair), Taheri, Saied (committee member), Wang, Linbing (committee member).
Subjects/Keywords: speed bump; energy harvester; modelling; design; vehicle dynamics
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APA (6th Edition):
Todaria, P. (2016). Design, Modelling, and Test of an Electromagnetic Speed Bump Energy Harvester. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/73795
Chicago Manual of Style (16th Edition):
Todaria, Prakhar. “Design, Modelling, and Test of an Electromagnetic Speed Bump Energy Harvester.” 2016. Masters Thesis, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/73795.
MLA Handbook (7th Edition):
Todaria, Prakhar. “Design, Modelling, and Test of an Electromagnetic Speed Bump Energy Harvester.” 2016. Web. 28 Feb 2020.
Vancouver:
Todaria P. Design, Modelling, and Test of an Electromagnetic Speed Bump Energy Harvester. [Internet] [Masters thesis]. Virginia Tech; 2016. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/73795.
Council of Science Editors:
Todaria P. Design, Modelling, and Test of an Electromagnetic Speed Bump Energy Harvester. [Masters Thesis]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/73795
Virginia Tech
2.
Wu, You.
Multi-source Energy Harvesting for Wildlife Tracking.
Degree: MS, Mechanical Engineering, 2015, Virginia Tech
URL: http://hdl.handle.net/10919/54022
► Sufficient power supply to run GPS machinery and transmit data on a long-term basis remains to be the key challenge for wildlife tracking technology. Traditional…
(more)
▼ Sufficient power supply to run GPS machinery and transmit data on a long-term basis remains to be the key challenge for wildlife tracking technology. Traditional ways of replacing battery periodically is not only time and money consuming but also dangerous to live-trapping wild animals. In this paper, an innovative wildlife tracking collar with multi-source energy harvester with advantage of high efficiency and reliability is proposed. This multi-source energy harvester entails a solar energy harvester and an innovative rotational electromagnetic energy harvester is mounted on the "wildlife tracking collar" which will extend the duration of wild life tracking by 20% time as was estimated. A feedforward and feedback control of DC-DC converter circuit is adopted to passively realize the Maximum Power Point Tracking (MPPT) logic for the solar energy harvester. A novel electromagnetic pendulum energy harvester with motion regulator is proposed which can mechanically rectify the irregular bidirectional swing motion of the pendulum into unidirectional rotational motion of the motor. No electrical rectifier is needed and voltage drops from diodes can be avoided, the EM pendulum energy harvester can provide 200~300 mW under the 0.4g base excitation of 4.5 Hz. The nonlinearity of the disengage mechanism in the pendulum energy harvester will lead to a broad bandwidth frequency response. Simulation results shows the broadband advantage of the proposed energy harvester and experiment results verified that at some frequencies over the natural frequency the efficiency is increased.
Advisors/Committee Members: Zuo, Lei (committeechair), Parker, Robert G. (committee member), Southward, Steve C. (committee member).
Subjects/Keywords: Multi-source energy harvester; wildlife tracking; electromagnetic energy harvester; Mechanical Motion Rectifier (MMR); solar energy harvester; Maximum Power Point Tracking (MPPT)
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APA (6th Edition):
Wu, Y. (2015). Multi-source Energy Harvesting for Wildlife Tracking. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/54022
Chicago Manual of Style (16th Edition):
Wu, You. “Multi-source Energy Harvesting for Wildlife Tracking.” 2015. Masters Thesis, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/54022.
MLA Handbook (7th Edition):
Wu, You. “Multi-source Energy Harvesting for Wildlife Tracking.” 2015. Web. 28 Feb 2020.
Vancouver:
Wu Y. Multi-source Energy Harvesting for Wildlife Tracking. [Internet] [Masters thesis]. Virginia Tech; 2015. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/54022.
Council of Science Editors:
Wu Y. Multi-source Energy Harvesting for Wildlife Tracking. [Masters Thesis]. Virginia Tech; 2015. Available from: http://hdl.handle.net/10919/54022
Virginia Tech
3.
Klein, Jackson Alexander.
Energy Harvesting Opportunities Throughout the Nuclear Power Cycle for Self-Powered Wireless Sensor Nodes.
Degree: MS, Mechanical Engineering, 2017, Virginia Tech
URL: http://hdl.handle.net/10919/78031
► Dedicated sensors are widely used throughout many industries to monitor everyday operations, maintain safety, and report performance characteristics. In order to adopt a more sustainable…
(more)
▼ Dedicated sensors are widely used throughout many industries to monitor everyday operations, maintain safety, and report performance characteristics. In order to adopt a more sustainable solution, much research is being applied to self-powered sensing, implementing solutions which harvest wasted ambient energy sources to power these dedicated sensors. The adoption of not only wireless sensor nodes, but also self-powered capabilities in the nuclear energy process is critical as it can address issues in the overall safety and longevity of nuclear power. The removal of wires for data and power transmission can greatly reduce the cost of both installation and upkeep of power plants, while self-powered capabilities can further reduce effort and money spent in replacing batteries, and importantly may enable sensors to work even in losses to power across the plant, increasing plant safety. This thesis outlines three harvesting opportunities in the nuclear energy process from: thermal, vibration, and radiation sources in the main structure of the power plant, and from thermal and radiation energy from spent fuel in dry cask storage. Thermal energy harvesters for the primary and secondary coolant loops are outlined, and experimental analysis done on their longevity in high-radiation environments is discussed. A vibrational energy harvester for large rotating plant machine vibration is designed, prototyped, and tested, and a model is produced to describe its motion and energy output. Finally, an introduction to the design of a gamma radiation and thermal energy harvester for spent nuclear fuel canisters is discussed, and further research steps are suggested.
Advisors/Committee Members: Zuo, Lei (committeechair), Huxtable, Scott T. (committee member), Pierson, Mark Alan (committee member).
Subjects/Keywords: Energy Harvesting; Nuclear Power Plant; Wireless Sensor Node; Electromagnetic Generator; Compliant Mechanism; Thermoelectric Generator; Gamma Radiation; MCNP Simulation; Gamma Heating; Dry Cask Storage
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APA (6th Edition):
Klein, J. A. (2017). Energy Harvesting Opportunities Throughout the Nuclear Power Cycle for Self-Powered Wireless Sensor Nodes. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78031
Chicago Manual of Style (16th Edition):
Klein, Jackson Alexander. “Energy Harvesting Opportunities Throughout the Nuclear Power Cycle for Self-Powered Wireless Sensor Nodes.” 2017. Masters Thesis, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/78031.
MLA Handbook (7th Edition):
Klein, Jackson Alexander. “Energy Harvesting Opportunities Throughout the Nuclear Power Cycle for Self-Powered Wireless Sensor Nodes.” 2017. Web. 28 Feb 2020.
Vancouver:
Klein JA. Energy Harvesting Opportunities Throughout the Nuclear Power Cycle for Self-Powered Wireless Sensor Nodes. [Internet] [Masters thesis]. Virginia Tech; 2017. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/78031.
Council of Science Editors:
Klein JA. Energy Harvesting Opportunities Throughout the Nuclear Power Cycle for Self-Powered Wireless Sensor Nodes. [Masters Thesis]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/78031
Virginia Tech
4.
Norman, Adam Edward.
A Fundamental Study of Advance Ratio, Solidity, Turbine Radius, and Blade Profile on the Performance Characteristics of Vertical Axis Turbines (VATs).
Degree: MS, Mechanical Engineering, 2016, Virginia Tech
URL: http://hdl.handle.net/10919/81836
► In this dissertation, various VAT parameters are investigated to determine the effect of the overall efficiency of the turbine at a high Reynolds number. To…
(more)
▼ In this dissertation, various VAT parameters are investigated to determine the effect of the overall efficiency of the turbine at a high Reynolds number. To increase the efficiency of the vertical axis turbines, 2D CFD simulations are completed in an effort to better understand the physics behind the operation of these turbines. Specifically, the effect of advance ratio, solidity, and wake interactions were investigated. Simulations were completed in OpenFOAM using the k-ω SST turbulence model at a nominal Reynolds number of 500,000 using a NACA 0015 airfoil. To simulate the motion of the turbine, Arbitrary Mesh Interfacing (AMI) was used. For all of the parameters tested, it was found that the geometric effective angle of attack seen by the turbine blades had a significant impact on the power extracted from the flow. The range of effective angles of attack was found to decrease as the advance ratio increased. In spite of this, a severe loss in the power coefficient occurred at an advance ratio of 2.5 during which the blade experienced dynamic stall. This effect was also seen when the number of turbine blades was changed to four, at a solidity of 1.08. This negative impact on performance was found to be due to the increase in the drag component of the tangential force when dynamic stall occurs. Results indicate that wake interactions between subsequent blades have a large impact on performance especially when the wake interaction alters the flow direction sufficiently to create conditions for dynamic stall.
To improve the performance of the VAT in the presence of dynamic stall, calculations were completed of a static twisted blade profile using GenIDLEST and OpenFOAM. There was found to be no improvement in the lift coefficient when comparing the twisted blade profile with a 2D blade at the same median angle of attack as the twisted blade. To further see the effects of the twisted blade, an effective VAT pitching motion was given to the blade and again compared to a 2D blade with the same motion. In this case there was significant improvement seen in the performance of the twisted blade.
Advisors/Committee Members: Tafti, Danesh K. (committeechair), Battaglia, Francine (committee member), Zuo, Lei (committee member).
Subjects/Keywords: Computational Fluid Dynamics (CFD); Reynolds Averaged Navier-Stokes (RANS); Large Eddy Simulation (LES) vertical axis turbine; dynamics stall; advance ratio; solidity; wake
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APA (6th Edition):
Norman, A. E. (2016). A Fundamental Study of Advance Ratio, Solidity, Turbine Radius, and Blade Profile on the Performance Characteristics of Vertical Axis Turbines (VATs). (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/81836
Chicago Manual of Style (16th Edition):
Norman, Adam Edward. “A Fundamental Study of Advance Ratio, Solidity, Turbine Radius, and Blade Profile on the Performance Characteristics of Vertical Axis Turbines (VATs).” 2016. Masters Thesis, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/81836.
MLA Handbook (7th Edition):
Norman, Adam Edward. “A Fundamental Study of Advance Ratio, Solidity, Turbine Radius, and Blade Profile on the Performance Characteristics of Vertical Axis Turbines (VATs).” 2016. Web. 28 Feb 2020.
Vancouver:
Norman AE. A Fundamental Study of Advance Ratio, Solidity, Turbine Radius, and Blade Profile on the Performance Characteristics of Vertical Axis Turbines (VATs). [Internet] [Masters thesis]. Virginia Tech; 2016. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/81836.
Council of Science Editors:
Norman AE. A Fundamental Study of Advance Ratio, Solidity, Turbine Radius, and Blade Profile on the Performance Characteristics of Vertical Axis Turbines (VATs). [Masters Thesis]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/81836
Virginia Tech
5.
Cooke, Daniel Benjamin.
Design and Optimization of a Self-powered Thermoelectric Car Seat Cooler.
Degree: MS, Mechanical Engineering, 2018, Virginia Tech
URL: http://hdl.handle.net/10919/83374
► It is well known that the seats in a parked vehicle become very hot and uncomfortable on warm days. A new self-powered thermoelectric car seat…
(more)
▼ It is well known that the seats in a parked vehicle become very hot and uncomfortable on warm days. A new self-powered thermoelectric car seat cooler is presented to solve this problem. This study details the design and optimization of such a device. The design relates to the high level layout of the major components and their relation to each other in typical operation. Optimization is achieved through the use of the ideal thermoelectric equations to determine the best compromise between power generation and cooling performance. This design is novel in that the same thermoelectric device is utilized for both power generation and for cooling. The first step is to construct a conceptual layout of the self-powered seat cooler. Using the ideal thermoelectric equations, an analytical model of the system is developed. The model is validated against experimental data and shows good correlation. Through a non-dimensional approach, the geometric sizing of the various components is optimized. With the optimal design found, the performance is evaluated using both the ideal equations and though use of the simulation software ANSYS. The final design consists of a flat absorber plate embedded into the car seat with a thermoelectric attached to the back. A finned heat sink is used to cool the thermoelectric. The device is shown to generate enough power to provide a reasonable temperature drop in the seat.
Advisors/Committee Members: Tian, Zhiting (committeechair), Zuo, Lei (committee member), Huxtable, Scott T. (committee member).
Subjects/Keywords: Non-dimensional Equations; Solar Thermoelectric Generator; Thermoelectric Cooler
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APA (6th Edition):
Cooke, D. B. (2018). Design and Optimization of a Self-powered Thermoelectric Car Seat Cooler. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/83374
Chicago Manual of Style (16th Edition):
Cooke, Daniel Benjamin. “Design and Optimization of a Self-powered Thermoelectric Car Seat Cooler.” 2018. Masters Thesis, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/83374.
MLA Handbook (7th Edition):
Cooke, Daniel Benjamin. “Design and Optimization of a Self-powered Thermoelectric Car Seat Cooler.” 2018. Web. 28 Feb 2020.
Vancouver:
Cooke DB. Design and Optimization of a Self-powered Thermoelectric Car Seat Cooler. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/83374.
Council of Science Editors:
Cooke DB. Design and Optimization of a Self-powered Thermoelectric Car Seat Cooler. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/83374
Virginia Tech
6.
Tan, Li.
A Computational Iteration Method to Analyze Mechanics of Timing Belt Systems with Non-Circular Pulleys.
Degree: MS, Mechanical Engineering, 2018, Virginia Tech
URL: http://hdl.handle.net/10919/84991
► Timing belt systems, usually consisting of a toothed belt and multiple pulleys, are used in many mechanical devices, especially in the internal combustion engine to…
(more)
▼ Timing belt systems, usually consisting of a toothed belt and multiple pulleys, are used in many mechanical devices, especially in the internal combustion engine to synchronize the rotation of the crankshafts and the camshafts. When the system operates, the belt teeth will be transmitted by the pulley teeth meshed with them. Timing belt drives can make sure that the engine' s valves open and close properly due to their precise transmission ratio. In this thesis, a quasi-static computational model is developed to calculate the belt load distributions and the torques around pulleys for different timing belt systems. The simplest system is a two-pulley system with one oval pulley and one circular pulley. This computational model is then extended to a two-pulley system with one special-shaped pulley and finally generalized to determine the load conditions for a multi-pulley system with multiple special-shaped pulleys. Belt tooth deflections, tooth loads, belt tension distributions, friction forces, and the effect of friction hysteresis have been taken into consideration. Results of these quantities are solved by a nested numerical iteration method. Periodic torques generated by the varied radius of noncircular pulley are calculated by this computational model to cancel the undesired external cyclic torque, which will increase the life of timing belts.
Advisors/Committee Members: Parker, Robert G. (committeechair), Zuo, Lei (committee member), Sandu, Corina (committee member).
Subjects/Keywords: Timing Belt; Non-circular Pulley; Torque.
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APA (6th Edition):
Tan, L. (2018). A Computational Iteration Method to Analyze Mechanics of Timing Belt Systems with Non-Circular Pulleys. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/84991
Chicago Manual of Style (16th Edition):
Tan, Li. “A Computational Iteration Method to Analyze Mechanics of Timing Belt Systems with Non-Circular Pulleys.” 2018. Masters Thesis, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/84991.
MLA Handbook (7th Edition):
Tan, Li. “A Computational Iteration Method to Analyze Mechanics of Timing Belt Systems with Non-Circular Pulleys.” 2018. Web. 28 Feb 2020.
Vancouver:
Tan L. A Computational Iteration Method to Analyze Mechanics of Timing Belt Systems with Non-Circular Pulleys. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/84991.
Council of Science Editors:
Tan L. A Computational Iteration Method to Analyze Mechanics of Timing Belt Systems with Non-Circular Pulleys. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/84991
7.
Pei, Yalu.
Multi-resonant Electromagnetic Shunt in Base Isolation for Vibration Damping and Energy Harvesting.
Degree: MS, Mechanical Engineering, 2017, Virginia Tech
URL: http://hdl.handle.net/10919/74975
► The objective of this thesis is to develop a dual-functional approach to effectively mitigate the earthquake induced vibrations of low- or mid-rise buildings, and at…
(more)
▼ The objective of this thesis is to develop a dual-functional approach to effectively mitigate the earthquake induced vibrations of low- or mid-rise buildings, and at the same time to efficiently harvest utility-scale energy by using an optimally configured multi-resonant electromagnetic shunt in base isolation. In this research, two multi-resonant shunt configurations, parallel and series, were proposed and optimized based on the H2 criteria when the base isolation system is subjected to ground acceleration excitations. The performance of the proposed multi-resonant electromagnetic shunt was compared with traditional multiple tuned mass dampers (TMDs) applied to the base isolation system. It shows that, for multiple TMDs and multi-resonant electromagnetic shunt dampers with 5% total stiffness ratio, the parallel shunt electromagnetic shunt can achieve the best vibration mitigation performance among other types of multi-resonant dampers, including parallel TMDs, series TMDs and the series electromagnetic shunt damper.
Case study of a base-isolated structure was analyzed to investigate the effectiveness of the proposed multi-resonant electromagnetic shunt. It shows that both multi-mode shunt circuits outperform single mode shunt circuit by suppressing the primary and the second vibration modes simultaneously. Comparatively, the parallel shunt circuit is more effective in vibration mitigation and energy harvesting, and is also more robust in parameter mistuning than the series shunt circuit. The time history response analysis shows that, under the recorded Northridge earthquake, the instant peak power and total average power capable to be harvested by the multi-resonant shunt can reach up to 1.18 MW and 203.37KW, respectively.
This thesis further experimentally validated the effectiveness of the multi-resonant electromagnetic shunt on a scaled-down base-isolated building. The impact hammer test shows that the multi-resonant electromagnetic shunt can achieve enhanced vibration suppression by reducing the first resonant peak by 27.50dB and the second resonant peak by 22.57dB regarding the primary structure acceleration. The shake table test shows that under scaled Kobe and Northridge earthquake signals, the electromagnetic shunt can effectively reduce the vibration resonant peak value by 38.92% and 66.61%, respectively. The voltage simultaneously generated in the multi-mode shunt circuit was also obtained, which demonstrated the dual functions of the multi-resonant electromagnetic shunt in base isolation.
Advisors/Committee Members: Zuo, Lei (committeechair), Hajj, Muhammad R. (committee member), Priya, Shashank (committee member).
Subjects/Keywords: Base isolation; Vibration damping; Energy harvesting; Electromagnetic shunt; Multi-mode resonant circuits
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APA (6th Edition):
Pei, Y. (2017). Multi-resonant Electromagnetic Shunt in Base Isolation for Vibration Damping and Energy Harvesting. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/74975
Chicago Manual of Style (16th Edition):
Pei, Yalu. “Multi-resonant Electromagnetic Shunt in Base Isolation for Vibration Damping and Energy Harvesting.” 2017. Masters Thesis, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/74975.
MLA Handbook (7th Edition):
Pei, Yalu. “Multi-resonant Electromagnetic Shunt in Base Isolation for Vibration Damping and Energy Harvesting.” 2017. Web. 28 Feb 2020.
Vancouver:
Pei Y. Multi-resonant Electromagnetic Shunt in Base Isolation for Vibration Damping and Energy Harvesting. [Internet] [Masters thesis]. Virginia Tech; 2017. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/74975.
Council of Science Editors:
Pei Y. Multi-resonant Electromagnetic Shunt in Base Isolation for Vibration Damping and Energy Harvesting. [Masters Thesis]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/74975
8.
Martin, Dillon Minkoff.
Hydrodynamic Design Optimization and Wave Tank Testing of Self-Reacting Two-Body Wave Energy Converter.
Degree: MS, Mechanical Engineering, 2017, Virginia Tech
URL: http://hdl.handle.net/10919/80298
► As worldwide energy consumption continues to increase, so does the demand for renewable energy sources. The total available wave energy resource for the United States…
(more)
▼ As worldwide energy consumption continues to increase, so does the demand for renewable energy sources. The total available wave energy resource for the United States alone is 2,640 TWh/yr; nearly two thirds of the 4,000 TWh of electricity used in the United States each year. It is estimated that nearly half of that available energy is recoverable through wave energy conversion techniques. In this thesis, a two-body 'point absorber' type wave energy converter with a mechanical power-takeoff is investigated. The two-body wave energy converter extracts energy through the relative motion of a floating buoy and a neutrally buoyant submerged body. Using a linear frequency-domain model, analytical solutions of the optimal power and the corresponding power-takeoff components are derived for the two-body wave energy converter. Using these solutions, a case study is conducted to investigate the influence of the submerged body size on the absorbed power of the device in regular and irregular waves. Here it is found that an optimal mass ratio between the submerged body and floating buoy exists where the device will achieve resonance. Furthermore, a case study to investigate the influence of the submerged body shape on the absorbed power is conducted using a time-domain numerical model. Here it is found that the submerged body should be designed to reduce the effects of drag, but to maintain relatively large hydrodynamic added mass and excitation force. To validate the analytical and numerical models, a 1/30th scale model of a two-body wave energy converter is tested in a wave tank. The results of the wave tank tests show that the two-body wave energy converter can absorb nearly twice the energy of a single-body 'point absorber' type wave energy converter.
Advisors/Committee Members: Zuo, Lei (committeechair), Parker, Robert G. (committee member), Tafti, Danesh K. (committee member).
Subjects/Keywords: ocean wave energy harvesting; wave energy converter; point absorber; two-body; hydrodynamics; power optimization; shape optimization
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APA (6th Edition):
Martin, D. M. (2017). Hydrodynamic Design Optimization and Wave Tank Testing of Self-Reacting Two-Body Wave Energy Converter. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/80298
Chicago Manual of Style (16th Edition):
Martin, Dillon Minkoff. “Hydrodynamic Design Optimization and Wave Tank Testing of Self-Reacting Two-Body Wave Energy Converter.” 2017. Masters Thesis, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/80298.
MLA Handbook (7th Edition):
Martin, Dillon Minkoff. “Hydrodynamic Design Optimization and Wave Tank Testing of Self-Reacting Two-Body Wave Energy Converter.” 2017. Web. 28 Feb 2020.
Vancouver:
Martin DM. Hydrodynamic Design Optimization and Wave Tank Testing of Self-Reacting Two-Body Wave Energy Converter. [Internet] [Masters thesis]. Virginia Tech; 2017. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/80298.
Council of Science Editors:
Martin DM. Hydrodynamic Design Optimization and Wave Tank Testing of Self-Reacting Two-Body Wave Energy Converter. [Masters Thesis]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/80298
9.
Wang, Dong.
Image-based Vehicle Localization.
Degree: MS, Computer Engineering, 2019, Virginia Tech
URL: http://hdl.handle.net/10919/90795
► In modern days, global positioning system (GPS) is the major approach to locate positions. However, GPS is not as reliable as we thought. Under some…
(more)
▼ In modern days, global positioning system (GPS) is the major approach to locate positions. However, GPS is not as reliable as we thought. Under some environmental situations, GPS cannot provide continuous navigation information. Besides, GPS signals can be jammed or spoofed by malicious attackers. In this thesis, we aim to explore how to locate the vehicle’s position without using GPS sensor. Here, we propose a novel image-based vehicle localization by utilizing vision sensor and computer vision techniques to extract vehicle surrounding text landmarks and to locate the vehicle position. Various tools and techniques are explored in the process of the research. With the explored result, we propose several localization models and simulate an experiment to prove the robustness of these models.
Advisors/Committee Members: Yang, Yaling (committeechair), Zuo, Lei (committee member), Plassmann, Paul E. (committee member).
Subjects/Keywords: image-based; vehicle localization; text landmark
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APA (6th Edition):
Wang, D. (2019). Image-based Vehicle Localization. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/90795
Chicago Manual of Style (16th Edition):
Wang, Dong. “Image-based Vehicle Localization.” 2019. Masters Thesis, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/90795.
MLA Handbook (7th Edition):
Wang, Dong. “Image-based Vehicle Localization.” 2019. Web. 28 Feb 2020.
Vancouver:
Wang D. Image-based Vehicle Localization. [Internet] [Masters thesis]. Virginia Tech; 2019. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/90795.
Council of Science Editors:
Wang D. Image-based Vehicle Localization. [Masters Thesis]. Virginia Tech; 2019. Available from: http://hdl.handle.net/10919/90795
10.
Yuan, Yue.
Backpack Energy Harvester with Human Walking Model.
Degree: MS, Mechanical Engineering, 2017, Virginia Tech
URL: http://hdl.handle.net/10919/77920
► The objective of this thesis is to design, analyze, and fabricate an innovative backpack energy harvester for human walking. To model human walking with backpack…
(more)
▼ The objective of this thesis is to design, analyze, and fabricate an innovative backpack energy harvester for human walking. To model human walking with backpack energy harvester, a simple dual-mass model has been developed and studied first. Dual-mass model for three types of distinct harvesters were investigated, pure damping, traditional rack pinion energy harvester and our MMR based energy harvester. A comparison in the output power and human comfort between the three types of harvesters is discussed. However, the dual-mass model could not effectively represent human walking in real situation with sinusoidal input, like M shaped Ground Reaction Force (GRF), vertical Center of Mass (COM) motion, etc. Thus, a bipedal walking model has been proposed to simulate human walking with backpack harvester.
Experiments were conducted to compare power output and efficiency of MMR based backpack energy harvester with traditional rack pinion backpack energy harvester, and verify conclusions from the bipedal walking model that the proposed backpack energy harvester using mechanical motion rectifier (MMR) mechanism has larger power output than traditional backpack energy harvester at different walking speed. In human treadmill test, subjects were asked to wear the backpack frame which embedded with harvesters walking on a treadmill. Two walking speed, 3mph and 3.5mph, and four resistor values has been tested. The test results showed that the MMR based backpack energy harvester generated more power regardless of resistor values and walking speed. Up to 4.84W average power and instant power of 12.8W could be obtained while the subject walking on the treadmill at 3.5mph speed with MMR based backpack energy harvester.
Advisors/Committee Members: Zuo, Lei (committeechair), Mueller, Rolf (committee member), Queen, Robin M. (committee member).
Subjects/Keywords: Energy harvesting; Mechanical motion rectifier (MMR); Backpack energy harvester
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APA (6th Edition):
Yuan, Y. (2017). Backpack Energy Harvester with Human Walking Model. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/77920
Chicago Manual of Style (16th Edition):
Yuan, Yue. “Backpack Energy Harvester with Human Walking Model.” 2017. Masters Thesis, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/77920.
MLA Handbook (7th Edition):
Yuan, Yue. “Backpack Energy Harvester with Human Walking Model.” 2017. Web. 28 Feb 2020.
Vancouver:
Yuan Y. Backpack Energy Harvester with Human Walking Model. [Internet] [Masters thesis]. Virginia Tech; 2017. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/77920.
Council of Science Editors:
Yuan Y. Backpack Energy Harvester with Human Walking Model. [Masters Thesis]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/77920
11.
Racioppo, Peter Charles.
Design and Control of a Cable-Driven Articulated Modular Snake Robot.
Degree: MS, Mechanical Engineering, 2018, Virginia Tech
URL: http://hdl.handle.net/10919/91983
► This thesis presents the design and control of a cable-actuated mobile snake robot. The goal of this research is to reduce the size of snake…
(more)
▼ This thesis presents the design and control of a cable-actuated mobile snake robot. The goal of this research is to reduce the size of snake robots and improve their locomotive efficiency by simultaneously actuating groups of links to fit optimized curvature profiles. The basic functional unit of the snake is a four-link, single degree of freedom module that bends using an antagonistic cable-routing scheme. Elastic elements in series with the cables and the coupled nature of the mechanism allow each module to detect and automatically respond to obstacles. The mechanical and electrical designs of the bending module are presented, with emphasis on the cable-routing scheme, key optimizations, and the use of series elastic actuation. An approximate expression for the propulsive force generated by a snake as a function of its articulation (i.e. the number of links it contains divided by its body length) is derived and a closed-form approximation for the optimal phase offset between joints to maximize the speed of a snake is obtained by simplifying a previous result. A simplified model of serpentine locomotion that considers the forces acting on a single link as it traverses a sinusoid is presented and compared to a detailed multibody dynamic model. Control strategies for snake robots with coupled joints are developed, along with a feedback linearization of the joint dynamics. Experimental studies of force control, locomotion, and adaptation to obstacles using a fully integrated prototype are presented and compared with simulated results.
Advisors/Committee Members: Ben-Tzvi, Pinhas (committeechair), Wicks, Alfred L (committee member), Zuo, Lei (committee member).
Subjects/Keywords: robot dynamics; mobile robots; force control; modeling
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APA (6th Edition):
Racioppo, P. C. (2018). Design and Control of a Cable-Driven Articulated Modular Snake Robot. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/91983
Chicago Manual of Style (16th Edition):
Racioppo, Peter Charles. “Design and Control of a Cable-Driven Articulated Modular Snake Robot.” 2018. Masters Thesis, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/91983.
MLA Handbook (7th Edition):
Racioppo, Peter Charles. “Design and Control of a Cable-Driven Articulated Modular Snake Robot.” 2018. Web. 28 Feb 2020.
Vancouver:
Racioppo PC. Design and Control of a Cable-Driven Articulated Modular Snake Robot. [Internet] [Masters thesis]. Virginia Tech; 2018. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/91983.
Council of Science Editors:
Racioppo PC. Design and Control of a Cable-Driven Articulated Modular Snake Robot. [Masters Thesis]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/91983
12.
Chu, Chiang-Kai.
Energy Redistribution with Controllable Binary State Latch Element.
Degree: MS, Mechanical Engineering, 2017, Virginia Tech
URL: http://hdl.handle.net/10919/78336
► An application of binary state latch device with proper real-time control algorithm for energy redistribution application is introduced in this thesis. Unlike traditional tuned vibration…
(more)
▼ An application of binary state latch device with proper real-time control algorithm for energy
redistribution application is introduced in this thesis. Unlike traditional tuned vibration
absorber, the latch device can be viewed as variable semi-active dampers such as magnetorheological
(MR) and piezoelectric friction dampers. The distinct difference between other
semi-active dampers and our latch device is that other semi-active dampers can provide continuous
resistance according to the amount of input current, however, the binary latch device
can only provide two different values of resistance - either the maximum or no resistance
at all. This property brings the latch possibly having higher maximum and minimum ratio
of resistance than MR dampers. As for the operating structure, the mechanism of latch
element is nearly the same as the piezoelectric friction dampers which the resistance force is
provided according to the normal force acting on two rough plates. Nonetheless, because of
the characteristic of the binary states output of the latch element, this make it very different
from the ordinary variable dampers. Since it is either being turned on or turned off, a novel
control law is required for shifting energy. Also, because of the simplicity of the binary states
output, it is very accessible to implement the controller on Field Programmable Gate Array
(FPGA). With this accessibility, it is promising to apply plenty of latch elements in the same
time for large scale application, such as multi-agent networks. In this thesis, an energy-based
analytic solution is proposed to illustrate the universal latch-off condition. And a latch-on
condition under ideal situations is discussed. At the end, a control law under nonideal condition
is being suggested for real-time periodically excited system. We found that energy
redistribution is achievable by using the proper control law under fairly broad conditions.
Advisors/Committee Members: Southward, Steve C. (committeechair), Zuo, Lei (committee member), Kurdila, Andrew J. (committee member).
Subjects/Keywords: Energy redistribution; Vibration control; Variable Structure System
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APA (6th Edition):
Chu, C. (2017). Energy Redistribution with Controllable Binary State Latch Element. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78336
Chicago Manual of Style (16th Edition):
Chu, Chiang-Kai. “Energy Redistribution with Controllable Binary State Latch Element.” 2017. Masters Thesis, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/78336.
MLA Handbook (7th Edition):
Chu, Chiang-Kai. “Energy Redistribution with Controllable Binary State Latch Element.” 2017. Web. 28 Feb 2020.
Vancouver:
Chu C. Energy Redistribution with Controllable Binary State Latch Element. [Internet] [Masters thesis]. Virginia Tech; 2017. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/78336.
Council of Science Editors:
Chu C. Energy Redistribution with Controllable Binary State Latch Element. [Masters Thesis]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/78336
Virginia Tech
13.
Mao, Yincan.
Passive Balancing of Switching Transients between Paralleled SiC MOSFETs.
Degree: PhD, Electrical Engineering, 2018, Virginia Tech
URL: http://hdl.handle.net/10919/82203
► The SiC MOSFET has attracted interest due to its superior characteristics compared to its Si counterpart. Several SiC MOSFETs are usually paralleled to increase current…
(more)
▼ The SiC MOSFET has attracted interest due to its superior characteristics compared to its Si counterpart. Several SiC MOSFETs are usually paralleled to increase current capability, considering cost effectiveness and manufacturability. Current unbalance among the MOSFETs is a concern as it affects reliability. The two main causes are asymmetrical layout and parameter mismatch. The variation in parameters, unlike circuit or module layout, is unavoidable during production. Among all the parameters of MOSFET, the spreads in on-state resistance (Rds(on)) and threshold voltage (Vth) are the major concerns during paralleling. The disparity in Rds(on) causes static current unbalance which is self-limited due to the positive temperature coefficient of Rds(on). Its influence is not investigated here. The threshold voltage Vth has a negative temperature coefficient, forcing the MOSFET with lower Vth to carry more current during switching transient. Paralleled MOSFETs are usually de-rated to guarantee safe operation. Balancing of peak currents during switching transient isthe goal of this work.
Integration of current/voltage sensors into paralleled structure is difficult in real application. Complicated feedback loop design and separate gate drivers also need to be avoided in perspective of cost and volume. Passive balancing solutions are investigated in this dissertation. The inductors and resistors most effective in improving current sharing are identified by parametric analysis. Their current balancing mechanisms are analyzed in circuit point of view. The design guidelines involving the magnitude of Vth mismatch, current rise time, and unbalance percentage are derived for the selection of passive components. The theory upholds well when substantial parasitics from device package and layout exist.
Several passive balancing structures are analyzed and compared in terms of current balancing capability, voltage stress, total switching loss, and switching loss difference. All of them can provide much better current and power balancing without increasing switching loss. Some of the them may increase the stress-inducing inductance, which can be reduced by negative magnetic coupling. Perfect coupling between power-source inductors would enable current matching without penalty on voltage stress.
Common-source inductance (Lcm) is effective in dynamic balancing, but at the expense of higher switching loss. It is not considered in power module application because Kelvin connection is normally applied. However, wire bond inside the package of discrete MOSFETs and part of the external leads are inevitable and add to Lcm. Peak-current and switching energy mismatches vary with operating conditions (including input voltage, input current, and switching speed). Design guidelines and procedures that are valid for wide operating range are provided for cases with and without Lcm.
This dissertation also models the switching energy and switching energy mismatch of paralleled MOSFETs. The influence of operating conditions, passive balancing…
Advisors/Committee Members: Ngo, Khai D. T. (committeechair), Lu, Guo Quan (committee member), Ha, Dong S. (committee member), Zuo, Lei (committee member), Burgos, Rolando (committee member).
Subjects/Keywords: paralleled SiC MOSFETs; dynamic balancing; passive compensation; magnetic coupling; modeling
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APA (6th Edition):
Mao, Y. (2018). Passive Balancing of Switching Transients between Paralleled SiC MOSFETs. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/82203
Chicago Manual of Style (16th Edition):
Mao, Yincan. “Passive Balancing of Switching Transients between Paralleled SiC MOSFETs.” 2018. Doctoral Dissertation, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/82203.
MLA Handbook (7th Edition):
Mao, Yincan. “Passive Balancing of Switching Transients between Paralleled SiC MOSFETs.” 2018. Web. 28 Feb 2020.
Vancouver:
Mao Y. Passive Balancing of Switching Transients between Paralleled SiC MOSFETs. [Internet] [Doctoral dissertation]. Virginia Tech; 2018. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/82203.
Council of Science Editors:
Mao Y. Passive Balancing of Switching Transients between Paralleled SiC MOSFETs. [Doctoral Dissertation]. Virginia Tech; 2018. Available from: http://hdl.handle.net/10919/82203
Virginia Tech
14.
Liu, Yilun.
Design, Modeling and Control of Vibration Systems with Electromagnetic Energy Harvesters and their Application to Vehicle Suspensions.
Degree: PhD, Mechanical Engineering, 2016, Virginia Tech
URL: http://hdl.handle.net/10919/73387
► Instead of dissipating vibration energy into heat waste via viscous damping elements, this dissertation proposes an innovative vibration control method which can simultaneously mitigate vibration…
(more)
▼ Instead of dissipating vibration energy into heat waste via viscous damping elements, this dissertation proposes an innovative vibration control method which can simultaneously mitigate vibration and harvest the associated vibration energy using electromagnetic energy harvesters. This dissertation shows that the electromagnetic energy harvester can work as a controllable damper as well as an energy harvester. The semi-active control of a linear electromagnetic energy harvester, for improvement of suspension performance, has been experimentally implemented in a scaled-down quarter-car suspension system. While improving performance, power produced by the harvester can be harvested through energy harvesting circuits.
This dissertation also proposes a mechanical-motion-rectifier(MMR)-based electromagnetic energy harvester using a ball-screw mechanism and two one-way clutches for the application of replacing the viscous damper in vehicle suspensions. Compared to commercial linear harvesters, the proposed design is able to provide large damping forces and increase power-dissipation density, making it suitable to vehicle suspensions. In addition, the proposed MMR-based harvester can convert reciprocating vibration into unidirectional rotation of the generator. This feature significantly increases energy-harvesting efficiency by enabling the generator to rotate at a relatively steady speed during irregular vibrations and improves the system reliability by reducing impact forces among transmission gears. Extensive theoretical and experimental analysis have been conducted to characterize the proposed MMR-based energy harvester. The coupled dynamics of the suspension system with the MMR-based energy harvester are also explored and optimized. Furthermore, a new control algorithm is proposed to control the MMR-based energy harvester considering its unique dynamics induced by the one-way clutches. The results show that the controlled proposed electromagnetic energy harvester can possibly improve ride comfort of vehicles over conventional oil dampers and simultaneously harvest the associated vibration energy.
Advisors/Committee Members: Zuo, Lei (committeechair), Ngo, Khai D. (committee member), Sandu, Corina (committee member), Parker, Robert G. (committee member), Ferris, John B. (committee member).
Subjects/Keywords: Vibration control; Semi-active suspension control; Energy harvesting; Electromagnetic damper; Mechanical motion rectifier
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APA (6th Edition):
Liu, Y. (2016). Design, Modeling and Control of Vibration Systems with Electromagnetic Energy Harvesters and their Application to Vehicle Suspensions. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/73387
Chicago Manual of Style (16th Edition):
Liu, Yilun. “Design, Modeling and Control of Vibration Systems with Electromagnetic Energy Harvesters and their Application to Vehicle Suspensions.” 2016. Doctoral Dissertation, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/73387.
MLA Handbook (7th Edition):
Liu, Yilun. “Design, Modeling and Control of Vibration Systems with Electromagnetic Energy Harvesters and their Application to Vehicle Suspensions.” 2016. Web. 28 Feb 2020.
Vancouver:
Liu Y. Design, Modeling and Control of Vibration Systems with Electromagnetic Energy Harvesters and their Application to Vehicle Suspensions. [Internet] [Doctoral dissertation]. Virginia Tech; 2016. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/73387.
Council of Science Editors:
Liu Y. Design, Modeling and Control of Vibration Systems with Electromagnetic Energy Harvesters and their Application to Vehicle Suspensions. [Doctoral Dissertation]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/73387
Virginia Tech
15.
Dai, Xiang.
Nonlinear Dynamics and Vibration of Gear and Bearing Systems using A Finite Element/Contact Mechanics Model and A Hybrid Analytical-Computational Model.
Degree: PhD, Mechanical Engineering, 2017, Virginia Tech
URL: http://hdl.handle.net/10919/78861
► This work investigates the dynamics and vibration in gear systems, including spur and helical gear pairs, idler gear trains, and planetary gears. The spur gear…
(more)
▼ This work investigates the dynamics and vibration in gear systems, including spur and helical gear pairs, idler gear trains, and planetary gears.
The spur gear pairs are analyzed using a finite element/contact mechanics (FE/CM) model.
A hybrid analytical-computational (HAC) model is proposed for nonlinear gear dynamics.
The HAC predictions are compared with FE/CM results and available experimental data for validation.
Chapter ref{{CH:GP_Strain}} investigates the static and dynamic tooth root strains in spur gear pairs using a finite element/contact mechanics approach.
Extensive comparisons with experiments, including those from the literature and new ones, confirm that the finite element/contact mechanics formulation accurately predicts the tooth root strains.
The model is then used to investigate the features of the tooth root strain curves as the gears rotate kinematically and the tooth contact conditions change.
Tooth profile modifications are shown to strongly affect the shape of the strain curve.
The effects of strain gage location on the shape of the static strain curves are investigated.
At non-resonant speeds the dynamic tooth root strain curves have similar shapes as the static strain curves.
At resonant speeds, however, the dynamic tooth root strain curves are drastically different because large amplitude vibration causes tooth contact loss.
There are three types of contact loss nonlinearities: incomplete tooth contact, total contact loss, and tooth skipping, and each of these has a unique strain curve.
Results show that different operating speeds with the same dynamic transmission error can have much different dynamic tooth strain.
Chapters ref{{CH:HAC_2DSingle}}, ref{{CH:HAC_2DMultiple}}, and ref{{CH:HAC_3DSingle}} develops a hybrid-analytical-computational (HAC) method for nonlinear dynamic response in gear systems.
Chapter ref{{CH:HAC_2DSingle}} describes the basic assumptions and procedures of the method, and implemented the method on two-dimensional vibrations in spur gear pairs.
Chapters ref{{CH:HAC_2DMultiple}} and ref{{CH:HAC_3DSingle}} extends the method to two-dimensional multi-mesh systems and three-dimensional single-mesh systems.
Chapter ref{{CH:HAC_2DSingle}} develops a hybrid analytical-computational (HAC) model for nonlinear dynamic response in spur gear pairs.
The HAC model is based on an underlying finite element code.
The gear translational and rotational vibrations are calculated analytically using a lumped parameter model, while the crucial dynamic mesh force is calculated using a force-deflection function that is generated from a series of static finite element analyses before the dynamic calculations.
Incomplete tooth contact and partial contact loss are captured by the static finite element analyses, and included in the force-deflection function.
Elastic deformations of the gear teeth, including the tooth root strains and contact stresses, are calculated.
Extensive comparisons with finite element calculations and available experiments validate the HAC model in predicting…
Advisors/Committee Members: Parker, Robert G. (committeechair), Sandu, Corina (committee member), Cooley, Christopher G. (committee member), Zuo, Lei (committee member).
Subjects/Keywords: Gears; Bearings; Nonlinear Dynamics; Efficient; Accurate
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APA (6th Edition):
Dai, X. (2017). Nonlinear Dynamics and Vibration of Gear and Bearing Systems using A Finite Element/Contact Mechanics Model and A Hybrid Analytical-Computational Model. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78861
Chicago Manual of Style (16th Edition):
Dai, Xiang. “Nonlinear Dynamics and Vibration of Gear and Bearing Systems using A Finite Element/Contact Mechanics Model and A Hybrid Analytical-Computational Model.” 2017. Doctoral Dissertation, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/78861.
MLA Handbook (7th Edition):
Dai, Xiang. “Nonlinear Dynamics and Vibration of Gear and Bearing Systems using A Finite Element/Contact Mechanics Model and A Hybrid Analytical-Computational Model.” 2017. Web. 28 Feb 2020.
Vancouver:
Dai X. Nonlinear Dynamics and Vibration of Gear and Bearing Systems using A Finite Element/Contact Mechanics Model and A Hybrid Analytical-Computational Model. [Internet] [Doctoral dissertation]. Virginia Tech; 2017. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/78861.
Council of Science Editors:
Dai X. Nonlinear Dynamics and Vibration of Gear and Bearing Systems using A Finite Element/Contact Mechanics Model and A Hybrid Analytical-Computational Model. [Doctoral Dissertation]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/78861
16.
Wu, Yongjia.
Thermoelectric Energy Harvesting for Sensor Powering.
Degree: PhD, Mechanical Engineering, 2019, Virginia Tech
URL: http://hdl.handle.net/10919/90891
► The dissertation addressed some critical issues in thermoelectric energy harvesting and broadened its application for energy recovery and sensor powering. Some of the most advanced…
(more)
▼ The dissertation addressed some critical issues in thermoelectric energy harvesting and broadened its application for energy recovery and sensor powering. Some of the most advanced technologies were developed to improve the energy conversion efficiency and reliability of the thermoelectric energy harvesters. In this dissertation, a general and comprehensive thermodynamic model for a commercial thermoelectric generator (TEG) was established. The model can be used to optimize the design of the existing commercial TEG modules. High performance heat sink design was critical to maximize the temperature drop in the TEG module, thus increase the power output and energy conversion efficiency of the TEG. An innovative heat sink design integrated with self-oscillating impinging jet generated by the fluidic oscillator arrays were designed to cool the cold end of the TEG, thus enhance the performance of the TEG. The performance of the heat sink was characterized by large eddy simulation. A single thermoelectric material only had high thermoelectric performance in a narrow temperature range. A segmented TEG could achieve a high energy conversion efficiency over a wide temperature range by adopting different materials which had high thermoelectric performance at low, moderate, and hight temperature ranges. However, the material compatibility mismatch had been a practical problem that hindered the further improvement of energy conversion efficiency of the segmented TEG. In this dissertation, a novel method was developed to eliminate the compatibility mismatch problem via optimizing the geometry of the thermo-elements. A segmented TEG with an unprecedented efficiency of 23.72% was constructed using the method proposed in this dissertation. The complex geometry structure of the established thermo-elements would introduce extra difficulty in fabrication. Thus selective laser melting, a high-temperature additive manufacture method, was proposed for the fabrication. A physical model based on the v conservation equations was built to guide the selective-laser-melting manufacturing of the optimized segmented TEG mentioned above. In this dissertation, two thermoelectric energy harvesters were built for self-powered sensors to in-situ monitor the interior conditions in nuclear canisters. The sensors, taking advantage of the thermal energy existing in the local environment, can work continuously and provide tremendous data for system monitor and diagnosis without external energy supply. Also, a compact thermoelectric energy harvester was developed to power the gas sensor for combustion monitoring and control.
Advisors/Committee Members: Zuo, Lei (committeechair), Diller, Thomas E. (committee member), Heibel, Michael David (committee member), Qiao, Rui (committee member).
Subjects/Keywords: Thermoelectric; energy harvesting; heat transfer; sensor powering
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APA (6th Edition):
Wu, Y. (2019). Thermoelectric Energy Harvesting for Sensor Powering. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/90891
Chicago Manual of Style (16th Edition):
Wu, Yongjia. “Thermoelectric Energy Harvesting for Sensor Powering.” 2019. Doctoral Dissertation, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/90891.
MLA Handbook (7th Edition):
Wu, Yongjia. “Thermoelectric Energy Harvesting for Sensor Powering.” 2019. Web. 28 Feb 2020.
Vancouver:
Wu Y. Thermoelectric Energy Harvesting for Sensor Powering. [Internet] [Doctoral dissertation]. Virginia Tech; 2019. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/90891.
Council of Science Editors:
Wu Y. Thermoelectric Energy Harvesting for Sensor Powering. [Doctoral Dissertation]. Virginia Tech; 2019. Available from: http://hdl.handle.net/10919/90891
Virginia Tech
17.
Rahman, Imran.
Electrical Load Disaggregation and Demand Response in Commercial Buildings.
Degree: PhD, Electrical Engineering, 2020, Virginia Tech
URL: http://hdl.handle.net/10919/96602
► Electrical power systems consist of a large number of power generators connected to consumers through a complex system of transmission and distribution lines. Within the…
(more)
▼ Electrical power systems consist of a large number of power generators connected to consumers through a complex system of transmission and distribution lines. Within the electric grid, a continuous balance between generation and consumption of electricity must be maintained., ensuring stable operation of the grid. When electricity demand is high, Demand Response (DR) is a method that can be used to reduce user loads, restoring the balance between demand and supply of electricity.
Based on data from the Energy Information Administration (EIA), half of all commercial buildings in the US measure 5,000 square feet or smaller in size, whereas the majority of the other half is made up of medium-sized commercial buildings measuring in at between 5,001 to 50,000 square feet. This makes these commercial buildings an ideal target for participating in DR. In this dissertation, two broad solutions for commercial building DR have been presented.
The first is a load disaggregation technique, where power consumption and activity of individual HVACs can be obtained, using a single power meter. The second work focuses on a DR algorithm, that controls single floor HVAC and lighting loads in a commercial building, based on a user generated bid price for electricity, user preferences and load priorities, when electricity demand is at its peak.
Advisors/Committee Members: Rahman, Saifur (committeechair), Pipattanasomporn, Manisa (committeechair), Zuo, Lei (committee member), Dhillon, Harpreet Singh (committee member), De La Reelopez, Jaime (committee member).
Subjects/Keywords: Load Disaggregation; Demand Response; Double-Auction; Bid Price; Load Scheduler; Load Priorities; User Preferences
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APA (6th Edition):
Rahman, I. (2020). Electrical Load Disaggregation and Demand Response in Commercial Buildings. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/96602
Chicago Manual of Style (16th Edition):
Rahman, Imran. “Electrical Load Disaggregation and Demand Response in Commercial Buildings.” 2020. Doctoral Dissertation, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/96602.
MLA Handbook (7th Edition):
Rahman, Imran. “Electrical Load Disaggregation and Demand Response in Commercial Buildings.” 2020. Web. 28 Feb 2020.
Vancouver:
Rahman I. Electrical Load Disaggregation and Demand Response in Commercial Buildings. [Internet] [Doctoral dissertation]. Virginia Tech; 2020. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/96602.
Council of Science Editors:
Rahman I. Electrical Load Disaggregation and Demand Response in Commercial Buildings. [Doctoral Dissertation]. Virginia Tech; 2020. Available from: http://hdl.handle.net/10919/96602
Virginia Tech
18.
Kim, Hongjip.
Enhanced Energy Harvesting for Rotating Systems using Stochastic Resonance.
Degree: PhD, Mechanical Engineering, 2020, Virginia Tech
URL: http://hdl.handle.net/10919/96728
► In this dissertation, a novel energy harvesting strategy for rotating systems was proposed by taking advantage of stochastic resonance. Stochastic resonance is referred to as…
(more)
▼ In this dissertation, a novel energy harvesting strategy for rotating systems was proposed by taking advantage of stochastic resonance. Stochastic resonance is referred to as a physical phenomenon that is manifest in nonlinear bistable systems whereby a weak periodic signal can be significantly amplified with the aid of inherent noise or vice versa. Stochastic resonance can thus be used to amplify the noisy and weak vibration motion.
Through mathematical modeling, this dissertation shows that stochastic resonance is particularly favorable to energy harvesting in rotating systems.Both numerical and experimental results show that stochastic resonance energy harvester has higher power and wider bandwidth than linear harvesters under a rotating environment.
The dissertation also investigates how stochastic resonance changes for the various types of excitation that occur in real-world applications.
The dissertation finally proposed two real applications of stochastic resonance energy harvesting. First, stochastic resonance energy harvester for oil drilling applications is presented. Energy harvester for smart tires is also proposed. The results show that larger power output and wider bandwidth can be obtained by applying the proposed harvesting strategy to the rotating system.
Advisors/Committee Members: Zuo, Lei (committeechair), Hajj, Muhammad Ramiz (committee member), Furukawa, Tomonari (committee member), Parker, Robert G. (committee member).
Subjects/Keywords: Energy Harvesting; Rotating Systems; Stochastic Resonance; Self-tuning; FPK equation; Potential asymmetry; Weak periodic potential
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APA (6th Edition):
Kim, H. (2020). Enhanced Energy Harvesting for Rotating Systems using Stochastic Resonance. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/96728
Chicago Manual of Style (16th Edition):
Kim, Hongjip. “Enhanced Energy Harvesting for Rotating Systems using Stochastic Resonance.” 2020. Doctoral Dissertation, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/96728.
MLA Handbook (7th Edition):
Kim, Hongjip. “Enhanced Energy Harvesting for Rotating Systems using Stochastic Resonance.” 2020. Web. 28 Feb 2020.
Vancouver:
Kim H. Enhanced Energy Harvesting for Rotating Systems using Stochastic Resonance. [Internet] [Doctoral dissertation]. Virginia Tech; 2020. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/96728.
Council of Science Editors:
Kim H. Enhanced Energy Harvesting for Rotating Systems using Stochastic Resonance. [Doctoral Dissertation]. Virginia Tech; 2020. Available from: http://hdl.handle.net/10919/96728
19.
Chen, Jie.
Design and analysis of a thermoelectric energy harvesting system for powering sensing nodes in nuclear power plant.
Degree: MS, Mechanical Engineering, 2016, Virginia Tech
URL: http://hdl.handle.net/10919/64792
► In this work, a thermoelectric energy harvester system aimed at harvesting energy for locally powering sensor nodes in nuclear power plant coolant loops has been…
(more)
▼ In this work, a thermoelectric energy harvester system aimed at harvesting energy for locally powering sensor nodes in nuclear power plant coolant loops has been designed, fabricated and tested. Different mathematical modeling methods have been validated by comparing with experimental results. The model developed by this work has the best accuracy in low temperature range and can be adapted and used with any heat sink, heat pipe, or thermoelectric system, and have proven to provide results closely matching experimental data. Using the models, an optimization of the thermoelectric energy harvesting system has been performed which is applicable to any energy harvester of this variety.
With experimental validation, the system is capable of generating sufficient energy to power all the sensors and electronical circuits designed for this application. The effect of gamma radiation on this thermoelectric harvester has also been proved to be small enough through radiation experiment.
Advisors/Committee Members: Zuo, Lei (committeechair), Vick, Brian (committee member), Heibel, Michael David (committee member), Huxtable, Scott T. (committee member).
Subjects/Keywords: thermoelectric generator; nuclear power plant monitoring; modeling; optimization
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APA (6th Edition):
Chen, J. (2016). Design and analysis of a thermoelectric energy harvesting system for powering sensing nodes in nuclear power plant. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/64792
Chicago Manual of Style (16th Edition):
Chen, Jie. “Design and analysis of a thermoelectric energy harvesting system for powering sensing nodes in nuclear power plant.” 2016. Masters Thesis, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/64792.
MLA Handbook (7th Edition):
Chen, Jie. “Design and analysis of a thermoelectric energy harvesting system for powering sensing nodes in nuclear power plant.” 2016. Web. 28 Feb 2020.
Vancouver:
Chen J. Design and analysis of a thermoelectric energy harvesting system for powering sensing nodes in nuclear power plant. [Internet] [Masters thesis]. Virginia Tech; 2016. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/64792.
Council of Science Editors:
Chen J. Design and analysis of a thermoelectric energy harvesting system for powering sensing nodes in nuclear power plant. [Masters Thesis]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/64792
20.
Xing, Shaoxu.
Design of Power Converter and Wireless Data Acquisition System for TEG Energy Harvester.
Degree: MS, Mechanical Engineering, 2016, Virginia Tech
URL: http://hdl.handle.net/10919/73361
► In order to avoid the accidents like Fukushima Disaster and monitor the operation status of nuclear power plant, a wireless sensor system which is powered…
(more)
▼ In order to avoid the accidents like Fukushima Disaster and monitor the operation status of nuclear power plant, a wireless sensor system which is powered by the Thermoelectric Generator (TEG) Energy Harvester is designed and built. Meanwhile, a power converter circuit has also been designed to converter the output voltage of TEG Energy Harvester to a DC voltage to charge the battery or power the application systems. Several prototypes based on this power converter circuit have been built for Thermoelectric Generator (TEG) energy harvester and tested in both working and laboratory conditions.
The reliability of the TEG Energy Harvester system in the gamma radiation environment has been examined in the experiments. Based on the experiments results, the design was optimized. And an optimized Maximum Power Point Tracking algorithm has also been applied in the prototype to extract the maximum power from the TEG Energy Harvester in all conditions. The TEG Energy Harvester system would be greatly simplified as a new type of sensor will be applied. The design of the signal conditioning circuit for this sensor has also been presented.
Advisors/Committee Members: Zuo, Lei (committeechair), Ngo, Khai D. (committee member), Wicks, Alfred L. (committee member), Yang, Yaling (committee member).
Subjects/Keywords: Energy Harvester; Power Converter; Data Acquisition; Wireless Communication; MPPT; Sensor
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APA (6th Edition):
Xing, S. (2016). Design of Power Converter and Wireless Data Acquisition System for TEG Energy Harvester. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/73361
Chicago Manual of Style (16th Edition):
Xing, Shaoxu. “Design of Power Converter and Wireless Data Acquisition System for TEG Energy Harvester.” 2016. Masters Thesis, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/73361.
MLA Handbook (7th Edition):
Xing, Shaoxu. “Design of Power Converter and Wireless Data Acquisition System for TEG Energy Harvester.” 2016. Web. 28 Feb 2020.
Vancouver:
Xing S. Design of Power Converter and Wireless Data Acquisition System for TEG Energy Harvester. [Internet] [Masters thesis]. Virginia Tech; 2016. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/73361.
Council of Science Editors:
Xing S. Design of Power Converter and Wireless Data Acquisition System for TEG Energy Harvester. [Masters Thesis]. Virginia Tech; 2016. Available from: http://hdl.handle.net/10919/73361
21.
Lu, Ming.
Synergetic Attenuation of Stray Magnetic Field in Inductive Power Transfer.
Degree: PhD, Electrical and Computer Engineering, 2017, Virginia Tech
URL: http://hdl.handle.net/10919/78621
► Significant stray magnetic field exists around the coils when charging the electric vehicles (EVs) with inductive power transfer (IPT), owning to the large air gap…
(more)
▼ Significant stray magnetic field exists around the coils when charging the electric vehicles (EVs) with inductive power transfer (IPT), owning to the large air gap between the transmitter and receiver. The methods for field attenuation usually introduce extra losses and reduce the efficiency. This study focuses on the synergetic attenuation of stray magnetic field which is optimized simultaneously with the efficiency. The optimization is realized with Pareto front.
In this dissertation, three methods are discussed for the field attenuation. The first method is to tune the physical parameters of the winding, such as the inner radii, outer radii, distribution of the turns, and types of the litz wires. The second method is to add metal shields around the IPT coils, in which litz wires are used as shields to reduce the shielding losses. The third method is to control the phases of winding currents, which avoids increasing the size and weight of the IPT coils.
To attenuate the stray magnetic field by tuning the physical parameters, the conventional method is to sweep all the physical parameters in finite-element simulation. This takes thousands of simulations to derive the Pareto front, and it's especially time-consuming for three-dimensional simulations. This dissertation demonstrates a faster method to derive the Pareto front. The windings are replaced by the lumped loops. As long as the number of turns for each loop is known, the efficiency and magnetic field are calculated directly from the permeance matrices and current-to-field matrices. The sweep of physical parameters in finite-element simulation is replaced by the sweep of the turns numbers for the lumped loops in calculation. Only tens of simulations are required in the entire procedure, which are used to derive the matrices. An exemplary set of coils was built and tested. The efficiency from the matrix calculation is the same as the experimental measurement. The difference for stray magnetic field is less than 12.5%.
Metal shields attenuate the stray magnetic field effectively, but generates significant losses owning to the uneven distribution of shield currents. This dissertation uses litz wires to replace the conventional plate shield or ring shield. Skin effect is eliminated so the shield currents are uniformly distributed and the losses are reduced. The litz shields are categorized to two types: shorted litz shield and driven litz shield. Circuit models are derived to analyze their behaviors. The concept of lumped-loop model is applied to derive the Pareto front of efficiency versus stray magnetic field for the coils with litz shield. In an exemplary IPT system, coils without metal shield and with metal shields are optimized for the same efficiency. Both the simulation and experimental measurement verify that the shorted litz shield has the best performance. The stray magnetic field is attenuated by 65% compared to the coils without shield.
This dissertation also introduces the method to attenuate the stray magnetic field by controlling the phases of…
Advisors/Committee Members: Ngo, Khai D. T. (committeechair), Burgos, Rolando (committee member), Lu, Guo Quan (committee member), Manteghi, Majid (committee member), Zuo, Lei (committee member).
Subjects/Keywords: Inductive power transfer; planar coils; high efficiency; proximity-effect loss; magnetic field; shield; multi-objective optimization; Pareto front
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APA ·
Chicago ·
MLA ·
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CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Lu, M. (2017). Synergetic Attenuation of Stray Magnetic Field in Inductive Power Transfer. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/78621
Chicago Manual of Style (16th Edition):
Lu, Ming. “Synergetic Attenuation of Stray Magnetic Field in Inductive Power Transfer.” 2017. Doctoral Dissertation, Virginia Tech. Accessed February 28, 2020.
http://hdl.handle.net/10919/78621.
MLA Handbook (7th Edition):
Lu, Ming. “Synergetic Attenuation of Stray Magnetic Field in Inductive Power Transfer.” 2017. Web. 28 Feb 2020.
Vancouver:
Lu M. Synergetic Attenuation of Stray Magnetic Field in Inductive Power Transfer. [Internet] [Doctoral dissertation]. Virginia Tech; 2017. [cited 2020 Feb 28].
Available from: http://hdl.handle.net/10919/78621.
Council of Science Editors:
Lu M. Synergetic Attenuation of Stray Magnetic Field in Inductive Power Transfer. [Doctoral Dissertation]. Virginia Tech; 2017. Available from: http://hdl.handle.net/10919/78621
. 
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