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- Tao, Sha
(author)
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Mobile Phone-based Vehicle Positioning and Tracking and Its Application in Urban Traffic State Estimation
- 2012
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Licentiate thesis (other academic/artistic)abstract
- Enabling the positioning and tracking of mobile phones has emerged as a key facility of existing and future generation mobile communication systems. This feature provides opportunities for many value added location-based services and systems. For instance, mobile phones are increasingly employed in traffic information systems and present several advantages over traditional sensor-based traffic systems. However, there are still plenty of aspects that must be investigated and addressed towards the fully operational deployment. The aim of the research performed in this thesis is to examine and propose solutions to two of the problems in the deployment of a mobile phone-based smart traffic information system. The first problem investigated is the mobile phone-based vehicle positioning and tracking. The investigation starts with a comprehensive study of mobile positioning with emphasis on existing standardizations. Based on the mobile location methods standardized in UMTS, possible hybrid solutions are proposed. In addition, a tool for simulating one of the UMTS mobile positioning methods (i.e., OTDOA) in vehicular environment is developed. A Kalman filter-based hybrid method, which can track the mobile phones traveling on-board vehicles, is then implemented. This method fuses two of the UMTS standard methods (i.e., OTDOA and A-GPS) location estimates at the state-vector level. Statistical simulation results demonstrate that the hybrid method can provide better position and velocity estimations than each individual method. The second problem addressed is the mobile phone-based urban traffic state estimation. A traffic simulation-based framework is proposed to emulate and evaluate the operation of urban traffic state estimation with A-GPS mobile phones as probes. Based on the emulated mobile phone probe data, algorithms of location data processing/filtering and average speed estimation are developed and then evaluated by comparing against “ground truth” data from the traffic simulation. Moreover, the estimated average speeds are classified to different traffic condition levels, which are prepared for displaying a traffic map on the mobile phone display. The achieved simulation results demonstrate the effectiveness of the proposed method, which is fundamental for the subsequent development of a mobile phone-based smart traffic information system demonstrator.
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| 2. |
- Katic, Janko
(author)
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Efficient Energy Harvesting Interface for Implantable Biosensors
- 2015
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Licentiate thesis (other academic/artistic)abstract
- Energy harvesting is identified as a promising alternative solution for powering implantable biosensors. It can completely replace the batteries, which are introducing many limitations, and it enables the development of self-powered implantable biosensors. An interface circuit is necessary to correct for differences in the voltage and power levels provided by an energy harvesting device from one side, and required by biosensor circuits from another. This thesis investigates the available energy harvesting sources within the human body, selects the most suitable one and proposes the power management unit (PMU), which serves as an interface between a harvester and biosensor circuits. The PMU targets the efficient power transfer from the selected source to the implantable biosensor circuits.Based on the investigation of potential energy harvesting sources, a thermoelectric energy harvester is selected. It can provide relatively high power density of 100 μW/cm2 at very low temperature difference available in the human body. Additionally, a thermoelectric energy harvester is miniature, biocompatible, and it has an unlimited lifetime.A power management system architecture for thermoelectric energy harvesters is proposed. The input converter, which is the critical block of the PMU, is implemented as a boost converter with an external inductor. A detailed analysis of all potential losses within the boost converter is conducted to estimate their influence on the conversion efficiency. The analysis showed that the inevitable conduction and switching losses can be reduced by the proper sizing of the converter’s switches and that the synchronization losses can be almost completely eliminated by an efficient control circuit. Additionally, usually neglected dead time losses are proved to have a significant impact in implantable applications, in which they can reduce the efficiency with more than 2%.An ultra low power control circuit for the boost converter is proposed. The control is utilizing zero-current switching (ZCS) and zero-voltage switching (ZVS) techniques to eliminate the synchronization losses and enhance the efficiency of the boost converter. The control circuit consumes an average power of only 620 nW. The boost converter driven by the proposed control achieves the peak efficiency higher than 80% and can operate with harvested power below 5 μW. For high voltage conversion ratios, the proposed boost converter/control combination demonstrates significant efficiency improvement compared to state-of-the-art solutions.
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| 3. |
- Katic, Janko, 1986-
(author)
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Highly-Efficient Energy Harvesting Interfaces for Implantable Biosensors
- 2017
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Doctoral thesis (other academic/artistic)abstract
- Energy harvesting is identified as an alternative solution for powering implantable biosensors. It can potentially enable the development of self-powered implants if the harvested energy is properly handled. This development implies that batteries, which impose many limitations, are replaced by miniature harvesting devices. Customized interface circuits are necessary to correct for differences in the voltage and power levels provided by harvesting devices from one side, and required by biosensor circuits from another. This thesis investigates the available harvesting sources within the human body, proposes various methods and techniques for designing power-efficient interfaces, and presents two CMOS implementations of such interfaces.Based on the investigation of suitable sources, this thesis focuses on glucose biofuel cells and thermoelectric harvesters, which provide appropriate performance in terms of power density and lifetime. In order to maximize the efficiency of the power transfer, this thesis undertakes the following steps. First, it performs a detailed analysis of all potential losses within the converter. Second, in relation to the performed analysis, it proposes a design methodology that aims to minimize the sum of losses and the power consumption of the control circuit. Finally, it presents multiple design techniques to further improve the overall efficiency.The combination of the proposed methods and techniques are validated by two highly efficient energy harvesting interfaces. The first implementation, a thermoelectric energy harvesting interface, is based on a single-inductor dual-output boost converter. The measurement results show that it achieves a peak efficiency of 86.6% at 30 μW. The second implementation combines the energy from two sources, glucose biofuel cell and thermoelectric harvester, to accomplish reliable multi-source harvesting. The measurements show that it achieves a peak efficiency of 89.5% when the combined input power is 66 μW.
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