Examensarbeten för masterexamen

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    Fault Tracing Bot in Electric Drive Software Using Machine Learning
    (2023) Jai Prakash, Soundarya; Gopinath, Hariharan; Chalmers tekniska högskola / Institutionen för elektroteknik; Eriksson, Thomas; Farsi, Mohammad
    The Electric Drive Software Continuous Deployment (EDCD) team at Volvo Car Corporation is working towards figuring out the automation of the analysis of the build log data obtained as a result of the continuous software integration for Electronic Control Unit (ECUs) using Machine Learning. Machine Learning is expected to be used in building a fault tracing bot, whose main goal is to analyse the provided log data and find the underlying meaning or information through it with minimum or zero human interaction. As this is an ongoing process and the creation of such log data will never really end, this project could make it easier for the analysis of big projects in getting instant data. At first, we are working on the data cleaning and the preprocessing of the big unstructured log data, followed by the labeling of the data by the clustering process. Lastly, the machine learning algorithm is used to predict the classification of the newly fed data. Many different machine learning algorithms have been implied to compare and get the best accuracy predicting algorithm among them.
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    Human detection and pose estimation using ceiling mounted cameras
    (2023) Ravi, Harish; Madhavan, Harish; Chalmers tekniska högskola / Institutionen för elektroteknik; Åkesson, Knut
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    The design and usability of an eHealth demonstrator aimed to facilitate the prevention and care of persons with diabetes at risk to develop diabetic foot ulcers
    (2023) Ravichandran, Shivani; Chalmers tekniska högskola / Institutionen för elektroteknik; Candefjord, Stefan
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    Design And Analysis Of Wireless Power Transfer Using High Frequency Resonant Inductive Coupling By Changing The Coil Geometry
    (2024) Gouthamas, Nagendra; Bandi, Adarsh; Chalmers tekniska högskola / Institutionen för elektroteknik; Thiringer, Torbjörn; Thiringer, Torbjörn; Larsson, Fredrik
    Abstract In this thesis, we have developed a wireless power transfer system for a space of dimensions (15cm x 15cm x 15cm), utilizing a series-connected transmitter (Tx) coil to generate an equally distributed electromagnetic field inside the space. This field can be picked up by a solenoid receiver (Rx) coil placed anywhere within the space to power a DC load. To develop the proposed system, we have studied a conventional wireless power transfer system fromWurth Electronics and investigated various coil geometries for both Tx and Rx. The conventional wireless power system has been examined regarding the influence of coil geometry, alignment between the transmitter (Tx) and receiver (Rx), as well as the coil parameters on efficiency. The wireless power system from Wurth Electronics is tested with different Rx coil geometries to evaluate interoperability between various Tx and Rx coil geometries, as well as to compare the coupling coefficient and magnetic field density of different Rx coil geometries with misalignment in order to evaluate most suitable Rx coil geometry for the proposed wireless power system. The different Rx coil geometries investigated are: concentric, solenoid, and center-tapped circular coil. The comparison is based on different alignment conditions between the transmitter and receiver coils. We find, from the results obtained by investigating different Rx coil geometries with the conventional system, that the solenoid coil geometry with a core provides a stable coupling coefficient under various misalignment conditions. Thus, the solenoid Rx geometry can be optimized to enhance coupling between the transmitter and receiver coils. Additionally, test results show that the use of center-tapped circular coils in wireless power power system helps in improving range from 30mm to 180mm compared to conventional wireless power system with concentric coils. However, the improved range is only achievable with significantly higher number of coil turns compared to concentric coils which reduces efficiency. Also, a unique BJT based automatically switching transmitter circuit is required for the center-tapped circular coils which makes it a non-viable solution due to inefficiency of the BJTs. Further a suitable transmitter coil geometry is investigated for use in combination with the solenoid receiver to demonstrate the proposed wireless power system within a space of dimensions (15 cm x 15 cm x 15 cm). Three different transmitter coils are investigated: the concentric coil, 2-series connected concentric coil, and 8-series connected concentric coil. A half-bridge transmitter circuit is designed to drive the various transmitter coils. The experimental and simulation results indicate that the concentric transmitter coil with a large diameter enhances high power transfer and better range due to a more effective distribution of the magnetic field. However, when using a solenoid receiver coil, the power transfer efficiency drops by 28% compared to the efficiency of 75% under aligned operation. Consequently, the concentric transmitter coil is designed with the coil turns distributed into smaller areas, forming a 2-series connected coil. Test results reveal that it was possible to transfer 10W of power at an efficiency of 75% when the coils were perfectly aligned. In contrast, when the coils were misaligned, power transfer efficiency of up to 48% was achieved. This is in contrast to the power transfer efficiency of 6% under misaligned conditions in the conventional wireless power system. The 2-series connected concentric Tx coil is then extended to an 8-series connected concentric Tx coil to form a space of dimensions (15 cm x 15 cm x 15 cm) in combination with a solenoid Rx coil. Simulation results indicate that the coupling coefficient between Tx & Rx improved by approximately 11% and measurement results show that power transfer efficiency improved by 4% compared to the 2-series connected concentric Tx coil. Similarly, when the solenoid Rx coil was rotated or misaligned with the Tx coil, the efficiency improved by approximately 33% compared to the 2-series connected concentric Tx coil. The increase in efficiency and coupling with Tx and Rx is mainly due to distribution of coil turns into smaller areas and then connecting them in series which improved the magnetic field distribution compared to other coil geometries. Hence, the 8-series connected concentric coil as Tx and solenoid as Rx are selected as the suitable Tx and Rx coils, respectively, for the proposed wireless power system. In comparison to the conventional wireless power system, the efficiency remains approximately the same at 80% when the coils were perfectly aligned and efficiency improved by more than 60% when the coils were misaligned.
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    Modelling and Simulation of DC/DC Converter-Based Active Cell Balancing for Battery Management Systems
    (2023) GANGAMAGALA MAHANTHAPPA, VIKAS; SOLLAPURA VASANNA, SRINIDHI; Chalmers tekniska högskola / Institutionen för elektroteknik; Zou, Changfu; Li, Yang
    Abstract The transition to sustainable transportation was initiated to mitigate the effects of global warming and decrease CO2 emissions. Electric vehicles are at the forefront of this revolution and rapid technological advancements have been made in the development of electric powertrain’s components, particularly lithium-ion (Li-ion) batteries. These breakthroughs have played a significant role in increasing vehicle performance and range, prompting automotive companies to accelerate their transition to more sustainable vehicles. Li-ion batteries are prominent in their specific energy and specific power while the battery pack comprises low-voltage battery cells connected in series and parallel to meet the voltage and current requirements of the electric vehicles. However, since the cells are limited by voltage and capacity, a serious inconsistency between the cell’s voltage and state of charge (SoC) is generated because of the manufacturing inconsistencies of the individual cells in the battery pack. This leads to growth over time after a number of charging and discharging cycles because of different self-discharge rates, internal resistance, and operating temperature, which will affect the efficiency and life of the entire battery pack. It has become inevitable to keep the cells balanced to achieve the effective usage of energy and to enhance the battery life. This thesis starts with a comprehensive literature study and investigation of different types of cell balancing techniques with a focus on converter-based active balancing. A choice has been made after evaluating the performance and suitability of different converters considering the balancing method, balancing speed, balancing time, and control complexity. In MATLAB/Simulink, a bi-directional buck-boost converter was designed and simulated by integrating with the battery string, performing energy exchange between cells with different SoCs using a state-space modeling approach and cascaded PID control. An easy-to-implement and effective algorithm has been developed, tested, and validated to perform the balancing action in various operating scenarios.