Electrical Engineering

Welcome to the Master Thesis Presentation Integrated Fast Battery Charger Using an Electrically Excited Synchronous Machine Based Drive System&nbsp;By Xinyu Ma &nbsp; Master’s thesis conducted at Chalmers&nbsp; Supervisor: Luca Boscaglia Examiner: Yujing Liu&nbsp; Opponent: Shinuo Fang &nbsp; Time: 14:30-15:30 &nbsp;on Friday, 12 December 2025 Place: E2 Room 3340 Blå rummet, Department of Electric Engineering
Abstract: This thesis investigates an integrated fast battery charging system utilizingan Electrically Excited Synchronous Machine (EESM) based drive topology. The aim is to reuse the existing traction inverter and machine windings as part of a DC/DC boost converter, thereby reducing system cost and size. To achieve this goal, three levels of simulation were carried out. First, an excitation-based Finite Element Analysis (FEA) was performed to determine losses and inductances of the EESM under various operating conditions. Second, a system-level co-simulation between FE analysis and circuit analysis was conducted, in which the electromagnetic model of the machine interacted dynamically with the converter and control system. This enabled real-time calculation of inductances and losses under variations in both shift angle and rotor position. Finally, a Simulink-based system simulation was carried out to analyze current ripple, torque generation, and efficiency across different frequencies. The results show that phase-shift modulation predominantly affects the current waveform and ripple behaviour, while the magnetic coupling and inductance remain almost constant. Increasing the switching frequency reduces stator core losses but has minimal impact on copper losses. Overall, the proposed integrated EESM-based fast charger demonstrates high feasibility and efficiency. It achieves compact system integration, stable electromagnetic performance, and effective control of current ripple and core losses - offering a sustainable approach for future electric vehicle charging architectures.
Welcome!
Xinyu, Luca &amp; Yujing

Welcome to MSc thesis presentation by Palash Bhaumik &nbsp; Title: “Analysis of Electric Conductivity Variance in the Insulation of HVDC Cables” &nbsp; Date: Thursday, December 18, 2025 Time: 11:00 – 12:00 Place: Fredrik Lamm &nbsp; Supervisors: Markus Jarvid and Espen Doedens (Nexans Norway AS), Xiangdong Xu (Chalmers, EPE) Examiner: &nbsp;Yuriy Serdyuk Opponent: Malte Rosengren &nbsp;&nbsp; Abstract: Power cables with insulation based on cross-linked polyethylene (XLPE) are used in high voltage direct current (HVDC) onshore and offshore power grids to transmit large amounts of electric energy over long distances. One of the important aspects to be considered when designing the insulation system of such cables is the variation of the electric conductivity of the insulation material in radial direction between the energized conductor and grounded screen. Since the conductivity of XLPE is dependent on electric field strength and temperature, predicting its actual changes in the cable is challenging and typically is done based on some empirical formulas. These, however, do not take into account the effect of the diffusion of impurities and byproducts introduced into the material during the manufacturing process on conductivity variations.&nbsp; In the thesis, the electric conductivity of XLPE was measured using material samples taken from continuous peelings of the insulation of a real cable. This allowed for examining its field and temperature dependencies at different distances from the conductor, i.e. at different contents of byproducts. The experimentally obtained material properties were further utilized as input for a computer model, which was developed to analyze the dynamics of space charge accumulation and corresponding electric field in the cable. The results outlined in the thesis are essential for improving the design rules for HVDC cables to ensure their reliable and safe operation.
Everyone is most welcome! &nbsp; Palash and Yuriy

Welcome to the Master Thesis Presentation Implementation of CAD/CAM for 2.5-axis machine By Johan Ljunggren
Examiner: Erik Agrell&nbsp; Opponents: Patrik Lindström &nbsp; Time: 15:00-16:00 &nbsp;on 18 December 2025 Place: Room 3311, Lunnerummet
Abstract: 
This paper presents the design, implementation, and evaluation of a two-dimensional (2D) plotting system incorporating a custom embedded motion controller. The controller provides an Application Programming Interface (API) that enables direct execution of drawing operations on paper or other materials. In contrast to conventional computer-numerical-control (CNC) workflows based on G-code interpretation, the proposed system employs a WebSocket-based communication protocol that allows commands to be transmitted directly from a client interface to the device firmware. This approach reduces architectural complexity, eliminates legacy translation stages, and enables real-time, network-based interaction using standard web technologies.
The novelty of the work lies in its simplicity, universality, and accessibility: it bypasses outdated, legacy solutions (such as G-code), uses network-enabled browser control, and is implemented with a minimal code base. It included sourcing and assembling the mechanical and electronic components, building the custom plotter, and developing firmware that supports homing, calibration, pen control, and both linear and diagonal motion.
Empirical evaluation demonstrated that the prototype exhibited consistent operational stability, achieving a linear positional accuracy of ±0.3 mm over 100 mm travel distances, with marginally higher deviation observed during diagonal motion. The system was constructed for under 200 USD, underscoring its economic viability and adaptability for broader use cases. The study also documents technical challenges encountered during development and explains how iterative development resolved these issues.
In conclusion, this work provides a validated proof of concept for direct, WebSocket-based API control as a technically sound and practical alternative to G-code for robotic actuation. The findings indicate that such an architecture can facilitate more agile and accessible computer-controlled manufacturing workflows, with potential applicability in educational contexts, prototyping environments, and industrial domains requiring lightweight, network-enabled motion-control solutions.
Keywords
ESP32 · WebSockets · Motion Control · Firmware · CAD/CAM · Embedded Systems

Welcome!
Johan and Erik

Welcome to the Master Thesis Presentation
Multi-Modal 3D Reconstruction of Railway Infrastructure&nbsp;Using LiDAR based Depth Priors
Presenter: Damodar Datta Kancharla
Examiner: Fredrik Kahl
Time: 10.00 am, Friday December 19, 2025&nbsp;
Place: Landahlsrummet (E2 Room 7430)
Abstract Railway infrastructure maintenance relies on accurate 3D condition assessment, typically performed using data collected by train-mounted measurement systems. State of the art solutions employ high-speed 2D LiDAR profilers to capture the scene geometry with sub-centimeter precision. However, due to their strictly orthogonal&nbsp;scanning, these systems suffer from a specific blind spot: they fail to capture planar objects facing the direction of travel (e.g., signage), necessitating forward-facing&nbsp;images to recover complete scene structure. The standard railway acquisition trajectory is predominantly a forward linear motion with front-facing cameras. This&nbsp;configuration poses several geometric challenges, specifically low parallax and high&nbsp;structural symmetry, which cause standard Structure-from-Motion (SfM) pipelines to fail or produce noisy reconstructions.
In this work, we address these challenges by proposing a reconstruction pipeline&nbsp;that leverages the aggregated 2D LiDAR scans as a geometric prior. We extend&nbsp;the Monocular Surface Priors for Robust Structure-from-Motion (MP-SfM) pipeline&nbsp;by back-projecting the accumulated point cloud to generate consistent, dense depth&nbsp;priors. Additionally, we refine the camera poses via a joint global bundle adjustment that integrates multi-view constraints with these geometric priors. The proposed method is evaluated on a custom dataset containing synchronized imagery, calibrated camera parameters, and highly accurate LiDAR scans. Experimental&nbsp;evaluation on a custom survey-grade dataset of real railway corridors demonstrates&nbsp;that our approach achieves sub-centimeter accuracy on track structures (Chamfer&nbsp;distance: 0.24 m vs. 2.45 m for COLMAP SfM, 0.26 m for Metric3D monocular&nbsp;depth). The method successfully reconstructs objects in the LiDAR blind spot that&nbsp;standard SfM completely misses, while maintaining metric scale verified through&nbsp;ETCS marker dimensional measurement (error &lt; 10 mm).

Welcome!
Damodar Datta and Fredrik

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Presentation of master thesis

Master thesis presentations at Electrical Engineering

12 December, 2025

14.30-15.30 Xinyu Ma, MPEPO

18 December, 2025

11.00-12.00 Palash Bhaumik, MPEPO

15.00-16.00 Johan Ljunggren, TIELL

19 December, 2025

10.00-11.00 Damodar Datta Kancharla, MPCAS