Chalmers Open Digital Repository

Welcome to Chalmers Open Digital Repository!

Here you can find:

Student theses and papers
Digital special collections, such as Chalmers modellkammare
Selected project reports

Research publications, reports and dissertations can be found in research.chalmers.se

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Now showing 1 - 2 of 2

Recent Submissions

Extending a Distributed Multi-Robot Coordination Infrastructure with Predicated Broadcast and Multicast Communication
(2026) Hägglund, Tobias; Wallin, Filip
Multi-robot systems operating in distributed environments require coordination mechanisms that are both scalable and flexible. Existing approaches commonly rely on centralized controller or undiscriminating broadcast communication, both of which introduces limitations: centralization creates single points of failure and communication bottlenecks, while broadcast-based coordination results in unnecessary message processing by robots for whom a given task is irrelevant. This thesis addresses these limitations by extending an existing ROS2-based decentralized coordination infrastructure developed at Chalmers with two new predicate-based communication mechanism: predicate-based broadcast and predicate-based multicast. Predicate-based broadcast enables system-wide message distribution in which only robots whose locally stored traits satisfy a specified boolean predicate respond to and act upon a coordination request. Predicate-based multicast extends this further by facilitating communication within dynamically formed subgroups of eligible robots, selected throughout a decentralized election process. Formal semantics are provided for both these mechanisms. The implementation preserves the core design principles of the inherited infrastructure, that is, decentralized decision making, agent anonymity, and global message ordering guarantees. The mechanisms was evaluated through two simulation scenarios using RViz. The results demonstrate that selective coordination can be achieved without the need for a centralized knowledge of robot capabilities or identities. It also shows that temporary multicast groups can be formed and dissolved at runtime, and that message ordering is maintained during the lifecycle of the coordination group. The results indicate that predicatebased communication is a viable approach for achieving selective coordination in decentralized multi robot systems.
Road Section Weather and Vehicle Energy Consumption Modeling
(2026) Eriksson, Otto; Liu, Kaiyuan
Accurate vehicle energy consumption modeling for heavy-duty trucks requires precise characterization of aerodynamic drag and rolling resistance, both of which are highly sensitive to local weather and road conditions. Existing models often rely on standard atmospheric assumptions or dedicated on-board sensors, which limits their ability to capture real-world operating conditions. To address this, the present work proposes an integrated physics-based modeling framework that links road-segment level meteorological data to vehicle motion resistance without requiring additional sensing hardware. For the wind prediction model, a topographical model is used as a base and further corrected with a two-layer wind speed correction model developed to translate regional meteorological station measurements into local road-level wind estimates. The successive layers account for a global power law bias and geographic environment effects through clustering of road segments into sheltered and wind-amplified categories. Validated against over 200 repeated real-world journeys on RV (Riksväg) 40, Sweden, the model achieves a 48.4% reduction in mean absolute error over the regional baseline, consistently across seasons and travel directions, compared to using measurements from regional meteorological stations. A wind direction model in the form of a polynomial is incorporated to complete the wind characterization. For the rolling resistance component, a two-state tire thermodynamic observer is formulated, estimating tire bulk temperature from standard Tire Pressure Monitoring System (TPMS) measurements and an external temperature sensor via a Kalman filter. This enables model-based prediction of temperature-dependent rolling resistance as a function of ambient conditions and driving dynamics, without dedicated thermal sensors. The proposed framework provides a scalable, low-cost approach to weather-aware energy consumption forecasting, directly applicable to range prediction and route planning for heavy-duty trucks operating under dynamic real-world road section conditions.
Cam Phaser Simulation in GT-Suite
(2026) Sankar, Sarath
Cam phasers enable variable valve timing by changing the angular position of the camshaft relative to the crankshaft. In heavy-duty diesel engines, cam phasing can support functions such as thermal management, engine braking, and potential replacement of certain conventional engine components. Understanding the internal behaviour of a cam phaser is therefore important for further system development. However, existing supplier models provide limited access to the internal hydraulic and mechanical behaviour of the system. This thesis develops an in-house system-level model of a hydraulic Cam Torque Actuated vane phaser in GT-SUITE. The model combines the hydraulic, mechanical, and electrical domains of the system, with particular focus on the Oil Control Valve and the internal oil flow paths governing phaser operation. The model is calibrated against test-cell measurements. The results show that the model captures the actuator and cam phasing behaviour observed in the measure ments, although some deviation remain. Beyond reproducing measurable system responses, the physics-based model enables investigation of internal quantities and oil flow behaviour that cannot be directly measured in the test setup. The de veloped model therefore provides a basis for improved understanding and further development of the cam phaser system.
Enhancing Web Accessibility Remediation with LLM-based IDE Extensions
Luo, Dantong
AI coding assistants offer opportunities for web accessibility support, but evidence on how accessibility-focused guidance affects code accessibility and developer experience remains limited. This thesis presents A11yHelper, a Visual Studio Code extension integrated with GitHub Copilot Chat, and compares its accessibility quality, perceived usability, and tool preference with GitHub Copilot and CodeA11y. The evaluation combined a fixed-prompt experiment and a controlled user study with 18 participants. Both covered five tasks from two repositories. The analysis used task-specific three-level quality ratings, the SUS score, preferences between the two tools used, and descriptive categorization of written reasons. Quality differences depended on the task. A11yHelper had higher mean scores than GitHub Copilot on form labeling and keyboard navigation in both evaluations, while GitHub Copilot matched or exceeded its means on the remaining tasks. Both scored higher than CodeA11y on the task requiring information distributed across a larger file. Alternative text remained difficult, with only two of 36 user-study artifacts rated Good. Mean SUS scores were 79.38 for GitHub Copilot, 76.46 for A11yHelper, and 59.58 for CodeA11y, preference counts followed the same ordering. The study contributes an integrated accessibility assistant and descriptive evidence of its task-specific strengths and limitations.
Reactive Whole-Body Control for Grasping Moving Objects with Mobile Manipulators
(2026) Li, Dongxiang; Zhou, Shijie
Grasping moving objects remains challenging for fixed-base manipulators because their limited workspace prevents them from continuously tracking objects that move beyond their reachable area. This limitation is particularly important in human–robot collaborative scenarios. In this work, we propose a framework for grasping moving objects with a mobile manipulator that dynamically repositions its base to expand its reachable workspace and improve grasp feasibility. To coordinate the system motion, we adopt a reactive whole-body control strategy that treats the mobile base and manipulator as a unified kinematic system. As the object moves, the target pre-grasp pose is updated based on the estimated object pose, allowing the robot to track and approach a grasp-relevant target. The proposed method is validated in both simulation and real-world experiments, demonstrating the effectiveness of the unified control strategy for coordinated tracking and grasp-oriented motion generation when interacting with moving objects.