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Senast publicerade

Mot automatisera gångbedömning med sensorfusion: Sensorsynkronisering och etablering av ground truth för segmentering
(2026) Florén, Frida; Ibrahim, Mustafa; Norresjö, Lina; Sahlström, Vincent; Ukash, Abdulkatir; Zetterlund, Rebecca
Idag används Timed Up and Go (TUG)-testet ofta för att bedöma balans- och gångförmåga hos äldre. Bedömningen bygger på visuella observationer där endast den totala testtiden registreras. Detta kan ge en begränsad bild av patientens rörelseförmåga och försvårar identifieringen av vilka delmoment som behöver förbättras. Med hjälp av sensorteknik går det att få mer objektiva och detaljerade insikter om personers balans- och gångfunktion. Detta kandidatarbete utgör ett första steg mot en sensorfusionbaserad metod för automatisering av TUG-testet. Arbetet fokuserade på tre områden: datainsamling, synkronisering mellan radar- och IMU-sensorer samt etablering av ground truth baserad på Motion Capture (MoCap)-data. Data samlades in med samtliga system från gruppmedlemmar, handledare samt frivilliga forskningspersoner som utförde TUG testet. Vidare utvecklades en metod för tidsmässig synkronisering av sensorsigna lerna, samt en automatiserad segmenteringsalgoritm för att identifiera TUG-testets olika delmoment utifrån MoCap-data. Resultaten visade att den signalbaserade metoden fungerade väl för tidsmässig synkronisering mellan IMU- och radarsensorerna, vilket är avgörande för fusion av data från dessa två typer av sensorer. Den automatiserade segmenteringsmetoden uppvisade en felnivå som var jämförbar med variationen mellan manuella annoteringar. Detta tyder på att metoden kan användas som referens vid framtida utveckling och validering av sensorfusionbaserade system för förbättrad fallriskbedömning och individanpassad rehabilitering.
Promoting viability of 3D-bioprinted adipose tissue
(2026) Hilmersson, Hugo
Bioprinting is a promising technique for soft tissue reconstruction and enables custom design of autologous tissue that could replace lost tissue, restore function and reduce the need for donor tissues. Ensuring survival and nutrient supply to the tissue remains a major challenge. Due to ethical reasons, methods to study viability and vascularization in vitro needs to be developed. This thesis aims to evaluate methods to study viability of bioprinted adipose tissue in vitro. The second aim is to assess if addition of adipose derived human stromal vascular fraction (SVF) to 3D- bioprinted tissues promotes adipocyte viability in vitro. Microfragmented, human adipose tissue combined with an oxidized nanofibrillated cellulose hydrogel and alginate solution was bioprinted and stabilized through cross-linking using CaCl2. SVF was cultured and added to the bioink pre- and post- printing. Viability was measured with a metabolic assay, alamar Blue, combined with fluorescence assays and histology during culture in vitro for 14 days. Efforts to create a model where SVF could be concentrated were done by evaluation of potential sacrificial inks. The results showed an almost linear trend between adipose tissue content and reduction of the alamar Blue reagent. Printed adipose tissue without SVF could be determined dead after three days in vitro. Furthermore, the assay indicated that infusing and covering bioprinted adipose tissue with SVF could promote viability for 14 days in vitro with a constant 20 % reduction. The majority of the sacrificial inks exhibited low viscosity, clumping or problems when extruded. However, combining porous gelatine microcarriers with an equal amount of cellulose hydrogel or gelatine produced a network with adequate fidelity. Conclusions were that alamar Blue assay can be used to measure viability of bioprinted adipose tissue. Moreover, addition of SVF in and on the bioprinted construct can promote viability of the adipose tissue. Finally, more research is needed to combine these findings with sacrificial inks to promote vascularization. This thesis provide a foundation for future research in creating and promoting vascular networks in bioprinted tissue used for reconstruction surgery.
Modelling of subcooled liquid hydrogen fueling system
(2026) Farzaneh, Azimi; Canullo, Niccolo´
In order to reduce greenhouse gas emissions in the transportation sector, hydrogen is recognized as a promising fuel alternative, particularly for heavy-duty applications where high energy density is required. Subcooled Liquid Hydrogen (sLH2) is of significant importance due to its superior volumetric energy density and higher mass flow rates, outperforming compressed gaseous hydrogen in terms of rapid and high-capacity refuelling. However, challenges related to refuelling duration and storage capacity must be addressed, especially for heavy-duty vehicles requiring large hydrogen quantities. The initial thermodynamic state of the tank and the State of Charge (SoC) at the time of refuelling significantly dictate the maximum mass of hydrogen that can be effectively stored. The objectives of this thesis are to investigate the sLH2 refuelling system to determine the optimal initial conditions for truck tanks and to identify other critical factors influencing the process. Furthermore, the thermal behavior and pressure dynamics of sLH2 during refuelling and storage are complex phenomena that require advanced numerical modelling for system optimization. Given its capability for 1D CFD and its reliability in vehicle system simulation, GT-SUITE was selected as the modelling tool to allow for rapid and accurate analysis. Initially, the refuelling system was modeled and validated. Subsequently, the defuelling process was modeled to determine the initial thermodynamic of the tank and SoC. Finally, a sensitivity analysis was performed to identify the key parameters affecting the refuelling system’s performance. The results indicate that since the tank pressure must be maintained at a specific level due to fuel cell demand, the initial tank temperature has a predominant impact on the final hydrogen storage mass and the overall system efficiency.
Harmonic distortion analysis involving submarine cables for offshore wind power plants
(2026) Hassellöf, Gabriel
With offshore wind power plants (OWPPs) getting larger and more common, the connection requirements at the point of common coupling (PCC) become more important. OWPPs often use converters that produce harmonics, and reactive components such as long high voltage AC (HVAC) submarine export cables further influence the harmonic content seen at the PCC. This thesis looks at voltage harmonics up to the 63rd order at the PCC between an OWPP and the main grid. An aggregated type IV OWPP with grid-following converters was modeled in PSCAD, and the harmonic content was analyzed in MATLAB using a fast Fourier transform (FFT). The simulated cases varied three factors: grid strength (a stronger and a weaker grid, relative to each other), HVAC export cable length (50 km and 100 km), and the order of voltage harmonic injected from the main grid (5th and 9th). Results are presented in the voltage and harmonic impedance domains. The impedance analysis focuses on the resistive component, since the reactive component remained inductive for all simulated cases. Grid strength was the dominant factor in the post-energization transient. Weaker grids produced a total harmonic distortion (THD) of 31-41 %, which is 2-4 times higher than the 9-19% seen for stronger grids in the same cases. A sensitivity check on later FFT windows showed that both grid configurations settle at a similar low THD around 2 %. The 2-4 times ratio is therefore specific to the post-energization transient, rather than the steady-state. The aggregated model is appropriate for studying the interaction between grid strength, cable parameters, and injected harmonics. Within the factors studied, grid strength had a much larger effect on THD than cable length, which means that grid reinforcement is more impactful than cable routing for limiting harmonic distortion at the PCC. The harmonic content was dominated by lower order harmonics, which is relevant for the design of harmonic filters and STATCOM compensation.
Tillämpning av artificiell intelligens inom mekanisk konstruktion
(2026) Brunzell, Andreas; Edelvik , Ingemar; Olsson, Tim
The increasing availability of large language models and AI-based development tools has opened new possibilities for integrating artificial intelligence into engineering workflows. This thesis investigates how AI can be applied as a support tool in a CAD-based design process, with focus on geometry generation, automated assembly operations, and component dimensioning. The study was conducted through a practical implementation in Autodesk Fusion, where an AI agent in the development environment Cursor was connected to the CAD system via a Model Context Protocol server, enabling direct interaction between the AI agent and the CAD environment. The results demonstrate that AI-assisted CAD workflows are practically feasible and can contribute to increased efficiency in well-defined and recurring design tasks. However, the reliability of AIgenerated results was found to be highly dependent on the clarity of user instructions, and manual verification remained necessary throughout the process. A key finding is that the time required to verify AI-generated outputs in many cases exceeds the time savings gained through automation, particularly for more complex tasks. For AI-based CAD workflows to become genuinely competitive with traditional methods, model reliability must improve to a level where users can trust generated results without reviewing each step individually. The study concludes that while AI holds significant promise for the future of CAD-based engineering, its full potential is contingent on continued improvements in both model quality and cost-effectiveness