Chalmers Open Digital Repository

Välkommen till Chalmers öppna digitala arkiv!

Här hittar du:

Studentarbeten utgivna på lärosätet, såväl kandidatarbeten som examensarbeten på grund- och masternivå
Digitala specialsamlingar, som t ex Chalmers modellkammare
Utvalda projektrapporter

Forskningspublikationer, rapporter och avhandlingar hittar du i research.chalmers.se

Enheter i Chalmers ODR

Välj en enhet för att se alla samlingar.

Visar 1 - 2 av 2

Senast publicerade

Reduced-Order Modeling in Nonlinear Driveline Systems
(2026) Enström, William; Johnsson, Alexander
This thesis presents and investigates different approaches for constructing reducedorder BEV driveline models in state-space form using a data-driven approach. Existing Multi-Body Dynamic (MBD) models of the full driveline are often computationally demanding, while reduced models of sub-parts may lack a clear connection to the full-scale model and to one another. In order to improve simulation times while maintaining consistency with the more general MBD model, local Linear Time-Invariant (LTI) models are identified around selected operating points using subspace system identification methods and data generated from the larger MBD model. However, system internal periodic disturbances related to driveline rotation complicate the system identification as it contaminates the externally forced response. Two methods addressing this are investigated: Removing the frequency components associated with these disturbances from the data, or augmenting the model with additional input signals with those frequencies. Both methods improve the model quality by reducing the effect of the periodic disturbances. The model constructed by including additional input signals is also shown to more accurately reproduce the amplitude and frequency of the periodic disturbance. In order to model gyroscopic effects, such as resonance frequencies depending on the operating speed, several local LTI models are identified at different operating points. The local models are combined by either linear interpolation of the matrix elements, fitting a basis function to the matrix elements or by interpolating the outputs of each model. All three methods result in models with similar input-output accuracy, but differ in their requirements when creating the local models. In particular, methods based on output interpolation do not require system internal consistency between local models, unlike methods that rely on the local models sharing a common state-space realization. The disturbance-modeling approach based on additional input signals is also extended to the Linear Parametric Variant (LPV) framework, enabling the resulting models to capture both the speed-dependent system dynamics and the periodic disturbances associated with driveline rotation.
Integrating Highly Conductive 2D Materials in Metal Matrix
(2026) Berntsson, Sanna
MXenes have attracted significant attention in recent due to their high electrical conductivity and potential for usage in composite material. This thesis investigated Ti3C2Tx MXene/Al composites with varying aluminum content to see whether the conductivity of the composites can overcome the one for pure aluminum. The MX ene was synthesized through an in-situ HF etching process, mixed with aluminium powder, pressed into coin-like pellets, and sintered in argon atmosphere at 550 ◦C. Contact conductivity and Rockwell hardness measurements where performed, as well as microstructure analysis through SEM and EDX. The results showed that high-Al composites showed measurable conductivity and im proved mechanical integrity, while lower-Al composites exhibited fragile behaviour and measurement challenges. Sintering influenced both conductivity and hardness, indicating strong dependence on densification and microstructure. This was sup ported by the microstructure analysis. The study demonstrates the importance of composition and thermal processing in determining the electrical and mechanical properties of MXene/Al composites. None of the composites overcame the electrical performance for pure aluminium, however there are many aspects of this project that could be investigated further before declaring MXene/Al composites not useful for electrical transport applications. These aspects include examining the residual aluminium in the pure MXene samples and comparing the results of other sinter ing methods better suited for powder composites, such as spark plasma sintering (SPS).
Towards Qualification of Female Human Body Model for Virtual Testing: Setup for 50th percentile female human body model and parametric study of the boundary conditions
(2026) Dhamane, Pushkar Mahesh
Road traffic injuries pose a major global safety challenge for vehicle occupants and vulnerable road users, such as pedestrians and cyclists. To prevent injuries, crash testing plays a vital role in automotive safety assessment. While early biomechanical evaluations relied on post-mortem human surrogates (PMHS), standard physical crash testing today is primarily conducted using Anthropomorphic Test Devices (ATDs). However, ATDs possess structural limitations: their rigid responses cannot fully replicate complex human soft-tissue and skeletal injury mechanisms. Additionally, physical testing using ATDs is constrained by high financial costs and testing complexity. To address this limitation, virtual testing is being proposed as a complement to physical testing for vehicle safety assessment, for example the HBM4VT framework under Euro NCAP has established qualification protocols for the 50th percentile male HBM (50M) through the Crash Protection 550 (CP550) protocols. This thesis evaluates the biofidelity scoring of a 50th percentile female HBM (50F) across key hub impact scenarios: Kroell (frontal thoracic), Viano (thoracic, abdominal, and pelvic), Compigne (shoulder), and Agnew (angled thoracic) and performs a parametric study on uncertainties that can influence the biofidelity scores. Simulation results were compared against experimental post-mortem human subject (PMHS) reference corridors generated using the ARCGen, with objective metric scores calculated using the Ellipse and Dynamic arc-length warping (DALW) scoring method and, ISO 18571. Evaluated parameters included physical setup variables (seating angle, HBM posture, and arm orientation) and ARCGen algorithmic parameters (cut_simulation with boolean values and number of warping points (nWarpCtrlPts) ranging from 0 to 5. Results demonstrate that scores exhibit higher sensitivity to physical setup variations than corridor algorithm configurations.
Cost-Latency Benchmarking for Time-Series Forecasting - Hardware-Aware Evaluation of Deep Learning Architectures for Financial Planning
(2026) Asplund, Gustaf; Bjerhem Aronsson, Felix
Enterprise financial planning is increasingly moving from statistical forecasting toward deep learning, which captures more complex patterns at the product level but raises the cost of serving forecasts. The hardware for these workloads is often chosen through heuristics rather than measurement, and existing serving research has focused on computer vision and language rather than time-series forecasting. This thesis develops a workload-aware benchmarking framework that characterizes the cost-latency trade-offs of deep learning forecasting architectures across commodity cloud hardware. Six forecasting models spanning distinct computational classes were benchmarked on eleven Azure instances, examining how the operational intensity of each architecture sits against the roofline limits of the hardware, how far cost-latency behavior on real enterprise resource planning data diverges from simpler synthetic data, and how a Pareto analysis can guide the choice of a hardware and model pair under a given latency constraint. Operational intensity stayed within a narrow band across the tested models, yet the point at which a workload becomes compute- or memory-bound shifted with the hardware, so the same model could be bound differently from one machine to the next. The cost-latency outcome thus depends on the model and hardware as a pair rather than on the architecture alone, and this shows in the provisioning results. Neither the largest CPU nor the newest accelerator reliably improved serving performance and an older, lower-tier GPU instance offered the best overall balance for the workloads tested. The framework itself, rather than any single figure, is the more transferable result, and the comparison with synthetic data suggests it can stand in as a cheap first pass for narrowing the hardware search before real-data runs settle a final deployment.
Control Design for Differential Lock Synchronization in Heavy-Duty Trucks
(2026) Johansson, Hampus; Karlhager, Lukas
Heavy-duty trucks operating in low-traction environments rely on differential locks to maintain traction when a wheel spins out. These locks are commonly implemented with dog clutches, which require the connected shafts to be speed-matched before they can engage. Following a spin-out, achieving this match can force the driver to slow down or stop, wasting vehicle momentum and creating a safety risk on slopes. This thesis develops and compares active control strategies that synchronize the differential shafts after a wheel spin-out, enabling faster and safer dog clutch engagement. Individual wheel brakes and engine torque are used as actuators. A driveline model is derived for both the open and locked inter-axle differential configurations. A tire force estimator based on a Kalman filter provides feedforward disturbance cancellation, and a state transformation resolves an observability problem that arises when the inter-axle differential is locked. Three model-based controllers are designed and evaluated: a Linear-Quadratic Regulator (LQR), a Model Predictive Controller (MPC), and a Sliding Mode Controller (SMC). They are compared in simulation across split-friction and gravel road scenarios, using performance metrics for synchronization time, velocity loss, driver disturbance, and control effort, with tuning parameters swept to map the trade-offs between objectives. No significant trade-off is found between synchronization time and the remaining metrics: faster synchronization consistently coincides with lower velocity loss and does not worsen driver disturbance or control effort. A control strategy that follows the principles of the SMC is found to be best suited to the problem’s disturbance-heavy nature. Active engine torque control reduces velocity loss when traction allows, while on low-traction surfaces it must instead be limited to avoid excessive brake demand.