Mekanik och maritima vetenskaper (M2) // Mechanics and Maritime Sciences (M2)
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Browsar Mekanik och maritima vetenskaper (M2) // Mechanics and Maritime Sciences (M2) efter Program "Applied physics (MPAPP), MSc"
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- PostActive Vision System with Human Detection - Using RGB-D images and machine learning algorithms(2012) Berggren, Andreas; Björklund, Eric; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsThis master's thesis will focus on an active safety system for the protection of humans close to commercial construction equipments. The purpose is therefore to propose sensors and algorithms suitable for human detection and furthermore to demonstrate a proof of concept. Early on in the project it was decided to use RGB-D images, which is a conventional color image together with a depth map. This report analyzes both a Kinect sensor and a stereo vision system in order to generate a depth map. Machine learning algorithms were used to classify humans where an artificial neural network was found to be the best performing classifier. Finding informative features is important to facilitate classification. Several imaging features were tested and the six most interesting are presented in this report. The feature called fourier descriptor showed the best performance.
- PostCFD Modeling of an Air-Cooled Data Center(2015) Wibron, Emelie; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsFortlax is an air-cooled data center in Norrbotten. The potential of future investments in data centers is prosperous, but sustainability is an increasingly important factor. It is important to make sure that the data centers are sufficiently cooled while too much forced cooling leads to economical losses and a waste of energy. The purpose of this thesis is to develop a CFD model of a server room at Fortlax data center that accurately predicts the temperature and flow field. The goal is to develop the CFD model in order to evaluate different cooling systems and also improve the placement of the server racks. Most of the server racks are only half full at the moment, but the heat load is supposed to increase in the near future. Therefore, it has been assumed that all the server racks generate full heat load. The commercial CFD software ANSYS CFX 16.0 has been used to perform the simulations. The current cooling system with the current placement of the server racks resulted in some insufficiently cooled server racks. The performance of the cooling system was significantly improved when the hard-floor configuration was replaced by a raised-floor configuration. The design strategy based on hot/cold-aisles has become the standard when raised-floor configurations are used. However, the raised-floor configuration with parallel rows of server racks turned out to be the setup that performed best based on the performance metrics that were used to evaluate the results in this thesis.
- PostDriver response to a lane-departure prevention system - Based on real-world traffic data(2015) Liljeblad, Linus; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsToday, there are commercially available cars with some kind of lane-departure prevention system, with the purpose of stopping the driver from unintentionally crossing the lane marker. The latest versions of the system does not only warn the driver, but is actually trying to steer the car back on the right track when the driver fails to steer the car sufficiently. The systems applies torque on the steering rack which then translates into the wheel as well as the steering wheel and effects both the driver and the car. The driver's reaction to this kind of intervention has been studied before in experiments but never investigated in real-world traffic data. This thesis describes a methodology to understand driver response to a lane-departure prevention system based on an analysis of real-world traffic data. As far as the author is aware, this type of analysis has never been done before, and therefore it constitutes an important part of the understanding of driver behaviour. The purpose was to develop a methodology that could describe the drivers reaction when external torque from the lane-departure prevention system was applied. The study show that it was possible to give a rather good description of how the driver reacts to an externally applied torque. A reaction was noticeable for almost every intervention when only looking at the torques in the system, but a distinct visible reaction was only noticeable in 11:6% and 19:1% of the initial (0 s{0:5 s) and whole intervention respectively. The difference in applied torque between the driver and the lane-departure prevention system also showed that the driver tends to take more control over the steering wheel when the duration of intervention was longer than 0:5 second, than when the intervention was shorter or in the initial phase of a longer intervention. The study further show that it was possible to describe and understand the movement of the steering wheel by analysing the steering wheel angle and its rate. Finally, the fraction of the driver reaction with respect to the other torques in the system that effects the steering could be calculated and analysed.
- PostLane Departure Warning and Object Detection Through Sensor Fusion of Cellphone Data(2015) Eriksson, Jesper; Landberg, Jonas; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsThis master thesis focus on active safety for the automotive industry. The aim is to test an inexpensive implementation of some common functions realized using a cellphone to gather data. A Matlab Simulink model is developed for the purpose, and then the agility of the model is tested by generating c code and running it on a single board computer. A robust lane detection algorithm is developed by using Hough lines. To better cope with curves in the road, the Hough lines are combined with a parabolic second degree fitting. The Hough lines are also used for a Lane Departure Warning system. Using edge filtering and connected component labeling an obstacle warning is implemented. Overall the model works well and is fast enough to meet the real time requirements when run on a computer. On the Raspberry Pi 2 chosen as the single board computer the processing is unfortunately not quite fast enough for high speed driving. However when the object detection is removed the Raspberry Pi 2 meets the real time requirements as well.
- PostMachine learning for vehicle concept candidate population & verification(2017) Grevholm, Björn; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsThe aim of this M.Sc. thesis is to evaluate the potential of using machine learning to support concept phase decisions to balance the thermal properties of an automobile. With the use of computer scripts, the relevant measurement data is extracted from repositories and is used to train an artificial neural network which can identify the importance of the different parameters that are involved in tuning the vehicle thermal attributes. After data for several car models has been used to train Machine Learning (ML) tools, this configuration used in predicting parameters affecting engine under hood thermal behaviour. A neural network based ranking procedure which may make it possible to reduce the order of concept decision space is also proposed. After several vehicle families gone through this prediction phase, a clustering of vehicle classes may allow for prediction and optimisation of new families, if errors due to assumptions and underlying mathematics are quantified. The project has the added benefit of allowing Volvo Car Corporation (VCC) to reuse the large amount of data which are seldom used after the initial project delivery date. Measurements collected in VCC’s wind tunnels are the main source of data for this thesis but the open-source script based method can be used on other type of data from other disciplines. A possible outcome of the thesis might be recommendation for updated procedures in creating and storing data to easier integration into machine learning based investigations.
- PostModelling Object Movement Around an Ego Vehicle(2019) MacIsaac, Ian; Hultberg, Johan; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Wolff, Krister; Wolff, Krister; Karlsson, Tobias; Sancar, EmreOne problem for automated vehicles is that the tra c environment surrounding a vehicle is diverse and populated by a large set of interacting agents in the form of drivers. With a model for vehicle movement in tra c, developers will be able design autonomous vehicles with better path planning functionalities. In this thesis models for vehicle movement around an ego vehicle are developed in a data-driven manner with di erent machine learning techniques. Analysis is done to nd how accuracy is related to the prediction horizon, and to determine which features are most important. It is clear that more features are not always better as removing unnecessary features provides better results. When comparing the models, baselines based on equations of motion with constant velocity or acceleration have been used. All methods provide better predictions compared to the baselines, and can make predictions for longer horizons. For longitudinal position prediction, results are promising. In latitudinal direction the results are less impressive, especially lane changes are di cult to predict, due to the low amount of lane changes in the training data. That leads to analyzing in what other situations the prediction accuracy is limited by the data set, rather than by the model itself. For example how the accuracy is correlated with the speed of the ego vehicle. It is clear that the models performs best in situations that is well represented in the training data. To make a model that handles rare situations, a lot of data with those situations is needed.
- PostPrediction of High-Speed Planing Hull Resistance and Running Attitude - A Numerical Study Using Computational Fluid Dynamics(2015) Frisk, David; Tegehall, Linda; Chalmers tekniska högskola / Institutionen för sjöfart och marin teknik; Chalmers University of Technology / Department of Shipping and Marine TechnologyAccurate predictions of the resistance and running attitude are key steps in the process of hull design and manufacturing. The predictions have traditionally relied on model testing, but this technique is both expensive and time consuming. In this study, the performance of CFD simulations of planing hulls is evaluated using two commercial software: ANSYS FLUENT, developed by ANSYS, Inc., and STAR-CCM+, developed by CD-adapco. This was done by predicting the steady resistance, sinkage and trim angle of one semi-planing and one planing hull in calm, unrestricted water. The Reynolds averaged Navier-Stokes equations with the SST k-! turbulence model was used along with the volume of fluid method to describe the two-phase flow of water and air around the hull. Furthermore, a two degrees of freedom solver was used together with dynamic mesh techniques to describe the fluid-structure interaction. The simulations were performed with both fixed and free sinkage and trim to make careful comparisons of the software and with experimental data. The results from the fixed sinkage and trim simulations of the planing hull in FLUENT and STAR-CCM+ show a good consistency. However, there is a significant difference in the pressure resistance obtained from the two codes that could not be explained. The free sinkage and trim simulations were mainly conducted in STAR-CCM+ due to problems with obtaining a stable solution in FLUENT. Froude numbers between 0.447 and 1.79 were simulated and the results follow the same trends as what is seen in the experimental data. The calculated resistance, sinkage and trim angle show good correspondence to experimental data in the planing region, where the errors of the predicted values are below 10%.
- PostSimulation of flow and combustion in H2/O2 rocket thrust chambers using a 2D spray combustion method(2012) Larsson, Erik; Chalmers tekniska högskola / Institutionen för tillämpad mekanik; Chalmers University of Technology / Department of Applied MechanicsA new parameter setting to simulate H2/O2 rocket thrust chambers is found for the currently used two-dimensional, axisymmetric CFD-code Rocflam-II at Astrium GmbH in Ottobrunn, Germany. The generation program used for creating the necessary equilibrium lookup tables to the simulation is validated against an older version to make the generation for different fuel mixtures more consistent. Calculation of the isothermal compressibility of a multiple phase mixture is implemented together with unsuccessful measures to significantly decrease computational power. The program is also successfully modified to generalize the number of reaction products treated. The influence of the table resolution to Rocflam-II simulations is studied using the Vinci subscale thrust chamber. The study shows upon a possibility to slightly increase precision of the simulated rocket performance values by adjusting the mixture fraction resolution. The resolutions of the other parameters are found to be acceptable in their default settings. A formulation change is implemented in the Rocflam-II source to increase consistency between injected liquid droplets of different propellants. New correction functions for the droplet distribution for “warm” and “cold” injection of H2 are found using the CALO test case. The new correction functions and the Rocflam-II formulation change are applied to full-scale simulations of the Vulcain 2 rocket engine with good agreement to previous simulation results.
- PostWhat are the effects of AEBS on collision avoidance?(2019) Rost, Louise; Sällberg, Joakim; Chalmers tekniska högskola / Institutionen för mekanik och maritima vetenskaper; Chalmers University of Technology / Department of Mechanics and Maritime SciencesAdvanced Emergency Braking System (AEBS) is an active safety system for Heavy Goods Vehicles (HGVs) which aims to prevent rear-end collisions, i.e. when a vehicle drives into the rear of the vehicle in front. This report investigates the performance of AEBS in Volvo HGVs, and describes under what circumstances the system intervenes correctly and incorrectly respectively. Data from AEBS interventions by Volvo HGVs was analysed, and patterns of the incorrect interventions were identified. These patterns were translated into code, resulting in a program that automatically classifies the logged interventions as correct or incorrect. Different variables were investigated for the correct and incorrect interventions separately, for the purpose of finding factors that affect the performance of AEBS, i.e. under which circumstances the correct and the incorrect interventions occur. The majority of the incorrect interventions were found to be due to stationary targets, and only resulted in a short intervention with minor speed reduction. Therefore, it seems very unlikely that the incorrect interventions would cause collisions. The majority of the interventions were found to be true, and many of these interventions yielded a large speed reduction. Thus, AEBS interventions prevents many collisions.