| 11. |
- Degen, René, et al.
(författare)
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Methodical Approach to the Development of a Radar Sensor Model for the Detection of Urban Traffic Participants Using a Virtual Reality Engine
- 2021
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Ingår i: Journal of Transportation Technologies. - : Scientific Research Publishing. - 2160-0473 .- 2160-0481. ; 11:2, s. 179-195
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Tidskriftsartikel (refereegranskat)abstract
- New approaches for testing of autonomous driving functions are using VirtualReality (VR) to analyze the behavior of automated vehicles in variousscenarios. The real time simulation of the environment sensors is still a challenge.In this paper, the conception, development and validation of an automotiveradar raw data sensor model is shown. For the implementation, theUnreal VR engine developed by Epic Games is used. The model consists of asending antenna, a propagation and a receiving antenna model. The microwavefield propagation is simulated by a raytracing approach. It uses the methodof shooting and bouncing rays to cover the field. A diffused scatteringmodel is implemented to simulate the influence of rough structures on thereflection of rays. To parameterize the model, simple reflectors are used. Thevalidation is done by a comparison of the measured radar patterns of pedestriansand cyclists with simulated values. The outcome is that the developedmodel shows valid results, even if it still has deficits in the context of performance.It shows that the bouncing of diffuse scattered field can only be doneonce. This produces inadequacies in some scenarios. In summary, the papershows a high potential for real time simulation of radar sensors by using raytracing in a virtual reality.
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| 12. |
- Degen, René, 1994-, et al.
(författare)
-
Stereoscopic Camera-Sensor Model for the Development of Highly Automated Driving Functions within a Virtual Test Environment
- 2023
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Ingår i: Journal of Transportation Technologies. - : Scientific Research Publishing. - 2160-0473 .- 2160-0481. ; 13:1, s. 87-114
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Tidskriftsartikel (refereegranskat)abstract
- The need for efficient and reproducible development processes for sensor and perception systems is growing with their increased use in modern vehicles. Such processes can be achieved by using virtual test environments and virtual sensor models. In the context of this, the present paper documents the development of a sensor model for depth estimation of virtual three-dimensional scenarios. For this purpose, the geometric and algorithmic principles of stereoscopic camera systems are recreated in a virtual form. The model is implemented as a subroutine in the Epic Games Unreal Engine, which is one of the most common Game Engines. Its architecture consists of several independent procedures that enable a local depth estimation, but also a reconstruction of a whole three-dimensional scenery. In addition, a separate programme for calibrating the model is presented. In addition to the basic principles, the architecture and the implementation, this work also documents the evaluation of the model created. It is shown that the model meets specifically defined requirements for real-time capability and the accuracy of the evaluation. Thus, it is suitable for the virtual testing of common algorithms and highly automated driving functions.
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| 13. |
- Degen, René, 1994-
(författare)
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Urban Virtual Test Field for HighlyAutomated Vehicle Systems
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Autonomous driving is one of the key technologies for increasing road safetyand reducing traffic volumes. Therefore, science and industry are workingtogether on new innovative solutions in this field of technology. One importantcomponent in this context is the approval and testing of new solution concepts,with special focus on the ones for urban environments. Not only because ofthe high diversity of traffic situations, but also because of the close contactbetween vulnerable road users (VRU) and automated vehicles.In the course of this work, a novel approach for testing automated drivingfunctions and vehicle systems in urban environments is presented. The goal isto create a safe and valid environment in which the automated vehicle and theVRU can meet and interact. The basis is a highly realistic virtual model of acity center. The physical behavior of the vehicle and VRU is recorded usingmeasurement technology and transferred to the virtual city model.Based on representative urban traffic scenarios, the functionality of the urbantest field is investigated from various points of view. Thereby, the focus is onreal-time capability and the quality of interaction between the vehicle and theVRU.The investigations show that both the real-time capability and the interactionpossibilities could be demonstrated. Further, the developed methodologies aresuitable for real time applications.
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| 14. |
- Degen, René, 1994-
(författare)
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Virtual Test Field for Highly Automated Vehicle Systems in Urban Environments
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Autonomous driving was and is one of the most important research and innovation drivers in the automotive and supplier industry. In addition to the predicted energy savings, a reduction in the number of accidents and their level of damage is also expected. In particular, the functional testing and legislation of highly automated driving functions play a decisive key role here. This results in a justified need for innovation and research and means major challenges for the entire technology sector. Traditional methods such as real-world tests and X-in-the-loop tests for proving functional safety still have their justification, but cannot answer all the questions posed by the diverse requirements in daily use. In particular, urban environments with highly complex traffic scenarios and diverse groups of actors can only be mapped to a limited extent using existing methods.In this work, a novel approach for testing automated vehicle systems in urban environments is presented. The goal is to create a safe and valid environment in which the vehicle under test can interact with real road users under realistic conditions. The basis is a highly realistic virtual model of a German city center. The physical behavior of the vehicle and the pedestrian is measured and transferred to the virtual city model in real time. Sensor models enable the interaction of the vehicle with the virtual environment and the pedestrian. With the help of different studies with different focuses, both individual functionalities as well as the overall functionality are finally evaluated.
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| 15. |
- Degen, René, et al.
(författare)
-
Virtual Urban Traffic Infrastructure for Testing Highly Automated Mobility Systems
- 2021
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Konferensbidrag (refereegranskat)abstract
- Recently, virtual realities and simulations play important roles in the development of urban traffic infrastructure. By anappropriate abstraction, they help to design, investigate and communicate inner-city development processes. Especially,to investigate interactions between infrastructure and future mobility participants, a valid virtual model is essential forfunctionality and reliability.The aim of this study is the investigation of interactions between a virtual infrastructure model and virtual sensor modelsof highly automated mobility systems. The overall system consists of a georeferenced virtual city model and probabilisticsensor models, which are part of an automated vehicle model. The virtual environment comprises a comprehensive,virtual 3D model of a representative German inner-city scene, considering specific height coordinates. The probabilisticsensor models represent real radar and lidar sensors and comprehensively replicate their physical functionalityin a virtual environment. Considering different levels of detail, the realistic representation of physical effects of thevirtual city model on the virtual sensors is investigated. The investigated scenarios are derived from representativeurban traffic situations. The complexity as well as the level of information of the virtual city scenarios is iterativelyincreased. Subsequently, the effects on the model validity of the overall system is checked and analysed.The results show that the developed virtual environment performs well for different levels of detail of representativevirtual traffic scenes. In addition, the selected modelling depth is very suitable for the high-performance investigationof interaction between virtual urban environment and virtual autonomous vehicle.
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| 16. |
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| 17. |
- Ekergård, Boel, 1985-, et al.
(författare)
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Eddy Current Losses in Solid Pole Shoes in a Two-Pole Permanent Magnet Motor
- 2021
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Ingår i: Engineering. - : SCIRP. - 1947-3931 .- 1947-394X. ; 13:10, s. 536-543
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this paper is to present the eddy current losses in solid pole shoes in a permanent magnet two-pole electric motor. In the presented paper, the authors have chosen to work with three different analytical models, Carter’s theory, Gibb’s theory and Lawrenson’s theory, each with different degree of accuracy and simplifications. The results from the analytical models all present relatively low eddy current losses, giving the designer valuable arguments to utilize solid pole shoes, as a rotor with solid poles is from a construction point of view a more suitable choice, increasing the mechanical stability and reducing the production cost, compared to the laminated design.
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| 18. |
- Ekergård, Boel, 1985-, et al.
(författare)
-
Longitudinal end effects in a linear wave power generator
- 2020
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Ingår i: Energies. - : MDPI AG. - 1996-1073 .- 1996-1073. ; 13:2
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Tidskriftsartikel (refereegranskat)abstract
- Even though the magnetic circuit of a linear electric machine is very similar to a rotating electric machine, they diverge in one fundamental property. The linear generator is open in both ends, i.e., the magnetic circuit is non-symmetric. This paper investigates and discusses the drawbacks of this non-symmetric design in a linear permanent magnet generator, installed in a wave energy conversion system. A two-dimensional geometry has been utilized for the numerical calculations in a finite element method simulation tool. The results present an increased cogging force and significant core losses in the translator as consequences of the longitudinal ends in the machine.
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| 19. |
- Eklund, Petter, 1989-, et al.
(författare)
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Experimental Evaluation of a Rare Earth-Free Permanent Magnet Generator
- 2021
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Ingår i: IEEE Transactions on Energy Conversion. - Piscataway : Institute of Electrical and Electronics Engineers (IEEE). - 1558-0059 .- 0885-8969. ; 36:1, s. 3-10
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Tidskriftsartikel (refereegranskat)abstract
- Low speed, high torque machines are used in wind turbines where the turbine rotor is directly connected to the generator. A permanent magnet synchronous generator using high-energy rare-earth permanent magnets (PMs) is one common choice for this application, but rare-earth PMs have supply insecurities and cost risks. A rare-earth free 32-pole PM generator, using ferrite PMs in a spoke-type rotor, for use in a 12 kW experimental wind turbine is built and tested. Voltages and currents at load and no load are measured, as well as the magnetic field in the end regions of the machine. The generator can deliver the required power at nominal speed and has low harmonic content in the output. The electrical measurements are compared to two-dimensional finite element design calculations and the experimental results are lower than expected from simulations. The measured voltage is lower than expected, requiring a higher current than calculated for the rated power. Three-dimensional magnetic field simulations show that there are leakage flux paths in the end-regions that the two-dimensional design calculations overlook, explaining the discrepancy between simulations and measurements.
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| 20. |
- Fjellstedt, Christoffer
(författare)
-
Grid connection of offshore renewable energy sources
- 2023
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In order to achieve net zero emissions from the electricity sector, the proportion of renewable energy sources connected to the electrical grid needs to be increased significantly in the coming years. Established renewable energy sources, such as wind power and solar power, will certainly be crucial in achieving this. However, marine energy sources, like marine current power and wave power, have the potential to significantly contribute to the increase of electricity from renewable energy. An important area of study to enable the use of marine energy sources is how to construct electrical systems for offshore renewable energy. Therefore, this thesis addresses some challenges regarding the grid connection of offshore renewable energy.Two important questions for offshore renewable energy are how the offshore electrical grid is constructed and how the power is transmitted to the shore. In the thesis, a review of AC and DC collection grid topologies is presented. Furthermore, HVAC and HVDC transmission for offshore applications are compared in a literature review. It is concluded that for transmission distances longer than 50 km to 100 km, the preferred technology appears to be HVDC.Regardless of how the offshore collection grid is constructed, the energy converters need to be connected to the collection grid and the distribution grid. Uppsala University has deployed a marine current energy converter in the river Dalälven in Söderfors, Sweden. The electrical grid connection system at the test site is based on a B2B converter technology. In the thesis, a simulation model of the grid connection system of the energy converter is presented.The grid connection system at the Söderfors test site includes an LC-filter connected to a power transformer. A novel transfer function is derived for this system and the transfer function is verified with simulations and experimental investigations. It is shown that the derived transfer function is able to capture the frequency response of the experimental system.
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