| 1. |
- Linden, Joakim, et al.
(författare)
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Curating Datasets for Visual Runway Detection
- 2021
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Ingår i: 2021 IEEE/AIAA 40TH DIGITAL AVIONICS SYSTEMS CONFERENCE (DASC). - : IEEE. - 9781665434201
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Konferensbidrag (refereegranskat)abstract
- In Machine Learning systems, several factors impact the performance of a trained model. The most important ones include model architecture, the amount of training time, the dataset size and diversity. In the realm of safety-critical machine learning the used datasets need to reflect the environment in which the system is intended to operate, in order to minimize the generalization gap between trained and real-world inputs. Datasets should be thoroughly prepared and requirements on the properties and characteristics of the collected data need to be specified. In our work we present a case study in which generating a synthetic dataset is accomplished based on real-world flight data from the ADS-B system, containing thousands of approaches to several airports to identify real-world statistical distributions of relevant variables to vary within our dataset sampling space. We also investigate what the effects are of training a model on synthetic data to different extents, including training on translated image sets (using domain adaptation). Our results indicate airport location to be the most critical parameter to vary. We also conclude that all experiments did benefit in performance from pre-training on synthetic data rather than using only real data, however this did not hold true in general for domain adaptation-translated images.
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| 2. |
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| 3. |
- Alégroth, Emil, et al.
(författare)
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Replicating Rare Software Failures with Exploratory Visual GUI Testing
- 2017
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Ingår i: IEEE Software. - : IEEE Computer Society. - 0740-7459 .- 1937-4194. ; 34:5, s. 53-59
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Tidskriftsartikel (refereegranskat)abstract
- Saab AB developed software that had a defect that manifested itself only after months of continuous system use. After years of customer failure reports, the defect still persisted, until Saab developed failure replication based on visual GUI testing. © 1984-2012 IEEE.
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| 4. |
- Caselli, Lucrezia, et al.
(författare)
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Interaction of nanoparticles with lipid films : the role of symmetry and shape anisotropy
- 2022
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 24:5, s. 2762-2776
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Tidskriftsartikel (refereegranskat)abstract
- The bioactivity, biological fate and cytotoxicity of nanomaterials when they come into contact with living organisms are determined by their interaction with biomacromolecules and biological barriers. In this context, the role of symmetry/shape anisotropy of both the nanomaterials and biological interfaces in their mutual interaction, is a relatively unaddressed issue. Here, we study the interaction of gold nanoparticles (NPs) of different shapes (nanospheres and nanorods) with biomimetic membranes of different morphology, i.e. flat membranes (2D symmetry, representative of the most common plasma membrane geometry), and cubic membranes (3D symmetry, representative of non-lamellar membranes, found in Nature under certain biological conditions). For this purpose we used an ensemble of complementary structural techniques, including Neutron Reflectometry, Grazing Incidence Small-Angle Neutron Scattering, on a nanometer lengthscale and Confocal Laser Scanning Microscopy on a micrometer length scale. We found that the structural stability of the membrane towards NPs is dependent on the topological characteristic of the lipid assembly and of the NPs, where a higher symmetry gave higher stability. In addition, Confocal Laser Scanning Microscopy analyses highlighted that NPs interact with cubic and lamellar phases according to two distinct mechanisms, related to the different structures of the lipid assemblies. This study for the first time systematically addresses the role of NPs shape in the interaction with lipid assemblies with different symmetry. The results will contribute to improve the fundamental knowledge on lipid interfaces and will provide new insights on the biological function of phase transitions as a response strategy to the exposure of NPs.
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| 5. |
- Fresk, Emil, et al.
(författare)
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A Generalized Reduced-Complexity Inertial Navigation System for Unmanned Aerial Vehicles
- 2017
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Ingår i: IEEE Transactions on Control Systems Technology. - : IEEE. - 1063-6536 .- 1558-0865. ; 25:1, s. 192-207
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a generic approach to attitude and position estimation, suited for any type of unmanned aerial vehicle, is presented. This will be achieved by establishing a generic framework, which can be extended using adaptive methods to determine the thrust properties of the engines and the mass of the aircraft, while keeping the overall computational complexity of the system low. Furthermore, the effect of magnetic disturbances will be reduced in a novel way by confining the magnetic errors to affect only heading, without compromising the pitch and roll estimation of the system with error-based estimation. The efficacy of the proposed framework will be evaluated through extended simulations and experimental validations on a multirotor. Finally, guidelines will be provided toward: 1) an implementation with a reduced computational complexity and 2) the utilization of the square-root formulations of the extended Kalman filter for extending the dynamic range of the filter.
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| 6. |
- Fresk, Emil
(författare)
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The Core of Aerial Robotic Workers : Generalized Modeling, Estimation, and Control
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis we are going to explore what the operational core, both mathematically and algorithmically, of an Aerial Robotic Worker consists of, in order to estimate its egomotion and parameters, and adaptively control the aerial vehicle. Moreover, the aim of this thesis is to be a condensed reference for the corresponding areas of aerial robotics, in order to provide a stable and complete foundation on which one can continue research on. The areas that are covered in this Thesis are: 1) the fundamental modeling of the generalized aerial vehicle, where the kinematics, sensors and motor/thrust models will be presented together with simplified models for the motor characteristics, which will form the basis for all the future derivations, 2) how to model, calibrate and compensate for the errors existing in, and induced into, cheap accelerometers and gyroscopes, as these sensors constitute the aerial platform's core sensor suite as the inertial sensor. Successful methodologies and results are presented and evaluated to show that the cost of calibration can be dramatically reduced without loss of accuracy nor mechanical complexity. 3) How to perform inertial sensor driven egomotion and parameter estimation to lay the foundation for adaptive control strategies, where specific weight will be put on the successful development of a new profound sensory system which has the possibility to replace GPS in robotics applications, while also being able to perform indoors and in GPS denied environments, and which was the core of the localization module done in the AEROWORKS project, enabling the full, high accuracy localization around tall, GPS interfering infrastructure. And finally 4) how to utilize the estimation in low and high-level adaptive controllers, where specific results on how to successfully compensate for the movement of the center of gravity, together with the reduction of thrust over time due to declining battery voltage. Moreover we will explore the use case of Aerial Robotic Workers in real life applications and we will identify and comment on potential future directions of these aerial robotic systems and the impact theses can have in both research and society.
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| 7. |
- Gustafsson, Emil
(författare)
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Design and application of experimental methods for steel sheet shearing
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Shearing is the process where sheet metal is mechanically cut between two tools. Various shearing technologies are commonly used in the sheet metal industry, for example, in cut to length lines, slitting lines, end cropping etc. Shearing has speed and cost advantages over competing cutting methods like laser and plasma cutting, but involves large forces on the equipment and large strains in the sheet material. The constant development of sheet metals toward higher strength and formability leads to increased forces on the shearing equipment and tools.Shearing of new sheet materials imply new suitable shearing parameters. Investigations of the shearing parameters through live tests in the production are expensive and separate experiments are time consuming and requires specialized equipment. Studies involving a large number of parameters and coupled effects are therefore preferably performed by finite element based simulations. Accurate experimental data is still a prerequisite to validate such simulations. There is, however, a shortage of accurate experimental data to validate such simulations.In industrial shearing processes, measured forces are always larger than the actual forces acting on the sheet, due to friction losses. Shearing also generates a force that attempts to separate the two tools with changed shearing conditions through increased clearance between the tools as result. Tool clearance is also the most common shearing parameter to adjust, depending on material grade and sheet thickness, to moderate the required force and to control the final sheared edge geometry.In this work, an experimental procedure that provides a stable tool clearance together with accurate measurements of tool forces and tool displacements, was designed, built and evaluated. Important shearing parameters and demands on the experimental set-up were identified in a sensitivity analysis performed with finite element simulations under the assumption of plane strain. With respect to large tool clearance stability and accurate force measurements, a symmetric experiment with two simultaneous shears and internal balancing of forces attempting to separate the tools was constructed.Steel sheets of different strength levels were sheared using the above mentioned experimental set-up, with various tool clearances, sheet clamping and rake angles. Results showed that tool penetration before fracture decreased with increased material strength. When one side of the sheet was left unclamped and free to move, the required shearing force decreased but instead the force attempting to separate the two tools increased. Further, the maximum shearing force decreased and the rollover increased with increased tool clearance.Digital image correlation was applied to measure strains on the sheet surface. The obtained strain fields, together with a material model, were used to compute the stress state in the sheet. A comparison, up to crack initiation, of these experimental results with corresponding results from finite element simulations in three dimensions and at a plane strain approximation showed that effective strains on the surface are representative also for the bulk material.A simple model was successfully applied to calculate the tool forces in shearing with angled tools from forces measured with parallel tools. These results suggest that, with respect to tool forces, a plane strain approximation is valid also at angled tools, at least for small rake angles.In general terms, this study provide a stable symmetric experimental set-up with internal balancing of lateral forces, for accurate measurements of tool forces, tool displacements, and sheet deformations, to study the effects of important shearing parameters. The results give further insight to the strain and stress conditions at crack initiation during shearing, and can also be used to validate models of the shearing process.
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| 8. |
- Gustafsson, Emil, et al.
(författare)
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Design and validation of a sheet metal shearing experimental procedure
- 2014
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Ingår i: Journal of Materials Processing Technology. - : Elsevier. - 0924-0136 .- 1873-4774. ; 214:11, s. 2468-2477
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Tidskriftsartikel (refereegranskat)abstract
- Throughout the industrial processes of sheet metal manufacturing and refining, shear cutting is widely used for its speed and cost advantages over competing cutting methods. Industrial shears may include some force measurement possibilities, but the force is most likely influenced by friction losses between shear tool and the point of measurement, and are in general not showing the actual force applied to the sheet. Well defined shears and accurate measurements of force and shear tool position are important for understanding the influence of shear parameters. Accurate experimental data are also necessary for calibration of numerical shear models. Here, a dedicated laboratory set-up with well defined geometry and movement in the shear, and high measurability in terms of force and geometry is designed, built and verified. Parameters important to the shear process are studied with perturbation analysis techniques and requirements on input parameter accuracy are formulated to meet experimental output demands. Input parameters in shearing are mostly geometric parameters, but also material properties and contact conditions. Based on the accuracy requirements, a symmetric experiment with internal balancing of forces is constructed to avoid guides and corresponding friction losses. Finally, the experimental procedure is validated through shearing of a medium grade steel. With the obtained experimental set-up performance, force changes as result of changes in studied input parameters are distinguishable down to a level of 1%.
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| 9. |
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| 10. |
- Gustafsson, Emil, et al.
(författare)
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Direct Adhesive Measurements between Wood Biopolyrner Model Surfaces
- 2012
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 13:10, s. 3046-3053
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Tidskriftsartikel (refereegranskat)abstract
- For the first time the dry adhesion was measured for an all-wood biopolymer system using Johnson-Kendall-Roberts (JKR) contact mechanics. The polydimethylsiloxane hemisphere was successfully surface-modified with a Cellulose I model surface using layer-by-layer assembly of nanofibrillated cellulose and polyethyleneimine. Flat surfaces of cellulose were equally prepared on silicon dioxide substrates, and model surfaces of glucomannan and lignin were prepared on silicon dioxide using spin-coating. The measured work of adhesion on loading and the adhesion hysteresis was found to be very similar between cellulose and all three wood polymers, suggesting that the interaction between these biopolymers do not differ greatly. Surface energy calculations from contact angle measurements indicated similar dispersive surface energy components for the model surfaces. The dispersive component was dominating the surface energy for all surfaces. The JKR work of adhesion was lower than that calculated from contact angle measurements, which partially can be ascribed to surface roughness of the model surfaces and overestimation of the surface energies from contact angle determinations.
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