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Botschek, David Tobias; Kuijper, Arjan [1. Review]; Kohlhammer, Jörn [2. Review]; Franek, Andreas [3. Review]

Inside-out Tracking of Fastening Tools in Safety Relevant Applications


Darmstadt, TU, Master Thesis, 2021

In any manufacturing process, quality assurance is of great importance to obtain functioning product. While this used to be a manual task, a lot of work is put into the automation of quality assurance. The reasons for reducing human interaction in this process are e.g. higher precision, less human error and cost reduction. Although these advantages were already known for a long time, it is still a lot of work to adapt methods for a specific use case. One such application is fastening screws[79]. This is a ubiquitous task in nearly any manufacturing process which makes it an interesting research topic. Besides the possibility to check if every screw is fastened, it is also important that they are fastened in the right order, e.g. to prevent unwanted forces on the material. Several different approaches to solving this task are conceivable. This work proposes one such approach using a simulated tool with a camera attached to it. To measure its movement, Simultaneous Localization and Mapping (SLAM) algorithms are used, fed with the camera data. Finally, an examination of an experiment is provided to that regard. Several SLAM implementations are adapted and tested on a new dataset recorded with an Azure Kinect camera as well as a Google Pixel 3 smartphone. To evaluate the results, the screws positions are calculated for the different recorded scenarios from the camera trajectories. Additionally, the deviation between the this trajectory and ground truth recorded with a measuring arm is computed as a measure for the global accuracy of the SLAM algorithms.

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Olbrich, Manuel; Franek, Andreas; Weber, Daniel

Interacting with FEM Simulated Tubes in AR


HCI International 2021 – Late Breaking Papers

Lecture Notes in Computer Science (LNCS), 13095

This paper presents the results of a study the authors conducted to identify the opportunities and challenges of interfacing complex engineering simulations run on dedicated systems with mobile devices visualizing the simulation results and providing inputs in real-time. We build upon an existing finite element method (FEM) simulation, which we tuned to deliver snapshots to an Augmented Reality (AR) application for real-time visualization. On this basis we develop interaction designs for tablets and Optical See-Through Head-Mounted Displays (OST-HMD) utilizing the interaction methods available on such mobile devices to manipulate FEM simulated tubes in AR, as well as an evaluation of these interaction designs. Our design goal is an intuitive workflow concept that allows usage of an AR application without training overhead. To this end we introduce movable proxies on the virtual tube that provide the simulation with input data. Since the described client devices belong to very different device classes, we show intuitive interaction designs for all of them. Our client application is supposed to be run at the tube installation site, so we can not rely on stable high bandwidth connections to the simulation server in every case. Therefore, we implemented an asynchronous communication, enabling the use with reduced update rates. Our system enables the user to quickly reconfigure tube configurations and compare different approaches. At the same time the interaction is intuitive so training the user is unnecessary.

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Shahid, Muhammad Ali; Jesche, Benjamin-Paul; Olbrich, Manuel; Graf, Holger; Franek, Andreas; Kuijper, Arjan; Bockholt, Ulrich; Schmitt, Michael

Measurement Based AR for Geometric Validation Within Automotive Engineering and Construction Processes


Virtual, Augmented and Mixed Reality. Industrial and Everyday Life Applications

International Conference Virtual Augmented and Mixed Reality (VAMR) <12, 2020, Copenhagen, Denmark>

Lecture Notes in Computer Science (LNCS), 12191

We look at the final stages of the automobile design process, during which the geometric validation process for a design, in particular for the vehicle front end, is examined. A concept is presented showing how this process can be improved using augmented reality. Since the application poses high accuracy requirements the augmented reality also needs to be highly accurate and of measurable quality. We present a Measurement Based AR approach to overlaying 3D information onto images, which extends the existing process and is particularly suited to the application in question. We also discuss how the accuracy of this new approach can be validated using computer vision methods employed under the appropriate conditions. The results of an initial study are presented, where the overlay accuracy is expressed in image pixels as well as millimeters followed by a discussion on how this validation can be improved to meet the requirements posed by the application.

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Berndt, René; Tuemmler, Carl; Kehl, Christian; Aehnelt, Mario; Grasser, Tim; Franek, Andreas; Ullrich, Torsten

Open Problems in 3D Model and Data Management


Proceedings of the 15th International Joint Conference on Computer Vision, Imaging and Computer Graphics Theory and Applications

International Joint Conference on Computer Vision, Imaging and Computer Graphics Theory and Applications (VISIGRAPP) <15, 2020, Valetta, Malta>

In interdisciplinary, cooperative projects that involve different representations of 3D models (such as CAD data and simulation data), a version problem can occur: different representations and parts have to be merged to form a holistic view of all relevant aspects. The individual partial models may be exported by and modified in different software environments. These modifications are a recurring activity and may be carried out again and again during the progress of the project. This position paper investigates the version problem; furthermore, this contribution is intended to stimulate discussion on how the problem can be solved.

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Borrmann, Daniel; Kuijper, Arjan [1. Gutachter]; Franek, Andreas [2. Gutachter]

Incorporating the Unscented Transform in Rao-Blackwellised Visual-Inertial SLAM


Darmstadt, TU, Master Thesis, 2016

Monocular visual-inertial simultaneous localisation and mapping (SLAM) systems use a single camera and inertial sensors to build a sparse map of an environment and to simultaneously estimate the camera's position. Applications can be found, for example, in the robotics domain or in virtual and augmented reality applications. Nowadays, monocular visual SLAM systems are capable of operating in real-time on different platforms. The application of Rao-Blackwellised filtering techniques in visual SLAM has further improved the real-time capability and maximum map size of these systems. In many implementations, extended Kalman filters (EKFs) are used to estimate the camera's pose and landmark positions. Since the required dynamic and measurement functions in a visual SLAM system are usually non-linear, EKF-based implementations need to linearise these functions, which leads to linearisation errors in the state estimate. In these cases, the unscented Kalman filter (UKF) proved to provide better results in many scenarios. In this thesis, the unscented transform (UT) is incorporated into a Rao-Blackwellised visual-inertial SLAM system. It shows how the camera state and landmark positions can be estimated in unscented Rao-Blackwellised filtering. To this end, an appropriate motion model, as well as an inverse depth parametrisation for the landmark estimation, are incorporated into the filter. The proposed filter is tested on a visual-inertial dataset in different setups. Results are given for the UKF-based Rao- Blackwellised filter and an equivalent EKF-based implementation, to enable comparison between the two approaches.

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Franek, Andreas; Ackermann, Jens [Betreuer]; Goesele, Michael [Gutachter]

Enhancing GPS Precision using Structure from Motion


Darmstadt, TU, Master Thesis, 2013

GPS positional data has been used to enhance Structure from Motion (SfM) reconstructions of large scenes [Lhu11, Ell04]. Here we evaluate the opposite approach; utilizing SfM reconstructions of scenes between 50 and 500m to enhance the GPS meta data associated with the images used in SfM. These images are here taken from online community photo collections. The statistical properties of SfM reconstructed camera positions and GPS measurements are considered and found to be very distinct. Further, the distribution of geotags created manually by users and that of GPS receiver created geotags in online community photo collections is examined. The result shows that images in online community photo collections scarcely contain reliable GPS meta data. Because of this it is hard to estimate a transformation between GPS and SfM space. With such a transformation it is possible to improve the accuracy of inaccurate geotags and create geotags for images not containing one previously. An algorithm is designed that suits the statistical properties of SfM reconstructions and GPS measurements. Using this algorithm it is possible to enhance the geotags of SfM image bundles even when only few reliable are present initially.

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Franek, Andreas; Bein, Matthias [Betreuer]

Evolutionäre B-Spline Approximation mit markierten und uniformen Knoten


Darmstadt, TU, Bachelor Thesis, 2010

B-Splines eignen sich zur Approximation von Hand eingegebener Kurven. In diesem speziellen Fall soll eine Approximation gefunden werden die möglichst nah an der eingegebenen Kurve ist, jedoch durch wenige Kontrollpunkte definiert ist. Die Approximation solch einer Kurve ist jedoch ein schwieriges Optimierungsproblem. Evolutionäre Algorithmen haben sich bei dieser Art von Optimierungsproblemen als nützlich erwiesen. Auch in anderen Arbeiten wurden schon evolutionäre Algorithmen zur Approximation mit B-Splines eingesetzt. Da die hier verwendete Repräsentation der B-Splines sehr speziell ist sind die dort verwendeten Techniken allerdings nur bedingt anwendbar. Die Approximation von Kurven durch B-Splines ebenso wie Evolutionäre Algorithmen haben viele austauschbare Komponenten, wie beispielsweise Fitnessfunktion, das Maß mit dem die Kontrollpunkte den Fehler beeinflussen, Seeding- und Evolutionsfunktionen. Um den Algorithmus erweiterbar für diese verschiedenen Möglichkeiten und auch neue Entwicklungen zu machen wird der Algorithmus in ein Framework eingebettet.