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An advanced structural mechanical approach to fatigue lifetime prediction of submarine cables
Published in C. Guedes Soares, Developments in Renewable Energies Offshore, 2020
C. Otto, C. Schuett, S. Kosleck, P. Menzel
In conclusion, here an approach based on arbitrarily complex, reduced order linear finite element method (FEM) models and non-linear flexible multibody systems (MBS) has been employed. For this purpose, the cable is first divided into a finite number of interconnected flexible elements and implemented into a flexible MBS. Also, the so-called floating frame of reference formulation (compare e.g. (Shabana 2014)) is used, which superimposes a small and linear local deformation of the reduced order FEM model onto a large, non-linear movement of the local reference frame (compare Figure 3). Thus, by dividing the cable into a finite number of interconnected elements, the approach is capable of reproducing non-linear deformations of the cable on a global scale. Here, the flexibility of the elements themselves is depicted using reduced order FEM models of the according cable sections. In this context, the number of degrees of freedom is reduced by employing model order reduction techniques as for instance modal reduction or component mode synthesis (compare e.g. (Gasch, Knothe, & Liebich 2012) or (Koutsovasilis 2009)). The main advantage of this approach is, that by choosing appropriate reduction techniques and parameters, the reduced order models are capable of generating physically accurate yet performant depictions of the cable’s dynamic deformations. Especially the choice of the base vectors for the reduction can provide significant advantages in performance whilst retaining the required accuracy (for more information refer to e.g. (Koutsovasilis 2009)). At the same time, the unreduced model can be arbitrarily complex. Thus, as illustrated in Figure 2, e.g. high resolution beam models or even volume models can be used as a basis for the reduced order elements. In doing so, it is possible to obtain a sufficiently precise representation of the deformations at selected locations in the cable by projecting the results of the reduced order model back to the unreduced original model.
Three-dimensional CityGML building models in mobile augmented reality: a smartphone-based pose tracking system
Published in International Journal of Digital Earth, 2021
Christoph Blut, Jörg Blankenbach
One of the challenges of realizing a mobile AR system aimed at these use cases is the 3D registration in real time, i.e. accurately aligning the virtual 3D models with reality, so they seamlessly are integrated into the scene or overlay their physical counterparts as closely as possible. The estimation and synchronization of translation and rotation in real time is, generally, referred to as pose tracking (Schmalstieg and Höllerer 2016), which is possible in a local and a global reference frame. In a local reference frame, poses, for example, can be tracked relative to an arbitrary starting point, in a global reference frame, poses are determined in a global reference system, for example, in the World Geodetic System 1984 (WGS84).