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Das vom BMWi geförderte Forschungsprojekt SyNErgie (03/2015 bis 05/2018) beschäftigt sich mit der Weiterentwicklung von Netzplanungsprozessen [1]. Im Fokus steht dabei die Modellierung von Blindleistungsflüssen und die dezentrale Nutzung von Blindleistungsquellen (z. B. Wechselrichter, Ladedrosseln, Kondensatoren) in Mittelspannungsnetzen, über welche der Blindleistungshaushalt letztendlich beeinflusst werden soll. Diese Veröffentlichung konzentriert sich auf die konzipierte Erweiterung des Netzplanungsprozesses zur Einbindung von Blindleistungsquellen im Verteilungsnetz in ein Blindleistungsmanagement. Deren einzelne Phasen werden erläutert und anschließend die Netz-Sensitivitäts- und -Restriktionsanalyse anhand eines realen Mittelspannungsnetzes demonstriert. Abschließend werden mögliche Abschwächungs- und Verstärkungseffekte im Hinblick auf einen Blindleistungsabruf über mehrere Spannungsebenen hinweg diskutiert.
Automatisiertes Fahren stößt derzeit noch auf große Skepsis. Eine disruptive Strategie bei der Einführung (voll-)automatisierten Fahrens könnte daher auf fehlende Akzeptanz treffen. Um dem zu entgehen, laufen evolutionäre Strategien darauf hinaus, durch die Entwicklung adaptiver Fahrassistenzsysteme Vertrautheit, Vertrauen und damit Akzeptanz bei den prospektiven NutzerInnen zu schaffen. Erste Ergebnisse einer Pilotstudie lassen jedoch Zweifel an der Nachhaltigkeit dieser Strategie aufkommen.
Dynamical Investigation of Crawling Motion System based on a Multistable Tensegrity Structure
(2018)
The basic idea of this article is the utilization of the multistable character of a compliant tensegrity structure to control the direction of motion of a crawling motion system. A crawling motion system basing on a two-dimensional tensegrity structure with multiple stable equilibrium states is considered. This system is in contact with a horizontal plane due to gravity. For a selected harmonic actuation of the system small oscillations around the given equilibrium state of the tensegrity structure occur and the corresponding uniaxial motion of the system is evaluated. A change of the equilibrium state of the tensegrity structure yields to novel configuration of the entire system. Moreover, the motion behavior of the novel configuration is totally different although the actuation strategy is not varied. In particular, the direction of motion changes. Therefore, this approach enables a uniaxial bidirectional crawling motion with a controllable direction of motion using only one actuat or with a selected excitation frequency.
A novel type of a vibration driven motion system based on a compliant tensegrity structure with multiple stable equilibrium states is considered. These equilibrium configurations correspond to different prestress states with different dynamical properties. Therefore, the motion characteristics can be varied by changing the equilibrium state. For the application in the fields of mobile robotics, these discrete adjustable dynamics are advantageous. The vibration modes of the structure as well as the corresponding motion characteristics of the system can be adapted to the given environmental conditions in order to ensure a reliable motion. In this paper, dynamical investigations of an exemplary two-dimensional multistable tensegrity structure are considered. For the chosen parameter values the structure features two relevant equilibrium configurations. The resulting motion system is in contact to a horizontal plane due to gravity and the actuation is realized by the harmonic variation of the length of a single tensioned member. The motion of the system is simulated for various actuation frequencies with the different equilibrium states as an initial configuration. A uniaxial or a planar movement occurs depending on the selection of the actuated member within the tensegrity structure. The steady state motion is evaluated regarding motion characteristics like the steady state velocity. Moreover, the influences on the motion behavior caused by the different equilibrium states as an initial condition are emphasized. (C) 2018 Elsevier Ltd. All rights reserved.
This paper deals with the locomotion by tilting sequences of shape-variable compliant tensegrity structures. The shape of these structures is controlled by manipulating their prestress state. The tensegrity structure is tilting as consequence of a suitable variation of its shape. By multiple repetition of such tilting sequences a motion is generated. Quasi-static considerations for the considered structures are presented in order to estimate the actuation parameters. For a proper number of actuators this quasi-static approach enables an analytical calculation of the actuation parameters of the structure in order to control the geometrical configuration as required. As an example a two-dimensional tensegrity structure which is in contact with a horizontal plane due to gravity is considered. By successive tilting sequences a uniaxial motion results. The excitation of the structure is calculated for a given change of shape with the quasi-static analysis. The according results are compared with transient dynamic simulations. Qualitative conclusions about the motion behavior and the usability of the quasi-static approach are given.
Various numerical approaches have been developed in the last years aimed to simulate the ductile fracture propagation in pipelines transporting CO2 or natural gas. However, a reliable quantification of the influence of material plasticity on the fracture resistance is still missing. Therefore, more accurate description of the material plasticity on the ductile fracture propagation is required based on a suitable numerical methodology.
In this study, different plasticity and fracture models are compared regarding the ductile fracture propagation in X100 pipeline steel with the objective to quantify the influence of plasticity parameters on the fracture resistance. The plastic behavior of the investigated material is considered by the quadratic yield surface in conjunction with a non-associated quadratic plastic flow potential. The strain hardening can be appropriately described by the mixed Swift-Voce law. The simulations of ductile fracture are conducted by an uncoupled, modified Mohr-Coulomb (MMC) and the micromechanically based Gurson-Tvergaard-Needleman (GTN) models. In contract to the original GTN model, the MMC model is capable of describing ductile failure over wide range of stress states. Thus, ductile fracture resistance can be estimated for various load and fracture scenarios. Both models are used for the simulation of fracture propagation in DWTT and 3D pressurized pipe sections. The results from the present work can serve as a basis for establishing the correlation between plasticity parameters and ductile fracture propagation.