Scientific publications without theses

Results: 318
Created on: Tue, 07 Feb 2023 23:05:51 +0100 in 0.0520 sec


Platl, Vivien; Lechner, Leo; Mattheis, Thomas; Zentner, Lena
Free vibration of compliant mechanisms based on Euler-Bernoulli-Beams. - In: Microactuators, Microsensors and Micromechanisms, (2023), S. 1-18

This paper presents an analytical approach for computing the natural frequencies of planar compliant mechanisms consisting of any number of beam segments. The approach is based on the Euler-Bernoulli Beam theory and the transfer matrix method (TMM), which means there is no need for a global dynamics equation, but instead low-order matrices are used which result in high computational efficiency. Each beam segment is elastic, thin, has a different rectangular cross-section or a different orientation and is treated as an Euler-Bernoulli beam. The approach in principle does not differentiate between the flexure hinges, and the more rigid beam sections, both are treated as beams. The difference in stiffness solely results from the changes in the cross sections and length. A finite element analysis (FEA), as often used in practical applications, has been carried out for various geometries to serve as state-of-the-art reference models to which the results obtained by the presented analytical method could be compared. Various test specimens (TS) consisting of concentrated and distributed compliance in various degrees of complexity were produced and measured in free- and forced vibration testing. The results from experiments and the FEA compared to those of the proposed method are in very good correlation with an average deviation of 1.42%. Furthermore, the analytical method is implemented into a readily accessible computer-based calculation tool which allows to calculate the natural frequencies efficiently and to easily vary different parameters.



https://doi.org/10.1007/978-3-031-20353-4_1
Henning, Stefan; Zentner, Lena
Analytical characterization of spatial compliant mechanisms using beam theory. - In: Microactuators, Microsensors and Micromechanisms, (2023), S. 61-76

Due to the advantages of compliant mechanisms, they are widely used in technical fields such as precision engineering, measurement and medical technology. The movement of the mostly monolithically designed mechanisms is primarily achieved by bending the individual structural sections. Due to geometric nonlinearities caused by large deflections, the analytical description of the deformation behavior under the influence of external loads is not trivial. While plane compliant mechanisms can be reliably calculated with different models, the analysis of spatial compliant mechanisms is accordingly more difficult. Due to the complexity of the motion, simplifications are often made in the model assumptions, which have a detrimental effect on the precision of the results. Therefore, this paper presents a method to apply nonlinear beam theory to complex spatial structures that can include both curved sections and sections with non-constant cross-sections. Using selected examples of varying complexity, the model is validated using FEM simulations. In addition, a procedure to characterize branched spatial compliant mechanisms with the proposed analytical model and to calculate their deformation is explained. By efficiently solving the analytical model numerically, the deformed state of the mechanism can be obtained in seconds. Therefore, the model is particularly suitable for early stages of development or iterative synthesis tasks.



https://doi.org/10.1007/978-3-031-20353-4_5
Zirkel, Marten; Luo, Yinnan; Römer, Ulrich; Fidlin, Alexander; Zentner, Lena
Development of a database to simulate and adapt compliant mechanisms to a given characteristic for improving energy efficiency of a walking robot. - In: Microactuators, Microsensors and Micromechanisms, (2023), S. 46-60

Compliant mechanisms with variable geometric parameters are investigated for the application in a bipedal robot to improve its walking efficiency. These mechanisms have nonlinear torque-angle characteristics and act like torsion springs to change the systems free oscillation frequency. High energy efficiency is achieved if the free oscillation frequency matches the step frequency, meaning the that the robot walks in resonance. For this purpose, the desired characteristic of the optimized elastic coupling is identified via optimization. Then, a database is developed, which consists of boundary conditions and beam elements. In this paper, there are three boundary conditions and three beam elements for demonstration purpose. To simulate a large number of compliant mechanisms with different characteristics, two boundary conditions and a beam element can be combined. The boundary conditions serve as bearing types to connect the beam element to the thighs of a robot. The large deformation behavior is assumed to be simulated by the Euler-Bernoulli beam theory, which is validated by FEM models. Thus, the desired characteristic from the proceeding optimization process is realized by a specific compliant mechanism.



https://doi.org/10.1007/978-3-031-20353-4_4
Pandey, Ashok Kumar; Pal, Prem; Nagahanumaiah, ; Zentner, Lena
Microactuators, Microsensors and Micromechanisms : MAMM 2022
1st ed. 2023.. - Cham : Springer International Publishing, 2023. - 1 Online-Ressource(XIII, 364 p. 234 illus., 186 illus. in color.). - (Mechanisms and Machine Science ; 126) ISBN 978-3-031-20353-4

This book brings together investigations which combine theoretical and experimental results related to such systems as flexure hinges and compliant mechanisms for precision applications, the non-linear analytical modeling of compliant mechanisms, mechanical systems using compliance as a bipedal robot and reconfigurable tensegrity systems and micro-electro-mechanical systems (MEMS) as energy efficient micro-robots, microscale force compensation, magnetoelectric micro-sensors, acoustical actuators and the wafer bonding as a key technology for the MEMS fabrication. The volume gathers the contributions presented at the 6th Conference on Microactuators, Microsensors and Micromechanisms (MAMM), held in Hyderabad, India in December 2022. The aim of the conference was to provide a special opportunity for a know-how exchange and collaboration in various disciplines concerning systems pertaining to micro-technology. The conference was organized under the patronage of IFToMM (International Federation for the Promotion of Mechanism and Machine Science).



https://doi.org/10.1007/978-3-031-20353-4
Jahn, Hannes; Henning, Stefan; Zentner, Lena
A method for optimising compliant mechanisms :
Eine Methode zur Optimierung nachgiebiger Mechanismen. - In: Getriebetagung 2022, (2022), S. 133-142

In diesem Beitrag wird eine Methode vorgestellt, mit deren Hilfe nachgiebige Mechanismen bezüglich ihres Verformungsverhaltens optimiert werden können. Berechnungsgrundlage der Methode ist die Theorie großer Verformungen stabförmiger Strukturen. Die Berechnung erfolgt mit numerischen Lösungsverfahren in Python. Für die Optimierung werden Festkörpergelenke entlang einer vorgegebenen Balkenachse verschoben. Durch Parameterstudien dreier Mechanismen wird zunächst die Auswirkung der Gelenkposition auf das Verformungsverhalten herausgestellt. Abschließend wird die Berechnungsmethode mit Hilfe von den aus den Parameterstudien resultierenden Ergebnissen erfolgreich verifiziert.



Henning, Stefan;
Modellbasierte Entwicklung von Methoden, Algorithmen und Werkzeugen zur Analyse und Synthese nachgiebiger Mechanismen. - Ilmenau : Universitätsverlag Ilmenau, 2022. - 1 Online-Ressource (XXI, 184 Seiten, Seite XXIII-LV). - (Berichte der Ilmenauer Mechanismentechnik (BIMT) ; Band 7)
Technische Universität Ilmenau, Dissertation 2022

Nachgiebige Mechanismen sind in technischen Anwendungen weit verbreitet, insbesondere in der Robotik, Präzisions-, Mess- und Medizintechnik. Ihr Verformungsverhalten wird maßgeblich durch die Gestaltung ausgewählter nachgiebiger Strukturabschnitte, beispielsweise durch die gezielte Reduktion der Querschnittsabmessungen, beeinflusst. Die Bewegung des Mechanismus erfolgt vorwiegend durch Biegung dieser Abschnitte. Die Berechnung des Verformungsverhaltens unter dem Einfluss äußerer Belastungen stellt aufgrund von geometrischer Nichtlinearität eine anspruchsvolle Aufgabe bei der Analyse und Synthese nachgiebiger Mechanismen dar. Daher wird in dieser Arbeit ein Beitrag zur analytischen Modellbildung und damit zum Analyse- und Syntheseprozess geleistet. Die Modellgleichungen werden für ebene und räumliche Anwendungsfälle gegeben. Mit Hilfe dieser können nachgiebige Mechanismen mit variierenden Querschnitten, Krümmungen, Werkstoffen und Verzweigungen charakterisiert werden. Für die Betrachtung beliebiger Mechanismen werden die Gleichungen in einer rekursiven Form gegeben. Aufgrund von Strukturabschnitten unterschiedlicher Querschnitte werden, über reine Biegung hinaus, auch Querkraftschub und Querkontraktion im Modell berücksichtigt. Es werden Untersuchungen durchgeführt um zu definieren, wann diese Effekte, in Abhängigkeit der Geometrie, zu berücksichtigen sind. Auf Basis dieser Untersuchungen werden Empfehlungen für die zu verwendende Theorie gegeben. Durch die Formulierung der Gleichungen in einer einheitlichen Form wird ermöglicht, die Theorie für einzelne Abschnitte eines nachgiebigen Mechanismus individuell anzupassen. Weiterhin wird das Modell durch Beispielmechanismen für zwei- und dreidimensionale Anwendungsfälle mit Hilfe der Finiten-Elemente-Methode und experimentellen Untersuchungen validiert. Dabei werden die Empfehlungen der einzusetzenden Theorie angewendet. Daraufhin werden Algorithmen zur Dimensionierung einzelner Festkörpergelenke und nachgiebiger Mechanismen gegeben. Dadurch kann deren Bewegungsverhalten im Hinblick auf konkrete Zielkriterien verbessert werden. Abschließend werden die Methoden in drei eigenständig ausführbare Softwarewerkzeuge implementiert, die frei zur Verfügung gestellt sind. Durch deren Entwicklung wird ein Beitrag zum Entwurf sowie zur Analyse und Synthese von Festkörpergelenken und nachgiebigen Mechanismen geleistet.



https://dx.doi.org/10.22032/dbt.53126
Zentner, Lena; Henning, Stefan; Fröhlich, Thomas
Design of compliant mechanisms based on rigid-body mechanisms. - In: Romanian journal of technical sciences, ISSN 2601-5811, Bd. 67 (2022), 1, S. 61-78

The design of compliant mechanisms is a much more complicated task than their analysis. Consequently, there are many more methods available for the analysis of compliant mechanisms than for their synthesis. In this article, a contribution to the synthesis of compliant mechanisms is made by presenting a comparison of two different methods for their design. In both methods rigid-body systems are used as a basis for compliant mechanisms. Depending on the task of the compliant mechanism, one of these methods can be selected and applied. The deviations between the results of the used theory and measurement results as well as FEM results are less than 5.5 % for displacements and acting forces. Selected mechanisms for the realization of a straight-line motion of a point and for given relative motions are presented as examples.



Platl, Vivien; Zentner, Lena
An analytical method for calculating the natural frequencies of spatial compliant mechanisms. - In: Mechanism and machine theory, Bd. 175 (2022), 104939, S. 1-17

Compliant mechanisms are becoming increasingly important in both research and industry. The design and the static analysis of such mechanisms has made much progress in recent years, yet comparatively little research has been done on their dynamic behaviour. The aim of this paper is to advance the dynamic analysis of spatial compliant mechanisms by pursuing the calculation of their natural frequencies. So far, their determination is only possible with time-consuming 3D-FEM simulations or via pseudo-rigid-body models and Lagrangian equations. An analytical method is developed to simplify and accelerate the calculation of the natural frequencies of compliant mechanisms. The method is integrated into an algorithm on which a graphical user interface is developed to allow the design and calculation of the system in the most time efficient and intuitive way. The results are verified by 3D-FEM simulations and validated through an experiment. The evaluation shows good agreement with the reference models. The results of this paper allow a reliable and efficient calculation of natural frequencies and serve to facilitate further work regarding the dynamic analysis of compliant mechanisms.



https://doi.org/10.1016/j.mechmachtheory.2022.104939
Harfensteller, Felix; Henning, Stefan; Zentner, Lena; Husung, Stephan
Modeling of corner-filleted flexure hinges under various loads. - In: Mechanism and machine theory, Bd. 175 (2022), 104937, S. 1-11

Compliant mechanisms are widely applied in precision engineering, measurement technology and microtechnology, due to their potential for the reduction of mass and assembly effort through the integration of functions into fewer parts and an increasing motion repeatability through less backlash and wear, if designed appropriately. However, a challenge during the design process is the handling of the multitude of geometric parameters and the complex relations between loads, deformations and strains. Furthermore, some tasks such as the dimensioning by means of optimization or the modeling for a controller design require a high number of analysis calculations. From this arises the need for sufficient computational analysis models with low calculation time. Existing studies of analysis models are mostly based on selected load cases, which may limits their general validity. The scope of this article is the comparison of models for the analysis of corner-filleted flexure hinges under various loads, to determine their advantages, disadvantages and application fields. The underlying methods of the study can further be used to evaluate future models based on a broad selection of possible load cases.



https://doi.org/10.1016/j.mechmachtheory.2022.104937
Platl, Vivien; Lechner, Leo; Mattheis, Thomas; Zentner, Lena
Development of a calculation tool for the natural frequencies of planar compliant mechanisms :
Entwicklung eines Berechnungstools für die Eigenfrequenzen von planaren nachgiebigen Mechanismen. - In: Achte IFToMM D-A-CH Konferenz 2022, (2022), insges. 2 S.

https://doi.org/10.17185/duepublico/75420