Wissenschaftliche Veröffentlichungen ohne Studienabschlussarbeiten

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Herrmann, David; Schaeffer, Leon; Schmitt, Lukas; Körber, Wolfgang; Merker, Lukas; Zentner, Lena; Böhm, Valter
Compliant robotic arm based on a tensegrity structure with x-shaped members. - In: IEEE Xplore digital library, ISSN 2473-2001, (2024), S. 1042-1047

The use of intrinsically compliant tensegrity structures in manipulation systems is an attractive research topic. In this paper a 3D compliant robotic arm based on a stacked tensegrity structure consisting of x-shaped rigid members is considered. The rigid members are interconnected by a net of prestressed, tensioned members with pronounced intrinsic elasticity and by inelastic tensioned members. The system's motion is achieved by length-change of the inelastic tensioned members. The operating principle of the system is discussed with the help of kinematic considerations and verified by experiments.



https://doi.org/10.1109/RoboSoft60065.2024.10521941
Jahn, Hannes; Fröhlich, Thomas; Zentner, Lena
Analytical description of transversally symmetric hinges with semicircular contours. - In: Advances in mechanism and machine science, (2024), S. 502-509

Compliant mechanisms are becoming increasingly important, especially in force measurement and weighing technology, due to their zero backlash, wear resistance, and zero friction. Their deformation under external forces can be analyzed well with analytical calculations and FEM simulations. Analytically, only mechanisms with symmetrical and longitudinally symmetrical hinges are described. This paper presents a method that allows transversally symmetric hinges to be described analytically. The model must be computed numerically due to the built neutral fiber and the nonlinearities in the used calculation method. The developed method is then compared with FEM calculations in a parameter study and considered to be validated. Finally, outlooks are formulated on how the created method can for instance be used to develop load cells for later calculations. Moreover, it is shown to what extent it is possible to implement this method for general calculations of compliant mechanisms.



https://doi.org/10.1007/978-3-031-45709-8_49
Platl, Vivien; Zentner, Lena
An analytical approach for calculating the first natural frequency of flexure hinges with variable cross-sections for compliant mechanisms. - In: Advances in mechanism and machine science, (2024), S. 491-501

In this paper, we present an analytical approach for enabling the calculation of the natural frequencies of flexure hinge contours with variable cross-sections. In regard to the planned implementation of this approach into an existing analytical method based on Euler-Bernoulli-beams and the transfer matrix method, the flexure hinges will be discretized into a specific amount of individual beam segments with constant cross-sections. Three possible discretization approaches are presented, the optimum numbers of segments is found and the influence of the mass on the actual natural frequency calculation is discussed. The analytical method is finally validated on a compliant parallel four-bar linkage. The studies show that the presented approaches yield sufficiently accurate results for the calculation of the natural frequencies of compliant mechanisms with flexure hinges with variable cross-sections.



https://doi.org/10.1007/978-3-031-45709-8_48
Schmitz, Maximilian; Bisinger, Jochen; Zentner, Lena
Potentials of an early digital twin for dimensional vehicle concept creation in the concept phase. - In: Advances in mechanism and machine science, (2024), S. 806-814

In more than 100 years of automotive technology, existing vehicle architectures have evolved and aligned with the requirements of combustion engine drive technology. The automotive industry is currently in a turbulent phase of transformation. Vehicle development must adapt to battery-electric powertrains in a short time. Automation of driving functions, electrification and connectivity are leading to revolutionary changes in the vehicle as a product. At the same time, digitalization, a changed competitive environment, shorter development cycles and a stronger focus on in-vehicle software are also causing radical changes in the vehicle development process. As a result of this transformation, established standard concepts and solutions are being called into question. In the early phase of vehicle design, answers to the changed framework conditions and new questions must be found quickly. Solutions must be achieved in a shorter time and a high degree of maturity must be ensured. Here, the methods of digital, virtual product development open up new opportunities and possibilities. The assignment of geometric parameters in the vehicle concept phase to technical requirements and the knowledge of the interactions of these parameters with each other enable early evaluation of the vehicle concepts. The article describes the use of a development methodology by means of a digital twin in the early phase of vehicle concept development and shows interfaces, potentials and challenges that an introduction of this methodology including the connection of different digital representatives in the concept phase entails.



https://doi.org/10.1007/978-3-031-45709-8_78
Sindersberger, Dirk;
Development of a self-sensing electroadhesive soft gripper : implementation of magnetic and electrically conductive hybrid materials to improve workpiece ejection. - Ilmenau : Universitätsbibliothek, 2023. - 1 Online-Ressource (xviii, 149 Seiten)
Technische Universität Ilmenau, Dissertation 2023

Gegenstand der Arbeit ist die Neuentwicklung eines elektroadhäsiven Greifers für den Einsatz in der soft robotics, welcher durch die Verwendung von sogenannten "smart materials" sowohl die Problematik der Ablöseverzögerung durch elektrostatische Restladungen umgehen als auch seinen Verformungszustand durch self-sensing Eigenschaften bestimmbar machen soll. Die verbesserte Werkstückablösung resultiert aus einer nach innen gerichteten Wölbung der weichen Greiferoberfläche, die durch einen magnetischen Antrieb hervorgerufen wird. Zur Erfüllung der self-sensing Bedingung werden Eigenschaften des magnetischen Antriebs verwendet, die den Einwölbungsgrad der Greiferoberfläche messtechnisch bestimmbar machen. Gleichzeitig dient die Verformungsdetektion zur Vermessung sowie zum Greifen von nicht-planaren Werkstücken mit begrenzter räumlicher Topologie. Die Erzeugung des elektrischen Feldes geschieht durch extrinsisch elektrisch leitfähige thermoplastische Elektroden, wobei eine bestimmte Anordnung eine Verformung der Greifoberfläche erlaubt. Ein aus den Konstruktionsergebnissen entwickelter Prototyp dient dem funktionellen Nachweis der Greifkraftentwicklung, der self-sensing Eigenschaft und der verbesserten Werkstückablösung durch die Oberflächenverformung. Grundlage ist die Analyse bestehender Greiftechniken und des aktuellen Entwicklungsstandes nachgiebiger elektroadhäsiver Greifer sowie die theoretische Beschreibung der elektroadhäsiven Kräfte und der magnetosensitiven und elektrisch leitfähigen Polymere. Ausgehend von der Festlegung der Fähigkeiten im Systemdesign werden im Verlauf der Entwicklungsarbeit die Materialien auf deren Eignung im Bereich der soft robotics ausgewählt und geprüft. Im Vordergrund der Entwicklung steht stets das Überwinden der Ablöseproblematik durch die positiven Eigenschaften neuer Materialien. Die Materialienauswahl der nachgiebigen Trägerstruktur des Gesamtsystems wird durch die Aspekte der soft robotics eingeschränkt und ausgewählt. Der mittels eines magnetosensitiven Elastomers realisierte Antrieb zur Oberflächenverformung wird in seiner Funktion analysiert und realisiert. Sowohl das Material für die Elektroden als auch das Material für das Dielektrikum werden gemäß anwendungsnaher Kriterien festgelegt, das resultierende elektrische Feld simuliert und anschließend realen Messungen gegenübergestellt. Mittels einer integrierten Sensorspule wird die self-sensing Eigenschaft realisiert und deren Einsatzfähigkeit experimentell bestätigt. Die Arbeit schließt mit den Ergebnissen der elektroadhäsiven Greifkräfte des aus dem Entwicklungsprozesses hervorgegangenen Prototypen ab.



https://doi.org/10.22032/dbt.59199
Gast, Simon;
Ein Beitrag zur Untersuchung der Deformation magneto-sensitiver Elastomere und deren Nutzung als Sensorelement. - Ilmenau : Universitätsbibliothek, 2023. - 1 Online-Ressource (XII, 127 Seiten, Seite XIV-XXXVII)
Technische Universität Ilmenau, Dissertation 2023

Magneto-sensitive Elastomere sind magnetische Hybridwerkstoffe, die aufgrund ihrer spezifischen Eigenschaften aktuell im Fokus der anwendungsorientierten Forschung stehen. Die Kopplung von elastischer und elektromagnetischer Energie innerhalb des Werkstoffes bietet besonderes Potential im Bereich der mechanischen Sensoren. Hier werden für die Erfassung mechanischer Größen (beispielsweise Kraft und Verschiebung) bevorzugt biegeelastische Strukturen (Verformungskörper) eingesetzt. Die Arbeit ist in zwei Bereiche unterteilt. Der erste Teil stellt die Simulation einer zweischichtigen biegeelastischen Struktur mit magneto-sensitiven Elastomer vor. Mit einem analytischen Modell gelingt es, die dynamische Verformung des Balkens vorherzusagen. Dieses basiert auf einem Timoshenko-Balken und berücksichtigt ein äußeres Magnetfeld. Mit asymptotischen Methoden erfolgt eine Näherungslösung für die Durchbiegung des Balkens. Ein Vergleich mit numerischen Lösungen zeigt, dass die verwendete Methode für mehrere Periodendurchläufe eine ausreichende Güte aufweist. Im zweiten Teil der Arbeit wird die modellbasierte Entwicklung und experimentelle Untersuchung eines neuartigen taktilen Sensors vorgestellt. Dieser zeichnet sich durch einen Schichtaufbau mit einem Spulen-Array und magneto-sensitiven Elastomer aus. Die Messaufgabe des Sensors beinhaltet in erster Linie die Erfassung der Kontaktstelle einer Beanspruchung an der Sensoroberfläche. Zu der Entwicklung des Sensors zählt das Abbilden des magneto-mechanischen Verhaltens des Systems auf Basis von analytischen und numerischen Methoden. Dabei gelingt die theoretische Vorhersage des Sensorsignals, die Identifikation kritischer Systemparameter und die Grobauslegung des Sensors selbst. Im Anschluss erfolgt der Entwurf eines Prototyps, der eine Positionsbestimmung eines eindringenden Körpers in einer Richtung erlaubt. Unter anderem erfolgt die Untersuchung einer variablen Verschaltung mehrerer Spulen und eine mathematische Analyse der Signale. Hiermit gelingt die Positionsbestimmung unabhängig vom Querversatz und der Eindringtiefe. Schließlich bietet die Arbeit einen Funktionsnachweis für den taktilen Sensor, der eine Positions- und Kraftbestimmung erlaubt.



https://doi.org/10.22032/dbt.59060
Herrmann, David; Schaeffer, Leon; Zentner, Lena; Böhm, Valter
Theoretical considerations on 3D tensegrity joints for the use in manipulation systems. - In: Engineering for a changing world, (2023), 3.3.060, S. 1-13

This paper presents a comprehensive analysis of a three-dimensional compliant tensegrity joint structure, examining its actuation, kinematics, and response to external loads. The study investigates a baseline configuration and two asymmetric variants of the joint. The relationship between the shape parameter and the parameters of the tensioned segments is derived, enabling the mathematical description of cable lengths for joint actuation. Geometric nonlinear static finite element simulations are performed to analyze the joint's response under various load conditions. The results reveal the joint's range of motion, the effect of different stiffness configurations, and its deformation behavior under external forces. The study highlights the asymmetric nature of the joint and its potential for targeted motion restriction. These findings advance the general understanding of the behavior of the considered tensegrity joint and provide valuable insights for their design and application in soft robotic systems.



https://doi.org/10.22032/dbt.58888
Hermoza-Llanos, Estefania; Rodríguez Hernández, Jorge A.; Zentner, Lena
Development of a novel synthesis method of a rigid-body four-bar linkage into a compliant mechanism. - In: Engineering for a changing world, (2023), 3.3.004, S. 1-12

The four-bar linkage mechanism is widely used in various machinery applications. This study presents a synthesis method to transform a rigid-body four-bar mechanism into a compliant mechanism using four leaf-type hinges based on linear theory and Castigliano's Theorem. The objective is to determine the dimensions and configuration of a flexible four-bar mechanism that replicates the behavior of the initial rigid-body mechanism. The meeting point between the two mechanisms is the flexure hinge of the compliant mechanism, which is determined using the Pseudo-Rigid-Body model (PRBM). To validate the proposed method, a program based on non-linear theory is employed. The results confirm that the dimensional differences between the two are minimal, ranging from 0% to 0.13%. This study demonstrates the feasibility of synthesizing a Rigid-Body Four-Bar Mechanism into a compliant mechanism using the PRBM, as long as the deformations are within the linear domain.



https://doi.org/10.22032/dbt.58886
Torres Melgarejo, Mario André; Henning, Stefan; Zentner, Lena; Theska, René
Synthesis of optimized compliant mechanisms for ultra-precision applications. - In: Engineering for a changing world, (2023), 1.4.071, S. 1-9

Compliant mechanisms for ultra-precision applications are often required to achieve highest accuracy over largest possible ranges of motion along multiple axes. The typical synthesis approach for such high demands is based on the substitution of the revolute joints of a suitable rigid-body model with optimized flexure hinges. However, during the transition from rigid-body model to compliant mechanism, the effects of multiple input parameters are still widely unknown. Among them are the degrees of freedom of the rigid-body model, the integration of the drive elements, as well as the coupling of mechanisms to achieve multiple motion axes. The following contribution expands the fundamentals of the synthesis of compliant mechanisms based on rigid-body models for their application in ultra-precision technologies. Based on the investigation of the aforementioned parameters as well as the knowledge gained from previous research work, a novel synthesis method has been developed.



https://doi.org/10.22032/dbt.58844
Platl, Vivien; Zentner, Lena
Eigenfrequenzberechnung von Parallelschwingen mit unterschiedlichen Festkörpergelenkkonturen. - In: 15. Kolloquium Getriebetechnik, (2023), S. 67-72


   

... bis 2022 vom ehem. FG Technische Mechanik

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Prem, Nina; Schale, Florian; Sindersberger, Dirk; Zimmermann, Klaus
Thermosensitive elastomers for shape adaption of soft robotic systems. - In: ACTUATOR 2022: International Conference and Exhibition on New Actuator Systems and Applications, (2022), S. 290-293

Recent advances in soft robotics demonstrate robust and versatile performance for dexterous grasping and manipulation. Due to their intrinsically mechanical compliance, soft robots passively adapt their shape to an object during contact. This results in large contact patches and damping of contact dynamics, which compensates for uncertainties in sensing, modeling, and actuation. Therefore, the behavior of soft robots is also determined by contact-based deformations. Building these kinds of compliant structures by using thermosensitive hybrid materials of polydimethylsiloxane and different thermoplastic filler particles as thermosensitive elastomers (TSE) the design could receive a higher versatility and extra functionality. Thermosensitive elastomers (TSE) consist of an addition curing RTV-2 silicone in which different thermoplastic filler particles are embedded. These thermoplastic particles are polycaprolactone (PCL), polyamide-6 (PA6) and polymethylmethacrylat (PMMA) with melting temperatures in the range of 58deg C to 215deg C. In certain examinations, soft magnetic carbonyl iron particles (CIP) are also included to prove the compatibility of the two particle types within the polydimethylsiloxane (PDMS) matrix and to utilize a possible symbiotic effect of the particle mixtures. By means of mechanical tests, the thermosensitive hybrid materials enable shape changes by applying both external heat and stress/force. With a low melting point in the range of 58 deg C to 60 deg C, PCL offers good application potential compared to the other thermoplastic filler particles. One of PCL most important and application-oriented phenomena is the shape memory effect, which results from internal stresses between elastomer molecular chains and PCL particles. Whereby the external shape arises from the equilibrium of all internal forces. Consequently, the material composites can be referred to as both TSE and shape memory polymers (SMP). By adding soft magnetic particles, an accelerated heat distribution within the samples was detected, which results in a faster occurrence of the corresponding effects. Micro computed tomography (mu-CT) and scanning electron microscopy (SEM) examinations indicate that a homogeneous distribution of PCL and CIP within the thermosensitive elastomer prevails. Moreover, the TSE additionally contain CIP can combine the benefits of temperature and magnetic field effects. Due to the material's ability to imprint or adapt to any shape, thermosensitive elastomers as shape memory polymers represent a potential opportunity to modify pre-existing robotic components. Depending on the initial design and force application, the modified systems could adapt to almost any shape under the influence of temperature. This leads to their use in a variety of applications in adaptive sensors, smart actuators, and gripping elements in soft robotics.



https://ieeexplore.ieee.org/document/9899226
Merker, Lukas;
Vibrissa-inspired tactile sensing : object shape detection under frictional influences. - Ilmenau, 2022. - x, 154 Seiten
Technische Universität Ilmenau, Dissertation 2022

Die taktile Sensorik birgt große Potenziale für die Weiterentwicklung von technischen Geräten und deren Einsatz in unstrukturierten Umgebungen. Häufig sind taktile Sensorkonzepte von der Natur inspiriert, z.B. durch die mystazialen Vibrissen der Ratte. Diese speziellen Tasthaare dienen als multimodale Sensoren, die Ratten u.a. zur Objektformkennung befähigen. Die vorliegende Arbeit verfolgt einen biomimetischen Ansatz mit dem Ziel der Weiterentwicklung vibrissen-inspirierter Sensoren für die 3D-Objektformerkennung unter Reibungseinflüssen. Das biologische Vorbild Vibrisse besteht im Wesentlichen aus einem hochflexiblen, nicht-sensorischen Haarschaft, welcher in seinen eigenen Follikel-Sinus-Komplex eingebettet ist, der sensorische Komponenten enthält. Diese Struktur wird abstrahiert und auf ein technisches Sensorkonzept übertragen. Zur Realisierung der Objektabtastung wird ein schlanker, einseitig eingespannter, hochflexibler Taster durch lineare Verschiebung der Einspannung entlang des Zielobjekts gestrichen. Die resultierenden Lagerreaktionen dienen als einzige Observablen für die Rekonstruktion von Kontaktpunktfolgen zwischen Taster und Objekt, die schließlich auf die Form des letzteren schließen lassen. Zu diesem Zweck wird das Sensorkonzept mechanisch modelliert und mithilfe von Modellgleichungen beschrieben. Aufbauend auf der Analyse der 2D-Objektabtastung und -Rekonstruktion unter Reibungseinflüssen wird das Modell auf den allgemeinen 3D Fall erweitert. In Simulationen und Experimenten wird die allgemeine Umsetzbarkeit der Objektformerkennung demonstriert. Simulationsbasierte Parameterstudien verdeutlichen zudem den Einfluss der (Coulomb) Reibung auf die Lagerreaktionen und die Rekonstruktionsergebnisse. Während die Lagerreaktionen signifikant von Reibungseffekten beeinflusst werden, ist der Fehler der rekonstruierten Kontaktpunkte reibungsinvariant (unbeeinflusst durch den Reibungskoeffizienten). Diese Erkenntnisse werden im Zusammenhang mit den experimentellen Ergebnissen diskutiert. Darüber hinaus wird für den Fall der 2D-Objektabtastung ein Ansatz zur Rekonstruktion von Reibungsparametern vorgestellt, für den ein erster experimenteller Konzeptnachweis erbracht wird. Schließlich wird das Sensormodell mit Blick auf das biologische Vorbild durch Implementierung einer elastischen Lagerung und einer rotatorischen Abtastkinematik angepasst.



Becker, Tatiana; Stolbov, Oleg V.; Biller, Armin M.; Borin, Dmitry Yu.; Stolbova, Olga S.; Zimmermann, Klaus; Raikher, Yuriy L.
Shape-programmable cantilever made of a magnetoactive elastomer of mixed content. - In: Smart materials and structures, ISSN 1361-665X, Bd. 31 (2022), 10, 105021, S. 1-14

This work presents an approach to the macroscopic field-controlled mechanics of magnetoactive elastomers of mixed content, which are a special type of smart materials made of an elastic composite and a combination of two essentially different ferromagnetic fillers. High-coercive particles of NdFeB-alloy powder for the magnetically hard (MH) filler and carbonyl iron powder particles with nearly zero coercivity for the magnetically soft (MS) filler are usually used. The MH particles are tens-of-micron in size and impart to the elastomer a remanent magnetisation, whereas due to the MS particles of several microns in size, the elastomer acquires a high magnetic susceptibility. Since large MH particles once magnetised in a strong field possess their own fields to which the MS particles are susceptible, the overall elastomer magnetisation as well as its mechanical response greatly depends on the relative concentration of both fillers. This work particularly studies the bending deformation of horizontally fixed magnetoactive cantilevers with the permanent magnetisation along the length axis under the action of gravity and a vertically applied uniform magnetic field. The cantilevers of the same geometry and fixed NdFeB content but different carbonyl iron concentration are considered. The magnetomechanical model is developed based on the finite-strain theory assuming the plane-stress approximation of the two-dimensional cantilever of infinite width. The magnetic energy comprises two magnetic terms, one of which is qualitatively linear and the other one is quadratic in the applied field strength. The numerically calculated field-programmed equilibrium bending shapes of the cantilevers are compared with the experimentally observed shapes. The model provides good agreement with the experiment up to moderate concentrations of the MS filler, when the coefficients of customary interpolation formulas for the concentration dependencies of elastic modulus and magnetic susceptibility are properly adjusted.



https://doi.org/10.1088/1361-665X/ac8f79
Chavez, Jhohan; Böhm, Valter; Becker, Tatiana; Gast, Simon; Zeidis, Igor; Zimmermann, Klaus
Actuators based on a controlled particle-matrix interaction in magnetic hybrid materials for applications in locomotion and manipulation systems. - In: Magnetic hybrid-materials, (2022), S. 653-680

The paper deals with the investigation of magneto-sensitive elastomers (MSE) and their application in technical actuator systems. MSE consist of an elastic matrix containing suspended magnetically soft and/or hard particles. Additionally, they can also contain silicone oil, graphite particles, thermoplastic components, etc., in various concentrations in order to tune specific properties such as viscosity, conductivity and thermoelasticity, respectively. The focuses of investigations are the beneficial properties of MSE in prototypes for locomotion and manipulation purposes that possess an integrated sensor function. The research follows the principle of a model-based design, i.e. the working steps are ideation, mathematical modelling, material characterization as well as building first functional models (prototypes). The developed apedal (without legs) and non-wheeled locomotion systems use the interplay between material deformations and the mechanical motion in connection with the issues of control and stability. Non-linear friction phenomena lead to a monotonous forward motion of the systems. The aim of this study is the design of such mechanical structures, which reduce the control costs. The investigations deal with the movement and control of 'intelligent' mechanisms, for which the magnetically field-controlled particle-matrix interactions provide an appropriate approach. The presented grippers enclose partially gripped objects, which is an advantage for handling sensitive objects. Form-fit grippers with adaptable contour at the contact area enable a uniform pressure distribution on the surface of gripped objects. Furthermore, with the possibility of active shape adaptation, objects with significantly differing geometries can be gripped. To realise the desired active shape adaptation, the effect of field-induced plasticity of MSE is used. The first developed prototypes mainly confirm the functional principles as such without direct application. For this, besides the ability of locomotion and manipulation itself, further technological possibilities have to be added to the systems.



Becker, Tatiana; Raikher, Yuriy L.; Stolbov, Oleg V.; Böhm, Valter; Zimmermann, Klaus
Magnetoactive elastomers for magnetically tunable vibrating sensor systems. - In: Magnetic hybrid-materials, (2022), S. 625-652

Magnetoactive elastomers (MAEs) are a special type of smart materials consisting of an elastic matrix with embedded microsized particles that are made of ferromagnetic materials with high or low coercivity. Due to their composition, such elastomers possess unique magnetic field-dependent material properties. The present paper compiles the results of investigations on MAEs towards an approach of their potential application as vibrating sensor elements with adaptable sensitivity. Starting with the model-based and experimental studies of the free vibrational behavior displayed by cantilevers made of MAEs, it is shown that the first bending eigenfrequency of the cantilevers depends strongly on the strength of an applied uniform magnetic field. The investigations of the forced vibration response of MAE beams subjected to inplane kinematic excitation confirm the possibility of active magnetic control of the amplitude-frequency characteristics. With change of the uniform field strength, the MAE beam reveals different steady-state responses for the same excitation, and the resonance may occur at various ranges of the excitation frequency. Nonlinear dependencies of the amplification ratio on the excitation frequency are obtained for different magnitudes of the applied field. Furthermore, it is shown that the steady-state vibrations of MAE beams can be detected based on the magnetic field distortion. The field difference, which is measured simultaneously on the sides of a vibrating MAE beam, provides a signal with the same frequency as the excitation and an amplitude proportional to the amplitude of resulting vibrations. The presented prototype of the MAE-based vibrating unit with the field-controlled "configuration" can be implemented for realization of acceleration sensor systems with adaptable sensitivity. The ongoing research on MAEs is oriented to the use of other geometrical forms along with beams, e.g. two-dimensional structures such as membranes.



Wittke, Martin; Wolf, Matthias; Weigert, Florian; Darnieder, Maximilian; Gerlach, Erik; Zimmermann, Klaus; Theska, René
Investigations on a torque-compensating adjustment drive for mechanically sensitive devices. - In: Proceedings of the 22nd International Conference of the European Society for Precision Engineering and Nanotechnology, (2022), S. 81-82

Boeck, Thomas; Sanjari, Seyed Loghman; Becker, Tatiana
Parametric instability of a vertically driven magnetic pendulum with eddy-current braking by a flat plate. - In: Nonlinear dynamics, ISSN 1573-269X, Bd. 109 (2022), 2, S. 509-529

The vertically driven pendulum is one of the classical systems where parametric instability occurs. We study its behavior with an additional electromagnetic interaction caused by eddy currents in a nearby thick conducting plate that are induced when the bob is a magnetic dipole. The known analytical expressions of the induced electromagnetic force and torque acting on the dipole are valid in the quasistatic limit, i.e., when magnetic diffusivity of the plate is sufficiently high to ensure an equilibrium between magnetic field advection and diffusion. The equation of motion of the vertically driven pendulum is derived assuming that its magnetic dipole moment is aligned with the axis of rotation and that the conducting plate is horizontal. The vertical position of the pendulum remains an equilibrium with the electromagnetic interaction. Conditions for instability of this equilibrium are derived analytically by the harmonic balance method for the subharmonic and harmonic resonances in the limit of weak electromagnetic interaction. The analytical stability boundaries agree with the results of numerical Floquet analysis for these conditions but differ substantially when the electromagnetic interaction is strong. The numerical analysis demonstrates that the area of harmonic instability can become doubly connected. Bifurcation diagrams obtained numerically show the co-existence of stable periodic orbits in such conditions. For moderately strong driving, chaotic motions can be maintained for the subharmonic instability.



https://doi.org/10.1007/s11071-022-07555-8
Behn, Carsten; Will, Christoph; Merker, Lukas; Steigenberger, Joachim
Bending vibration systems which are complementary with respect to eigenvalues. - In: Mechatronics and life sciences, (2022), S. 277-286

In developing prototypes, one fundamental activity is to model appropriate systems which mimic fundamental features of (biological) paradigms. In this way, we set up different models for the investigation of natural frequencies. The aim is to detect object contacts of technical sensors in observing their vibration behavior. For this, we compare the range and the shift of natural frequencies determined from the analysis of the arising two-point boundary-value problems. In particular, we found two systems with complementary spectra of eigenvalues. Considering boundary damping we analyzed these eigenvalues in the first octant of the complex plane. The fundamental result is that these two systems offer no common eigenvalue, they are alternative. This is an interesting and unique observation.



Zimmermann, Martin;
Untersuchung des Feuchtetransportes und dessen Einfluss auf Form- und Eigenspannungsänderungen in Furnieren. - Düren : Shaker Verlag, 2022. - XII, 181 Seiten. - (Berichte aus der Mechanik)
Technische Universität Ilmenau, Dissertation 2021

ISBN 978-3-8440-8523-5

Gegenstand der vorliegenden Arbeit ist, die Untersuchung der Feuchteaufnahme und -weiterleitung in Furnieren, wie sie während der industriellen Verarbeitung vorkommt. Es steht damit die Aufnahme von freiem Wasser einschließlich der damit einhergehenden quellungsbedingten Form- und Eigenspannungsänderungen bei Furnieren im Fokus der Betrachtungen. Hierzu werden, nach Vorstellung ausgewählter Grundlagen aus Forschung und Technik, Konzeption und Realisierung experimenteller Untersuchungen erläutert. Die am Beispiel von Rotbuchenfurnier (Fagus Sylvatica L.) durchgeführten Untersuchungen unterscheiden dabei zwischen Versuchsreihen zur Wasseraufnahme und der damit verbundenen Verformungsentwicklung. Die Randbedingungen der verschiedenen Messreihen berücksichtigen für Holz typische anatomische Eigenschaften (z. B. Faserausrichtung), relevante Befeuchtungsszenarien aus der industriellen Furnierverarbeitung (einseitige, zweiseitige und allseitige Feuchtezufuhr) sowie Einflüsse aus der Furnierherstellung (Unterscheidung rissbehaftete/rissfreie Furniersichtseite). Darüber hinaus ist die mathematische Beschreibung der Feuchtebewegung in Furnieren Gegenstand der Arbeit. So werden auf Basis der Fick’schen Diffusionsgesetze, mit Hilfe der Finite-Elemente-Methode, feuchteabhängige Kennwertverläufe (Transportkoeffizienten) für longitudinalen und radialen Feuchtetransport in Rotbuchenfurnier abgeleitet. Im Ergebnis kann festgehalten werden, dass der Feuchtetransport in Furnier sehr gut mit Hilfe der entwickelten Modelle beschrieben werden kann. Ferner werden, basierend auf den durchgeführten Untersuchungen, ein für Furnier typisches und von Vollholzerzeugnissen abweichendes Verformungsverhalten herausgestellt sowie allgemeine Aussagen zur Formstabilität von Furnieren abgeleitet.



Chavez, Jhohan; Böhm, Valter; Becker, Tatiana; Gast, Simon; Zeidis, Igor; Zimmermann, Klaus
Actuators based on a controlled particle-matrix interaction in magnetic hybrid materials for applications in locomotion and manipulation systems. - In: Physical sciences reviews, ISSN 2365-659X, Bd. 7 (2022), 11, S. 1263-1290

The paper deals with the investigation of magneto-sensitive elastomers (MSE) and their application in technical actuator systems. MSE consist of an elastic matrix containing suspended magnetically soft and/or hard particles. Additionally, they can also contain silicone oil, graphite particles, thermoplastic components, etc., in various concentrations in order to tune specific properties such as viscosity, conductivity and thermoelasticity, respectively. The focuses of investigations are the beneficial properties of MSE in prototypes for locomotion and manipulation purposes that possess an integrated sensor function. The research follows the principle of a model-based design, i.e. the working steps are ideation, mathematical modelling, material characterization as well as building first functional models (prototypes). The developed apedal (without legs) and non-wheeled locomotion systems use the interplay between material deformations and the mechanical motion in connection with the issues of control and stability. Non-linear friction phenomena lead to a monotonous forward motion of the systems. The aim of this study is the design of such mechanical structures, which reduce the control costs. The investigations deal with the movement and control of 'intelligent' mechanisms, for which the magnetically field-controlled particle-matrix interactions provide an appropriate approach. The presented grippers enclose partially gripped objects, which is an advantage for handling sensitive objects. Form-fit grippers with adaptable contour at the contact area enable a uniform pressure distribution on the surface of gripped objects. Furthermore, with the possibility of active shape adaptation, objects with significantly differing geometries can be gripped. To realise the desired active shape adaptation, the effect of field-induced plasticity of MSE is used. The first developed prototypes mainly confirm the functional principles as such without direct application. For this, besides the ability of locomotion and manipulation itself, further technological possibilities have to be added to the systems. The first steps are therefore being taken towards integrated MSE based adaptive sensor systems.



https://doi.org/10.1515/psr-2019-0087