A vibrissa-inspired highly flexible tactile sensor: scanning 3D object surfaces providing tactile images. - In: Sensors, ISSN 1424-8220, Bd. 21 (2021), 5, 1572, insges. 29 S.
Just as the sense of touch complements vision in various species, several robots could benefit from advanced tactile sensors, in particular when operating under poor visibility. A prominent tactile sense organ, frequently serving as a natural paragon for developing tactile sensors, is the vibrissae of, e.g., rats. Within this study, we present a vibrissa-inspired sensor concept for 3D object scanning and reconstruction to be exemplarily used in mobile robots. The setup consists of a highly flexible rod attached to a 3D force-torque transducer (measuring device). The scanning process is realized by translationally shifting the base of the rod relative to the object. Consequently, the rod sweeps over the object’s surface, undergoing large bending deflections. Then, the support reactions at the base of the rod are evaluated for contact localization. Presenting a method of theoretically generating these support reactions, we provide an important basis for future parameter studies. During scanning, lateral slip of the rod is not actively prevented, in contrast to literature. In this way, we demonstrate the suitability of the sensor for passively dragging it on a mobile robot. Experimental scanning sweeps using an artificial vibrissa (steel wire) of length 50 mm and a glass sphere as a test object with a diameter of 60 mm verify the theoretical results and serve as a proof of concept.
https://doi.org/10.3390/s21051572
Entwicklung und Charakterisierung fluidmechanischer nachgiebiger Aktuatoren am Beispiel eines multifunktionalen Sauggreifers. - Ilmenau : Universitätsverlag Ilmenau, 2021. - 1 Online-Ressource (183, A-1 - A-53, LII Seiten). - (Berichte der Ilmenauer Mechanismentechnik ; Band 6)
Technische Universität Ilmenau, Dissertation 2020
Zum Greifen verschiedener Greifobjekte finden fluidmechanische nachgiebige Aktuatoren (FNA) auf Silikonbasis als Greifer zunehmend Verbreitung. Aufgrund der stoffschlüssigen Bauweise ermöglichen diese die Integration verschiedener Funktionen auf Strukturebene. Vor allem zur Senkung des Hygienerisikos sind FNA für Greifaufgaben in Reinräumen und der Verpackungsindustrie in Form geschlossener Sauggreifer besonders geeignet. Die Untersuchung derartiger Sauggreifer ist Gegenstand dieser Arbeit. Im Rahmen der Arbeit wird ausgehend von verschiedenen Anwendungen eine allgemeine Klassifikation für FNA vorgestellt und entwickelte FNA anhand dieser eingeordnet. Die Entwicklung von FNA wird am Beispiel des geschlossenen Sauggreifers detailliert beschrieben. Eine der Besonderheiten des geschlossenen Sauggreifers ist, dass er im Gegensatz zu offenen Sauggreifern greifobjektseitig eine Membran aufweist. Die Membran ermöglicht neben der Trennung des Mediums im Innenraum des Sauggreifers vom Umgebungsmedium, auch das aktive, zeitlich sowie örtlich gezielte Ablegen von Greifobjekten. Eine weitere Besonderheit des gewählten Beispiels ist dessen nichtlineare Federkennlinie. Diese führt zu einem Bewegungsverhalten mit Durchschlag und ermöglicht die Adaption an verschiedene Objektlagen und -formen. Durch Modellbetrachtungen und experimentelle Untersuchungen von ausgewählten Geometrie und Materialparametern werden Beeinflussungsmöglichkeiten der Durchschlaggrößen aufgezeigt. Die Formulierung einer allgemeinen Vorgehensweise für das Erreichen festgelegter FNA-Kennwerte bilden dabei einen wesentlichen Beitrag dieser Arbeit. Darüber hinaus werden prinzipielle Lösungen für die Implementierung einer stoffkohärenten sowie nachgiebigen Sensorik für FNA auf Silikonbasis vorgestellt. Die Umsetzung der Sensorik wird am Beispiel des Sauggreifers beschrieben. Die Möglichkeit zur Ableitung qualitativer Aussagen zu Greifzustand, Greifobjektleitfähigkeit sowie zu den Greifprozessphasen wird diskutiert. Die für die Herstellung und Erprobung des multifunktionalen Sauggreifers notwendigen neuartigen Werkzeuge, Vorrichtungen und Prozesse werden im Rahmen der Arbeit jeweils beschrieben. Durch die Gesamtschau der untersuchten FNA-Eigenschaften, nichtlinearen Kennlinie, Adaptivität sowie Sensorisierung liefert die Arbeit einen Beitrag zu multifunktionalen FNA sowie auch zum Vorgehen bei deren Entwicklung.
https://doi.org/10.22032/dbt.46923
Dynamics of a magnetic pendulum in the presence of an oscillating conducting plate. - In: Proceedings in applied mathematics and mechanics, ISSN 1617-7061, Bd. 20 (2021), 1, e202000083, insges. 2 S.
A pendulum with an attached permanent magnet moving near a conductor is a typical experiment for the demonstration of electromagnetic braking. When the conductor itself moves, it can transfer energy to the pendulum. We study a simple but exact analytical model where the conductor is a horizontally unbounded flat plate. For this geometry, eddy currents and induced Lorentz force due to the motion of a magnetic dipole are known analytically in the quasistatic limit. A vertical oscillation of such a horizontal plate located beneath the magnet is considered. In this setup, the vertical position of the pendulum is an equilibrium point when the magnetic moment of the magnet is perpendicular to its plane of motion. Depending on the strength of the magnetic dipole moment, the frequency and amplitude of the plate as well as the distance between plate and magnet, the plate oscillation can destabilize the equilibrium. The stability limits for weak electromagnetic coupling are computed analytically using the harmonic balancing method. For stronger coupling, the stability limits are obtained numerically using Floquet analysis. Chaotic motions with finite amplitudes are also found.
https://doi.org/10.1002/pamm.202000083
Microactuators, microsensors and micromechanisms : MAMM 2020. - Cham : Springer, 2021. - 1 Online-Ressource (viii, 148 Seiten). - (Mechanisms and machine science ; Volume 96) ISBN 978-3-030-61652-6
Description based on publisher supplied metadata and other sources.
Intro -- Preface -- Contents -- A Novel Planar Two-Axis Leaf-Type Notch Flexure Hinge with Coincident Rotation Axes and Its Application to Micropositioning Stages -- 1 Introduction -- 2 Design of the Two-Axis Leaf-Type Notch Flexure Hinge -- 3 FEM-Based Investigation of the TLNFH -- 3.1 FEM Model -- 3.2 Parametric Study -- 3.3 Discussion of Results -- 4 Application to Compliant Micropositioning Stages -- 4.1 10-Hinge Rectilinear Stage -- 4.2 12-Hinge XY Stage -- 5 Conclusions -- References -- Characterization of Thin Flexure Hinges for Precision Applications Based on First Eigenfrequency -- 1 Introduction -- 2 Materials and Methods -- 2.1 Experiment -- 2.2 Theoretical Approaches -- 3 Results and Discussion -- 4 Conclusions and Outlook -- References -- Optimization of Compliant Path-Generating Mechanisms Based on Non-linear Analytical Modeling -- 1 Introduction -- 2 Analytical Model -- 2.1 Large Deflections of Rod-Like Structures -- 2.2 Modeling of Compliant Mechanisms as Continua -- 3 Verification of the Analytical Model by FEM Simulation -- 3.1 Analytical Solution -- 3.2 FEM Simulation -- 3.3 Results and Discussion -- 4 Analytical Optimization of Example Compliant Path-Generating Mechanisms -- 5 Conclusions -- References -- Modelling and Investigation of a Compliant Cable-Driven Finger-Like Mechanism -- 1 Introduction -- 2 Basic Concept of Compliant Cable-Driven Mechanism -- 3 Model and Simulation -- 3.1 Mechanical Model -- 3.2 Mathematical Model -- 4 Calculation Results -- 4.1 Bending Shapes Without Consideration of Gravity -- 4.2 Bending Shapes Under Consideration of Gravity -- 4.3 Bending Moment -- 5 Experimental Validation of the Model -- 5.1 Experimental Setup and Test Procedure -- 5.2 Test Results -- 6 Conclusions -- References -- Reconfigurable Planar Quadrilateral Linkages Based on the Tensegrity Principle -- 1 Introduction.
https://ebookcentral.proquest.com/lib/kxp/detail.action?docID=6381324
A novel planar two-axis leaf-type notch flexure hinge with coincident rotation axes and its application to micropositioning stages. - In: Microactuators, microsensors and micromechanisms, (2021), S. 1-14
Compliant mechanisms with flexure hinges are well-suited for high-precision applications due to their smooth and repeatable motion. However, the synthesis of planar compliant mechanisms based on notch flexure hinges is mostly limited to the use of single-axis hinges due to the lack of certain multiple-axis flexure hinges. This contribution introduces a novel planar leaf-type notch flexure hinge with two coincident rotation axes based on circular pre-curved leaf springs. A generally suitable hinge geometry is determined through a parametric study using the finite element method (FEM). Finally, the two-axis flexure hinge is applied and investigated for the use in two planar micropositioning stages for the rectilinear guidance of an output link with a large centimeter stroke. The presented two-axis flexure hinge turns out to be a suitable approach to monolithically connect three links of a compliant mechanism in a planar and precise way.
https://doi.org/10.1007/978-3-030-61652-6_1
Characterization of thin flexure hinges for precision applications based on first eigenfrequency. - In: Microactuators, microsensors and micromechanisms, (2021), S. 15-24
Flexure hinges with small cross-section heights are state of the art in numerous precision engineering applications due to their capability for smooth and repeatable motion. However, the high sensitivity to manufacturing influences represents a challenge. We propose a characterization method for flexure hinges based on the measurement of the free oscillation, to enable the consideration of manufacturing influences in the early stages of the design process. Three semi-circular flexure hinges with different cross-section heights and highly accurate geometry were investigated experimentally to compare them with three theoretical modeling approaches. The results for the three flexure hinge specimens showed small deviations to the predicted values from the models which is in agreement with the results of dimensional measurements. With each modeling approach, a deviation of the minimal notch height from the nominal value can be calculated. This value, in turn, can be used as manufacturing allowance for subsequent manufacturing of compliant mechanisms using the same manufacturing method. An exemplary compliant parallel-crank mechanism proves the applicability of the concept to compliant mechanisms with multiple flexure hinges.
https://doi.org/10.1007/978-3-030-61652-6_2
Optimization of compliant path-generating mechanisms based on non-linear analytical modeling. - In: Microactuators, microsensors and micromechanisms, (2021), S. 25-35
Monolithic compliant mechanisms are often used in precision engineering applications for path-generating tasks due to their many advantages. They are mostly realized with concentrated compliance in form of notch flexure hinges and achieve their motion due to bending of the hinges. This contribution presents the non-linear analytical modeling of compliant mechanisms with power function-based notch flexure hinges and their efficient optimization of the elasto-kinematic path-generating properties using MATLAB. Different planar mechanisms are analytically characterized with the theory for large deflections of curved rod-like structures. A verification of the analytical model is exemplified by FEM simulations for a four-hinge Watt mechanism as a point guidance mechanism and for a 12-hinge pantograph mechanism as a plane guidance mechanism. Further, the exponents of the power function contours for each hinge are individually optimized on the example of an Evans and a Roberts mechanism. This is achieved with the goal of minimizing the straight-line deviation of their coupler points realizing a stroke of 10 mm.
https://doi.org/10.1007/978-3-030-61652-6_3
Modelling and investigation of a compliant cable-driven finger-like mechanism. - In: Microactuators, microsensors and micromechanisms, (2021), S. 36-47
This paper deals with the modelling of a compliant finger-like mechanism that is actuated by a single cable. The mechanism has a desired elastic deformation behavior which can be adjusted by the mechanism design. The modelling of the compliant mechanism is based on the nonlinear theory of large deformations of curved rods. The known theory is extended by a novel approach of modelling the interaction between the cable and the mechanism itself. In addition, the influence of the gravity is discussed. The resulting model is verified by experiments.
https://doi.org/10.1007/978-3-030-61652-6_4
Reconfigurable planar quadrilateral linkages based on the tensegrity principle. - In: Microactuators, microsensors and micromechanisms, (2021), S. 48-57
A feasible possibility to develop planar reconfigurable mechanisms is introduced in this work. Applying the tensegrity principle to common four-bar linkages allows a controllable change between two configurations of the mechanism. These two states correspond to different working spaces which vary regarding to the kinematic and mechanical properties. Therefore, the reconfiguration of the mechanism enables two different operation modes. Hence, this kind of mechanism enables the advantageous properties of conventional linkages with an additional enhanced adaptability of the kinematic and mechanic behavior. Beside the conceptual design of such tensegrity-based mechanisms, a reconfigurable four-bar parallel linkage is considered exemplarily. Numerical simulations are evaluated focusing on the kinematic behavior and the structural mechanics of this mechanism. Especially the reconfiguration of the mechanism by changing between two different working spaces is considered. The simulation results clarify the benefit of utilizing the tensegrity principle in mechanism theory. Adding only a few members to the original linkage enables a reconfigurable mechanism with comparable complexity.
https://doi.org/10.1007/978-3-030-61652-6_5
Parameter study of compliant elements for a bipedal robot to increase its walking efficiency. - In: Microactuators, microsensors and micromechanisms, (2021), S. 58-75
In this paper, we introduce a method to place compliant elements with parameters that can be adjusted during operation in the joints of the bipedal walker to improve its energy efficiency. The bipedal walking robot is modelled with five rigid segments and driven by electric motors in its revolute joints. Minimizing the energy consumption of locomotion is formulated as a numerical optimization problem. An Euler-Bernoulli beam is used to describe the nonlinear behavior, caused by large deflections, of a compliant element loaded with forces and moments. The static problem for the beam deflection for given boundary conditions is solved numerically. Four parameters defining either the undeformed geometry or the boundary conditions are varied to modify the torque that this compliant element exerts on two robot segments connected by a revolute joint. The torque-deflection dependence and its dependence on the four different parameters is approximated by simple ansatz functions via fitting. The fitted functions are then included in a numerical optimization problem to determine the optimal parameters of the compliant element and the corresponding energy optimal gait simultaneously. We evaluate the optimized energy efficiency at different walking speeds, where the robot has different optimal gaits or parameters of the compliant elements. Two kinds of elastic couplings are investigated: the elastic coupling between the robot's upper body and its thighs; or between the robot's thighs and shanks. These specific compliant elements show a negligible performance gain from nonlinearity due to the small active operating range of these joints. However, the practicability of the proposed method for combining the detailed, model-based description of manufacturable compliant elements and the optimization of the overall robot system to achieve maximum energy efficiency is successfully demonstrated.
https://doi.org/10.1007/978-3-030-61652-6_6