@article{BeckerRaikherStolbovetal., author = {Becker, Tatiana I. and Raikher, Yuriy L. and Stolbov, Oleg V. and B{\"o}hm, Valter and Zimmermann, Klaus}, title = {Magnetoactive elastomers for magnetically tunable vibrating sensor systems}, series = {Physical Sciences Reviews}, volume = {7}, journal = {Physical Sciences Reviews}, number = {10}, publisher = {de Gruyter}, issn = {2365-659X}, doi = {10.1515/psr-2019-0125}, pages = {1 -- 28}, abstract = {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 in-plane 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.}, language = {de} } @inproceedings{SchorrSchaleOtterbachetal., author = {Schorr, Philipp and Schale, Florian and Otterbach, Jean Marc and Zentner, Lena and Zimmermann, Klaus and B{\"o}hm, Valter}, title = {Investigation of a Multistable Tensegrity Robot applied as Tilting Locomotion System}, series = {Proceedings of the 2020 IEEE International Conference on Robotics and Automation (ICRA): 31 May-31 August 2020, Paris}, booktitle = {Proceedings of the 2020 IEEE International Conference on Robotics and Automation (ICRA): 31 May-31 August 2020, Paris}, doi = {10.1109/ICRA40945.2020.9196706}, pages = {2932 -- 2938}, abstract = {This paper describes the development of a tilting locomotion system based on a compliant tensegrity structure with multiple stable equilibrium configurations. A tensegrity structure featuring 4 stable equilibrium states is considered. The mechanical model of the structure is presented and the according equations of motion are derived. The variation of the length of selected structural members allows to influence the prestress state and the corresponding shape of the tensegrity structure. Based on bifurcation analyses a reliable actuation strategy to control the current equilibrium state is designed. In this work, the tensegrity structure is assumed to be in contact with a horizontal plane due to gravity. The derived actuation strategy is utilized to generate tilting locomotion by successively changing the equilibrium state. Numerical simulations are evaluated considering the locomotion characteristics. In order to validate this theoretical approach a prototype is developed. Experiments regarding to the equilibrium configurations, the actuation strategy and the locomotion characteristics are evaluated using image processing tools and motion capturing. The results verify the theoretical data and confirm the working principle of the investigated tilting locomotion system. This approach represents a feasible actuation strategy to realize a reliable tilting locomotion utilizing the multistability of compliant tensegrity structures.}, language = {en} } @inproceedings{SchorrBoehmZentneretal., author = {Schorr, Philipp and B{\"o}hm, Valter and Zentner, Lena and Zimmermann, Klaus}, title = {Design of a Vibration Driven Motion System Based on a Multistable Tensegrity Structure}, series = {ICINCO 2018: proceedings of the 15th International Conference on Informatics in Control, Automation and Robotics, Porto, Portugal, July 29-31, 2018}, volume = {613}, booktitle = {ICINCO 2018: proceedings of the 15th International Conference on Informatics in Control, Automation and Robotics, Porto, Portugal, July 29-31, 2018}, editor = {Gusikhin, Oleg and Madani, Kurosh}, publisher = {Springer}, address = {Cham}, isbn = {978-3-030-31992-2}, doi = {10.1007/978-3-030-31993-9_14}, pages = {302 -- 317}, abstract = {In this paper a novel approach to realize a uniaxial bidirectional vibration driven motion system with controllable direction of motion is investigated. The considered motion system bases on a tensegrity structure with multiple stable equilibrium configurations. The structure is in contact with a horizontal plane due to gravity and the actuation is realized by the harmonic change of the length of a selected member. Beside varying the actuation parameters, the direction of motion can be controlled by changing the equilibrium configuration of the tensegrity structure. In this paper the topology of the tensegrity structure and the parameter values are chosen appropriately to provide two symmetric equilibrium configurations. A change of the equilibrium state yields a novel configuration of the entire motion system which is symmetric to the original state. Utilizing the symmetry of the system the same actuation yields an opposite motion. This approach represents a reliable opportunity to control the direction of motion by changing the equilibrium state for constant actuation parameters. This paper focuses on the parameter selection and the design of the actuation of the vibration driven motion system. The working principle of the vibration driven motion system is verified by numerical simulations. This contribution represents the theoretical investigation for the further development of a prototype.}, language = {en} } @article{ChavezVegaBoehmBeckeretal., author = {Chavez Vega, Jhohan Harvey and B{\"o}hm, Valter and Becker, Tatiana I. and Gast, Simon and Zeidis, Igor and Zimmermann, Klaus}, title = {Actuators based on a controlled particle-matrix interaction in magnetic hybrid materials for applications in locomotion and manipulation systems}, series = {Physical Sciences Reviews}, volume = {7}, journal = {Physical Sciences Reviews}, number = {11}, publisher = {de Gruyter}, doi = {10.1515/psr-2019-0087}, pages = {1263 -- 1290}, abstract = {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.}, language = {en} } @article{ChavezVegaSchorrKaufholdetal., author = {Chavez Vega, Jhohan Harvey and Schorr, Philipp and Kaufhold, Tobias and Zentner, Lena and Zimmermann, Klaus and B{\"o}hm, Valter}, title = {Influence of Elastomeric Tensioned Members on the Characteristics of Compliant Tensegrity Structures in Soft Robotic Applications}, series = {Procedia Manufacturing}, volume = {52}, journal = {Procedia Manufacturing}, publisher = {Elsevier}, issn = {2351-9789}, doi = {10.1016/j.promfg.2020.11.048}, pages = {289 -- 294}, abstract = {The use of mechanically prestressed compliant structures in soft robotics is a recently discussed topic. Tensegrity structures, consisting of a set of rigid disconnected compressed members connected to a continuous net of prestressed elastic tensioned members build one specific class of these structures. Robots based on these structures have manifold shape changing abilities and can adapt their mechanical properties reversibly by changing of their prestress state according to specific tasks. In the paper selected aspects on the potential use of elastomer materials in these structures are discussed with the help of theoretical analysis. Therefore, a selected basic tensegrity structure with elastomer members is investigated focusing on the stiffness and shape changing ability in dependence of the nonlinear hyperelastic behavior of the used elastomer materials. The considered structure is compared with a conventional tensegrity structure with linear elastic tensioned members. Finally, selected criterions for the advantageous use of elastomer materials in compliant tensegrity robots are discussed.}, language = {en} } @inproceedings{BoehmSchorrFeldmeieretal., author = {B{\"o}hm, Valter and Schorr, Philipp and Feldmeier, T. and Chavez Vega, Jhohan Harvey and Henning, S. and Zimmermann, Klaus and Zentner, Lena}, title = {An Approach to Robotic End Effectors Based on Multistable Tensegrity Structures}, series = {New Trends in Mechanism and Machine Science: 8th European Conference on Mechanism Science (EuCoMeS), 2020}, booktitle = {New Trends in Mechanism and Machine Science: 8th European Conference on Mechanism Science (EuCoMeS), 2020}, publisher = {Springer}, doi = {10.1007/978-3-030-55061-5_53}, pages = {470 -- 478}, abstract = {In this paper compliant multistable tensegrity structures with discrete variable stiffness are investigated. The different stiffness states result from the different prestress states of these structures corresponding to the equilibrium configurations. Three planar tensegrity mechanisms with two stable equilibrium configurations are considered exemplarily. The overall stiffness of these structures is characterized by investigations with regard to their geometric nonlinear static behavior. Dynamical analyses show the possibility of the change between the equilibrium configurations and enable the derivation of suitable actuation strategies.}, language = {en} } @article{BeckerBoehmSchaleetal., author = {Becker, Tatiana I. and B{\"o}hm, Valter and Schale, Florian and Zimmermann, Klaus}, title = {Vibrating sensor unit made of a magnetoactive elastomer with field-adjustable characteristics}, series = {Journal of Magnetism and Magnetic Materials}, volume = {498}, journal = {Journal of Magnetism and Magnetic Materials}, number = {March}, publisher = {Elsevier}, doi = {10.1016/j.jmmm.2019.166196}, abstract = {The present work deals with the investigation of the oscillatory behavior displayed by a vibrating sensor unit made of a magnetoactive elastomer (MAE). Since this type of smart materials consists of an elastic matrix and micro-magnetic particles, it reveals exceptional magnetic-field-dependent material properties. The forced vibration response under the bending of the MAE unit subjected to in-plane harmonic kinematic excitation of the housing is studied. It is found that the amplitude-frequency characteristics of the MAE unit can be changed considerably by means of an external homogeneous magnetic field. With and without applied field, the unit displays different steady-state responses for the same excitation, and the resonance occurs at various ranges of the excitation frequency. The nonlinear phenomenon of the resonance hysteresis is observed depending on whether the excitation frequency increases or decreases. It is shown that the MAE vibrations can be detected based on the magnetic field distortion measurements. The presented prototype of the MAE-based vibrating unit with field-adjustable "configuration" can be potentially implemented for realization of acceleration sensor systems with adaptive sensitivity.}, language = {en} }