@article{SchorrChavezVegaZentneretal., author = {Schorr, Philipp and Chavez Vega, Jhohan Harvey and Zentner, Lena and B{\"o}hm, Valter}, title = {Reconfiguration of planar quadrilateral linkages utilizing the tensegrity principle}, series = {Mechanism and machine theory}, journal = {Mechanism and machine theory}, number = {156}, publisher = {Elsevier}, doi = {10.1016/j.mechmachtheory.2020.104172}, abstract = {The development of reconfigurable planar four-bar linkages by applying the tensegrity principle is considered. Conventional quadrilateral linkages enable two operation modes differing in the kinematic behavior. However, a change between these states is not possible due to the geometric constraints. To enable a reconfiguration between the different modes one-sided limited nonholonomic constraints are introduced in this work. This issue is realized by applying ropes that cannot resist compression. However, to guarantee an appropriate load case in operation a prestress within the mechanism is required. Hence, the linkage is extended to a tensegrity-based mechanism. The structural dynamics are derived using the LAGRANGE formalism and the structural behavior is evaluated using numerical simulations. Furthermore, a prototype of an exemplary tensegrity-based mechanism is manufactured and experiments regarding the mechanical properties, in particular the reconfiguration, are performed. The results suggest the potential benefit of applying the tensegrity principle within conventional planar four-bar linkages.}, language = {en} } @article{ChavezVegaZiolkowskiSchorretal., author = {Chavez Vega, Jhohan Harvey and Ziolkowski, Marek and Schorr, Philipp and Spiess, Lothar and B{\"o}hm, Valter and Zimmermann, Klaus}, title = {A method to approach constant isotropic permeabilities and demagnetization factors of magneto-rheological elastomers}, series = {Journal of Magnetism and Magnetic Materials}, volume = {527}, journal = {Journal of Magnetism and Magnetic Materials}, publisher = {Elsevier}, doi = {10.1016/j.jmmm.2021.167742}, abstract = {The use of non-conventional materials is nowadays of much interest in scientific community. Magneto-rheological elastomers are hybrid materials, which in presence of magnetic fields state a change in their mechanical properties. They are composed by an elastomeric matrix with embedded magnetic particles. One of the most attractive features of these materials is that as soon as the magnetic field is removed from the material, the original mechanical properties are completely recovered, with negligible differences in comparison to the original state. This paper focuses on the study of magnetic characteristics of these smart materials, such as relative permeability and demagnetizing factors, for samples with different volume concentration of ferromagnetic particles.}, 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} } @inproceedings{ChavezVegaSchorrScharffetal., author = {Chavez Vega, Jhohan Harvey and Schorr, Philipp and Scharff, Moritz and Schale, Florian and B{\"o}hm, Valter and Zimmermann, Klaus}, title = {Towards Magneto-Sensitive Elastomers Based End-Effectors for Gripping Application Technologies}, series = {2019 IEEE International Conference on Mechatronics (ICM), 18-20 March 2019, Ilmenau, Germany}, volume = {1}, booktitle = {2019 IEEE International Conference on Mechatronics (ICM), 18-20 March 2019, Ilmenau, Germany}, publisher = {IEEE}, doi = {10.1109/ICMECH.2019.8722922}, pages = {217 -- 222}, abstract = {Nowadays, the demands in engineering systems become more challenging and the use of conventional materials for certain applications is not suitable. This issue encourages the investigation of novel and innovative materials in soft robotics field. A promising approach is the consideration of magneto-sensitive elastomers (MSE). These materials enable a useful adaptability responding to their mechanical properties. By applying a static magnetic field, the static and dynamic characteristics can be tuned. However, currently the knowledge about the correlations are not satisfying and the resulting material properties can only be predicted approximately with the use of time-expensive simulations regarding to the nano scale. Therefore, feasible material simulations of the description of the mechanical behavior are necessary. In this paper experimental studies of the influence of a static magnetic field on the mechanical properties and shape adaptability of MSE are presented. Furthermore, based on these results a simulation for the material behavior is executed. These results can be implemented into further simulations for various MSE exemplars.}, language = {en} } @inproceedings{SchorrChavezVegaZentneretal., author = {Schorr, Philipp and Chavez Vega, Jhohan Harvey and Zentner, Lena and B{\"o}hm, Valter}, title = {Reconfigurable Planar Quadrilateral Linkages Based on the Tensegrity Principle}, series = {Microactuators, Microsensors and Micromechanisms, MAMM, 2020}, booktitle = {Microactuators, Microsensors and Micromechanisms, MAMM, 2020}, editor = {Zentner, Lena and Strehle, Steffen}, publisher = {Springer International Publishing}, address = {Cham}, isbn = {978-3-030-61651-9}, doi = {10.1007/978-3-030-61652-6_5}, pages = {48 -- 57}, abstract = {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.}, language = {en} }