Labor Finite-Elemente-Methode (FEM)
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Die vorliegende Arbeit untersucht die Topologie und das mechanische Verhalten von 2D-Tensegrity-Netzen auf Basis regelmäßiger, polygonaler Grundformen. Ausgehend von grundlegenden geometrischen Überlegungen zu Dreiecks-, Quadrat- und Sechseck-Tessellierungen werden unterschiedliche Tensegrity-Basiseinheiten entwickelt und systematisch zu periodischen Netzstrukturen kombiniert. Der Fokus liegt dabei auf quadratischen Tensegrity Zellen. Neben etablierten heterogenen Netzstrukturen, die aus der Kombination unterschiedlicher Drucksegmenttypen bestehen, werden erstmals homogene Tensegrity-Netze mit einheitlicher Drucksegmenttopologie untersucht. Durch die Einführung neuartiger Drucksegmente mit rechteckiger Außenform können Tensegrity-Netze mit deutlich kleineren Leerstellen aufgebaut werden. Die mechanische Charakterisierung erfolgt mittels geometrisch und statisch nicht- linearer Finite-Element-Analysen sowie anhand von Flexibilitätsellipsen elementarer Einheiten . Die Ergebnisse zeigen, dass sich durch gezielte Variation von Geometrie, Vorspannung und innerer Topologie sowohl Steifigkeit als auch kollisionsfreie Verformbarkeit der Netze gezielt einstellen lassen. Damit leisten die untersuchten Strukturen einen Beitrag zum geometriebasierten Entwurf materialeffizienter und adaptiver Tragwerkskonzepte.
Soft tensegrity structures with variable stiffness and shape changing abil-ity hold significant potential for soft robotic applications. With few exceptions, this class of structures primarily consists of tensioned and compressed members (at least some of which are compliant) forming a prestressed, stable equilibrium state. Con-sequently, changes in prestress of the structures enable independent or combined adjustments of shape and stiffness, which can be achieved actively or passively. This article explores the fundamental realization principles of soft tensegrity structures focusing on application examples, including manipulators, force and contact sensors, multistable soft grippers, and locomotion systems. Additionally, it highlights the potential of smart materials for passive stiffness modulation. The findings highlight that soft tensegrity structures, characterized by variable stiffness and shape changing capabilities, play a crucial role in advancing the performance and adaptability of soft robotic systems.
This paper presents a conceptual sensor design for planar force/torque measurement based on fiber optic sensing. The design includes two rigid bodies, one acting as a reference frame and the other as a force/torque transducer. Both bodies are indirectly connected by prestressed segments of a fiber optic sensor, which act as both structural components and sensing elements to detect changes in their optical path lengths. We derive the non-linear model equations describing the overall deformation state of the sensor when subjected to arbitrary force/torque pairs under static conditions. These equations are solved for three different application scenarios: force sensing, torque sensing, and combined force/torque sensing. We outline the measuring range of the sensor and identify ways of influencing this range. Moreover, we discuss the uniqueness of the mapping between the detected lengths of the optical fiber segments and the applied load. In doing so, we provide a promising simulation-based proof of concept for the presented sensor design.
This paper presents a modular tensegrity-based robotic system with fully integrated actuation inside each compressed member, eliminating external cables and base structures. The design decouples actuation from prestress, enabling precise motion control while preserving high structural compliance and robustness. Experimental investigations demonstrate bio-inspired locomotion modes, such as laternal undulation, rectilinear, and sidewinding. Compared to conventional tensegrity systems, the proposed system offers simplified assembly and adjustable stiffness by replacing the tensioned members. The system’s modularity and self-sufficient actuation enable its functionality as both a manipulator and a locomotion platform, representing an universal tensegrity architecture for diverse robotic applications.
This paper presents a compliant, modular, tendondriven manipulator based on tensegrity joints. The design and motion are inspired by the structure and spiral-like grasping behavior of the seahorse tail. The characteristic prestress of the tensegrity-structure significantly influences its gripping capabilities and can be precisely adjusted. Additionally, the modular design allows for scalability to meet various application and size requirements. Potential applications include, but are not limited to, soft gripping in human-interactive environments, as well as active or passive structures in biomedical engineering solutions.
This paper explores the integration of deformable compressed members into tensegrity structures, focusing on their application in robotic systems. A comprehensive investigation of the mechanical behavior of these members is presented, including their deformation characteristics and the influence of geometric parameters. The analysis demonstrates that these compliant members can be used for actuation within tensegrity structures without plastic deformation. Two different tensegrity structures, based on the needle tower topology, are employed to analyze the workspace and manipulation capabilities. Experimental validation is provided through a prototype incorporating the actuated compressed members, showcasing their potential for defined manipulation and tilting motions in the structure. The findings suggest that the proposed system can achieve precise and controlled deformation, enabling innovative applications in soft robotics and deployable structures. The results provide insights into the design and actuation of fully compliant tensegrity systems, offering a foundation for future research and practical implementations.
Compliant Tensegrity Robotic Arm with Continuously Adjustable Stiffness for Versatile Operation
(2025)
This paper presents a compliant tensegrity robotic arm design that overcomes limitations related to stiffness variation and cascaded actuation. Due to the special design and actuation strategy, the system offers a large workspace using a small number of actuators and system parts. Key features include intrinsic compliance, enhanced stability in various configurations, and a modular tendon-driven actuation system that facilitates continuous stiffness adjustment for adaptive manipulation tasks. The system’s kinematics and actuation strategy are validated experimentally. Results demonstrate an increased workspace and precise control, offering potential applications in dynamic and human-interactive environments.
The hand is one of the most anatomically complex parts of the human body due to its wide range of independent movements. The multi axial movement space of the hand is based on the wrist joint. An injury in this important body part often requires medical intervention in the form of a hand orthosis, which restricts the movement space of a patient’s hand to prevent further damage to internal bones and ligaments. The hand orthosis in this research project is based on the principle of tensegrity structures, which allows for multi axial movement of the hand, without using conventional joint elements. In addition to the theoretical simulation of this medical device a test stand was developed to investigate the experimental characteristics of the orthosis. By replicating a human hand with an attached orthosis, the test rig enables experimental measurements on joint deflection and basic muscle and wrist forces via a cable-based actuating system. To achieve more precise measurements and improved operability of the test stand, the wiring of the electrical components was optimized, as well as improvements in measurement and control engineering, were implemented.
