A Bio-Inspired Tensegrity Manipulator with Multi-DOF, Structurally Compliant Joints

Most traditional robotic mechanisms feature inelastic joints that are unable to robustly handle large deformations and off-axis moments. As a result, the applied loads are transferred rigidly throughout the entire structure. The disadvantage of this approach is that the exerted leverage is magnified at each subsequent joint possibly damaging the mechanism. In this paper, we present two lightweight, elastic, bio-inspired tensegrity robotics arms which mitigate this danger while improving their mechanism's functionality. Our solutions feature modular tensegrity structures that function similarly to the human elbow and the human shoulder when connected. Like their biological counterparts, the proposed robotic joints are flexible and comply with unanticipated forces. Both proposed structures have multiple passive degrees of freedom and four active degrees of freedom (two from the shoulder and two from the elbow). The structural advantages demonstrated by the joints in these manipulators illustrate a solution to the fundamental issue of elegantly handling off-axis compliance.Comment: IROS 201

Theoretical considerations on 3D tensegrity joints for the use in manipulation systems

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

Object Manipulation with Modular Planar Tensegrity Robots

This thesis explores the creation of a novel two-dimensional tensegrity-based mod- ular system. When individual planar modules are linked together, they form a larger tensegrity robot that can be used to achieve non-prehensile manipulation. The first half of this dissertation focuses on the study of preexisting types of tensegrity mod- ules and proposes different possible structures and arrangements of modules. The second half describes the construction and actuation of a modular 2D robot com- posed of planar three-bar tensegrity structures. We conclude that tensegrity modules are suitably adapted to object manipulation and propose a future extension of the modular 2D design to a modular 3D design

Análise estática, dinâmica e modal de estruturas e mecanismos tensegrity

Orientador: Paulo Roberto Gardel KurkaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia MecânicaResumo: O desenvolvimento de estruturas mais leves, finas, rígidas ou inteligentes é um desafio constante entre engenheiros e cientistas de qualquer área. Sistemas tensegrity, que são formados por corpos rígidos em compressão e cabos em tração, têm perspectiva de serem amplamente aplicados pelas indústrias espacial, civil, mecânica, aeronáutica ou biomédica. O projetista de um tensegrity pode controlar sua rigidez e formato através da mudança de tensão nos cabos, cujos comportamentos são explorados neste trabalho via protótipos e simulações. Um modelo foi sugerido para otimizar massa e volume de uma antena de satélite, o mecanismo tensegrity foi criado para ser lançado num formato colapsado, economizando volume dentro do foguete, e expandido no espaço através da contração de determinados cabos. Em seguida, as tensões dos cabos de um prisma tensegrity foram variadas e a mudança na rigidez foi avaliada por análise modal. Por fim, uma torre tensegrity bidimensional foi submetida a grandes deformações, sua análise estática não linear foi implementada e as frequências naturais das posições deformadas foram calculadas. As três metodologias foram implementadas e, posteriormente, validadas em três experimentos distintos, estes ressaltando os efeitos de cada propriedade em avaliação. O objetivo deste trabalho é propor um procedimento para desenvolver o projeto e construção de uma estrutura tensegrity que englobe as três metodologias: definindo sua expansão a partir de uma configuração colapsada, o controle da rigidez quando estável e a nova posição caso algum esforço provoque grandes deformações. Portanto, além do objetivo prático do primeiro tópico, este trabalho tem como meta fornecer uma documentação geral de soluções relacionadas a estruturas e mecanismos tensegrityAbstract: The development of lighter, thinner, stiffer or smarter structures is a constant challenge among engineers and scientists of all fields. Tensegrity systems, which are formed by rigid bodies under compression and cables under traction, are likely to be largely used by the space, civil, mechanical, aeronautical and biomedical industries. The designer of a tensegrity can control its stiffness and shape by changing the tension in the cables, these behaviours are explored in this work via prototypes and simulations. A model was suggested to optimize mass and volume of a satellite antenna, a tensegrity mechanism was created to be launched in a reduced shape, saving volume in the launcher, and expanded in space by pulling specific tendons. Secondly, the tensions of a tensegrity prism's cables were varied and the change in stiffness was assessed through modal analysis. Finally, a 2D tensegrity tower was put under large deformations, its nonlinear static analysis was implemented and the natural frequencies of the deformed configurations were calculated. All the three methodologies have been implemented and, later, validated through experiments designed to highlight each property of concern. The objective of this work is to propose procedures to develop and build a tensegrity structure that carry those three methodologies: defining its expansion from a compact configuration, its stiffness control once the expansion is finished and its new shape if any load generates large displacements. Thus, beyond the practical end of the first topic, the goal of this work is to provide a general document of solutions related to tensegrity structures and mechanismsMestradoMecanica dos Sólidos e Projeto MecanicoMestre em Engenharia Mecânica132166/2018-6CNP

Form- und Parameterfindung von multistabilen Tensegrity-Strukturen mittels Optimierungsalgorithmen und Anwendungen in der Greifertechnik

Der Gegenstand der Arbeit sind Tensegrity-Strukturen mit mehreren stabilen Gleichgewichtskonfigurationen, sogenannte multistabile Tensegrity-Strukturen. Im Vordergrund der Arbeit steht die Entwicklung von Algorithmen, mit denen solche Strukturen entworfen, untersucht und gezielt ausgelegt werden können. Dafür werden Möglichkeiten zur Bestimmung der Gleichgewichtskonfigurationen von multistabilen Tensegrity-Strukturen betrachtet. Des Weiteren wird untersucht, wie Tensegrity-Strukturen so ausgelegt werden können, dass sie vorgegebene Eigenschaften aufweisen. Dazu werden Kenngrößen zur Charakterisierung dieser Eigenschaften definiert. Für beide Aufgabenstellungen werden Optimierungsprobleme hergeleitet. Zur Lösung dieser Optimierungsprobleme werden Algorithmen entworfen, getestet und analysiert. Aufbauend auf diesen theoretischen Untersuchungen liegt ein weiterer Schwerpunkt dieser Arbeit in der Betrachtung der Einsatzmöglichkeiten von multistabilen Tensegrity-Strukturen in der Greifertechnik. Es werden verschiedene Konzepte für die Entwicklung von Greifern aus diesen Strukturen diskutiert. Zu ausgewählten Konzepten erfolgen weiterführende Betrachtungen, unter anderem durch Einbeziehung dynamischer Analysen. Neben theoretischen Untersuchungen dieser Greifer werden die wichtigsten Erkenntnisse experimentell an Funktionsmustern überprüft und potentielle Einsatzgebiete werden aufgezeigt.The thesis considers tensegrity structures with several stable equilibrium configurations, so-called multistable tensegrity structures. The first part of the thesis is dedicated to the development of algorithms to design, examine and construct multistable tensegrity structures. For that, theoretical results to obtain the different equilibrium configurations of multistable tensegrity structures are derived. Further, methods to design tensegrity structures that have specific properties are investigated. Parameters that characterise these properties are defined. For these tasks optimisation problems are derived and algorithms to solve these problems are developed, tested and analysed. The second part of the thesis builds on these theoretical investigations to consider the application of multistable tensegrity structures in gripper technology. Different concepts to develop multistable tensegrity grippers are discussed. Further investigations, including dynamic analyses, are carried out for selected concepts. In addition to the theoretical considerations, the most important results are tested with development samples of the grippers and potential application fields are revealed