In silico case studies of compliant robots: AMARSI deliverable 3.3

In the deliverable 3.2 we presented how the morphological computing ap- proach can significantly facilitate the control strategy in several scenarios, e.g. quadruped locomotion, bipedal locomotion and reaching. In particular, the Kitty experimental platform is an example of the use of morphological computation to allow quadruped locomotion. In this deliverable we continue with the simulation studies on the application of the different morphological computation strategies to control a robotic system

Design and Control of Compliant Tensegrity Robots Through Simulation and Hardware Validation

To better understand the role of tensegrity structures in biological systems and their application to robotics, the Dynamic Tensegrity Robotics Lab at NASA Ames Research Center has developed and validated two different software environments for the analysis, simulation, and design of tensegrity robots. These tools, along with new control methodologies and the modular hardware components developed to validate them, are presented as a system for the design of actuated tensegrity structures. As evidenced from their appearance in many biological systems, tensegrity ("tensile-integrity") structures have unique physical properties which make them ideal for interaction with uncertain environments. Yet these characteristics, such as variable structural compliance, and global multi-path load distribution through the tension network, make design and control of bio-inspired tensegrity robots extremely challenging. This work presents the progress in using these two tools in tackling the design and control challenges. The results of this analysis includes multiple novel control approaches for mobility and terrain interaction of spherical tensegrity structures. The current hardware prototype of a six-bar tensegrity, code-named ReCTeR, is presented in the context of this validation

Modelling, design and control of a bird neck using tensegrity mechanisms

International audienceIn birds, the neck exhibits remarkable performances and serves as a dextrous arm for performing various tasks. Accordingly, it is an interesting bioinspiration for designing new manipulators with enhanced performances. This paper proposes a preliminary bird neck model using several stacked tensegrity crossed bar mechanisms. It addresses several issues regarding kinetostatic and dynamic modelling, design and control

Super Ball Bot - Structures for Planetary Landing and Exploration

Small, light-weight and low-cost missions will become increasingly important to NASA's exploration goals for our solar system. Ideally teams of dozens or even hundreds of small, collapsable robots, weighing only a few kilograms a piece, will be conveniently packed during launch and would reliably separate and unpack at their destination. Such teams will allow rapid, reliable in-situ exploration of hazardous destination such as Titan, where imprecise terrain knowledge and unstable precipitation cycles make single-robot exploration problematic. Unfortunately landing many lightweight conventional robots is difficult with conventional technology. Current robot designs are delicate, requiring combinations of devices such as parachutes, retrorockets and impact balloons to minimize impact forces and to place a robot in a proper orientation. Instead we propose to develop a radically different robot based on a "tensegrity" built purely upon tensile and compression elements. These robots can be light-weight, absorb strong impacts, are redundant against single-point failures, can recover from different landing orientations and are easy to collapse and uncollapse. We believe tensegrity robot technology can play a critical role in future planetary exploration

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

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

Prototype of a tensegrity manipulator to mimic bird necks

International audienceThis paper deals with the building of a 2D tensegrity mechanism. The considered mechanism is derived from the Snelson's X-shape mechanism and is used as an elementary part of the bird neck modelling. Indeed, an n-dof manipulator can be obtained by stacking in series n X-shape mechanisms. This paper explains the design and building process of a 1-dof prototype, both on hardware and software aspects, and will be used further to have experimental results on the dynamic modelling, control laws and ac-tuation strategy.Une structure de tenségrité est un assemblage d'éléments en compression (barres) et d'éléments en traction (câbles, ressorts) maintenus ensemble en équilibre [1],[2]. La tenségrité est connue en architecture et en art depuis plus d'un siècle [3] et est adaptée à la modélisation des organismes vivants [4]. Les mé-canismes de tenségrité ont été étudiés plus récemment pour leurs propriétés prometteuses en robotique telles que la faible inertie, la souplesse naturelle et la capacité de déploiement [5]. Un mécanisme de tenségrité est obtenu lorsqu'un ou plusieurs éléments sont actionnés. Ces travaux s'inscrivent dans le cadre du projet AVINECK, auquel participent des biologistes et des roboticiens dans le but principal de modéliser et de concevoir des cous d'oiseaux. En conséquence, une classe de manipulateurs de tenségrité planaire composée d'un assemblage en série de plusieurs mécanismes en X de Snelson [6], c'est-à-dire des mécanismes à quatre barres croisées avec des ressorts sur leurs côtés latéraux, a été choisie comme candidat approprié pour un modèle préliminaire plan d'un cou d'oiseau. Le prototype consiste en un mecanisme en X de Snelson. Les barres sont assemblées selon différents plans pour éviter les collisions internes. Le manipulateur est entraîné par des câbles parallèles aux res-sorts et traversant les axes grâce à des perçages. Chaque câble est attaché à un tambour. Le manipulateur est actionné par deux câbles, ce qui en fait un mécanisme antagoniste, dont on peut contrôler la raideur. Les pièces structurelles (barres, supports, tambours) sont imprimées en 3D en ABS. Chaque liaison pivot entre les barres et les axes est construite avec deux roulements qui assurent un centrage long, et toutes les pièces sont arrêtées axialement avec des colliers d'arbre. Nous avons décidé d'avoir une lon-gueur de barre transversale de 100 mm et une longueur de barre supérieure de 50 mm. Ces dimensions sont adaptées à plusieurs jeux de ressorts disponibles, c'est-à-dire que les ressorts considérés sont tou-jours en tension et ne sont pas trop étendus pour toutes les positions accessibles du manipulateur. Une fois la longueur et la raideur du ressort définies, le modèle statique est calculé afin d'obtenir la force d'entrée maximale pour les câbles. Cette force doit être suffisante pour actionner le mécanisme dans un grand espace de travail et pour résister aux chargements externes. La force appliquée par les câbles est directement liée au rayon du tambour et au couple du moteur. Le rayon du tambour influe également sur la vitesse de translation du câble. Un compromis est fait pour avoir des efforts et vitesses de câbles suffisants. Deux variateurs interagissent avec un microprocesseur sur lequel est programmé la loi de commande. Chaque moteur est équipé d'un codeur pour connaître la position réelle du mécanisme. Le bon compor-tement du mécanisme est assuré par une commande dynamique