The kinematic preshaping of triggered self-adaptive linkage-driven robotic fingers

In this paper, the issue of the kinematic - as opposed to dynamic - preshaping of self-adaptive robotic fingers driven by linkages is discussed. A method to obtain designs of these fingers capable of various behaviours during their closing motions is presented. The method is based on using triggered passive elements in carefully selected joints of the finger and the selection or optimization of geometric parameters to obtain particular kinematic relationships between the motions of the phalanges. This method is very general and can be applied to any self-adaptive robotic finger in order to obtain many different types of closing motions. Examples given in this paper are focusing on two different preshaping motions, the first one aims at allowing pinch grasps while the second mimics a human finger. The fundamental aim of this paper is to show that various preshapings of self-adaptive fingers are possible, not just one, and to give two step-by-step examples

Body Design Of Tendon-Driven Jumping Robot Using Single Actuator And Wire Set

Although a mechanism in which a single actuator and a wire passing through pulleys drive the joints is a strong candidate for realizing the dynamic behavior because of its appropriate weight and simple mechanism, the problem arises that the position of the pulley influences the dynamic behavior. This paper is focused on vertical jumping. In our research, we searched an appropriate set of positions of a pulley considering the practical development of the robot and derived the relationship between the position of the pulley and the force on the tips of the robot’s foot for jumping. Simulation results suggest the possibility that some sets of positions allow an error in the attachment of the pulley, and the derived relationship indicates that the ratio of the pulling force of wire and vertical force on the ground strongly constrain the position of the pulley

Conception de systèmes mécaniques auto-adaptatifs pour la locomotion

RÉSUMÉ Les mécanismes auto-adaptatifs (ou sous-actionnés) permettent d’accomplir des tâches complexes en utilisant un nombre minimal d’actionneurs. Leur caractéristique principale est la division de l’actionnement, à l’aide de mécanismes souvent différentiels, entre plusieurs mouvements de sortie dont la séquence de déclenchement peut être contrôlée à l’aide d’éléments passifs. Actuellement, ils sont majoritairement employés pour fabriquer des doigts ou de mains robotiques capables de s’adapter mécaniquement à la forme de l’objet à saisir, sans utiliser de contrôle en boucle fermée. Il est ainsi possible d’effectuer des économies substantielles en générant de manière purement mécanique un comportement qui nécessiterait autrement un grand nombre de moteurs et de capteurs. Dans ce projet, deux thèmes distincts, liés à l’application de cette philosophie de conception au domaine de la locomotion, sont explorés avec comme but principal de transférer l’expertise développée avec les doigts auto-adaptatifs vers de nouveaux cas d’utilisation. En premier lieu, un mécanisme de patte mécanique à deux degrés de liberté, actionné par un seul moteur, a été développé. En cas de collision avec un obstacle durant la phase de vol, le ratio de transmission de l’actionnement est altéré, combinant ainsi les deux degrés de liberté pour permettre à la patte de glisser le long de l’obstacle à la recherche d’un nouveau point d’appui. Ce mécanisme a été analysé en profondeur, notamment par le biais de la théorie des visseurs, afin de quantifier sa capacité d’adaptation. Il a ensuite été possible de procéder à une optimisation multi-objectifs visant à mettre en évidence le compromis entre les capacités d’adaptation de la patte et la qualité de la trajectoire générée. La validation expérimentale de ce mécanisme est également présentée. Le second thème relève du domaine de la réadaptation. Le mécanisme développé correspond à celui d’une orthèse entièrement passive, capable de générer des couples correcteurs sur les articulations de la hanche et du genou. Pour ce faire, un système de poulies non-circulaires et de câbles relie les rotations de ces deux articulations à l’allongement de deux ressorts. La synthèse des profils des poulies, par le biais d’une méthode graphique innovante, est décrite, de même que les résultats expérimentaux obtenus à l’aide du prototype réalisé. Les travaux réalisés dans le cadre du présent projet ont par ailleurs mené à d’autres contributions dans le domaine des poulies non-circulaires, soit un mécanisme d’équilibrage statique et un autre permettant de guider une plateforme suspendue le long d’une trajectoire de type « pick-and-place ».----------ABSTRACT Self-adaptive mechanisms (also referred to as underactuated) allow to perform complex tasks using only a minimal number of actuators. Their main characteristic is their ability to distribute actuation, often using differential mechanisms, between several output motions which can be triggered sequentially through the use of passive elements. As of now, they are mostly used in fingers and hands able to mechanically adapt to the shape of the grasped object, without relying on closed-loop control. Indeed, they allow for significant cost savings by generating purely mechanically a behavior which would otherwise require several motors and sensors. In this project, two separate themes, both linked to the application of this design philosophy to the field of locomotion, are explored. The main goal is to transfer existent expertise developed for self-adaptive fingers to new use cases. First, a two degree of freedom mechanical leg, driven by a single motor, has been developed. In case of an unexpected collision with an obstacle during the swing phase, the actuation transmission ratios are altered, thus combining both degrees of freedom to generate a sliding motion along the obstacle in search of the next foothold. This mechanism is here analyzed in depth through the application of screw theory, in order to quantify this adaptation capability. A multi-objective optimization was subsequently performed to highlight the trade-off between the mechanism’s adaptation to obstacles and the quality of the generated leg endpoint trajectory. Experimental results validating the increased reachable ground clearance for the proposed linkage are provided. The second theme belongs to the field of rehabilitation. The developed mechanism is a fully passive orthosis able to generate correcting torques to the hip and knee joints of the leg. This behavior is obtained by relating the elongations of two springs to these articular rotations by the means of cables and non-circular pulleys. The synthesis of the pulley profiles, through an innovative graphical method, as well as initial experimental results are presented. This project has also yielded relevant contributions to the field of non-circular pulleys, with one mechanism developed to achieve static balancing of a pendulum, and another guiding a suspended platform through a pick-and-place trajectory

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In this paper we discuss the design of the 100G capturing robot from the point of view of dynamic pre-shaping where all finger links make contact with the target object simultaneously. After briefly explaining the overview of the 100G capturing robot, we mathematically formulate the dynamic pre-shaping problem where we discuss how to determine the mechanical parameters, such as pulley positions, pulley radius, mass of finger link, and spring constant. We show a couple of experiments where the robot parameter is determined based on the dynamic pre-shaping problem. KEY WORDS—high speed capturing, wire drive robot, mechanism design, preshaping 1