1,720,960 research outputs found
Exploiting Adaptability in Soft Feet for Sensing Contact Forces
Full text linkThe large majority of legged robots currently employ ball-feet or flat-feet. More recently soft feet have been introduced, to improve walking performance on uneven grounds. Nevertheless, their novel adaptability requires sensor systems beyond traditional Force/Torque sensors to estimate the distribution of forces on the contact surface. This letter shows how a perception layer realized with Inertial Measurement Units allows a soft foot to reconstruct not only the shape of the foot - hinting at the shape of the ground beneath - but also, under precise hypotheses, the contact force distribution. The problem is theoretically formalized and analysed with a quasi-static approach in the Sagittal plane. Then, theoretical results are experimentally validated in a simplified foot-ground interaction scenario. The force reconstruction provided by the proposed method allows to correctly identify the sole contact location arising from obstacles with radius down to 1 cm
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Mechatronic Modelling, Control and Test of Bipedal Robot Walking on Compliant Feet
No full textThe majority of humanoid robots existing in literature adopt flat feet, a choice that can limit their performance when maneuvering over uneven terrains. Softfoot is a soft robotic foot, inspired to a human foot, that allows greater adaptability to the ground. In the first part of this thesis, carried out at GVLab of Tokyo University of Agriculture and Technology (TUAT), we analyzed the deformation of the plantar fascia of the Softfoot robotic foot, comparing it with the behavior of the human foot. Through Motion Capture it was possible to reconstruct the longitudinal deformation of both types of foot (along the walking direction), and the transverse deformation. We evaluated the adaptability of the robotic foot on obstacles and observed the comparison with the human foot. In the second part of the thesis, carried out at National Institute of Advanced Industrial Science and Technology (AIST), Japan, a soft robotic foot designed to adapt to the ground was proposed to overcome part of these limitations. This thesis presents the results of testing two such feet on the humanoid robot HRP-4, and compares them to what obtained with the original flat feet of the robot. After describing the soft foot and how it has been adapted to the robot, the biped is tested while balancing, stepping and walking. Tests are carried out on flat ground and on obstacles of different heights. For comparison purposes, the original HRP-4 controller has been used for both types of feet (except for re-evaluation of the CoM position). Analysis of the ankle pitch angle, ankle pitch torque, waist roll angle and waist pitch angle, show a substantial improvement in obstacle negotiation performance of HRP-4, when using the Softfoot, even without optimizing the controller to exploit the Softfoot features. Finally, in the last part, a static mathematical model was developed to reconstruct not only the shape of the foot, hinting at the shape of the ground beneath, but also, under precise hypotheses, the contact force distribution. The problem is theoretically formalized and analyzed in the simplified scenario derived from considering only the effects on the sagittal plane. Then, theoretical results are experimentally validated
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Semelle à rigidité variable en matériau souple pour robot humanoïdepour marcher sur des terrains irréguliers non coplanaires
No full textMarcher sur des terrains accidentés avec des humanoïdes est un défi de taille qui nécessite d'aborder divers aspects techniques et mécaniques pour assurer une locomotion sûre et stable.Dans cette thèse, nous abordons le problème du développement de solutions pour la marche humanoïde sur des terrains accidentés. Il s'agit d'un problème complexe impliquant plusieurs éléments : perception du terrain, stratégies de locomotion adaptatives, optimisation de la conception des pieds et des jambes et contrôle en temps réel et planification.Le développement d'un système de perception pour comprendre les caractéristiques des terrains, dont les variations d'élévation, de pente et de rugosité de la surface, est essentiel pour permettre au robot de naviguer efficacement sur ce type de terrains. Des stratégies de locomotion adaptatives permettant au robot d'ajuster dynamiquement le placement de ses pieds en fonction des conditions du terrain sont essentielles pour maintenir la stabilité et l'équilibre. Le développement de conceptions de pieds ou de jambes intégrant des matériaux souples et flexibles pour améliorer l’absorption des chocs sur des surfaces inégales est crucial pour garantir une locomotion sûre et efficace. La mise en œuvre d'algorithmes de contrôle et de planification en temps réel qui permettent au robot d'ajuster dynamiquement sa trajectoire de marche ou la pose de ses pieds pour naviguer sur des terrains complexes tout en assurant une locomotion fluide et continue.Pour la marche sur des terrains irréguliers non coplanaires, nous proposonsune solution comprenant plusieurs directions: perception du terrain; amélioration matériel avec des pieds humanoïdes à rigidité variable en fonction de la rugosité du sol; et amélioration du côté contrôle en développant des algorithmes qui ajustent le placement des pieds du robot selon la perception du sol.Concernant les résultats, à partir de l'analyse de simulation, nous démontrons que la modification de la rigidité des pieds humanoïdes par rapport à la rugosité du sol pendant la marche améliore la stabilité sur différents types de terrains, avec des roches, des obstacles et des graviers de différentes formes et hauteurs.Pour la perception du terrain, nous utilisons deux caméra stéréo-profondeur adaptés aux courtes distances, une pour chaque pied. Nous avons pu reconstruire en temps réel le profil du terrain lors de la marche pour chacun des pieds.Pour le côté hardware, nous concevons une structure souple, pneumatique, à rigidité variable. Cette structure constitue l'ossature de base d'une semelle pneumatique à rigidité variable pour humanoïdes. La rigidité variable est obtenue en mettant sous pression une paire de structures de type PneuNet placées de manière antagoniste. Nous proposons un procédé pour fabriquer une telle structure en combinant des techniques de moulage par insert et par injection à noyau perdu. Nous développons une méthode de contrôle de la pression de l'air et d'un modèle qui relie la pression et la rigidité en flexion que nous validons expérimentalement.Cette structure pneumatique souple est un sous-système de la semelle complète pour preuve de concept. Nous fabriquons actuellement la semelle complète de l'humanoïde.Pour le contrôle, nous introduisons un nouvel algorithme permettant de calculer avec précision l'angle et la position d'atterrissage du pied en fonction de la perception du terrain, afin d'améliorer la stabilité et l'équilibre pendant la locomotion. Cette planification de la pose du pied est basée sur un modèle conforme au pied, avec des éléments viscoélastiques entre dix blocs rigides. Nous testons l'algorithme en simulation et sur un vrai robot humanoïde. Les résultats démontrent l'efficacité exceptionnelle de l'algorithme pour réduire les cas de chutes de robots et améliorer la stabilité globale pendant la marche, ouvrant la voie à des conceptions de robots humanoïdes plus robustes et plus fiables dans des environnements dynamiques.Walking on uneven terrains with humanoids is a significant challenge that requires addressing various technical and mechanical aspects to ensure safe and stable locomotion.In this thesis, we address the problem of developing solutions for humanoid walking on uneven terrains is complex because involves several elements: terrain perception and mapping, adaptive locomotion strategies, foot and leg design optimization, real-time control, and planning.More in detail, developing a robust perception system to accurately detect and map the terrains' characteristics, including variation in elevation, slope, and surface roughness, is essential for enabling the robot to navigate uneven terrains effectively. Also, implementing adaptive locomotion strategies that allow the robot to dynamically adjust its gait and foot placement based on challenging terrain conditions is critical for maintaining stability and balance. Moreover, developing foot or leg designs that incorporate compliant and flexible materials to enhance shock absorption on uneven surfaces is crucial for ensuring safe and efficient locomotion. Finally, implementing real-time control and planning algorithms that enable the robot to dynamically adjust its walking trajectory or foot pose to navigate complex and challenging terrains while ensuring smooth and continuous locomotion.In order to face the problem of walking on uneven no-coplanar terrains, we proposea solution in multiple directions: ground scanning to detect terrains' characteristics, improving the hardware side with variable stiffness humanoid feet depending on ground roughness, and improving the control side by developing algorithms that adjust the robot's feet placement based on ground conditions for maintaining stability during walking.Regarding the results, starting from simulation analysis, we demonstrate that changing the stiffness of humanoid feet in conjunction with the ground roughness during the walk, improves the stability in different types of grounds, with rocks, obstacles, and gravels of different shapes and heights.For terrain perception, we use two stereo-depth camera sensors tailored for short distances, one for each foot. Here we were able to reconstruct the ground profile online during the walking for each of the feet proposing a solution to compensate the error of the foot pose estimation.For the hardware side, we design a pneumatic variable stiffness soft structure, and we manufacture by wax casting. This structure constitutes the basic framework for a pneumatic sole with variable stiffness for humanoids. Here, variable stiffness is obtained by pressurizing a pair of bending-type PneuNet-like structures placed in an antagonistic manner. We propose a process to fabricate a robust variable stiffness structure by combining insert molding and lost-core techniques. We develop the air pressure control method and a model that relates pressure and bending stiffness and we validate with experiments this analytical mode. The results showed fit with the analytical model showing the adequacy of the model.This soft pneumatic structure is a subsystem of the complete sole for the proof of concept. We are now manufacturing the complete sole of the humanoid.For the control side, we introduce a novel algorithm for accurately calculating the foot landing angle and position depending on ground scanning, in order to improve the stability and balance during locomotion and stationary poses. This foot pose planning is based on a foot-compliant model, with visco-elastic elements between ten rigid blocks, following the design of the real humanoid foot. We test the algorithm is tested in simulation and on a real humanoid robot. Results demonstrate the algorithm's exceptional efficacy in reducing instances of robot falls and enhancing overall stability during walking, paving the way for more robust and reliable humanoid robot designs in dynamic environments
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Semelle à rigidité variable en matériau souple pour robot humanoïdepour marcher sur des terrains irréguliers non coplanaires
No full textWalking on uneven terrains with humanoids is a significant challenge that requires addressing various technical and mechanical aspects to ensure safe and stable locomotion.In this thesis, we address the problem of developing solutions for humanoid walking on uneven terrains is complex because involves several elements: terrain perception and mapping, adaptive locomotion strategies, foot and leg design optimization, real-time control, and planning.More in detail, developing a robust perception system to accurately detect and map the terrains' characteristics, including variation in elevation, slope, and surface roughness, is essential for enabling the robot to navigate uneven terrains effectively. Also, implementing adaptive locomotion strategies that allow the robot to dynamically adjust its gait and foot placement based on challenging terrain conditions is critical for maintaining stability and balance. Moreover, developing foot or leg designs that incorporate compliant and flexible materials to enhance shock absorption on uneven surfaces is crucial for ensuring safe and efficient locomotion. Finally, implementing real-time control and planning algorithms that enable the robot to dynamically adjust its walking trajectory or foot pose to navigate complex and challenging terrains while ensuring smooth and continuous locomotion.In order to face the problem of walking on uneven no-coplanar terrains, we proposea solution in multiple directions: ground scanning to detect terrains' characteristics, improving the hardware side with variable stiffness humanoid feet depending on ground roughness, and improving the control side by developing algorithms that adjust the robot's feet placement based on ground conditions for maintaining stability during walking.Regarding the results, starting from simulation analysis, we demonstrate that changing the stiffness of humanoid feet in conjunction with the ground roughness during the walk, improves the stability in different types of grounds, with rocks, obstacles, and gravels of different shapes and heights.For terrain perception, we use two stereo-depth camera sensors tailored for short distances, one for each foot. Here we were able to reconstruct the ground profile online during the walking for each of the feet proposing a solution to compensate the error of the foot pose estimation.For the hardware side, we design a pneumatic variable stiffness soft structure, and we manufacture by wax casting. This structure constitutes the basic framework for a pneumatic sole with variable stiffness for humanoids. Here, variable stiffness is obtained by pressurizing a pair of bending-type PneuNet-like structures placed in an antagonistic manner. We propose a process to fabricate a robust variable stiffness structure by combining insert molding and lost-core techniques. We develop the air pressure control method and a model that relates pressure and bending stiffness and we validate with experiments this analytical mode. The results showed fit with the analytical model showing the adequacy of the model.This soft pneumatic structure is a subsystem of the complete sole for the proof of concept. We are now manufacturing the complete sole of the humanoid.For the control side, we introduce a novel algorithm for accurately calculating the foot landing angle and position depending on ground scanning, in order to improve the stability and balance during locomotion and stationary poses. This foot pose planning is based on a foot-compliant model, with visco-elastic elements between ten rigid blocks, following the design of the real humanoid foot. We test the algorithm is tested in simulation and on a real humanoid robot. Results demonstrate the algorithm's exceptional efficacy in reducing instances of robot falls and enhancing overall stability during walking, paving the way for more robust and reliable humanoid robot designs in dynamic environments.Marcher sur des terrains accidentés avec des humanoïdes est un défi de taille qui nécessite d'aborder divers aspects techniques et mécaniques pour assurer une locomotion sûre et stable.Dans cette thèse, nous abordons le problème du développement de solutions pour la marche humanoïde sur des terrains accidentés. Il s'agit d'un problème complexe impliquant plusieurs éléments : perception du terrain, stratégies de locomotion adaptatives, optimisation de la conception des pieds et des jambes et contrôle en temps réel et planification.Le développement d'un système de perception pour comprendre les caractéristiques des terrains, dont les variations d'élévation, de pente et de rugosité de la surface, est essentiel pour permettre au robot de naviguer efficacement sur ce type de terrains. Des stratégies de locomotion adaptatives permettant au robot d'ajuster dynamiquement le placement de ses pieds en fonction des conditions du terrain sont essentielles pour maintenir la stabilité et l'équilibre. Le développement de conceptions de pieds ou de jambes intégrant des matériaux souples et flexibles pour améliorer l’absorption des chocs sur des surfaces inégales est crucial pour garantir une locomotion sûre et efficace. La mise en œuvre d'algorithmes de contrôle et de planification en temps réel qui permettent au robot d'ajuster dynamiquement sa trajectoire de marche ou la pose de ses pieds pour naviguer sur des terrains complexes tout en assurant une locomotion fluide et continue.Pour la marche sur des terrains irréguliers non coplanaires, nous proposonsune solution comprenant plusieurs directions: perception du terrain; amélioration matériel avec des pieds humanoïdes à rigidité variable en fonction de la rugosité du sol; et amélioration du côté contrôle en développant des algorithmes qui ajustent le placement des pieds du robot selon la perception du sol.Concernant les résultats, à partir de l'analyse de simulation, nous démontrons que la modification de la rigidité des pieds humanoïdes par rapport à la rugosité du sol pendant la marche améliore la stabilité sur différents types de terrains, avec des roches, des obstacles et des graviers de différentes formes et hauteurs.Pour la perception du terrain, nous utilisons deux caméra stéréo-profondeur adaptés aux courtes distances, une pour chaque pied. Nous avons pu reconstruire en temps réel le profil du terrain lors de la marche pour chacun des pieds.Pour le côté hardware, nous concevons une structure souple, pneumatique, à rigidité variable. Cette structure constitue l'ossature de base d'une semelle pneumatique à rigidité variable pour humanoïdes. La rigidité variable est obtenue en mettant sous pression une paire de structures de type PneuNet placées de manière antagoniste. Nous proposons un procédé pour fabriquer une telle structure en combinant des techniques de moulage par insert et par injection à noyau perdu. Nous développons une méthode de contrôle de la pression de l'air et d'un modèle qui relie la pression et la rigidité en flexion que nous validons expérimentalement.Cette structure pneumatique souple est un sous-système de la semelle complète pour preuve de concept. Nous fabriquons actuellement la semelle complète de l'humanoïde.Pour le contrôle, nous introduisons un nouvel algorithme permettant de calculer avec précision l'angle et la position d'atterrissage du pied en fonction de la perception du terrain, afin d'améliorer la stabilité et l'équilibre pendant la locomotion. Cette planification de la pose du pied est basée sur un modèle conforme au pied, avec des éléments viscoélastiques entre dix blocs rigides. Nous testons l'algorithme en simulation et sur un vrai robot humanoïde. Les résultats démontrent l'efficacité exceptionnelle de l'algorithme pour réduire les cas de chutes de robots et améliorer la stabilité globale pendant la marche, ouvrant la voie à des conceptions de robots humanoïdes plus robustes et plus fiables dans des environnements dynamiques
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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