Visual cues have previously been classified as visual exproprioceptive, when defining the relative position of the body within the environment and are continuously updated while moving (online), and visual exteroceptive when describing static features of the environment which are typically elaborated offline (feedforward). However peripheral visual cues involved in the control of movement have not previously been clearly defined using this classification. Hence the role played by peripheral visual cues in the planning and/or online control of movement remains unclear. The aim of this thesis was to provide a systematic understanding of the importance of peripheral visual cues in several types of movement, namely overground locomotion, adaptive gait, postural stability and reaching and grasping. 3D motion capture techniques were used to collect limb and whole body kinematics during such movements. Visual peripheral cues were manipulated by visual field occlusion conditions or by the employment of point-lights in a dark room. Results showed that the visual cues provided by different parts of the peripheral visual field are mainly used for online fine tuning of limb trajectory towards a target (either a floor-based obstacle or an object to grasp). The absence of peripheral visual cues while moving disrupted the spatio-temporal dynamic relationship between subject and target and resulted in increased margins of safety between body and target and increased time and variability of several dependent measures. These findings argue in favour of the classification of peripheral visual cues as visual exproprioceptive.

Imagine that a robot fetched this thesis for you from a book shelf. How doyou think the robot would have been programmed? One possibility is thatexperienced engineers had written low level descriptions of all imaginabletasks, including grasping a small book from this particular shelf. A secondoption would be that the robot tried to learn how to grasp books from yourshelf autonomously, resulting in hours of trial-and-error and several bookson the floor.In this thesis, we argue in favor of a third approach where you teach therobot how to grasp books from your shelf through grasping by demonstration.It is based on the idea of robots learning grasping actions by observinghumans performing them. This imposes minimum requirements on the humanteacher: no programming knowledge and, in this thesis, no need for specialsensory devices. It also maximizes the amount of sources from which therobot can learn: any video footage showing a task performed by a human couldpotentially be used in the learning process. And hopefully it reduces theamount of books that end up on the floor. This document explores the challenges involved in the creation of such asystem. First, the robot should be able to understand what the teacher isdoing with their hands. This means, it needs to estimate the pose of theteacher's hands by visually observing their in the absence of markers or anyother input devices which could interfere with the demonstration. Second,the robot should translate the human representation acquired in terms ofhand poses to its own embodiment. Since the kinematics of the robot arepotentially very different from the human one, defining a similarity measureapplicable to very different bodies becomes a challenge. Third, theexecution of the grasp should be continuously monitored to react toinaccuracies in the robot perception or changes in the grasping scenario.While visual data can help correcting the reaching movement to the object,tactile data enables accurate adaptation of the grasp itself, therebyadjusting the robot's internal model of the scene to reality. Finally,acquiring compact models of human grasping actions can help in bothperceiving human demonstrations more accurately and executing them in a morehuman-like manner. Moreover, modeling human grasps can provide us withinsights about what makes an artificial hand design anthropomorphic,assisting the design of new robotic manipulators and hand prostheses. All these modules try to solve particular subproblems of a grasping bydemonstration system. We hope the research on these subproblems performed inthis thesis will both bring us closer to our dream of a learning robot andcontribute to the multiple research fields where these subproblems arecoming from. / QC 20111125

Made available in DSpace on 2016-06-02T20:19:12Z (GMT). No. of bitstreams: 1 2366.pdf: 2836882 bytes, checksum: 830fbd790291a65c5a129b167567f963 (MD5) Previous issue date: 2009-03-04 / Universidade Federal de Minas Gerais / The acquisition and the refinement of motor skills have been described to require a reciprocal relationship between organismic and environmental conditions. This interaction is evidenced in studies identifying the impact of intrinsic and extrinsic factors on functional skills such as reaching and grasping objects. Thus, Study 1 was conducted in order to review the research on factors influencing reaching and grasping in infants at risk for developmental delays. The review has shown that few studies have aimed to understand the development of actions performed by Down syndrome (DS) infants, and also that there is a lack of information about these infants abilities to adjust their intrinsic properties to environmental demands. Consequently, two studies have been carried out. Study 2 aimed to describe the kinematic characteristics of reaching movements in 4-6-month-old DS infants and to test the influence of intrinsic factors, namely Down syndrome and gross motor skill level, on reaching and grasping behaviors. Seven infants with DS and seven infants with typical development (TD) were assessed at 4, 5 and 6 months-old. Gross motor skill was assessed by using Alberta Infant Motor Scale (AIMS). Infants were placed in a baby chair reclined 50º from the horizontal. A soft object (12.5 cm in diameter) was presented at infant s midline, shoulders height, and arm s length. The following variables were analyzed: straightness index (SI), mean velocity, movement units, deceleration time and grasping frequency. DS infants demonstrate variability in the age of reaching acquisition. The DS and the level of gross motor skills were found to influence grasping frequency. Faced with a task that did not impose excessive demand, kinematic characteristics of reaching in DS infants were quite similar to typical infants, except for the number of movement units at 5 months, which was higher for DS infants, and for SI at 6 months, which was lower for these infants. On the other hand, grasping frequency was lower for DS infants. In order to understand DS infants ability to reach for and grasp objects of different sizes, Study 3 was carried out. Grasping and kinematic characteristics of reaches performed by the same infants for large and small objects were analyzed. These reaches were recorded during the same experimental procedure of Study 2. The object size has induced kinematic changes in reaches performed by DS infants, what suggests that they are exploring strategies to move. The adoption of variable movement strategies suggests perception of affordances of the objects. Nevertheless, DS infants failed to grasp the object, which may indicate that they need more experience in the task in order to adapt their actions to their intrinsic constraints. The results of this study point to the importance of considering the individual variability and the confluence of multiple factors in the development of reaching and grasping, since the organismic conditions in interaction with the task demands, were found to influence reaching and grasping performance. / A aquisição e refinamento de habilidades motoras envolvem uma relação recíproca entre o organismo e o ambiente. O efeito de tal interação pode ser evidenciado a partir de estudos que identifiquem o impacto de fatores intrínsecos e extrínsecos em habilidades funcionais como o alcance e apreensão de objetos. Dessa forma, foi desenvolvido o Estudo 1, com o intuito de revisar as pesquisas sobre os fatores que influenciam os movimentos de alcance e apreensão em lactentes expostos a risco para atraso no desenvolvimento. A partir dos resultados evidenciados, de que poucos estudos buscaram compreender organização das ações de lactentes com síndrome de Down (SD), em especial considerando as capacidades do organismo em ajustar-se perante informações do ambiente, foram desenvolvidos mais dois estudos. O Estudo 2 visou verificar as características cinemáticas do alcance manual de lactentes com SD de 4 a 6 meses e verificar a influência dos fatores intrínsecos síndrome de Down e nível de habilidade motora grossa nas habilidades de alcance e apreensão. Foram avaliados mensalmente 7 lactentes típicos (LT) e 7 lactentes com SD, dos 4 aos 6 meses de vida. O nível de habilidade motora grossa foi avaliado segundo a Alberta Infant Motor Scale (AIMS). Em seguida, os lactentes foram posicionados em uma cadeira infantil reclinada a 50º e foi apresentado um objeto na linha média do corpo a uma distância alcançável. Foram analisadas as variáveis cinemáticas índice de retidão (IR), velocidade média, unidades de movimento e tempo de desaceleração e a freqüência de apreensão do objeto. Constatou-se que os lactentes com SD apresentam variabilidade na idade de realização do alcance manual. A SD e o nível de habilidade motora grossa foram fatores intrínsecos que afetaram a tarefa de apreender o objeto. Diante de uma tarefa que não impôs excessiva demanda, os movimentos de alcance dos lactentes com SD não apresentaram características cinemáticas expressivamente diferentes dos lactentes típicos. Foram encontradas diferenças apenas no número de unidades de movimento aos 5 meses, que foi maior nos lactentes com SD, e no IR aos 6 meses de idade, que foi inferior nos mesmos lactentes. Além disso, verificou-se menor sucesso na apreensão dos objetos nos lactentes com SD. Com o intuito de compreender a capacidade de tais lactentes em alcançar e apreender o objetos de diferentes tamanhos, foi desenvolvido o Estudo 3. Dados adicionais coletados durante o procedimento experimental do estudo anterior foram analisados, desta vez sendo apresentados objetos grandes e pequenos. Os lactentes com SD apresentaram diferenças cinemáticas no alcance com relação a lactentes típicos ao alcançar objetos de diferentes tamanhos, o que sugere que estão explorando estratégias de movimento. A adoção de estratégias diferenciadas sugere percepção das affordances dos objetos, no entanto, como se observou pequena freqüência de apreensões dos objetos, acredita-se que os lactentes com SD estão explorando as possibilidades de ação, e podem necessitar mais tempo de experiência na tarefa a fim de adaptar as ações perante suas restrições intrínsecas. Os resultados do presente trabalho apontam para a importância de contemplar a variabilidade individual e a confluência de múltiplos fatores no desenvolvimento das habilidades de alcance e apreensão, visto que as capacidades orgânicas do indivíduo, em interação com as demandas da tarefa, influenciaram o desempenho nas tarefas de alcançar e apreender.

Made available in DSpace on 2016-06-02T20:19:18Z (GMT). No. of bitstreams: 1 4366.pdf: 1667152 bytes, checksum: e2c5f2da90a5571724bcc0550299f17d (MD5) Previous issue date: 2012-02-29 / Financiadora de Estudos e Projetos / Research has shown that bimanual actions are demonstrative of the functional brain development; thus it is relevant to investigate how interlimb coordination develops in typically-developing infants, as well as in infants with impaired brain organization, such as in the presence of Down syndrome (DS). Objectives: The aims of this study were as follows: 1) to study the development of interlimb coordination in typically-developing infants (TD) and in infants with DS while reaching and grasping objects with different sizes; and 2) to investigate changes in the interlimb relations during the stages after reaching emergence. Methods: Reaching movements performed by 8 TD infants and 7 infants with DS were monthly recorded between the ages of 4 and 8 months. The frequency of categories used during movement initiation, object touching and grasping; the frequency of reaching and the contribution of each arm were calculated. The effects of object size and of the time after reaching onset were analyzed in intra- and inter-group comparisons. Results: TD infants were able to change the configurations used in the movement initiation, object touching and grasping; their interlimb coordination changed from synchronic reaches to asynchrony or unimanual trajectories, based on object properties. Infants with DS only changed their grasping configurations; the strategies they used were not optimally adjusted to object properties; difficulties to grasp the objects were also evident. Conclusions: With the experience in reaching, interlimb coordination in TD infants is increasingly modulated by object properties in an anticipatory way. Infants with DS seem to need a longer time to use sensory information and to modulate reaching and grasping configurations. / Ações bimanuais refletem o desenvolvimento funcional de áreas cerebrais, assim, é necessário compreender o desenvolvimento da coordenação intermembros em lactentes típicos (LT) e com alterações na organização cerebral, como na síndrome de Down (SD). OBJETIVO: Estudar o desenvolvimento da coordenação intermembros em LT e com SD ao alcançar e apreender objetos distintos e identificar se há mudanças nas relações intermembros nos períodos após a aquisição do alcance. MÉTODOS: Oito LT e sete lactentes com SD com idade de 4 a 8 meses foram posicionados em uma cadeira infantil e objetos grandes e pequenos foram apresentados por 1 minuto cada. Foi calculada a frequência das variáveis categoriais adotadas no início e trajetória, toque e apreensão do objeto. O efeito do tamanho dos objetos e do tempo após a aquisição do alcance foi analisado nas comparações intra e entre grupos. RESULTADOS: LT mudaram as configurações de início, toque e apreensão do objeto nos períodos após a aquisição do alcance, evoluindo de movimentos sincrônicos para trajetórias assincrônicas ou unimanuais, atendendo às propriedades dos objetos. Lactentes com SD mudaram apenas as configurações de apreensão, apresentando estratégias menos ajustadas aos objetos e dificuldades para apreender os mesmos. CONCLUSÃO: Ao longo da experiência de alcançar, a coordenação intermembros em LT é modificada e progressivamente modulada pelas propriedades dos objetos de maneira antecipatória. Lactentes com SD parecem necessitar de mais tempo para utilizar informações sensoriais e modificar configurações do alcance e apreensão.

In this thesis we study the problem of robotic interaction with objects from a flexible perspective that complements the rigid force-closure approach. In a flexible interaction the object is not firmly bound to the robot (immobilized), which leads to many interesting scenarios. We focus on the secure kind of flexible interactions, commonly referred to as caging grasps. In this context, the adjective secure implies that the object is not able to escape arbitrarily far away from the robot which is caging it. A cage is a secure flexible interaction because it does not immobilize the object, but restricts its motion to a finite set of possible configurations. We study cages in two novel scenarios for objects with holes: caging through multi-agent cooperation and through dual-arm knotting with a rope. From these two case studies, we were able to analyze the caging problem in a broader perspective leading to the definition of a hierarchical classification of flexible interactions and cages. In parallel to the geometric and physical problem of flexible interactions with objects, we study also the problem of discrete action scheduling through a novel control architecture called Behavior Trees (BTs). In this thesis we propose a formulation that unifies the competing BT philosophies into a single framework. We analyze how the mainstream BT formulations differ from each other, as well as their benefits and limitations. We also compare the plan representation capabilities of BTs with respect to the traditional approach of Controlled Hybrid Dynamical Systems (CHDSs). In this regard, we present bidirectional translation algorithms between such representations as well as the necessary and sufficient conditions for translation convergence. Lastly, we demonstrate our action scheduling BT architecture showcasing the aforementioned caging scenarios, as well as other examples that show how BTs can be interfaced with other high level planners. / <p>QC 20170322</p>

Disposer d’un modèle numérique de doigt permettant de simuler le contact de façon réaliste serait un atout pour les domaines d’applications de la réalité virtuelle et de l’aide à la conception adaptée de matériel. De plus, savoir simuler un contact « biofidèle » entre les doigts et un objet permettrait de répondre à des questions de recherche fondamentale concernant la préhension (évaluation de la qualité d’une prise, choix de stratégies de préhension…).Les modèles existants dans la littérature sont variés en termes de propriétés matériaux et de géométrie mais aucun modèle ne s’impose pour prédire de façon satisfaisante le comportement mécanique de la pulpe des doigts. Cette thèse a pour objectif de proposer des lignes directrices pour le développement d’un modèle éléments finis de l’extrémité du doigt orienté vers la simulation de la manipulation fine.Dans un premier temps, la loi de comportement la plus simple possible mais rendant bien compte du comportement hyperélastique des tissus est identifiée. Ensuite, l’étude de modèles géométriques simplifiés permet de proposer un jeu de marqueurs géométriques permettant de construire un modèle idéalisé. Enfin, une campagne expérimentale innovante de chargements mécaniques sur le doigt sous IRM (8 sujets) permet d’enrichir la base de données des essais existants et de valider les hypothèses de modélisation faites en termes de loi de comportement et de géométrie / A fingertip model enabling realistic contact simulations would be an attractive feature in the virtual reality field and could help the design process of new products. Furthermore, such a tool would allow investigating fundamental research questions associated with prehension (assessment of the efficiency of a grasp, choice of a grasping strategy,…).Existent fingertip models exhibit various material properties and geometries but none of them stand out in the prediction of the mechanical behavior of the fingertip.The main topic of this PhD work is to propose general guidelines for the development of fingertip models dedicated to fine manipulation tasks. First a hyperslastic behavior law is identified, being both as simple as possible and enough complex to reproduce the non-linear behavior of the soft tissue. Then, a geometrical study permits to determine a set of geometric markers enabling the development of an idealized geometrical model. Finally, an MRI innovative experimental campaign of fingertip loading tests is performed (on 8 subjects) to expand the existent experimental database and validate the modeling assumptions made concerning the behavior law and the geometrical approach

La manipulation dextre est un sujet important dans la recherche en robotique et dans lequel peu de travaux ont abordé la manipulation d'objets déformables. De nouvelles applications en chirurgie, en industrie agroalimentaire ou encore dans les services à la personne nécessitent la maîtrise de la saisie et la manipulation d'objets déformables. Cette thèse s’intéresse à la manipulation d’objets déformables par des préhenseurs mécaniques anthropomorphiques tels que des mains articulées à plusieurs doigts. Cette tâche requière une grande expertise en modélisation mécanique et en commande : modélisation des interactions, perception tactile et par vision, contrôle des mouvements des doigts en position et en force pour assurer la stabilité de la saisie. Les travaux présentés dans cette thèse se focalisent sur la modélisation de la saisie d'objets déformables. Pour cela, nous avons utilisé une discrétisation par des systèmes masses-ressorts non-linéaires pour modéliser des corps déformables en grands déplacements et déformations tout en ayant un coût calculatoire faible. Afin de prédire les forces d’interactions entre main robotique et objet déformable, nous avons proposé une approche originale basée sur un modèle rhéologique visco-élasto-plastique pour évaluer les forces tangentielles de contact et décrire la transition entre les modes d’adhérence et de glissement. Les forces de contact sont évaluées aux points nodaux en fonction des mouvements relatifs entre les bouts des doigts et les facettes du maillage de la surface de l’objet manipulé. Une autre contribution de cette thèse consiste à utiliser de cette modélisation dans la planification des tâches de manipulation d’objets déformables 3D. Cette planification consiste à déterminer la configuration optimale de la main pour la saisie de l’objet ainsi que les trajectoires à suivre et les efforts à appliquer par les doigts pour contrôler la déformation de l’objet tout en assurant la stabilité de l’opération. La validation expérimentale de ces travaux a été réalisée sur deux plateformes robotiques : une main Barrett embarquée sur un bras manipulateur Adept S1700D et une main Shadow embarquée sur un bras manipulateur Kuka LWR4+. / Dexterous manipulation is an important issue in robotics research in which few works have tackled deformable object manipulation. New applications in surgery, food industry or in service robotics require mastering the grasping and manipulation of deformable objects. This thesis focuses on deformable object manipulation by anthropomorphic mechanical graspers such as multi-fingered articulated hands. This task requires a great expertise in mechanical modeling and control: interaction modeling, tactile and vision perception, force / position control of finger movements to ensure stable grasping. The work presented in this thesis focuses on modeling the grasping of deformable objects. To this end, we used a discretization by non-linear mass-spring systems to model deformable bodies in large displacements and deformations while having a low computational cost. To predict the interaction forces between robot hand and deformable object, we proposed an original approach based on a visco-elasto-plastic rheological model to evaluate tangential contact forces and describe the transition between the sticking and slipping modes. The contact forces are evaluated at nodes as function of the relative movements between the fingertips and the surface mesh facets of the manipulated object. Another contribution of this thesis is the use of this model in the planning of 3D deformable object manipulation tasks. This planning consists in determining the optimal configuration of the hand for grasping the objects as well as the paths to track and the efforts to be applied by the fingers to control the deformation of the object while ensuring the stability of the operation. The experimental validation of this work has been carried out on two robotic platforms: a Barrett hand embedded on a Adept S1700D ® manipulator and a Shadow hand embedded on a Kuka LWR4+® manipulator.

In der vorliegenden Arbeit wurde eine vergleichende Analyse der Hand- und Armfunktion von gesunden rechtshändigen alten und jungen Personen vorgenommen und dabei insbesondere der modulare Aufbau von Greifmustern analysiert. Es wurden vier Handfunktionstests durchgeführt: eine Tapping-Aufgabe an einer Computertastatur, eine Handkraftmessung mit dem Martin-Vigori-meter, der Jebsen-Taylor Test of Hand Function und eine standardisierte Greifaufgabe nach vier Greifobjekten (Münze, Kronkorken, kleine Dose, große Dose) mit Aufzeichnung der Handbewe-gungen mit einem Sensorhandschuh (Wü-Glove) und der Armbewegungen mit ultraschallemittierenden Markern. Die Auswertung der Greifaufgabe erfolgte zum einen nach kinematischen Aspekten (Dauer, maximale Geschwindigkeit, maximale Beschleunigung), zum anderen wurde mittels Hauptkomponentenanalyse der modulare Aufbau von Greifmustern untersucht und mittels Ähnlichkeitsanalysen (u.a. Mahalanobis-Distanz) die Finger- und Armkonfigurationen bei Objektkontakt verglichen. Daten von 66 Probanden wurden ausgewertet. Vollständige Datensätze lagen von 10 jungen (20-33 J.) und 10 alten (61-85 J.) Probanden vor. Junge Probanden zeigten erwartungsgemäß eine größere Handkraft und Fingerschnelligkeit und eine bessere Leistung im Jebsen-Taylor Test of Hand Function. Die Greifmuster der älteren Probanden waren verglichen mit den jungen Probanden interindividuell variabler, gleichzeitig aber ökonomischer organisiert. Diese ökonomischere Organisation kann als Folge impliziter Lernprozesse bei individuell unterschiedlichen Greiferfahrungen in Abhängigkeit des Alters gedeutet werden. Zunehmendes Lebensalter muss somit nicht nur mit einer Abnahme motorischer Funktionen verbunden sein, sondern kann auch positive Auswirkungen auf die Steuerung der Handfunktion in Form einer Optimierung von Greifmustern durch implizite Expertise haben.

No description available.

A fundamental aspect to consider in factories is the transportation of the items at differentsteps in the production process. Conveyor belts do a great to bring items from point A topoint B but to load the item onto a working station it can demands a more precise and,in some cases, delicate approach. Nowadays this part is mostly handled by robotic arms.The issue encountered is that a robot arm extremity, its gripper, cannot directly instinctivelyknow how to grip an object. It is usually up to a technician to configure how andwhere the gripper goes to grip an item.The goal of this thesis is to analyse a problem given by a company which is to find a wayto automate the grasp pose synthesis of a new object with the adapted gripper.This automatized process can be separated into two sub-problems.First, how to choose the adapted gripper for a new object.Second, how to find a grasp pose on the object, with the previously chosen gripper.In the problem given by the company, the computer-aided design (CAD) 3D model of theconcerned object is given. Also, the grasp shall always be done vertically, i.e., the grippercomes vertically to the object and the gripper does not rotate on the x and y axis. Thegripper for a new object is selected between two kinds of grippers: two-finger paralleljawgripper and three-finger parallel-jaw gripper. No dataset of objects is provided.Object grasping is a well researched subject, especially for 2 finger grippers. However,few research is done for the 3 finger grippers grasp pose synthesis, or for gripper comparison,which are key part of the studied problem.To answer the sub-problems mentioned above, machine learning will be used for the gripperselection and a grasp synthesis method will be used for the grasp pose finding. However,due to the lack of gripper comparison in the related work, a new approach needsto be created, which will be inspired by the findings in the literature about grasp posesynthesis in general.This approach will consist of two parts.First, for each gripper and each object combination are generated some grasp poses, eachassociated with a corresponding score. The scores are used to have an idea of the bestgripper for an object, the best score for each gripper indicating how good a grasp couldbe on the object with said gripper.Secondly, the objects with their associated best score for each gripper will be used astraining data for a machine learning algorithm that will assist in the choice of the gripper.This approach leads to two research questions:“How to generate grasps of satisfying quality for an object with a certain gripper?”“Is it possible to determine the best gripper for a new object via machine learning ?”The first question is answered by using mathematical operations on the point cloud representationof the objects, and a cost function (that will be used to attribute a score), whileithe second question is answered using machine learning classification and regression togain insight on how machine learning can learn to associate object proprieties to gripperefficiency.The found results show that the grasp generation with the chosen cost function givesgrasp poses that are similar to the grasp poses a human operator would choose, but themachine learning models seem unable to assess grasp quality, either with regression orclassification.