31 research outputs found

    Perceiving virtual geographic slant: action influences perception

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    technical reportFour experiments varied the extent and nature of observer movement in a virtual environment to examine the influence of action on estimates of geographical slant. Previous slant studies demonstrated that people consciously overestimate hill slant but can still accurately guide an action toward the hill (Proffitt, Bhalla, Gossweiler & Midget, 1995). Related studies (Bhalla & Proffitt, 1999) suggest that one s potential to act may influence perception of slant and that distinct representations may independently inform perceptual and motoric responses. We found that in all conditions, perceptual judgments were overestimated and motoric adjustments were more accurate. The virtual environment allowed manipulation of the effort required to walk up simulated hills. Walking with the effort appropriate to the visual slant led to increased perceptual overestimation of slant compared to active walking with effort appropriate to level ground, while visually guided actions remained accurate

    Ankle-Actuated Human-Machine Interface for Walking in Virtual Reality

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    This thesis work presents design, implementation and experimental study of an impedance type ankle haptic interface for providing users with the immersive navigation experience in virtual reality (VR). The ankle platform enables the use of foot-tapping gestures to reproduce realistic walking experience in VR and to haptically render different types of walking terrains. The system is designed to be used by seated users allowing more comfort, causing less fatigue and motion sickness. The custom-designed ankle interface is composed of a single actuator-sensors system making it a cost-efficient solution for VR applications. The designed interface consists of a single degree of freedom actuated platform which can rotate around the ankle joint of the user. The platform is impedance controlled around the horizontal position by an electric motor and capstan transmission system. to perform walking in a virtual scene, a seated user is expected to perform walking gestures in form of ankle plantar-flexion and dorsiflexion movements causing the platform to tilt forward and backward. We present three algorithms for simulating the immersive locomotion of a VR avatar using the platform movement information. We also designed multiple impedance controllers to render haptic feedback for different virtual terrains during walking. We carried out experiments to understand how quickly users adapt to the interface, how well they can control their locomotion speed in VR, and how well they can distinguish different types of terrains presented through haptic feedback. We implemented qualitative questionnaires on the usability of the device and the task load of the experimental procedures. The experimental studies demonstrated that the interface can be easily used to navigate in VR and it is capable of rendering dynamic multi-layer complex terrains containing structures with different stiffness and brittleness properties

    Principles of energy optimization underlying human walking gait adaptations

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    Learning to move in novel situations is a complex process. We need to continually learn the changing situations and determine the best way to move. Optimization is a widely accepted framework for this process. However, little is known about algorithms used by the nervous system to perform this optimization. Our lab recently found evidence that people can continuously optimize energy during walking. My goal in this thesis is to identify principles of optimization, particularly energy optimization in walking, that govern our choice of movement in novel situations. I used two novel walking tasks for this purpose. For the first task, I designed, built, and tested a mechatronic system that can quickly, accurately, and precisely apply forces to a user’s torso. It changes the relationship between a walking gait and its associated energetic cost—cost landscape—to shift the energy optimal walking gait. Participants shift their gait towards the new optimum in these landscapes. In my second project, I aimed to understand how the nervous system identifies when to initiate optimization. I used my system to create cost landscapes of three different cost gradients. I found that experiencing a steeper cost gradient through natural variability is not sufficient to cue the nervous system to initiate optimization. For my third and fourth projects, I used the task of split-belt walking. I collaborated with another research group to analyse the mechanics and energetics of walking with different step lengths on a split-belt treadmill. I found that people can harness energy from a split-belt treadmill by placing their leading leg further forward on the fast belt, and that there may be an energy optimal gait. In my fourth project, I used computer modelling to identify that there may exist an energy optimal gait due to the trade-off between the cost of swinging the leg and the cost of redirecting the body center of mass when transitioning from step to step. Together, these projects develop a new system and a new approach to understand energy optimization in walking. They uncover principles governing the initiation of this process and our ability to benefit from it

    Master of Science

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    thesisPersons with Parkinson disease (PD) are at risk for fall-related injuries as 60-80% of persons with PD fall annually. Basic treadmill training among other forms of exercise are used to combat the motor symptoms of the disease which help to precipitate the falls, however, such training often fails to prepare its patients to be able to navigate through more challenging environments. In order to improve upon this deficiency in training regimes, virtual reality (VR) has more recently been used to boost effectiveness. The University of of Utah Treadport Active Wind Tunnel has been used for such VR rehabilitation in the past and current work is being done to improve upon the system. Therefore the purpose of this study was to characterize the gait of this fall-prone population on a combination of irregular surface and cross-slope conditions in order to accomplish the following goals: 1) Inform the general scientific community of the specific challenges that such environments present to those with PD so that such issues might be addressed during fall-prevention rehabilitation sessions in order to improve their effectiveness; 2) Provide biomechanical data that will be used to verify the ecological validity of the new VR training environment being created in the Treadport for use in PD rehabilitation research. The results of this study included that surface rather than slope was shown to have a more significant effect on the gait parameters of focus (i.e., spatiotemporal measures, lower limb kinematics, and trunk stability measures). Specific gait changes exhibited by the participants with PD (on a 0 degree slope) included the following: 1) adoption of more conservative step patterns, 2) significant changes in the range of motion across all lower limbs joints (while only the ankle was affected in the case of the control group), and 3) increased trunk center of mass (COM) acceleration variability in all directions (suggesting a challenge to stability in all planes of motion). In the case of surface effect on gait when on a 10 degree cross-slope, the overall stability of the participants was more threatened than by the surface effect on the 0 degree slope

    Studio e progettazione preliminare di un sistema di retroazione di forza innovativo per interfacce di locomozione in ambienti virtuali.

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    Titolo della tesi: Studio e progettazione preliminare di un sistema di retroazione di forza innovativo per interfacce di locomozione in ambienti virtuali. Riassunto: oggetto del presente lavoro è l’analisi e progettazione di un sistema robotico a tre gradi di libertà attuati, capace di riprodurre una forza di direzione generica in prossimità del baricentro di un utente in libero movimento su di una interfaccia di locomozione per ambienti virtuali. Scopo del sistema è una più fedele simulazione delle effettive condizioni di moto (approssimazione di effetti inerziali, variazione risultante delle forze percepite a differenti pendenze del terreno, presenza di ostacoli, ecc.). L'individuazione della configurazione cinematica adottata è stata effettuata tramite confronto di soluzioni, sia seriali che parallele, capaci di soddisfare i requisiti imposti ed ottimizzate geometricamente e staticamente sullo spazio di lavoro considerato, tramite programmazione di opportune funzioni di costo. La soluzione individuata, a cinematica parallela a tre DOF con aggiunta di un polso sferico passivo, è stata ulteriormente ottimizzata per minimizzare sia le coppie di attuazione richieste che le reazioni vincolari generate sulla struttura. La successiva fase di modellazione tramite CAD tridimensionale parametrico associativo ha consentito di effettuare le necessarie verifiche sia geometriche che costruttive, alcune effettuate tramite modelli agli elementi finiti. Il sistema cosi' ottenuto è unico nel suo genere sia per ambito applicativo che per potenzialità concesse nell'applicazione delle forze di simulazione. Thesis title: Analysis and preliminary design of an innovative force feedback system to locomotion interfaces for virtual environments. Abstract: scope of the present work is the analysis and preliminary design of a 3DOF robotic system, capable of producing generic forces approximately at the center of gravity of a user that is freely moving on a locomotion interface. The system main goal is a more compelling simulation of actual real motion conditions and effects (inertial effects, variation of resultant gravity force direction relative to ground slope, obstacles, etc. ). The adopted kinematic configuration has been defined by comparison of both serial and parallel solutions able to achieve the imposed requirements. Before comparison all solutions have been optimised geometrically and statically on the desired workspace by implementation of proper cost functions. The adopted solution, that is characterised by a 3DOF translating parallel mechanism with the addition of a passive serial wrist, has been further optimised to minimise actuators requirements and constraints reactions. Then a detailed system model has been realized by an associative 3D parametric CAD software, allowing for the necessary geometrical and constructive verifies, some of which have been realized by finite element models. The final system is innovative both for field of application and the improved potential in producing simulation forces

    Synthèse sur la conception, commande et planification de trajectoire d'une interface de locomotion pour la réadaptation de la marche

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    Tableau d'honneur de la Faculté des études supérieures et postdorales, 2016-2017Cette thèse synthétise la conception d'une plateforme de marche destinée à la réadaptation des membres inférieurs pour le mouvement de la marche. L'automatisation du travail des thérapeutes, la réduction de leur charge de travail et la diversification des exercices pour les patients est un atout par rapport aux outils existants sur le marché tels que les tapis roulants ou les allées instrumentées pour la réadaptation. La conception d'une interface de locomotion pour la simulation de la marche présente des défis en terme de performance et de stabilité du mécanisme, de même que pour assurer la sécurité de l'utilisateur. L'équilibre de l'utilisateur doit être préservé grâce à une interaction humain-robot souple durant la phase d'élancement du pied et une sensation de rigidité lors de la phase d'appui. Dans un premier temps, la thèse présente le mouvement de la marche humaine pour trois types de milieux, c'est-à-dire la marche au sol, la marche d'escalier ascendante et la marche d'escalier descendante. Entre autres, le chapitre 1 cible les points essentiels de la cinématique et de la dynamique des membres inférieurs afin d'établir les exigences physiques pour la conception de la plateforme de marche. Le chapitre 2 introduit l'architecture mécanique de l'interface de locomotion basé sur deux systèmes indépendants de courroies déplaçant les deux effecteurs dans les translations horizontale et verticale, correspondant au plan sagittal dans lequel la majeure partie du mouvement de marche s'effectue. L'architecture du routage de courroies découple les degrés de liberté et simplifie ainsi la commande de la plateforme en séparant chaque degré de liberté en système indépendant. Cette architecture augmente également le rendement des efforts articulaires transmis aux effecteurs comparativement à un système dont les degrés de liberté sont co-dépendants. La thèse introduit ensuite la commande mise en place pour l'interaction entre le mécanisme et l'opérateur. Les exigences cinématiques et dynamiques diffèrent selon la phase d'élancement et la phase d'appui de la marche. Ainsi, le chapitre 3 présente la stratégie mise en place dans la direction horizontale pour minimiser les forces d'interaction entre l'utilisateur et l'effecteur. La commande en force permet, dans un premier temps, de diminuer l'inertie apparente de l'effecteur ressentie par l'utilisateur. Par la suite, un mécanisme passif à câbles est utilisé en tant qu'interface pour réduire davantage l'impédance ressentie du système. Le chapitre 4, quant à lui, décrit la stratégie mise en place pour gérer la phase d'appui de la marche afin de générer la contrainte rigide nécessaire à la simulation du sol virtuel. Le chapitre introduit la commande pour générer la limite virtuelle ainsi que la mise en place du système d'équilibrage statique à ressort à gaz pour diminuer le travail des moteurs et supporter le poids de la personne. Finalement, le chapitre 5 introduit la commande haut niveau pour générer le mouvement infini sur l'interface de locomotion avec un algorithme de recul, ramenant l'utilisateur dans la direction opposée à son mouvement pour générer l'espace nécessaire aux prochaines phases de marche, dans la direction horizontale comme pour le fonctionnement d'un tapis de course et dans la direction verticale, comme pour le fonctionnement d'un escalier mécanique inversé.This thesis summarizes the design of a locomotion interface for gait rehabilitation. The aim of the mechanism is to alleviate the workload of therapists by automating the repetitive movements involved in the rehabilitation exercises. Moreover, by offering a larger panel of exercises, the locomotion interface should be an asset compared to standard treadmills or rehabilitation walkways. Walking simulation is a challenge in terms of performance, power and safety since the mechanism includes the user in the workspace of the effectors. The balance of the user should be ensured during the swing phase with a reduced human-robot interaction and reliable during the stance phase. First, Chapter 1 describes the walking motion, the stair climbing up and down movement and highlights their main kinematic and dynamic features. Chapter 2 then introduces the architecture of the locomotion interface based on independent belt routings which transmit the movement to two end-effectors that carry the user. Each foot platform has two degrees of freedom (dofs) corresponding to the horizontal and vertical translations in the sagittal plane. Decoupling the dofs simplifies the control of the locomotion interface and increases the efficiency of the torque of the motor sent to the end-effectors compared to systems with co-dependent degrees-of-freedom. Then, the thesis presents the strategies used to supervise the human-robot interaction. The kinematic and dynamic requirements are different during the swing phase and the stance phase of the human gait. Therefore, Chapter 3 introduces the force controllers that lighten the apparent inertia of the mechanism as well as the additional mechanism based on passive cables in order to further alleviate the impedance of the effector. Chapter 4 presents the controller that generates the vertical virtual constraint in order to produce the required reliable floor during the stance phase. The rendering of the virtual environment is improved with the implementation of a static balancing system based on gas springs that alleviates the workload of the motors that handle the weight of the user. Finally, Chapter 5 introduces the cancellation algorithm that generates the infinite environment. Horizontally, the user is brought backward such as on a treadmill. Vertically, the user is moved in the opposite direction of his/her movement such as in a reversed escalator

    Bio-Inspired Robotics

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    Modern robotic technologies have enabled robots to operate in a variety of unstructured and dynamically-changing environments, in addition to traditional structured environments. Robots have, thus, become an important element in our everyday lives. One key approach to develop such intelligent and autonomous robots is to draw inspiration from biological systems. Biological structure, mechanisms, and underlying principles have the potential to provide new ideas to support the improvement of conventional robotic designs and control. Such biological principles usually originate from animal or even plant models, for robots, which can sense, think, walk, swim, crawl, jump or even fly. Thus, it is believed that these bio-inspired methods are becoming increasingly important in the face of complex applications. Bio-inspired robotics is leading to the study of innovative structures and computing with sensory–motor coordination and learning to achieve intelligence, flexibility, stability, and adaptation for emergent robotic applications, such as manipulation, learning, and control. This Special Issue invites original papers of innovative ideas and concepts, new discoveries and improvements, and novel applications and business models relevant to the selected topics of ``Bio-Inspired Robotics''. Bio-Inspired Robotics is a broad topic and an ongoing expanding field. This Special Issue collates 30 papers that address some of the important challenges and opportunities in this broad and expanding field

    12th Man in Space Symposium: The Future of Humans in Space. Abstract Volume

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    The National Aeronautics and Space Administration (NASA) is pleased to host the 12th IAA Man in Space Symposium. A truly international forum, this symposium brings together scientists, engineers, and managers interested in all aspects of human space flight to share the most recent research results and space agency planning related to the future of humans in space. As we look out at the universe from our own uniquely human perspective, we see a world that we affect at the same time that it affects us. Our tomorrows are highlighted by the possibilities generated by our knowledge, our drive, and our dreams. This symposium will examine our future in space from the springboard of our achievements

    Analyse, commande et intégration d'un mécanisme parallèle entraîné par des câbles pour la réalisation d'une interface haptique comme métaphore de navigation dans un environnement virtuel

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    Un domaine de la recherche en ingénierie des systèmes est de développer des systèmes supervisés semi-autonomes qui interagissent à un très haut niveau avec l'humain. Ces systèmes intelligents ont les capacités d'analyser et de traiter certaines informations pour produire un comportement général observable par les capacités sensorielles et temporelles de l'humain. Il est donc nécessaire de définir un environnement créatif qui interface efficacement l'humain aux informations pour rendre de nouvelles expériences multi-sensorielles optimisant et facilitant la prise de décision. En d'autres mots, il est possible de définir un système multi-sensoriel par sa capacité à augmenter l'optimisation de la prise de décision à l'aide d'une interface qui définit un environnement adapté à l'humain. Un système haptique dans un environnement virtuel incluant une collaboration et une interaction entre l'humain, les mécanismes robotisés et la physique de la réalité virtuelle est un exemple. Un système haptique doit gérer un système dynamique non-linéaire sous-contraint et assurer sa stabilité tout en étant transparent à l'humain. La supervision de l'humain permet d'accomplir des tâches précises sans se soucier de la complexité de la dynamique d'interactions alors que le système gère les différents problèmes antagonistes dont de stabilité (délai de la communication en réseau, stabilité des rendus, etc.), de transparence et de performance. Les travaux de recherche proposés présentent un système multi-sensoriel visuo-haptique qui asservisse l'interaction entre l'humain, un mécanisme et la physique de l'environnement virtuel avec une commande bilatérale. Ce système permet à l'humain de réaliser des fonctions ou des missions de haut niveau sans que la complexité de la dynamique d'interaction limite la prise de décision. Plus particulièrement, il sera proposé de réaliser une interface de locomotion pour des missions de réadaptation et d'entraînement. Ce projet, qui est nommé NELI (Network Enabled Locomotion Interface), est divisé en plusieurs sous-systèmes dont le mécanisme entraîné par des câbles nommé CDLI ( Cable Driven Locomotion Interface ), le système asservi avec une commande bilatérale qui assure le rendu de la locomotion, la réalité virtuelle qui inclut la physique de l'environnement, le rendu haptique et le rendu visuel. Dans un premier temps, cette thèse propose une méthode qui assure la qualité de la réponse de la transmission en augmentant la transparence dynamique de l'asservissement articulaire d'une manière automatique. Une approche d'optimisation, basée sur une amélioration des Extremum Seeking Tuning, permet d'ajuster adéquatement les paramètres des régulateurs et définit le critère de l'assurance qualité dans le cas d'une production massive. Cet algorithme est ensuite utilisé, pour étudier le rendu d'impédance avec l'aide de la modélisation d'un câble et de l'enrouleur. Cette modélisation permet de définir un asservissement articulaire hybride qui est utilisé dans la commande hybride cartésienne afin d'assurer le rendu haptique. Dans un troisième temps, dans un contexte de sécurité, la gestion des interférences entre les pièces mécaniques de l'interface de locomotion est décrite avec une méthode d'estimation des collisions des câbles. Une démonstration des interférences entre les câbles de deux plates-formes est simulée démontrant la faisabilité de l'approche. Finalement, la définition d'un moteur physique par un rendu haptique hybride au niveau de la commande cartésienne est présentée en considérant la géométrie des points de contact entre le modèle du pied virtuel et un objet virtuel. Cette approche procure la stabilité d'interaction recherchée lors de la simulation d'un contact infiniment rigide. Un robot marcheur de marque Kondo est embarqué sur l'interface de locomotion pour interagir avec les objets virtuels. Les résultats de la marche du robot dans l'environnement virtuel concrétisent le projet et servent de démonstrateur technologique
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