Bipeds and quadrupeds are inherently unstable and their bodies sway during quiet stance and require complex patterns of muscle activation to produce direction-specific forces to control the body’s center of mass. The relative strength of length and force feedback within and across muscles collectively regulates the mechanical properties of the limb as a whole during standing and locomotion (Bonasera and Nichols 1994; Ross and Nichols 2009). Loss of posture control following spinal cord injury (SCI) is a major clinical challenge. While much is known about intermuscular force feedback during crossed extension reflex (XER) and locomotion in decerebrate cats, these have not been well characterized in animals with spinal cord injury. In this study, we mapped the distribution of heterogenic force feedback in hindlimb ankle extensor muscles using muscle stretch (natural stimulation) in intercollicular, non-locomoting, decerebrate cats with chronic lateral spinal hemisection (LSH). We also, determined the time of onset of redistribution of heterogenic force feedback following LSH by collecting force feedback data from cats with acute sci. In addition we revisited heterogenic force feedback between ankle extensors in decerebrate non-locomoting cats during mid-stance to ascertain whether these cats with intact spinal cord depict a certain pattern of force feedback. The goal was to ascertain whether the patterns and strength of feedback was different between the two states (cats with intact spinal cord and cats with SCI). We found that heterogenic feedback pathways remained inhibitory in non-locomoting decerebrate cats in two states. The latencies of inhibition also corresponded to those observed for force feedback from Golgi tendon organs. We observed variable patterns of force feedback between ankle extensors in decerebrate/control cats. On the other hand we observed consistent results in cats with chronic LSH exhibiting very strong distal to proximal pattern of inhibition from 2 weeks to 20 weeks following chronic LSH. The same results were obtained in acute LSH cats suggest that the change in neuromuscular system appears immediately after SCI and persists even after the animal start walking following SCI. The observed altered pattern of force feedback after spinal cord injury suggests either presence of a pattern intrinsic to the spinal cord or a unique pattern exhibited by the damaged spinal cord. The results are important clinically because even with vigorous rehabilitation attempts patients do not regain posture control after SCI even though they regain ability to walk. Therefore, to effectively administer treatment and therapy for patients with compromised posture control, a complete understanding of the circuitry is required.

Opening a door is still a hard problem in robotics. Many robotic manipulators use open-loop position control to open doors, which reduces reusability and reliability in the face of slight differences or sensor errors. Many others use force feedback or impedance control but skip past the problem of grabbing the handle, which could lead to failures due to sensor errors. This research assumes that perception is faulty, and uses joint-level force feedback to probe the location of the door and its handle before attempting to open it. The resulting control strategy is at least 33% faster than the open-loop control system it replaces, and had an 83% success rate during testing in place of the previous method's 60% success rate. / Master of Science

Force feedback during teleoperation and in Virtual Reality (VR) environments is becoming increasingly common. We are interested in understanding the impact of motion on the directional accuracy of force perception, as observed in a VR environment. We used a custom force-feedback system that pulled a handle with a force of 1.87N at various angles in front of N=14 subjects. The virtual environment showed a curved wall, which corresponded to the locations from which the force could physically originate. Subjects selected where they perceived the force to originate from with a virtual laser pointer and by orienting their head. We compared several conditions: the subject held the handle still; the subject moved the handle back and forth toward the center of the wall; the subject moved the handle back and forth across their body; and the subject moved the handle back and forth toward where they thought the force was originating. Subjects were able to localize the force with an average accuracy of 1-10 degrees depending on the force's location, which is better than previous studies. All conditions had similiar accuracies. Subjects had the best precision when they followed the force as compared to either of the other conditions with movement. / Master of Science / In recent years, robots combined with teleoperation, operating in a remote safe environment, has become a popular choice for replacing human workers in dangerous environments. Visual feedback and a sense of touch and motion, are two of the most common feedback modalities. Thus, Virtual Reality (VR) and force rendering are two main ways of conveying information to the operator during teleoperation.\newline Previous studies have investigated the effects of force feedback on the fingers, wrist, and arms but with limited movements and joint combinations. In this paper, we answered the question of how the planar arm movement impacts the force-directional perception accuracy by using a Virtual Reality (VR) system. To put in other words, we want to find out how accurate and precise a robot operator can feel the physical world through joysticks. If they are asked to do this many times in a row, how repeatable are their guesses? To study this, We asked subjects holding a handle made out of PVC pipe with a position sensor on it. The handle was attached to a motor, which pulled the handle away from the subjects during the experiment trial. The experiment consisted of four different conditions, which studied both stationary, when subjects holding the handle stationary and resist the pull by our motor, and movement, when subjects moving the handle in a certain direction while the handle was pulled by our motor. In each trial, subjects were first asked to resist the force according to the experiment condition, then use a laser pointer and head to both point and look at where they think the motor was pulling the handle from. Because of the use of the VR environment and position sensor, subjects reported their guesses intuitively by pointing and looking at, which eliminated the potential of misreporting guesses. The result of this study is important for designing an effective force feedback system for teleoperation. With this information, a force feedback system in a VR environment could be altered to convey information to a user more accurately, for example to correct any biases that the user may have in where they expect forces to originate.\newline Our results show that arm movements enhanced the force feedback precision without sacrificing the accuracy. Arm movements also improved the subjects' confidence level in how well they thought they could localize a force. The results also suggest that pointing with the head is significantly more precise compared with the hand. Such results can be used to implement a more effective force feedback system combined with a VR environment. Finally, our data also shows that hand had an opposite accuracy pattern compared with the head. Future works are needed to explain this opposite accuracy pattern.

O tratamento de reabilitação motora compreende o emprego de um conjunto de técnicas terapêuticas que visam incitar a ocorrência da plasticidade cerebral, atividade fisiológica na qual o sistema nervoso central busca estabelecer novas ligações sinápticas para promover a recuperação da função neuromuscular. Observando-se as técnicas atualmente empregadas e fundamentando-se no fato da criança apresentar alta capacidade de sofrer plasticidade neural, decidiu-se desenvolver um sistema mecatrônico interativo como ferramenta de auxílio ao tratamento de reabilitação de crianças com deficiência motora nas pernas. O presente trabalho descreve a implementação deste sistema, composto por uma bicicleta instrumentada, integrada a um ambiente virtual de aparência lúdica, desenvolvidos com o objetivo de proporcionar a execução dos exercícios físicos de forma divertida e cativante, estimulando a ocorrência de uma plasticidade neural mais rápida e eficiente. Ao final do trabalho são relatadas algumas demonstrações práticas realizadas, onde foram avaliados os níveis de motivação das crianças, além de alguns depoimentos médicos a respeito das expectativas do projeto. / The rehabilitation treatment consists in a set of therapeutic techniques that try to stimulate cerebral plasticity. Cerebral plasticity is a physiologic phenomenon where the brain searches for new neural connections to supply the deficient function. lt is known that the young brain has a high cerebral plasticity capacity. Based on this, an interactive mechatronic system was developed to assist the rehabilitation treatment of children with motor disturbances in their legs. This system is composed of an instrumented bicycle and an entertaining virtual world generated by computer, developed to stimulate the child to accomplish the physical activities in a captivating and fun way and, consequently, increasing the cerebral plasticity performance. ln the end of this document some practical experiments were reported, showing the motivation of the children. Some medical opinions regarding the expectations of the project were also reported.

O tratamento de reabilitação motora compreende o emprego de um conjunto de técnicas terapêuticas que visam incitar a ocorrência da plasticidade cerebral, atividade fisiológica na qual o sistema nervoso central busca estabelecer novas ligações sinápticas para promover a recuperação da função neuromuscular. Observando-se as técnicas atualmente empregadas e fundamentando-se no fato da criança apresentar alta capacidade de sofrer plasticidade neural, decidiu-se desenvolver um sistema mecatrônico interativo como ferramenta de auxílio ao tratamento de reabilitação de crianças com deficiência motora nas pernas. O presente trabalho descreve a implementação deste sistema, composto por uma bicicleta instrumentada, integrada a um ambiente virtual de aparência lúdica, desenvolvidos com o objetivo de proporcionar a execução dos exercícios físicos de forma divertida e cativante, estimulando a ocorrência de uma plasticidade neural mais rápida e eficiente. Ao final do trabalho são relatadas algumas demonstrações práticas realizadas, onde foram avaliados os níveis de motivação das crianças, além de alguns depoimentos médicos a respeito das expectativas do projeto. / The rehabilitation treatment consists in a set of therapeutic techniques that try to stimulate cerebral plasticity. Cerebral plasticity is a physiologic phenomenon where the brain searches for new neural connections to supply the deficient function. lt is known that the young brain has a high cerebral plasticity capacity. Based on this, an interactive mechatronic system was developed to assist the rehabilitation treatment of children with motor disturbances in their legs. This system is composed of an instrumented bicycle and an entertaining virtual world generated by computer, developed to stimulate the child to accomplish the physical activities in a captivating and fun way and, consequently, increasing the cerebral plasticity performance. ln the end of this document some practical experiments were reported, showing the motivation of the children. Some medical opinions regarding the expectations of the project were also reported.

Au cours des dernières décennies, les environnements virtuels se sont de plus en plus répandus et sont largement utilisés dans de nombreux domaines comme, par exemple, le prototypage, la formation à l’utilisation de différents outils/appareils, l’aide à la réalisation de tâches difficiles, etc. L’interaction avec la réalité virtuelle, ainsi que le retour d’effort, sont assurés par des interfaces haptiques. En général, ces systèmes sont affectés par des retards de communication et de traitement, entraînant une détérioration des performances. Dans cette thèse, une étude complète des méthodes existantes, les outils théoriques et de nouvelles solutions sont proposés dans le cadre de l’haptique. Dans un premier temps, une étude comparative, fondée sur des résultats expérimentaux obtenus sur un système haptique à un degré de liberté, met en évidence les avantages et les inconvénients des algorithmes de commande les plus classiques, transposés du domaine de la téléopération à l’haptique. Sont ensuite examinés les outils théoriques nécessaires à l’analyse de la stabilité des systèmes à retard selon différentes situations, tenant compte des limites physiques des plates-formes expérimentales considérées. En plus du cas classique du retard constant, des incertitudes sont également considérées et modélisées par plusieurs types de distributions (distribution uniforme, normale et gamma avec gap). Finalement, pour surmonter les inconvénients liés aux retards, deux nouvelles approches sont proposées. Tout d’abord, la commande de type prédicteur de Smith est reprise et une solution spécifique pour les systèmes haptiques est mise en oeuvre. L’idée principale consiste à introduire dans le prédicteur de Smith les forces liées à l’environnement en utilisant les informations complémentaires issues de la réalité virtuelle, en ce qui concerne les distances entre l’objet virtuel piloté et d’autres objets présents dans la scène. Pour surmonter la perte de performances induite par l’utilisation d’un gain fixe dans les correcteurs, commun à toutes les situations (mouvements libres ou restreints), la seconde approche propose un correcteur Proportionnel Dérivé incluant une stratégie de séquencement de gain en fonction de la distance jusqu’à une éventuelle collision. Les deux approches sont validées expérimentalement sur une plateforme haptique à trois degrés de liberté, pour différents scénarios de complexité progressive, partant de situations avec des mouvements simples - libre et restreints, des contacts avec des objets en mouvement, pour arriver à des situations plus complexes - boîte virtuelle avec des murs fixes ou mobiles. / During the last decades, virtual environments have become very popular and are largely used in many domains as, for example, prototyping, trainings for different devices, assistance in completing difficult tasks, etc. The interaction with the virtual reality, as well as the feedback force, is assured by haptic interfaces. Generally, such systems are affected by communication and processing time-delays, resulting in a deterioration of performances. In this thesis, a complete study of the existing methods, as well as theoretical tools and new solutions, are proposed for the haptic framework. First, a comparative study, based on the experimental results obtained on a 1-dof haptic system, highlights the advantages and drawbacks of the most common control algorithms ported from teleoperation to haptics. Next, the theoretical tools needed in analyzing the stability of the delayed systems in different situations, as well as the physical limitations of the experimental platforms considered, are examined. Besides the standard case of constant time-delays, uncertainties are also considered and modeled by different types of distributions (uniform, normal and gamma distribution with gap). In the sequel, for overcoming the drawback of time-delays, two new approaches are proposed. First, the use of Smith predictor-based control is addressed and a specific solution for haptic systems is developed and discussed. The main idea is to introduce into the Smith predictor the environmental forces by using the additional information from the virtual reality regarding the distances between the controlled virtual object and other objects in the scene. To overcome the loss of performances induced by using a fixed gain in the controllers for all situations (free or restricted motions), the second approach proposes a gain-scheduling Proportional Derivative control strategy depending on the distance until a possible collision. Both approaches are experimentally validated on a 3-dof haptic platform, under different scenarios elaborated gradually from simple situations - free and restricted motion, contacts with moving objects, to more complex situations - virtual box with fixed or moving sides.

Cette thèse étudie le problème du pilotage d'un système de direction découplé dans un véhicule. L'idée est de contrôler les deux sous-systèmes (système de restitution et système de braquage) constituant la direction de manière à : fournir au conducteur, par l'intermédiaire du volant, des sensations de conduite lui permettant d'appréhender le comportement dynamique de son véhicule ; procurer au conducteur une direction répondant à certains critères de confort ; permettre l'amélioration du comportement dynamique du véhicule en jouant sur la dynamique du système de direction. L'étude présente un modèle de référence décrivant le comportement souhaité d'un système de direction une fois implanté dans un véhicule. Ce modèle est construit de manière à prendre en compte l'influence des efforts extérieurs issus du contact pneus/sol, ceux-ci étant représentatifs du comportement dynamique du véhicule<br />Deux méthodes de commande sont proposées afin de reproduire le comportement du modèle de référence sur un système de direction découplée. Des essais sur prototype ont été réalisés et des résultats expérimentaux sont proposés.

<p>Automation in manufacturing has come far by using industrial robots. However, industrial robots require tremendous efforts in static calibration due to their lack of senses. Force and vision are the most useful sensing capabilities for a robot system operating in an unknown or uncalibrated environment [4]and by integrating sensors in real-time with industrial robot controllers, dynamic processes need far less calibration which leads to reduced lead time. By using robot systems which are more dynamic and can perform complex tasks with simple instructions, the production efficiency will rise and hence also the profit for companies using them. </p><p>Although much research has been presented within the research community, current industrial robot systems have very limited support for external sensor feedback, and the state-of-the-art robots today have generally no feedback loop that can handle external force- or position controlled feedback. Where it exists, feedback at the rate of 10 Hz is considered to berare and is far from real-time control. </p><p>A new system where the feedback control can be possible within a real-time behavior, developed at Lund Institute of Technology, has been implemented and deployed at Linköping Institute of Technology. </p><p>The new system for rapid feedback control is a highly complex system, possible to install in existing robot cells, and enables real-time (250 Hz) sensor feedback to the robot controller. However, the system is not yet fully developed, and a lot of issues need to be considered before it can reach the market in other than specific applications. </p><p>The implementation and deployment of the new interface at LiTH shows that the potential for this system is large, since it makes production with robots exceedingly flexible and dynamic, and the fact that the system works with real- time feedback makes industrial robots more useful in tasks for manufacturing.</p>

Many devices are available on the market for the evaluation and rehabilitation of patients suffering from muscular disorders. Most of them are small, low-cost, passive devices based on the use of springs and resistive elements and exhibit very limited (or even not any) evaluation capabilities; extended muscular force evaluation is only possible on stationary, expensive, multi-purpose devices, available only in hospitals, which offer many exercise modes (e.g. isokinetic mode) that are not available on other devices. The objective of this thesis is to make the functionalities currently only implemented on bulky multi-purpose devices available at a lower cost and in a portable fashion, enabling their use by a large number of independent practitioners and patients, even at home (tele-medecine applications). In order to achieve this goal, a portable rehabilitation device, using a magneto-rheological fluid brake as actuator, has been designed. This particular technology was selected for its high level of compactness, simple mechanical design, high controllability, smooth and safe operation. The first part of this thesis is devoted to the design of MR-fluid brakes and their experimental validation. The second part is dedicated to the design of the rehabilitation device and the comparison of its performances with a commercial multi-purpose device (CYBEX).

Ce projet s’inscrit dans l’effort développé par l’Agence Spatiale Européenne (ESA)pour robotiser les activités extravéhiculaires à bord de la Station Spatiale Internationale et lors des futures missions d’exploration planétaire. Un aspect important de ces projets concerne le retour de force et la capacité, pour la personne qui commande les mouvements du robot, à ressentir les efforts qui lui sont appliqués. Le but est d’améliorer la qualité et l’immersion de la téléopération. L’objectif de cette thèse est la conception d’une interface haptique de type exosquelette pour le bras, pour ces missions de téléopération à retour de force. Ce système doit permettre une commande intuitive du robot téléopéré tout en reproduisant le plus fidèlement possible les efforts. Les chapitres 2 et 3 présentent les études réalisées sur un banc de test à 1 degré de liberté, destinées à comprendre le contrôle haptique ainsi qu’à évaluer différentes technologies d’actionnements et de capteurs. Les principales méthodes de contrôle sont décrites théoriquement et comparées en pratique sur le banc de test. Les chapitres 4 et 5 décrivent le développement de l’exosquelette SAM destiné aux futures applications de téléopération spatiale. La conception cinématique, le choix des actionneurs et des capteurs sont décrits. Différentes méthodes de contrôle sont également comparées avec des expériences de réalité virtuelle (sans robot esclave) et de téléopération. Pour finir, le chapitre 6 présente le projet EXOSTATION, un démonstrateur de téléopération haptique spatiale, dans lequel SAM est utilisé comme interface maître.