Master of Science

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

Gait Rehabilitation Using Biomechanics and Exoskeletons

A healthy gait is often taken for granted when walking. However, if a stroke, spinal cord injury (SCI), or traumatic event occurs the ability to walk may be lost. In order to relearn how to walk, gait rehabilitation is required. Including arm swing in gait rehabilitation has been shown to help in this process. This thesis presents two tasks to investigate the mechanics of arm swing and ways to provide assistance to induce arm swing in gait rehabilitation. The firsts task completed was a study on the effects of forearm movement during gait. Twelve healthy subjects walked under three conditions at two self selected speeds. The first condition observed was natural walking, the second condition the subjects wore an artificial forearm with their forearms restricted, and the third condition the subjects’ forearms were restricted without the artificial forearm. It was observed that the the lower extremities’ range of motion and spatiotemporal parameters did not change between conditions. However when the subjects wore the artificial forearm, significant decreases were observed in the shoulders, trunk, interlimb coordination, and shoulder trunk correlations. In addition, increases in muscle activity also occurred in the biceps, trapezius, and posterior deltoids during the second condition. The amount of energy exerted also increased when wearing the artificial forearm, but not significantly. Only restraining the forearms mainly affected shoulder rotation at the subjects’ normal walking speed. These results indicate that the body actively controls forearm movements during walking to mitigate unwanted movements. It does this by reducing shoulder and trunk rotation. The second task was the design and validation of a distally located upper extremity exoskeleton to assist with arm swing during gait rehabilitation. This exoskeleton utilizes a hybrid double parallel linkage (DPL) that allows the exoskeleton to mimic the work-space of a healthy shoulder. The motor is distally located from the shoulder and located on a ALICE backpack. This provides several ergonomic benefits such as reducing the weight on the wearer’s arm. The torque is transferred from the motor to the arm through a pulley system. The exoskeleton’s ability to generate arm swing was validated on a passive dummy arm. The exoskeleton was tested under two conditions. The first condition was in-plane arm swing, which simulated motion strictly in the sagittal plane. The second condition was out-of-plane arm swing to simulate arm swing when the shoulder is internally rotated. Each condition was tested at frequencies of 0.67, 0.80, 1.10 Hz. It was observed that the exoskeleton can generate highly correlated movements in the passive arm at each of the tested frequencies with low time lags. In addition the exoskeleton was also tested on two subjects. Similarly, arm movements were highly coordinated to motor movements. Based on these results, this exoskeleton design has the potential to aid in gait rehabilitation

On treadmill automation and physiological control systems

This thesis deals with a new approach to Treadmill Automation and Physiological Control Systems that will serve as a platform for enhanced rehabilitation therapy, and will open up and facilitate a major new area of research in physiological control systems. On treadmill automation, the investigation focussed on the feasibility of a low-cost non- contact position control system with the aim of maintaining a subject at a prescribed position during a treadmill training exercise in order to ensure safety at all times. The development of an automatic speed control for the treadmill was first carried out using an identified model for the treadmill motor dynamics (response from speed command to actual belt speed). Subsequently, the positioning control system was designed and tested. The fundamental limitations to treadmill automation performance include low bandwidth and long time delays of the hardware (treadmill and ultrasonic sensor). Interactions between natural human control and the position controller, and spontaneous variability of human movement due to body oscillations and swaying, are discussed. On physiological control systems, we considered two key variables - the heart rate and oxygen uptake. The purpose of this is to develop a means of controlling exercise intensity during treadmill exercise. On the control of heart rate, a model of heart rate response to changes in speed was obtained via the system identification method. Thereafter, a heart rate controller was developed, tested, and evaluated on three healthy subjects during treadmill exercise. The results of the experiments demonstrated that the developed heart rate controller is superior to the in-built treadmill heart rate controller. A novel system is developed for the control of oxygen uptake, and is thus presented. The system proved that it is possible to control exercise intensity using the level of oxygen uptake during moderate exercise. The results of this work demonstrate that a linear first order model is able to sufficiently capture the complex dynamics of oxygen uptake during treadmill exercise. A controller was developed using this model and tested on healthy subjects. Six healthy active subjects participated completely in the tests. The results of the tests with these subjects establish the robustness of the controllers to inter-subject variability. Furthermore, the controller was refined and tuned to improve the performance of the control signal (treadmill speed). This was achieved by designing a controller that incorporated a pre-filter in the system. The results of the experiments using this set-up with the same set of healthy subjects show a significant improvement on the control signal (smoother treadmill speed)

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

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

Joint Trajectory Generation and High-level Control for Patient-tailored Robotic Gait Rehabilitation

This dissertation presents a group of novel methods for robot-based gait rehabilitation which were developed aiming to offer more individualized therapies based on the specific condition of each patient, as well as to improve the overall rehabilitation experience for both patient and therapist. A novel methodology for gait pattern generation is proposed, which offers estimated hip and knee joint trajectories corresponding to healthy walking, and allows the therapist to graphically adapt the reference trajectories in order to fit better the patient's needs and disabilities. Additionally, the motion controllers for the hip and knee joints, mobile platform, and pelvic mechanism of an over-ground gait rehabilitation robotic system are also presented, as well as some proposed methods for assist as needed therapy. Two robot-patient synchronization approaches are also included in this work, together with a novel algorithm for online hip trajectory adaptation developed to reduce obstructive forces applied to the patient during therapy with compliant robotic systems. Finally, a prototype graphical user interface for the therapist is also presented

Proceedings of the 9th international conference on disability, virtual reality and associated technologies (ICDVRAT 2012)

The proceedings of the conferenc

Federal Register

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