Spasticity is a neurological impairment that presents itself in the form of a continuous muscle contraction, with the key motor deficit being impaired hand function. Hand exoskeleton technologies play a vital role in the therapeutic rehabilitation of this condition. The optimal design of these devices is currently a challenge due to the limited availability of actuation devices that are light weight, portable, and aesthetically pleasing. Natural muscles have many favourable characteristics, such as their high power-to-weight ratio, efficient energy conversion, and fast actuation times. Unfortunately, traditional systems such as pneumatics muscles and electromagnetic motors have yet to attain similar properties. These traditional actuators exhibit hysteretic performance, high manufacturing cost, low stroke, and limited cycle life. In recent years a new category of actuators has been developed from highly twisted and coiled low-cost nylon fibres such as fishing line and conductive sewing thread. These muscles produce a high specific work per cycle with a reversible contraction. This thesis develops and tests these twisted and coiled polymer (TCP) actuators using various nylon and polyethylene polymers in order to establish a foundation for their implementation as a novel actuation device in a spastic hand exoskeleton. An initial comprehensive experimental evaluation of several nylon fibres is completed by attempting to reproduce the work of previous researchers. Subsequently, the information obtained is taken and adapted to the development of UHMWPE TCPs and other types of nylon monofilament. This thesis characterizes the contractility and force output of these novel actuation devices.

Pesquisas sobre próteses ativas e exoesqueletos têm se intensificado nas últimas décadas. Seu uso para reabilitação, aumento de força ou substituição de um membro debilitado já está sendo utilizado comercialmente. Porém, um dos desafios para o controle deste tipo de dispositivo é a identificação dos parâmetros das articulações humanas para que o equipamento simule o mesmo comportamento e a interface homem máquina seja mais eficaz e confortável. Este trabalho apresenta o desenvolvimento, construção e validação de um exoesqueleto que é um dispositivo para estudo da marcha. Em outras palavras, o exoesqueleto apresentado é capaz de medir a força de interação com o corpo humano bem como a posição angular das articulações do joelho e tornozelo durante a marcha. Com essas medições é possível calcular os parâmetros de impedâncias dessas articulações. A revisão bibliográfica sobre exoesqueletos foi necessária para a definição dos requisitos do projeto. O projeto do exoesqueleto desenvolvido pela autora durante o trabalho de conclusão de curso foi revisto de acordo com os requisitos estabelecidos. Assim, o novo projeto, chamado de Protótipo II ou ExoLoLi, é capaz de suprir as deficiências do primeiro projeto e atender a todos os requisitos para ser uma ferramenta de estudo da marcha. O ExoLoLi foi construído e experimentos preliminares foram realizados para a sua validação como ferramenta de estudo da marcha. Foi possível confirmar que o exoesqueleto faz as medições de força de interação e de posição corretamente. Também foi possível verificar que o exoesqueleto interfere no padrão natural da marcha. De qualquer forma, o exoesqueleto poderá ser usado, não apenas para o cálculo dos parâmetros de impedância, mas também para estudo de consumo energético com diferentes tipos de controle e para diferentes aplicações (como reabilitação e aumento de força), dependendo do controle programado para o seu funcionamento. / Research on active prosthetics and exoskeletons has been intensified in recent decades. Its use for rehabilitation, strength increase or replacement of a disabled member is already being used commercially. But one of the challenges for the control of this type of device is the identification of the human joint\'s parameters so the machine is able to simulate the same behavior and the man-machine interface is more effective and comfortable. This dissertation presents the development, construction and validation of an exoskeleton which is a device for gait study. In other words, the presented exoskeleton is capable of measuring the interaction force with the human body as well as the angular position of the knee and ankle joints during gait. With these measurements it is possible to calculate the impedance parameters of these joints. The literature review about exoskeletons was necessary to define the project requirements. The exoskeleton developed by the author to obtain the engineering degree (undergraduate paper) has been reviewed in accordance with the established requirements. So the new exoskeleton design, called as Prototype II or ExoLoLi, is able to address the weaknesses of the first project and meet all the requirements to be a gait study tool. The ExoLoLi was built and preliminary experiments were performed to validate it as gait study tool. It was confirmed that the exoskeleton is able to measure the interaction forces and the angular position correctly. It was also observed that the exoskeleton interferes at the natural gait pattern. Anyway, the exoskeleton can be used not only for calculating the human impedance parameters, but also to analyze the energy consumption using different control strategies and to be used in different applications (such as rehabilitation or strength increase) depending on the programmed control for its operation.

abstract: The human shoulder plays an integral role in upper limb motor function. As the basis of arm motion, its performance is vital to the accomplishment of daily tasks. Impaired motor control, as a result of stroke or other disease, can cause errors in shoulder position to accumulate and propagate to the entire arm. This is why it is a highlight of concern for clinicians and why it is an important point of study. One of the primary causes of impaired shoulder motor control is abnormal mechanical joint impedance, which can be modeled as a 2nd order system consisting of mass, spring and damper. Quantifying shoulder stiffness and damping between healthy and impaired subjects could help improve our collective understanding of how many different neuromuscular diseases impact arm performance. This improved understanding could even lead to better rehabilitation protocols for conditions such as stroke through better identification and targeting of damping dependent spasticity and stiffness dependent hypertonicity. Despite its importance, there is a fundamental knowledge gap in the understanding of shoulder impedance, mainly due to a lack of appropriate characterization tools. Therefore, in order to better quantify shoulder stiffness and damping, a novel low-inertia shoulder exoskeleton is introduced in this work. The device was developed using a newly pioneered parallel actuated robot architecture specifically designed to interface with complex biological joints like the shoulder, hip, wrist and ankle. In addition to presenting the kinematics and dynamics of the shoulder exoskeleton, a series of validation experiments are performed on a human shoulder mock-up to quantify its ability to estimate known impedance properties. Finally, some preliminary data from human experiments is provided to demonstrate the device’s ability to collect the measurements needed to estimate shoulder stiffness and damping while worn by a subject. / Dissertation/Thesis / Doctoral Dissertation Mechanical Engineering 2020

Walking Assist Exoskeletons are wearable devices that can allow individuals with mobility impairments to maintain their autonomy. The growing elderly population has benefited from these devices by receiving assistance at joints where their muscle function has declined. Typically, the primary objective of these exoskeletons has been to reduce the metabolic cost of walking, allowing users to walk for extended periods of time while reducing fatigue. However, this strategy does not directly address the growing concern that seniors are at an increased risk of falling and sustaining severe injuries due to falls. Gait and balance disorders are among the most common causes of falls in the elderly. As the Canadian population ages, it is increasingly important to investigate the musculoskeletal changes contributing to frontal-plane instability, as mediolateral and posterolateral falls are correlated with higher incidences of severe injuries. Specifically, the hip abductor and hip adductor muscles are essential in maintaining balance in the frontal plane, yet little research has been conducted on the effect of hip abduction-adduction exoskeleton assistance on the stability of elderly individuals. This thesis investigates the effect of introducing an assistive torque with a specific magnitude, timing, and location (i.e. applied to one or both legs) on the margin of stability of elderly individuals using the OpenSim biomechanics software. Simulations of four elderly subjects were conducted while the subjects stood in a quiet standing position with both feet on the ground. A lateral perturbation force of magnitude 5%, 10% or 15% of bodyweight was applied to the pelvis of each subject. The simulations were designed to provide elderly subjects with contralateral (i.e. the limb on the opposite side of the body as the perturbation), ipsilateral (i.e. the limb on the same side as the perturbation), or bilateral hip abduction-adduction assistive torque from a hip exoskeleton device after a perturbation force was applied to the pelvis. The simulated actuators mounted at the hip joints were massless, applied torque in the frontal plane, and could generate torque instantaneously based on user-defined inputs. The change in margin of stability was used to measure the effectiveness of each assistive strategy and for comparison across all subjects. The results of this study suggest that, as the perturbation magnitude increases, the hip abduction-adduction assistive exoskeleton should prioritize assistance applied to the contralateral limb. Regardless of the perturbation magnitude, each assistive strategy that was simulated (i.e. contralateral, ipsilateral and bilateral assistance) was able to improve the margin of stability. The greatest mean improvement on the margin of stability compared to the unassisted condition occurred when using the contralateral assistance strategy. For the 5%, 10% and 15% bodyweight perturbations, a contralateral assistance of 0.75 N·m/kg (torque normalized by the subject's mass) resulted in an improvement in the margin of stability of 13.1 ± 0.987 mm, 13.0 ± 0.946 mm and 13.1 ± 0.816 mm, respectively. The simulations also suggested that similar improvements on the margin of stability were experienced at smaller assistive torque magnitudes when the actuators provided torque to the body quicker following a perturbation. The results of this study can be used by exoskeleton designers to guide their decisions when developing abduction-adduction assistive exoskeletons that target mediolateral stability assistance in the elderly population.

Passive exoskeletons hold promise in reducing the risk of work-related musculoskeletal disorders, however further research is essential before widespread adoption can occur. This study explores the feasibility of using subjective measures of physical demand in place of costly and less practical objective measures. Normalized electromyography (nEMG) data and ratings of perceived exertion (RPE) were collected from seven different studies conducted by the Occupational Ergonomics and Biomechanics Lab (OEB lab). Employing a repeated measures three-way ANOVA, we assessed the influence of nEMG, gender, and exoskeleton type on RPE. Additionally, mean nEMG and RPE from seven passive exoskeleton-based studies conducted outside the OEB lab were assessed in order to determine if the findings from the OEB lab existed across other research environments. The results demonstrated a general positive linear trend between nEMG and RPE for both the individual and mean results. Substantial inconsistencies emerged when considering the influence of gender, exoskeleton type, and task conditions on the relationship between nEMG and RPE. These discrepancies underscore the need for more in-depth research into this topic, specifically investigating the effects of gender and exoskeleton design. / Master of Science / Passive exoskeletons, devices designed to improve safety and provide support to the body, offer the potential for reducing muscle strain and reducing work-related injury risk. However, before these devices can be widely adopted, more research is necessary. Subjective measures of exertion, an affordable and user-friendly alternative to objective measures, require further investigation before replacing traditional methods in exoskeleton research. This study explores the possible connection between subjective and objective assessments of physical demand during passive exoskeleton usage. We analyzed data from seven studies conducted by the Occupational Ergonomics and Biomechanics Lab (OEB lab), focusing on muscle activity (an objective measure) and perceived exertion (a subjective measure). Our analysis examined the relationship between these objective and subjective measures, as well as how gender, exoskeleton type, and task conditions influenced this relationship. Additionally, we considered mean values from seven passive exoskeleton studies conducted outside the OEB lab, to investigate whether our findings existed in other research environments. The results revealed that as muscle activity increased, perceived exertion tended to increase as well. Moreover, our findings demonstrated that gender, exoskeleton type, and task conditions did influence the relationship, although there was significant variability in how these factors affected it. This research sheds light on the potential for using subjective measures in exoskeleton studies, bringing us closer to making exoskeletons more practical and accessible for real-world applications while acknowledging the complexities of this relationship.

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