An aging population and rising prevalence in obesity, arthritis and diabetes are resulting in a great number of elders that are suffering from mobility challenges. Walking assist exoskeletons have the potential to help preserve mobility in elders. The most common type of exoskeleton relies on heavily, complex and expensive components to help their user walk effortlessly. Recent research on walking assist exoskeletons has shifted towards the creation of an entirely mechanical system called passive walking assist exoskeleton. This research aims to design, model and test a passive walking assist exoskeleton that reduces the felt weight of the user during gait. The assist is achieved by the action of a seat mechanism which constantly produces an upward force on the pelvis of the user. This thesis details the entire composition and assembly of such device. The proposed device was modelled in order to predict the assistance provided by the seat mechanism when standing and walking with the device. A human-sized prototype was built and tested in order to mechanically validate the proposed design. The test results validated the proposed seat mechanism which produces the desired upward force, but the use of the exoskeleton in its current state hindered the natural gait pattern of the user.

Occupational exoskeletons are designed to reduce workplace injury risk by decreasing work demands. Due to their relatively recent development, there has been limited research into potential unintended and undesirable consequences of wearing them. The goal of this thesis was to investigate the effects of exoskeleton use on reactive balance in response to simulated slips and trips. Five representative exoskeletons were investigated including leg-, back, and shoulder-support exoskeletons. This thesis consists of two studies: a smaller study investigating one exoskeleton and a larger one investigating multiple exoskeletons. Participants stood on a specialized treadmill, then abruptly and unexpectedly changing treadmill belt speed to simulate trip-like forward losses of balance or slip-like backward losses of balance. The results of the first study showed that a passive leg-support exoskeleton adversely reactive balance for both slips and trips. The results of the second study showed that back-support exoskeletons had a greater adverse effect on reactive balance compared to shoulder-support exoskeletons for both slips and trips. These exoskeletons affected reactive balance due to their interaction with stepping kinematics and movement constraints. This thesis provides important information that can be used to warn users of potential increased fall risks and inform exoskeleton manufacturers who may be able to modify designs to reduce any additional fall risk. / Master of Science / Occupational exoskeletons reduce muscle workload for workers during manual tasks. However, because of their additional weight and how they restrict movement, they can increase the risk of falling after a slip or a trip. The goal of this thesis was to see how exoskeletons affect balance after simulated slips and trips. Five exoskeletons were studied; These exoskeletons supported the legs, back, and shoulders. This thesis includes two studies: a smaller study with one exoskeleton and a larger one with multiple exoskeletons. In order to simulate a slip and trip, participants stood on a treadmill and then the treads would unexpectedly accelerate to a speed to make them lose their balance. The results of the first study showed that an exoskeleton that supported the legs negatively affected balance for both slips and trips. The results of the second study showed that exoskeletons that supported the back negatively affected balance more than those that supported the shoulders for both slips and trips. These exoskeletons affected balance due to them interacting with the legs and affected stepping. This thesis provides important information that can be used to warn workers of potential increased fall risks and inform exoskeleton manufacturers who may be able to help reduce any fall risk.

This thesis concerns the design, construction, control, and testing of soft robotic actuators to be used in a soft robotic exoskeleton; the Boa Exoskeleton could be used for joint rehabilitation including: wrist, elbow and possibly shoulder or any joint that requires a soft body actuator to aid with bending movement. We detail the design, modeling and fabrication of two types of actuators: Fiber-reinforced Actuator and PneuNet Actuator. Fiber-Reinforced actuator was chosen for the exoskeleton due to its higher force. The Fiber-Reinforced actuator molds were 3D printed, four models were made. Two materials were used to fabricate the models: Dragon Skin 30A and Sort-A-Clear 40A. Two number of windings: (n=40) and (n=25), actuators wrapped with carbon fiber. An air tank was used to supply pressure. The actuators were studied at different pressures. Pressure-force relation was studied, and a close to linear relationship was found. Boa Exoskeleton was made for wrist. Electromyography (EMG) was used; Four EMG receptors were put around the arm. EMG was utilized to actuate the Boa Exoskeleton and record the muscle movement. Five tests were done on six human subjects to validate the Boa Exoskeleton. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

The rationale behind this research originates from the lack of public health care in South Africa. There is an escalation in the number of stroke victims which is a consequence of the increase in hypertension in this urbanising society. This increase results in a growing need for physiotherapists and occupational therapists in this country which is further hindered by the division between urban and rural areas. The exoskeleton device has been formulated to encapsulate methodologies that enable the anthropomorphic integration between a biological and mechatronic limb. The physiotherapeutic mechanism was designed to be portable and adjustable, without limiting the spherical motion and workspace of the human arm. The exoskeleton was portable in the sense that it could be transported geographically and is a complete device allowing for motion in the shoulder, elbow, wrist and hand joints. The avoidance of singularities in the workspace required the implementation of non-orthogonal joints which produces extensive forward kinematics. Traditional geometric or analytical derivations of the inverse kinematics are complicated by the nonorthogonal layout. This hindrance was resolved iteratively via the Damped Least Squares method. The electronic and computer system allowed for professional personnel, such as an occupational therapist or a physiotherapist, to either change an individual joint or a combination of joints angles. A ramp PI controller was established to provide a smooth response in order to simulate the passive therapy motion. / Thesis (M.Sc.Eng)-University of KwaZulu-Natal, Durban, 2011.

Exoskeletons for rehabilitation commonly focus on gait training, despite the variety of human movements and functional assistance needed. Cable-driven exoskeletons have an advantage in addressing a variety of movements by being non-restrictive in their design. Additionally, these devices do not require complex mechanical joints to apply forces on the user or hinder the user's mobility. This accommodation of movement makes these cable-driven architectures more suitable for everyday movement. However, these flexible cable-driven exoskeletons often actuate a reduced number of actuated degrees-of-freedom to simplify their mechanical complexity. There is a need to design flexible and low-profile cable-driven exoskeletons to accommodate the movement of the user and be more flexible in their ability to actuate them. This thesis presents cable-driven exoskeleton designs that are used during walking and or squatting. These exoskeletons can be reconfigured to apply forces that are appropriate for these functional tasks. The three designs presented in this thesis are non-restrictive cable-driven designs that add minimal weight to the user. The first design shown is the cable-driven active leg exoskeleton previously developed by the Robotics and Rehabilitation Laboratory (C-ALEX, 10kg). The second and third designs are novel cable-driven architectures: (i) the modular C-ALEX (mC-ALEX, 3kg) and (ii) the soft C-ALEX (SC-ALEX, <1kg). A preliminary evaluation of the latter two devices was performed, and the results of these studies are presented to better understand the limitations and abilities of each design. The functionalities added to the latter two designs include the ability to reconfigure the robot's cable routing and attachment geometry, allowing the devices to apply torques through cables in the non-sagittal plane. These features will enable the robot to assist in tasks other than gait while still using the original C-ALEX design methods. Another feature added to the exoskeleton controller is to allow visual feedback through an Augmented Reality headset (the HoloLens) to incorporate visual feedback during tasks better. This feature is currently missing from the rehabilitation field using exoskeletons. The effects of using the C-ALEX with post-stroke participants were carried out to ascertain the efficacy of using a cable-driven system for gait adaptations in persons with gait impairments and compare their effectiveness against rigid-linked exoskeletons. The C-ALEX was assessed to induce a change in the walking patterns of ten post-stroke participants using a single-session training protocol. The ability of C-ALEX to accurately provide forces and torques in the desired directions was also evaluated to compare its design performance to traditional rigid-link designs. Participants were able to reach 91% ± 12% of their target step length and 89% ± 13 % of their target step height. The achieved step parameters differed significantly from participant baselines (p <0.05). To quantify the performance, the forces in each cable's out-of-the-plane movements were evaluated relative to the in-plane desired cable tension magnitudes. This corresponded to an error of under 2Nm in the desired controlled joint torques. This error magnitude is low compared to the system command torques and typical adult biological torques during walking (2-4%). These results point to the utility of using non-restrictive cable-driven architectures in gait retraining, in which future focus can be on rehabilitating gait pathologies seen in stroke survivors. Visual and force feedback are common elements in rehabilitation robotics, but visual feedback is difficult to provide in over-ground mobile exoskeleton systems. A preliminary study was carried out to assess the effects of providing force-only, force and visual, or visual-only feedback to three independent groups, each containing 8 participants. The groups showed an increase in normalized step height, (force and visual: 1.10 ± .13, force-only: 1.03 ± .23 visual-only: 1.61 ± .52) and decreased normalized trajectory tracking error (force and visual: 42.8% ± 23.4%, force: 47.6% ± 18.4% , visual-only: 114.2% ± 60.0%). Visual normalized step height differed significantly from force and visual and force-only normalized step height (p<0.005). Lap-wise normalized tracking error differed significantly ($p < 0.005$) within participants. The mC-ALEX and the HoloLens were used to test the effectiveness of robot force feedback compared to visual feedback with a squat task. The squat task aimed to have the user reach targets of 25%, 75%, and 125% of baseline squats depths through each feedback modality. The kinematic and foot loading effects were considered to establish the differences in user behavior when receiving both types of feedback. The results show that visual feedback has lower errors from targets with similar lower variability in user performance. The force feedback changed joint flexion profiles without changing foot loading biomechanics. When looking at the sessions in sequence, both feedback modalities reduced depth error magnitudes further along with the sessions time-wise. This is the first study where augmented in-field-of-view visual feedback and robotic feedback are used with the aim of changing the kinematics of a squatting task. Overall, this thesis contributes to expanding the capabilities of cable-driven exoskeletons in lower limb rehabilitative tasks. Three designs are evaluated to understand their on-user performance, with the latter two devices being novel designs. The devices are used in protocols that include visual feedback to ascertain their effects on movement adaptation through the two feedback modalities.

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Physical therapy is a field with ever increasing demands as the population ages, resulting in a larger number of individuals living with impairments. Therapy is both physically intensive and time intensive for physical therapists, and can require more than one therapist per patient. The use of technology can reduce both these physical and time demands if appropriately applied, while improving repeatability and providing quantitative evaluation of performance. Through these abilities, it may also improve the quality of life for patients. The work presented here explores how the mechanical and controller design of exoskeletons can be used to improve adaptations to new gait patterns in healthy individuals. Armed with this knowledge, new treatment methods can be adapted, applied, and validated for impaired populations with the intention of recovering a more natural gait pattern. First, the ALEX II device is presented. It is a unilateral device, designed to aid in gait training for stroke survivors. The previous version, ALEX I, had several limitations in terms of pelvic freedom, leg range of motion, and the support of the gravitational load. ALEX II was designed to address these issues. Next, a study is presented, using healthy young adults (N=30), in which ALEX II was used to explore how the amount of freedom allowed at the pelvis during gait training affects the level of adaptation subjects are able to achieve. This was evaluated for five separate configurations which resemble existing exoskeletons. It was found that intermediate levels of pelvic freedom degrade the amount of adaptation and that pelvic translation contributes more to this effect than hip abduction/adduction. The next work concerns the design of ALEX III, a bilateral device with twelve active degrees-of-freedom. ALEX III was created to increase the ability to explore the functionality required for gait training, which is why it is capable of controlling 4 degrees-of-freedom at each leg, and 4 degrees-of-freedom at the pelvis. This is followed by the the design of a new type of haptic feedback which utilizes a variable, viscous damping field, which increases the damping coeffiecent as the subject moves away from a specified path. This feedback type was tested in a set of experiments in healthy young adults. The first study (N=32) compared four different settings for the new feedback, finding that while all groups demonstrated adaptations in gait, the lowest rate of change of the damping field exhibited less adaptation. The final study (N=36) compared this haptic feedback to two previously used haptic feedback types. The previously used feedback strategies used a force that pushed the leg either towards or away from the desired path. All three of these strategies were found to produce similar levels of adaptation, however the damping field used much less external force. These findings may change the way exoskeletons for gait training are designed and increase their accessibility. While all the findings need to be validated in impaired populations they can still inform the design of future exoskeletons. The first finding, that providing an intermediate amount of freedom to the pelvis can interfere with gait training, suggests that future devices should have very high amounts of freedom or very restricted pelvic motions. The final finding, that damping fields can be used to induce gait adaptations using a much lower force, can drastically change exoskeleton design and how robotic therapy is provided. Exoskeletons can be made lighter as a result of the force being highly reduced so that lighter weight components can be used, and the dissipative nature of the force reduces dependence on heavy power sources because regenerative breaking can be used to power the device. These factors also make it possible to for devices to be used overground, which may make training more transferable to the real world.

Exoskeletons for gait training commonly use a rigid-linked "skeleton" which makes them heavy and bulky. Cable-driven exoskeletons eliminate the rigid-linked skeleton structure, therefore creating a lighter and more transparent design. Current cable-driven leg exoskeletons are limited to gait assistance use. This thesis presented the Cable-driven Active Leg Exoskeleton (C-ALEX) designed for gait retraining and rehabilitation. Benefited from the cable-driven design, C-ALEX has minimal weight and inertia (4.7 kg) and allows all the degrees-of-freedom (DoF) of the leg of the user. C-ALEX uses an assist-as-needed (AAN) controller to train the user to walk in a new gait pattern. A preliminary design of C-ALEX was first presented, and an experiment was done with this preliminary design to study the effectiveness of the AAN controller. The result on six healthy subjects showed that the subjects were able to follow a new gait pattern significantly more accurately with the help of the AAN controller. After this experiment, C-ALEX was redesigned to improve its functionality. The improved design of C-ALEX is lighter, has more DoFs and larger range-of-motion. The controller of the improved design improved the continuity of the generated cable tensions and added the function to estimate the phase of the gait of the user in real-time. With the improved design of C-ALEX, an experiment was performed to study the effect of the weight and inertia of an exoskeleton on the gait of the user. C-ALEX was used to simulate exoskeletons with different levels of weight and inertia by adding extra mass and change the weight compensation level. The result on ten subjects showed that adding extra mass increased step length and reduced knee flexion. Compensating the weight of the mass partially restored the knee flexion but not the step length, implying that the inertia of the mass is responsible for the change. This study showed the distinctive effect of weight and inertia on gait and demonstrated the benefit of a lightweight exoskeleton. C-ALEX was designed for gait training and rehabilitation, and its training effectiveness was studied in nine healthy subjects and a stroke patient. The healthy subjects trained with C-ALEX to walk in a new gait pattern with 30% increase in step height for 40 min. After the training, the subjects were able to closely repeat the trained gait pattern without C-ALEX, and the step height of the subjects increased significantly. A stroke patient also tested C-ALEX for 40 minutes and showed short-term improvements in step length, step height, and knee flexion after training. The result showed the effectiveness of C-ALEX in gait training and its potential to be used in stroke rehabilitation.

A control method is proposed for exercising specific muscles of a human's lower body. This is accomplished using an exoskeleton that imposes active force feedback control. The proposed method involves a combined dynamic model of the musculoskeletal system of the lower-body with the dynamics of pneumatic actuators. The exoskeleton is designed to allow for individual control of mono-articular or bi-articular muscles to be exercised while not inhibiting the subject's range of motion. The control method has been implemented in a 1-Degree of Freedom (DOF) exoskeleton that is designed to resist the motion of the human knee by applying actuator forces in opposition to a specified muscle force profile. In this research, there is a discussion on the model of the human's lower body and how muscles are affected as a function of joint positions. Then it is discussed how to calculate for the forces needed by a pneumatic actuator to oppose the muscles to create the desired muscle force profile at a given joint angles. The proposed exoskeleton could be utilized either for rehabilitation purposes, to prevent muscle atrophy and bone loss of astronauts, or for muscle training in general.

This thesis presents the development and implementation of a machine learning prediction model for concurrently aggregating interval linear step distance predictions before future foot placement. Specifically, on-body inertial measurement units consisting of accelerometers, gyroscopes, and magnetometers, through integrated development by Xsens, are used for measuring human walking behavior in real-time. The data collection process involves measuring activity from two subject participants who travel an intended course consisting of flat, stair, and sloped walking elements. This work discusses the formulation of the ensemble machine learning prediction algorithm, real-time application design considerations, feature extraction and selection, and experimental testing under which this system performed several different test case conditions. It was found that the system was able to predict the linear step distances for 47.2% of 1060 steps within 7.6cm accuracy, 67.5% of 1060 steps within 15.2cm accuracy, and 75.8% of 1060 steps within 23cm. For separated flat walking, it was found that 93% of the 1060 steps have less than 25% error, and 75% of the 1060 steps have less than 10% error which is an improvement over the commingled data set. Future applications and work to expand upon from this system are discussed for improving the results discovered from this work. / Master of Science