For over a century, technologists have strived to develop autonomous leg exoskeletons that reduce the metabolic energy consumed when humans walk and run, but such technologies have traditionally remained unachievable. In this thesis, I present the Augmentation Factor, a simple model that predicts the metabolic impact of lower limb exoskeletons during walking. The Augmentation Factor balances the benefits of positive exoskeletal mechanical power with the costs of mechanical power dissipation and added limb mass. These insights were used to design and develop an autonomous powered ankle exoskeleton. A lightweight electric actuator mounted on the lower-leg provides mechanical assistance to the ankle during powered plantar flexion. Use of the exoskeleton significantly reduced the metabolic cost of walking by 11 ± 4% (p = 0.019) compared to walking without the device. In a separate study, use of the exoskeleton reduced the metabolic cost of walking with a 23 kg weighted vest by 8 ± 3% (p = 0.012). A biomechanical study revealed that the powered ankle exoskeleton does not simply replace ankle function, but augments the biological ankle while assisting the knee and hip. Use of the powered ankle exoskeleton was shown to significantly reduced the mean positive power of the biological ankle by 0.033 ± 0.006 W/kg (p

What Is Powered Exoskeleton A mobile machine that is wearable over all or part of the human body, providing ergonomic structural support and powered by a system of electric motors, pneumatics, levers, hydraulics, or a combination of cybernetic technologies is referred to as a powered exoskeleton. Other names for this type of exoskeleton include power armor, powered armor, powered suit, cybernetic suit, cybernetic armor, exosuit, hardsuit, exoframe, or augmented mobility. The exoskeleton is expected to have a higher tolerance for mechanical stress, and its control system is supposed to be able to detect and coordinate with the motion that the user intends to make while also transmitting that information to motors that drive the gears. The user's shoulders, waist, back, and thighs are shielded from the effects of overload by the exoskeleton, which also helps to stabilize movement when the user is lifting and carrying large objects. How You Will Benefit (I) Insights, and validations about the following topics: Chapter 1: Powered exoskeleton Chapter 2: Functional electrical stimulation Chapter 3: Disability robot Chapter 4: HAL (robot) Chapter 5: Biomechatronics Chapter 6: LOPES (exoskeleton) Chapter 7: Gait training Chapter 8: Sarcos Chapter 9: Human Universal Load Carrier Chapter 10: ReWalk Chapter 11: Cyberdyne Inc. Chapter 12: SoldierStrong Chapter 13: Orthotics Chapter 14: Spinal locomotion Chapter 15: Homayoon Kazerooni Chapter 16: Ekso Bionics Chapter 17: Rehabilitation in spinal cord injury Chapter 18: Vanderbilt exoskeleton Chapter 19: Cadence Biomedical Chapter 20: Neuromechanics of orthoses Chapter 21: Proportional myoelectric control (II) Answering the public top questions about powered exoskeleton. (III) Real world examples for the usage of powered exoskeleton in many fields. (IV) 17 appendices to explain, briefly, 266 emerging technologies in each industry to have 360-degree full understanding of powered exoskeleton' technologies. Who This Book Is For Professionals, undergraduate and graduate students, enthusiasts, hobbyists, and those who want to go beyond basic knowledge or information for any kind of powered exoskeleton.

The major determinant of walking's metabolic cost is the work required to redirect the centre of mass velocity during step-to-step transitions. My first aim was to isolate transitions from other contributors to walking mechanics. The results demonstrated that sagittal plane rocking reproduced the important characteristics of walking's transitions including a strong dependence of work on step length and a proportional increase in metabolic cost. My second aim was to use rocking to gain insight into pathological gait's elevated cost. Physics-based mathematical models predict sub-optimal transitions occur when one or both legs are unable to generate mechanical power with the optimal timing and magnitude, requiring a greater magnitude of total work and an increase in metabolic cost. I tested this prediction by immobilising the ankle joints of healthy subjects to simulate sub-optimal transitions and found that joint immobilization indeed caused sub-optimal transitions thereby increasing transition work and metabolic cost.

Ankle exoskeletons are designed and personalized to enhance mobility in unimpaired adults and improve gait in individuals with motor impairments. Ankle exoskeletons are challenging to prescribe and optimize for an individual, resulting in inconsistent intervention outcomes. Quantifying and predicting changes in kinematics and muscle activity in response to varying exoskeleton properties may improve intervention outcomes, enhance mobility, and inform device design for individuals with diverse motor impairments. However, model-based approaches for understanding responses to ankle exoskeletons often rely on physiologically-detailed frameworks that require extensive experimental datasets to model heterogeneous physiology and motor control in individuals with motor impairments. To better understand responses to ankle exoskeletons across individuals with diverse physiology, the goal of this dissertation is to examine physiologically-detailed and non-physiological approaches to modeling and understanding responses to ankle exoskeletons in individuals with motor impairments and unimpaired adults. Cerebral palsy (CP) is one of the most common motor impairments among children and one of the largest groups who use ankle exoskeletons. Optimized powered and passive ankle exoskeletons have been shown to reduce the energetic demands of walking in children with CP. However, CP represents a heterogeneous population, with widely varying gait patterns. Understanding how heterogeneous kinematics and kinetics in CP alter exoskeletons impact on the energetic demands of walking could inform device design. Using subject-specific musculoskeletal simulations of walking with ankle exoskeletons, we found that idealized powered ankle exoskeletons reduced muscle demand in children with CP more than passive exoskeletons and that reductions in ankle plantarflexor demand drove overall muscle demand. However, walking speed and knee flexion angle impacted reductions in muscle demand. Powered ankle exoskeletons may, therefore, benefit children with CP, but may not provide benefits over optimized passive exoskeletons for all individuals. While musculoskeletal simulations provide a powerful platform to evaluate ‘what-if’ questions and probe complex systems, the underlying models often have normative assumptions about physiology and motor control that may limit their ability to accurately predict subject-specific responses to exoskeletons. Constructing dynamical models of walking with exoskeletons from data alone may enable exoskeleton responses to be predicted without detailed knowledge of an individual’s physiology. To test this theory, we built a passive ankle exoskeleton and collected extended treadmill walking data across four levels of dorsiflexion stiffness for 12 unimpaired adults. We developed three data-driven phase-varying models of each individual’s response to ankle exoskeleton torque and evaluated their predictive ability in unimpaired adults walking in bilateral ankle exoskeletons. We found that linear and nonlinear phase-varying models could accurately predict kinematic responses to torque but could not predict stride-to-stride variations in myoelectric responses. These models show promising potential to model responses to exoskeletons in individuals with motor impairments, though improving myoelectric predictions represents an exciting area of future research. While exoskeleton impacts on gait mechanics and energetics have been investigated, if and how an individual modulates their center-of-mass (COM) dynamics changes with ankle exoskeletons remains unclear. Quantifying changes in the whole-limb mechanisms describing COM dynamics with exoskeletons may identify characteristic sub-classes of responses to exoskeletons. We developed and identified template signatures – low-dimensional, physics-based representations of COM dynamics – during walking with and without passive ankle exoskeletons in 12 unimpaired adults and one individual with post-stroke hemiparesis. We found that the template signatures were consistent across unimpaired adults and were robust to changes in exoskeleton dorsiflexion stiffness. Conversely, the template signatures post-stroke reflected the individual’s increased paretic-limb stiffness and changed in response to exoskeletons. This work suggests that unimpaired COM dynamics do not change with passive ankle exoskeletons, but that COM dynamics in individuals post-stroke may adapt to ankle exoskeletons. This dissertation contributed to our knowledge of how ankle exoskeleton properties impact muscle demand and COM dynamics during walking, and the potential of data-driven modeling frameworks to quantify and predict responses to ankle exoskeletons. This knowledge may inform exoskeleton design and prescription, potentially improving exoskeleton efficacy for individuals with motor impairments. The research in this dissertation added to an existing open-source dataset for musculoskeletal simulations of walking in children with CP and created a novel, open-source dataset containing long time-series of walking with passive ankle exoskeletons in unimpaired adults. This research lays the foundation for future work aimed at identifying mechanisms driving heterogeneous responses to exoskeletons or other assistive devices in individuals with motor impairments.