The majority of powered lower-limb exoskeletons nowadays are designed to rigidly track time-based kinematic patterns, which forces users to follow specific joint positions. This kinematic control approach is limited to replicating the normative joint kinematics associated with one specific task and user at a time. These pre-defined trajectories cannot adjust to continuously varying activities or changes in user behavior associated with learning during gait rehabilitation. Time-based kinematic control approach must also recognize the user’s intent to transition from one task-specific controller to another, which is susceptible to errors in intent recognition and does not allow for a continuous range of activities. Moreover, fixed joint patterns also do not facilitate active learning during gait rehabilitation. People with partial or full volitional control of their lower extremities should be allowed to adjust their joint kinematics during the learning process based on corrections from the therapist. To address this issue, we propose that instead of tracking reference kinematic patterns, kinetic goals (for example, energy or force) can be enforced to provide a flexible learning environment and allow the user to choose their own kinematic patterns for different locomotor tasks. In this dissertation, we focus on an energetic control approach that shapes the Lagrangian of the human body and exoskeleton in closed loop. This energetic control approach, known as energy shaping, controls the system energy to a specific analytical function of the system state in order to induce different dynamics via the Euler-Lagrange equations. By explicitly modeling holonomic contact constraints in the dynamics, we transform the conventional Lagrangian dynamics into the equivalent constrained dynamics that have fewer (or possibly zero) unactuated coordinates. Based on these constrained dynamics, the matching conditions, which determine what energetic properties of the human body can be shaped, become easier to satisfy. By satisfying matching conditions for human-robot systems with arbitrary system dimension and degrees of actuation, we are therefore able to present a complete theoretical framework for underactuated energy shaping that incorporates both environmental and human interaction. Simulation results on a human-like biped model and experimental results with able-bodied subjects across a variety of locomotor tasks have demonstrated the potential clinical benefits of the proposed control approach.

Lower Limb Exoskeleton, a wearable robot that is designed to provide lower limb assistance to users, has been rapidly developed in the previous decade. The goal of these robots is to replace human labor with robots while still having humans involved. However, while these robot suits provide sufficient assistance to the users, the efficiency of the robot is often overseen. Thus, restrict the exoskeleton's operating time or required it to connect to an external power supply. However, there is plenty of energy wasted in human motions. In this study, we target "loaded bipedal walking" as the primary motion to assist. In chapter 2, we applied trajectory optimization on different mechanical designs for lower-limb exoskeletons. It is commonly known that humans tend to use more energy to walk compared to other limb-based locomotion animals. This higher energy usage is due to "heel strikes" and "negative work" during human gait. Passive walkers elevate this phenomenon by utilizing elastic joints that absorb/reuse some of the negative work. The objective of this study is to absorb energy at one phase of the gait cycle, store it, and then release it at a later phase through the use of a lower limb exoskeleton. Knee geometry is one important factor in energy efficiency during gait. Animals with reversed knees compared to humans (backward knee), such as ostriches, exhibit improved energy efficiency. As part of this study, new energy optimization strategies were developed utilizing collision-based ground reaction forces and a discrete lagrangian. The minimal cost of transport (CoT) gait patterns were calculated with both forward-knee and backward-knee human-exoskeleton models. Simulation results show that wearing a backward-knee exoskeleton can reduce the CoT by 15% of while carrying external loads ranging from 20 to 60 kg. In addition, when the exoskeleton utilized energy recycling, the CoT was shown to be further reduced to 35%. These simulation results suggested that the optimal design for an exoskeleton aimed at utilizing energy recycling principles should incorporate backward-knee configurations much like those found in energy-efficient biped/quadruped animals. In fact, since the potential energy sources (heel strikes, negative work) and the main energy consumer (ankle push-off) occurs in the opposite legs, the ideal actuators for the exoskeleton need to be able to recycle, store, and transfer energy between different legs. To satisfy the actuator's requirements from chapter 2, in chapter 3 we choose pneumatic actuators as the actuator for our exoskeleton. Pneumatic actuators are a popular choice for wearable robotics due to their high force-to-weight ratio and natural compliance, which allows them to absorb and reuse wasted energy during movement. However, traditional pneumatic control is energy inefficient and difficult to precisely control due to nonlinear dynamics, latency, and the challenge of quantifying mechanical properties. To address these issues, In chapter 3, we developed a wearable pneumatic actuator with energy recycling capabilities and applied the sparse identification of nonlinear dynamics (SINDy) algorithm to generate a nonlinear delayed differential model from simple pressure measurements. Using only basic knowledge of thermal dynamics, SINDy was able to train models of solenoid valve-based pneumatic systems with a training accuracy of 90.58% and a test accuracy of 86.44%. The generated model, when integrated with model predictive control (MPC), resulted in a 5% error in pressure control. By using MPC for human assistive impedance control, the actuator was able to output the desired force profile and recycle around 88% of the energy used in negative work. These results demonstrate an energy-efficient and easily calibrated actuation scheme for designing assistive devices such as exoskeletons and orthoses. In chapter 4, we presented Pneumatic Exoskeleton with Reversible Knee (PERK). It utilizes the pneumatic actuators we developed in chapter 3 and the control strategies we concluded in chapter 2. Three clinical trials were done on three different test subjects. The results showed despite different walking patterns across different test subjects, there is less potential energy change during the swing phase of walking, potentially reducing the energy loss during the heel strike. In addition, during the double support phase, there is less energy consumption in the pneumatic system while configuring it as backward-knee, indicating it is easier or more intuitive for the user to have the exoskeleton recycling the dissipated energy with the backward-knee mechanism.

The field of exoskeletons has undergone an evolution from complex full-body exoskeletons that did not (yet) produce the expected results towards simpler single-joint exoskeletons that can improve the mobility of people. While full-body and single-joint exoskeletons certainly have appropriate applications, we need to get a better understanding of the distal and proximal assistive mechanisms and provide insights that are currently lacking on how to assist walking in an even simpler way than single-joint exoskeletons. This dissertation details an iterative approach toward the development of simplified and efficient assistance strategies for improving human locomotion. We first conducted an experiment to observe the human response to proximal and distal perturbations by altering the treadmill grade and footwear inclination. The results indicate that the metabolic rate is predominantly sensitive to changes in the center of mass (COM) mechanics and further motivate the development of devices that can assist walking at the level of the COM. We then developed a robotic tether system that allows applying desired cyclic force profiles as a function of step time to provide whole-body assistance during walking. By leveraging the system capabilities, we performed an experiment and simple pendulum simulation to investigate the effects of timing and magnitude for non-constant force profiles at the COM. Through these experiments and the simulation, we found that assistance at the COM during the double stance phase can efficiently reduce the metabolic rate of walking half. Surprisingly, assisting propulsion did not maximize the reduction in metabolic rate, and our pendulum model revealed that the reduction in metabolic rate can instead be explained by the assistance of COM acceleration at the beginning of the step. Ultimately, our long term goal is to develop similar strategies to populations with gait disabilities, but as a primary step, we investigated the biomechanical mechanisms to assist lower limb joints using timed forward forces at the COM. To that end, we assessed the underlying mechanisms of muscle and joint parameters that explain the effects of timing and magnitude of horizontal forces at the COM on metabolic rate. The results show that the metabolically optimal timing assisted the ankle muscles that are responsible for push-off, and the knee and hip muscles that are responsible for collision. Based on these findings, it seems possible to assist different joints by different amounts by varying the timing of forces at the COM. This could be useful in clinical populations for providing ‘targeted’ joint-specific assistance without having to switch between different exoskeletons. We expect our experimental findings to provide knowledge on optimal force profiles that could be used for treadmill exercise therapy, motorized ‘rollator’-style assistive devices for walking, and even it could even inspire new strategies for combined actions of the ankle, knee, and hip of full-body exoskeletons. Timed forces at the COM could be used to assist patients with impaired gait and facilitate proactive user participation that has been identified as a critical factor in improving locomotor outcomes for rehabilitation robotics.

Designing Exoskeletons focuses on developing exoskeletons, following the lifecycle of an exoskeleton from design to manufacture. It demonstrates how modern technologies can be used at every stage of the process, such as design methodologies, CAD/CAE/CAM software, rapid prototyping, test benches, materials, heat and surface treatments, and manufacturing processes. Several case studies are presented to provide detailed considerations on developing specific topics. Exoskeletons are designed to provide work-power, rehabilitation, and assistive training to sports and military applications. Beginning with a review of the history of exoskeletons from ancient to modern times, the book builds on this by mapping out recent innovations and state-of-the-art technologies that utilize advanced exoskeleton design. Presenting a comprehensive guide to computer design tools used by bioengineers, the book demonstrates the capabilities of modern software at all stages of the process, looking at computer-aided design, manufacturing, and engineering. It also details the materials used to create exoskeletons, notably steels, engineering polymers, composites, and emerging materials. Manufacturing processes, both conventional and unconventional are discussed—for example, casting, powder metallurgy, additive manufacturing, and heat and surface treatments. This book is essential reading for those in the field of exoskeletons, such as designers, workers in research and development, engineering and design students, and those interested in robotics applied to medical devices.

A wearable robot is a mechatronic system that is designed around the shape and function of the human body, with segments and joints corresponding to those of the person it is externally coupled with. Teleoperation and power amplification were the first applications, but after recent technological advances the range of application fields has widened. Increasing recognition from the scientific community means that this technology is now employed in telemanipulation, man-amplification, neuromotor control research and rehabilitation, and to assist with impaired human motor control. Logical in structure and original in its global orientation, this volume gives a full overview of wearable robotics, providing the reader with a complete understanding of the key applications and technologies suitable for its development. The main topics are demonstrated through two detailed case studies; one on a lower limb active orthosis for a human leg, and one on a wearable robot that suppresses upper limb tremor. These examples highlight the difficulties and potentialities in this area of technology, illustrating how design decisions should be made based on these. As well as discussing the cognitive interaction between human and robot, this comprehensive text also covers: the mechanics of the wearable robot and it’s biomechanical interaction with the user, including state-of-the-art technologies that enable sensory and motor interaction between human (biological) and wearable artificial (mechatronic) systems; the basis for bioinspiration and biomimetism, general rules for the development of biologically-inspired designs, and how these could serve recursively as biological models to explain biological systems; the study on the development of networks for wearable robotics. Wearable Robotics: Biomechatronic Exoskeletons will appeal to lecturers, senior undergraduate students, postgraduates and other researchers of medical, electrical and bio engineering who are interested in the area of assistive robotics. Active system developers in this sector of the engineering industry will also find it an informative and welcome resource.

Wearable Robotics: Systems and Applications provides a comprehensive overview of the entire field of wearable robotics, including active orthotics (exoskeleton) and active prosthetics for the upper and lower limb and full body. In its two major sections, wearable robotics systems are described from both engineering perspectives and their application in medicine and industry. Systems and applications at various levels of the development cycle are presented, including those that are still under active research and development, systems that are under preliminary or full clinical trials, and those in commercialized products. This book is a great resource for anyone working in this field, including researchers, industry professionals and those who want to use it as a teaching mechanism. Provides a comprehensive overview of the entire field, with both engineering and medical perspectives Helps readers quickly and efficiently design and develop wearable robotics for healthcare applications

Bioinspired Legged Locomotion: Models, Concepts, Control and Applications explores the universe of legged robots, bringing in perspectives from engineering, biology, motion science, and medicine to provide a comprehensive overview of the field. With comprehensive coverage, each chapter brings outlines, and an abstract, introduction, new developments, and a summary. Beginning with bio-inspired locomotion concepts, the book's editors present a thorough review of current literature that is followed by a more detailed view of bouncing, swinging, and balancing, the three fundamental sub functions of locomotion. This part is closed with a presentation of conceptual models for locomotion. Next, the book explores bio-inspired body design, discussing the concepts of motion control, stability, efficiency, and robustness. The morphology of legged robots follows this discussion, including biped and quadruped designs. Finally, a section on high-level control and applications discusses neuromuscular models, closing the book with examples of applications and discussions of performance, efficiency, and robustness. At the end, the editors share their perspective on the future directions of each area, presenting state-of-the-art knowledge on the subject using a structured and consistent approach that will help researchers in both academia and industry formulate a better understanding of bioinspired legged robotic locomotion and quickly apply the concepts in research or products. - Presents state-of-the-art control approaches with biological relevance - Provides a thorough understanding of the principles of organization of biological locomotion - Teaches the organization of complex systems based on low-dimensional motion concepts/control - Acts as a guideline reference for future robots/assistive devices with legged architecture - Includes a selective bibliography on the most relevant published articles

Physical rehabilitation for walking recovery after spinal cord injury is undergoing a paradigm shift. Therapy historically has focused on compensation for sensorimotor deficits after SCI using wheelchairs and bracing to achieve mobility. With locomotor training, the aim is to promote recovery via activation of the neuromuscular system below the level of the lesion. What basic scientists have shown us as the potential of the nervous system for plasticity, to learn, even after injury is being translated into a rehabilitation strategy by taking advantage of the intrinsic biology of the central nervous system. While spinal cord injury from basic and clinical perspectives was the gateway for developing locomotor training, its application has been extended to other populations with neurologic dysfunction resulting in loss of walking or walking disability.

The new technological advances opened widely the application field of robots. Robots are moving from the classical application scenario with structured industrial environments and tedious repetitive tasks to new application environments that require more interaction with the humans. It is in this context that the concept of Wearable Robots (WRs) has emerged. One of the most exciting and challenging aspects in the design of biomechatronics wearable robots is that the human takes a place in the design, this fact imposes several restrictions and requirements in the design of this sort of devices. The key distinctive aspect in wearable robots is their intrinsic dual cognitive and physical interaction with humans. The key role of a robot in a physical human–robot interaction (pHRI) is the generation of supplementary forces to empower and overcome human physical limits. The crucial role of a cognitive human–robot interaction (cHRI) is to make the human aware of the possibilities of the robot while allowing them to maintain control of the robot at all times. This book gives a general overview of the robotics exoskeletons and introduces the reader to this robotic field. Moreover, it describes the development of an upper limb exoskeleton for tremor suppression in order to illustrate the influence of a specific application in the designs decisions.

The U.S. Census Bureau has reported that 56.7 million Americans had some type of disability in 2010, which represents 18.7 percent of the civilian noninstitutionalized population included in the 2010 Survey of Income and Program Participation. The U.S. Social Security Administration (SSA) provides disability benefits through the Social Security Disability Insurance (SSDI) program and the Supplemental Security Income (SSI) program. As of December 2015, approximately 11 million individuals were SSDI beneficiaries, and about 8 million were SSI beneficiaries. SSA currently considers assistive devices in the nonmedical and medical areas of its program guidelines. During determinations of substantial gainful activity and income eligibility for SSI benefits, the reasonable cost of items, devices, or services applicants need to enable them to work with their impairment is subtracted from eligible earnings, even if those items or services are used for activities of daily living in addition to work. In addition, SSA considers assistive devices in its medical disability determination process and assessment of work capacity. The Promise of Assistive Technology to Enhance Activity and Work Participation provides an analysis of selected assistive products and technologies, including wheeled and seated mobility devices, upper-extremity prostheses, and products and technologies selected by the committee that pertain to hearing and to communication and speech in adults.