A soft exoskeleton, also known as a soft wearable robot or a soft robotic exosuit, is a type of wearable robotic device designed to augment and enhance the physical abilities of the human body. Unlike traditional rigid exoskeletons, which are typically made of hard materials like metal and are worn over the user's limbs, soft exoskeletons are constructed from flexible and lightweight materials. Soft exoskeletons are designed to assist individuals with mobility impairments, aid in rehabilitation, augment human performance, and improve overall quality of life.
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The concept of exoskeletons can be traced back to science fiction literature, where authors envisioned mechanical suits that enhance human abilities. However, soft exoskeletons, as we know them today, have their roots in the development of soft robotics and advanced materials science. The evolution of soft exoskeletons can be divided into several key stages:
The Hardiman Project (1965–1971) was one of the earliest notable attempts at creating a powered exoskeleton was the Hardiman Project, sponsored by the U.S. military and developed by General Electric and the U.S. Army. The project aimed to create a full-body rigid exoskeleton to enhance the strength and endurance of soldiers and workers. Hardiman suit made lifting 250 pounds (110 kg) feel like lifting 10 pounds (4.5 kg). Powered by hydraulics and electricity, the suit allowed the wearer to amplify their strength by a factor of 25, so that lifting 25 pounds was as easy as lifting one pound without the suit. However, the project was discontinued due to technical challenges, including power supply and control issues. [2]
In the Soviet Union, research on powered exoskeletons was conducted under the Soviet Cybernetic Research Project [3] Scientists and engineers explored the development of exoskeletons for military applications, focusing on enhancing soldiers' physical capabilities. Bionics involves a comprehensive exploration of nature, incorporating technical elements into the study of flora and fauna. The discipline revolves around mimicking natural manufacturing processes, replicating biological techniques and mechanisms, and examining the social behavior of organisms. [4]
In the twilight of the 19th century, a Russian engineer named Nicholas Yagin embarked on a groundbreaking journey that would lay the foundation for a revolutionary technological leap – the creation of the world's first exoskeleton-like device. [5] It was the year 1890, an era characterized by rapid industrialization and a fervent spirit of innovation. Yagin, a visionary mind with a passion for engineering and human augmentation, dedicated himself to crafting a solution that would amplify the capabilities of the human body. Inspired by the marvels of nature and the intricate design of insects' exoskeletons, he envisioned a device [6] that could enhance human mobility and strength. The early exoskeleton prototype consisted of articulated joints and a network of gears, springs, and levers that responded to the wearer's movements. Its purpose was clear – to augment the human body, providing support and amplifying strength. [7] [8]
In the late 1970s, Dr. David A. Winter, a biomechanics researcher, made notable contributions to the field by focusing on the biomechanics of human locomotion. His work provided valuable insights into the design considerations for exoskeletons, emphasizing the need for a more holistic understanding of human movement. [9]
By the early 1980s researchers like Dr. Homayoon Kazerooni began to delve into the practical applications of exoskeletons for rehabilitation. In 1989, Dr. Kazerooni founded Berkeley Bionics, a pivotal moment that marked a shift toward the development of more user-friendly exoskeletons. However, during this period, rigid exoskeletons remained the primary focus, with limitations in terms of weight and mobility. [10] [11]
In 1983, the Massachusetts Institute of Technology (MIT) introduced the MIT Exoskeleton, a powered exoskeleton designed for rehabilitation purposes. This project, led by Dr. Steven Jacobsen, was a notable step forward in incorporating robotics into assistive devices. [12] [13]
A prototype of the Berkeley Lower Extremity Exoskeleton (BLEEX) arose in the late 1990s when the landscape of exoskeleton development was undergoing a transformative phase, with researchers and engineers exploring innovative ways to enhance human capabilities. The Berkeley Lower Extremity Exoskeleton (BLEEX) was one such pioneering project that laid the foundation for the advancements in powered exoskeletons. The BLEEX project, initiated by the Robotics and Human Engineering Laboratory at the University of California, Berkeley, sought to address the challenges associated with walking and carrying heavy loads. The primary goal was to develop a soft exoskeleton capable of reducing the metabolic cost of these activities, thereby providing a breakthrough in human augmentation technology. [14] The early prototypes of BLEEX showcased the integration of flexible materials and actuation systems, marking a departure from the more rigid exoskeleton designs of the time. Researchers focused on creating a symbiotic relationship between the wearer and the exoskeleton, emphasizing comfort and natural movement. As the project progressed into the 2000s, BLEEX gained recognition for its potential applications in various fields, including military, medical rehabilitation, and industrial settings. The soft exoskeleton concept pioneered by BLEEX became a catalyst for subsequent research in the development of wearable robotics. [15] [16]
In tandem with the BLEEX project, the 1990s witnessed a surge in pioneering research dedicated to harnessing the potential of exoskeletons within industrial settings. Rigid exoskeletons emerged as a promising solution, aiming to alleviate the physical strain encountered by workers engaged in tasks demanding heavy lifting and repetitive motions.
One remarkable example from this era involves the concerted efforts of a team of engineers led by Dr. Hiroshi Kobayashi [17] at the Tokyo University of Science. In 1995, this team introduced a groundbreaking powered exoskeleton specifically designed to assist construction workers in Japan. The exoskeleton, equipped with state-of-the-art intelligent actuators and motion sensors, was meticulously crafted to augment human strength and endurance, thereby alleviating the burdens associated with manual labor in the construction industry. [18] [19]
The impetus behind this development stemmed from a pressing need to address the high incidence of musculoskeletal injuries among construction workers, especially those involved in tasks requiring the lifting and transportation of heavy building materials. By integrating cutting-edge technology into the exoskeleton design, the engineering team sought to create a symbiotic relationship between man and machine, enhancing both productivity and occupational safety.
The impetus for early experiments often arose from military needs and industrial demands. In military contexts, exoskeleton research aimed to create powered exosuits that could amplify soldiers' strength, allowing them to carry heavier loads over long distances, navigate challenging terrains, and perform tasks that would be otherwise strenuous or dangerous. In the industrial sector, the focus was on developing exoskeletons to assist workers in tasks involving heavy lifting, repetitive motions, and prolonged periods of standing, thereby reducing the risk of work-related injuries and increasing productivity.
The evolution of soft exoskeletons is deeply intertwined with the contributions of pioneering innovators and researchers who pushed the boundaries of wearable robotics. As the technology shifted from rigid exoskeletons to softer, more flexible designs, several key figures and significant developments shaped the history of the soft exoskeletons.
Conor Walsh, [20] a Harvard University researcher, made significant strides in soft exoskeleton technology with the development of the Soft Exosuit. [21] Walsh's team at the Wyss Institute for Biologically Inspired Engineering created a lightweight and flexible exoskeleton that used textile-based actuators to assist specific muscle groups. This groundbreaking approach marked a departure from rigid structures, offering a more comfortable and natural wearing experience. [22] [23]
The Wyss Institute for Biologically Inspired Engineering continued to be at the forefront of soft exoskeleton research. Researchers at the institute focused on refining soft exosuit designs, integrating advanced sensors and control systems, and exploring diverse applications, including medical rehabilitation and enhancing human performance in various tasks.
Cyberdyne Inc., a Japanese robotics company founded by Dr. Yoshiyuki Sankai, developed the Hybrid Assistive Limb (HAL) exoskeleton. HAL was one of the first commercially available soft exoskeletons designed to enhance and support human mobility. The exoskeleton detected bioelectric signals from the wearer's muscles, enabling intuitive control of the device. HAL found applications in healthcare, aiding individuals with mobility impairments and contributing to the field of robotic-assisted rehabilitation.. [24] [25]
ReWalk Robotics, founded by Dr. Amit Goffer, introduced personal exoskeleton systems designed to assist individuals with spinal cord injuries in walking. These wearable devices used soft components and advanced motion sensors, allowing users to stand, walk, and climb stairs independently. ReWalk's exoskeletons represented a significant leap in assistive technology, enhancing the mobility and autonomy of individuals with paralysis. [26]
The outcomes of these early experiments were groundbreaking in concept, yet they faced formidable challenges. Rigid exoskeletons, although promising, often proved cumbersome and impractical for extended use. They limited natural movements, causing discomfort and hindering the wearer's agility. Moreover, power supply, control mechanisms, and the overall weight of these exoskeletons posed significant hurdles to their widespread adoption.
Despite these challenges, the early experiments with rigid exoskeletons marked a crucial step in the evolution of wearable robotics. They demonstrated the potential of augmenting human abilities through external systems, sparking curiosity and driving researchers to explore alternative approaches. It was from these challenges and insights that the shift toward soft materials and pneumatic actuators began, laying the groundwork for the development of soft exoskeletons in the subsequent decades.
The field of soft exoskeletons has witnessed rapid advancements in research and development, driven by the collaboration between experts in various disciplines such as engineering, biomechanics, materials science, and computer science.
Researchers have focused on developing advanced materials that strike a balance between flexibility, durability, and strength. Smart materials, including shape-memory alloys, flexible polymers, and lightweight composites, have been explored to create soft exoskeleton components. These materials enable the exoskeletons to conform to the wearer's body, ensuring a comfortable fit while providing the necessary support and assistance. [27]
The use of soft actuators, such as pneumatic artificial muscles and soft electroactive polymers, has changed the way soft exoskeletons operate. These actuators mimic natural muscle movements, allowing for smooth and precise assistance. Coupled with sensing technologies, such as flexible strain sensors and inertial measurement units, soft exoskeletons can detect the wearer's movements and intentions, enabling real-time adjustments and personalized support.
Intelligent control algorithms, often based on artificial intelligence and machine learning, enable the exoskeletons to adapt to the user's gait, posture, and terrain. These algorithms analyze sensor data and optimize assistance in realtime, providing a seamless and natural walking experience for users with mobility impairments. Significant strides have been made in enhancing the interaction between humans and soft exoskeletons through the implementation of intelligent control algorithms. These algorithms, often rooted in artificial intelligence and machine learning, have transformed the way soft exoskeletons respond to users' movements, leading to more intuitive and efficient assistive devices.
Researchers at Carnegie Mellon University, in collaboration with exoskeleton companies, pioneered the development of adaptive control algorithms for soft exoskeletons. [42] A groundbreaking study concerning human-in-the-loop optimization of exoskeleton assistance while walking, [43] published in Science, demonstrated the effectiveness of these algorithms in a real-time adjustment of exoskeleton assistance. Users with spinal cord injuries experienced a 30% improvement in walking efficiency, as the algorithms seamlessly adapted to changes in terrain and user posture.
Scientists at ETH Zurich delved into the application of deep learning models in soft exoskeleton control. A research paper published in 2020 8th IEEE RAS/EMBS International Conference for Biomedical Robotics and Biomechatronics (BioRob) [44] [ full citation needed ] outlined the integration of convolutional neural networks (CNNs) to analyze sensor data from wearable exoskeletons. The study showcased a 25% reduction in energy expenditure for users navigating varied terrains, emphasizing the role of deep learning in optimizing gait assistance.
The Rehabilitation Engineering Research Center (RERC) on Wearable Robotics conducted user-centric trials involving individuals with muscular dystrophy. Engineers at RERC developed a personalized control system based on reinforcement learning algorithms. The trials, spanning a year, revealed a 35% improvement in user-reported comfort and ease of use. The results were published in the Journal of NeuroEngineering and Rehabilitation, [45] underscoring the significance of user-centered approaches in control algorithm development. [46]
Soft exoskeletons, with their advanced technology and innovative designs, have found widespread applications across various industries, transforming the way people work, move, and live. As the field of soft exoskeletons continues to advance, several key industries have embraced this technology, leading to significant improvements in efficiency, safety, and quality of life.
Soft exoskeletons have revolutionized the field of healthcare and rehabilitation, offering hope and mobility to individuals with spinal cord injuries, stroke survivors, and neurological disorders. Companies like Ekso Bionics and ReWalk Robotics [47] have developed soft exoskeletons specifically designed for rehabilitation purposes. EksoGT, introduced in 2016, has been widely adopted in rehabilitation centers globally, assisting patients in regaining mobility and independence. ReWalk's ReStore Exo-Suit, [48] launched in 2019, has seen remarkable success in aiding stroke survivors during their recovery process, enhancing walking abilities and balance.
Soft exoskeletons have found a home in manufacturing and industrial settings, where they assist workers in lifting heavy loads and reduce the risk of musculoskeletal injuries. Hyundai Motor Company's wearable robot, the Hyundai Vest Exoskeleton (H-VEX), [49] [50] introduced in 2018, has been used in their assembly lines, improving productivity and reducing physical strain on workers. Ford Motor Company, in collaboration with Ekso Bionics, implemented the EksoVest (now it is the next evolution Ekso EVO) [51] in 15 of its plants across the globe, [52] supporting workers during overhead tasks and repetitive movements since 2017.
Soft exoskeletons have made significant strides in military applications, enhancing soldiers' endurance and reducing fatigue during long missions. The Tactical Assault Light Operator Suit (TALOS), developed by the United States Special Operations Command, incorporates soft exoskeleton components to augment soldiers' strength and agility. While still in the research and development phase, TALOS represents a pioneering effort in integrating soft exoskeletons into military operations, aiming to enhance soldiers' capabilities on the battlefield. [53]
Construction workers and heavy machinery operators often face physically demanding tasks, and soft exoskeletons have proven to be invaluable in these environments. Launched in 2019, the Levitate AIRFRAME [54] by Levitate Technologies is worn by construction workers to reduce fatigue and minimize the strain on the lower back and shoulders, allowing them to work more comfortably and efficiently. Additionally, companies like Sarcos Robotics have developed soft exoskeletons for industrial applications, including construction and infrastructure maintenance, enhancing workers' safety and productivity [55]
Soft exoskeletons have shown promise in improving the quality of life for the elderly and individuals with mobility impairments. The MyoSuit, [56] developed by MyoSwiss AG, is a wearable exoskeleton that provides support to the lower body, aiding individuals with mobility challenges. MyoSuit has gained recognition for its user-friendly design and effectiveness in enabling natural movements. [57] In Japan, the Hybrid Assistive Limb (HAL), developed by Cyberdyne Inc., has been used in rehabilitation centers to assist patients with mobility impairments, offering them the ability to stand, walk, and regain independence. [58] [59]
In 2018, companies like SuitX [60] introduced exoskeleton solutions, such as MAX, [61] specifically designed for workers in logistics and warehousing. MAX exoskeletons assist with lifting and carrying heavy loads, reducing the risk of injuries. The MAX exoskeleton integrates the backX, shoulderX, and legX systems, [62] forming a comprehensive full-body exoskeleton designed for diverse industrial settings. Its purpose is to minimize the stress on the knees, back, and shoulders, allowing users to extend their work duration with less fatigue and a decreased likelihood of injuries.
Hunic, [63] a notable player in the field (IFOY award winner), [64] has developed a patent-pending soft exoskeleton named SoftExo, known for its lightweight wearability, high performance, and ergonomic design. The SoftExo offers advancements in exoskeleton technology, contributing to the evolution of solutions aimed at enhancing the well-being and capabilities of workers in various industries [65]
Soft exoskeletons have been integrated into emergency response protocols, especially in disaster-prone regions. The XOS 2 exoskeleton, developed by Sarcos Robotics, has been used by emergency responders since 2016. By augmenting the wearers' strength, XOS 2 assists in lifting heavy debris and carrying essential equipment during rescue missions. This technology has been deployed in various disaster-stricken areas, enhancing the effectiveness of search and rescue operations [66] [67] [68]
Soft exoskeletons, like the MyoSuit [69] developed by MyoSwiss AG, have been employed in educational institutions and research laboratories since 2019. Researchers and students use MyoSuit to study human movement patterns, rehabilitation techniques, and biomechanics. [70] [71] This wearable exoskeleton provides valuable insights into assistive technologies, shaping the future of rehabilitation practices and human-machine interaction research.
In the entertainment industry, the Teslasuit, introduced in 2017, integrates soft exoskeleton technology with haptic feedback systems. [72] This suit provides users with immersive experiences in virtual and augmented reality environments. By delivering realistic sensations of touch and movement, the Teslasuit enhances gaming, simulations, and virtual experiences in entertainment attractions, making virtual worlds more engaging and interactive [73]
These notable soft exoskeleton solutions and their implementations in various industries underscore the significance of this technology in enhancing efficiency, safety, and user experience. As these innovations continue to evolve, they hold the promise of reshaping industries and improving the lives of individuals across diverse sectors.
Assistive technology (AT) is a term for assistive, adaptive, and rehabilitative devices for people with disabilities and the elderly. Disabled people often have difficulty performing activities of daily living (ADLs) independently, or even with assistance. ADLs are self-care activities that include toileting, mobility (ambulation), eating, bathing, dressing, grooming, and personal device care. Assistive technology can ameliorate the effects of disabilities that limit the ability to perform ADLs. Assistive technology promotes greater independence by enabling people to perform tasks they were formerly unable to accomplish, or had great difficulty accomplishing, by providing enhancements to, or changing methods of interacting with, the technology needed to accomplish such tasks. For example, wheelchairs provide independent mobility for those who cannot walk, while assistive eating devices can enable people who cannot feed themselves to do so. Due to assistive technology, disabled people have an opportunity of a more positive and easygoing lifestyle, with an increase in "social participation", "security and control", and a greater chance to "reduce institutional costs without significantly increasing household expenses." In schools, assistive technology can be critical in allowing students with disabilities to access the general education curriculum. Students who experience challenges writing or keyboarding, for example, can use voice recognition software instead. Assistive technologies assist people who are recovering from strokes and people who have sustained injuries that affect their daily tasks.
The Berkeley Lower Extremity Exoskeleton (BLEEX) is a robotic device that attaches to the lower body. Its purpose is to complement the user's strength by adding extra force to the user's lower extremity bodily movements. The BLEEX was funded by the Defense Advanced Research Projects Agency (DARPA), and developed by the Berkeley Robotics and Human Engineering Laboratory, a unit within the University of California, Berkeley Department of Mechanical Engineering. DARPA provided the initial $50 million of start-up funds in 2001.
The Hybrid Assistive Limb is a powered, soft-bodied exoskeleton suit developed by Japan's Tsukuba University and the robotics company Cyberdyne. It is designed to support and expand the physical capabilities of its users, particularly people with physical disabilities. There are two primary versions of the system: HAL 3, which only provides leg function, and HAL 5, which is a full-body exoskeleton for the arms, legs, and torso.
Bio-mechatronics is an applied interdisciplinary science that aims to integrate biology and mechatronics. It also encompasses the fields of robotics and neuroscience. Biomechatronic devices cover a wide range of applications, from developing prosthetic limbs to engineering solutions concerning respiration, vision, and the cardiovascular system.
Adaptable Robotics refers to a field of robotics with a focus on creating robotic systems capable of adjusting their hardware and software components to perform a wide range of tasks while adapting to varying environments. The 1960s introduced robotics into the industrial field. Since then, the need to make robots with new forms of actuation, adaptability, sensing and perception, and even the ability to learn stemmed the field of adaptable robotics. Significant developments such as the PUMA robot, manipulation research, soft robotics, swarm robotics, AI, cobots, bio-inspired approaches, and more ongoing research have advanced the adaptable robotics field tremendously. Adaptable robots are usually associated with their development kit, typically used to create autonomous mobile robots. In some cases, an adaptable kit will still be functional even when certain components break.
Human Universal Load Carrier, or HULC, is an un-tethered, hydraulic-powered anthropomorphic exoskeleton developed by Professor H. Kazerooni and his team at Ekso Bionics. It is intended to help soldiers in combat carry a load of up to 200 pounds at a top speed of 10 miles per hour for extended periods of time. After being under development at Berkeley Robotics and Human Engineering Laboratory since 2000, the system was announced publicly at the AUSA Winter Symposium on February 26, 2009, when an exclusive licensing agreement was reached with Lockheed Martin. Although the exoskeleton is powered and can be used, the project was a failure as it hindered certain movements and actually increased strain on muscles, going directly against what a powered exoskeleton is supposed to do.
A powered exoskeleton is 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, while allowing for sufficient limb movement with increased strength and endurance. The exoskeleton is designed to provide better mechanical load tolerance, and its control system aims to sense and synchronize with the user's intended motion and relay the signal to motors which manage the gears. The exoskeleton also protects the user's shoulder, waist, back and thigh against overload, and stabilizes movements when lifting and holding heavy items.
Homayoon Kazerooni is an Iranian-born American roboticist, mechanical engineering, and professor. He serves as a professor of mechanical engineering, and the director of the Berkeley Robotics and Human Engineering Laboratory at the University of California, Berkeley. Kazerooni is also the co-founder of Ekso Bionics and SuitX. As a noted authority on robotics, he is frequently profiled and quoted in the media.
Ekso Bionics Holdings Inc. is a company that develops and manufactures powered exoskeleton bionic devices that can be strapped on as wearable robots to enhance the strength, mobility, and endurance of industrial workers and people experiencing paralysis and mobility issues after a brain injury, stroke, multiple sclerosis (MS) or spinal cord injury. They enable individuals with any amount of lower extremity weakness, including those who are paralyzed, to stand up and walk.
Berkeley Robotics and Human Engineering Laboratory is managed and operated by University of California, Berkeley. The lab conducts scientific research on the design and control of a class of robotic systems worn or operated by humans to increase human mechanical strength.
Neuromechanics of orthoses refers to how the human body interacts with orthoses. Millions of people in the U.S. suffer from stroke, multiple sclerosis, postpolio, spinal cord injuries, or various other ailments that benefit from the use of orthoses. Insofar as active orthoses and powered exoskeletons are concerned, the technology to build these devices is improving rapidly, but little research has been done on the human side of these human-machine interfaces.
Cybathlon, a project of ETH Zurich, acts as a platform that challenges teams from all over the world to develop assistive technologies suitable for everyday use with and for people with disabilities. The driving force behind CYBATHLON is international competitions and events, in which teams consisting of technology developers from universities, companies or NGOs and a person with disabilities (pilot) tackle unsolved everyday tasks with their latest assistive technologies. Besides the actual competition, the Cybathlon offers a benchmarking platform to drive forward research on assistance systems for dealing with daily-life challenges, and to promote dialogue with the public for the inclusion of people with disabilities in society. The involvement of the pilot is considered essential both to the competition and in the development process, to ensure that the perspective and needs of end users are considered and addressed.
Proportional myoelectric control can be used to activate robotic lower limb exoskeletons. A proportional myoelectric control system utilizes a microcontroller or computer that inputs electromyography (EMG) signals from sensors on the leg muscle(s) and then activates the corresponding joint actuator(s) proportionally to the EMG signal.
Soft robotics is a subfield of robotics that concerns the design, control, and fabrication of robots composed of compliant materials, instead of rigid links. In contrast to rigid-bodied robots built from metals, ceramics and hard plastics, the compliance of soft robots can improve their safety when working in close contact with humans.
Sunil K. Agrawal is an Indian roboticist and professor of Fu Foundation School of Engineering and Applied Science with secondary appointment in Rehabilitation and Regenerative Medicine at Columbia University. Agrawal is the author of more than 500 journals, three books, and has 15 U.S. patents.
Leia Abigail Stirling is the Charles Stark Draper Professor of Aeronautics at Massachusetts Institute of Technology, where she is the co-director of the human systems laboratory. She was elected an American Association for the Advancement of Science Leshner Leadership Institute Fellow in 2019.
The Wyss Institute for Biologically Inspired Engineering is a cross-disciplinary research institute at Harvard University focused on bridging the gap between academia and industry by drawing inspiration from nature's design principles to solve challenges in health care and the environment. It is focused on the field of biologically inspired engineering to be distinct from bioengineering and biomedical engineering. The institute also has a focus on applications, intellectual property generation, and commercialization.
Robert D. Gregg is an American bioengineer, roboticist, inventor and academic. He is an associate professor at the University of Michigan.
Kyoungchul Kong is a South Korean mechanical engineer, entrepreneur, academic, and author. He was selected as one of the Leader Scientists from the National Research Foundation of Korea in 2023. He serves as an associate professor at the Korea Advanced Institute of Science and Technology (KAIST) and is the Chief Executive Officer (CEO) of Angel Robotics.
Elliott J Rouse is an American mechanical engineer, roboticist, and academic. He is an associate professor in the Departments of Robotics and Mechanical Engineering and Director of the Neurobionics Lab at the University of Michigan.