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A powered exoskeleton, also known as power armor, powered armor, powered suit, cybernetic suit, cybernetic armor, exosuit, hardsuit, exoframe or augmented mobility, is a mobile
machine A machine is a physical system using Power (physics), power to apply Force, forces and control Motion, movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to na ...
that is wearable over all or part of the
human body The human body is the structure of a Human, human being. It is composed of many different types of Cell (biology), cells that together create Tissue (biology), tissues and subsequently organ systems. They ensure homeostasis and the life, viabi ...
, providing
ergonomic Human factors and ergonomics (commonly referred to as human factors) is the application of psychological and physiological principles to the engineering and design of products, processes, and systems. Four primary goals of human factors learnin ...
structural support A structural support is a part of a building or structure that provides the necessary stiffness and strength in order to resist the internal forces (vertical forces of gravity and lateral forces due to wind and earthquakes) and guide them safely to ...
and powered by a system of
electric motor An electric motor is an Electric machine, electrical machine that converts electrical energy into mechanical energy. Most electric motors operate through the interaction between the motor's magnetic field and electric current in a Electromagneti ...
s,
pneumatics Pneumatics (from Greek ‘wind, breath’) is a branch of engineering that makes use of gas or pressurized air. Pneumatic systems used in industry are commonly powered by compressed air or compressed inert gases. A centrally located and elec ...
,
lever A lever is a simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, or ''fulcrum''. A lever is a rigid body capable of rotating on a point on itself. On the basis of the locations of fulcrum, load and effort, the lever is div ...
s,
hydraulics Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counter ...
or a combination of
cybernetic Cybernetics is a wide-ranging field concerned with circular causality, such as feedback, in regulatory and purposive systems. Cybernetics is named after an example of circular causal feedback, that of steering a ship, where the helmsperson ma ...
technologies, while allowing for sufficient
limb Limb may refer to: Science and technology *Limb (anatomy), an appendage of a human or animal *Limb, a large or main branch of a tree *Limb, in astronomy, the curved edge of the apparent disk of a celestial body, e.g. lunar limb *Limb, in botany, ...
movement with increased strength and endurance. The exoskeleton is designed to provide better
mechanical load Mechanical load is the physical stress on a mechanical system or component. Loads can be static or dynamic. Some loads are specified as part of the design criteria of a mechanical system. Depending on the usage, some mechanical loads can be measu ...
tolerance, and its
control system A control system manages, commands, directs, or regulates the behavior of other devices or systems using control loops. It can range from a single home heating controller using a thermostat controlling a domestic boiler to large industrial c ...
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 The human shoulder is made up of three bones: the clavicle (collarbone), the scapula (shoulder blade), and the humerus (upper arm bone) as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder mak ...
,
waist The waist is the part of the abdomen between the rib cage and hips. On people with slim bodies, the waist is the narrowest part of the torso. ''Waistline'' refers to the horizontal line where the waist is narrowest, or to the general appearan ...
,
back The human back, also called the dorsum, is the large posterior area of the human body, rising from the top of the buttocks to the back of the neck. It is the surface of the body opposite from the chest and the abdomen. The vertebral column run ...
and
thigh In human anatomy, the thigh is the area between the hip (pelvis) and the knee. Anatomically, it is part of the lower limb. The single bone in the thigh is called the femur. This bone is very thick and strong (due to the high proportion of bone ...
against overload, and stabilizes movements when lifting and holding heavy items. A powered exoskeleton differs from a passive exoskeleton, as the latter has no intrinsic
actuator An actuator is a component of a machine that is responsible for moving and controlling a mechanism or system, for example by opening a valve. In simple terms, it is a "mover". An actuator requires a control device (controlled by control signal) a ...
and relies completely on the user's own
muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...
s for movements, adding more stress and making the user more prone to
fatigue Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve ...
, although it does provide mechanical benefits and protection to the user. This also explains the difference of an exoskeleton to
orthotics Orthotics ( el, Ορθός, translit=ortho, lit=to straighten, to align) is a medical specialty that focuses on the design and application of orthoses, or braces. An is "an externally applied device used to influence the structural and functio ...
, as orthosis mainly aims to promote the progressively increased muscle work and, in the best case,
regain Regain Records was a Swedish-based independent record label. The label predominantly released death metal and black metal albums. Regain Records was founded from what remained of the former label, Wrong Again Records, by Per Gyllenbäck in 19 ...
and improve existing muscle functions. Currently, there are products that can help humans reduce their energy consumption by as much as 60 percent while carrying things.


History

The earliest-known exoskeleton-like device was an apparatus for assisting movement developed in 1890 by Russian engineer Nicholas Yagin. It used energy stored in compressed gas bags to assist in movement, although it was passive and required human power. In 1917, United States inventor Leslie C. Kelley developed what he called a pedomotor, which operated on steam power with artificial
ligaments A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body include the: * Peritoneal li ...
acting in parallel to the wearer's movements. This system was able to supplement human power with external power. In the 1960s, the first true 'mobile machines' integrated with human movements began to appear. A suit called
Hardiman Hardiman was the first attempt to build a practical powered exoskeleton, by General Electric between 1965 and 1971. The machine was intended to allow the wearer to lift loads of 1500 pounds (680 kg) with ease. The project was led by the eng ...
was co-developed by
General Electric General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable energ ...
and the
US Armed Forces The United States Armed Forces are the military forces of the United States. The armed forces consists of six service branches: the Army, Marine Corps, Navy, Air Force, Space Force, and Coast Guard. The president of the United States is the ...
. The suit was powered by hydraulics and electricity and amplified the wearer's strength by a factor of 25, so that lifting would feel like lifting . A feature called force feedback enabled the wearer to feel the forces and objects being manipulated. The Hardiman had major limitations, including its weight. It was also designed as a master-slave system: the operator was in a master suit surrounded by the exterior slave suit, which performed work in response to the operator's movements. The response time for the slave suit was slow compared to a suit constructed of a single layer, and bugs caused "violent and uncontrollable motion by the machine" when moving both legs simultaneously. Hardiman's slow walking speed of 0.76 metres per second (2.5 ft/s or just under 2 mph) further limited practical uses, and the project was not successful. At about the same time, early active exoskeletons and humanoid robots were developed at the
Mihajlo Pupin Institute Mihajlo Pupin Institute ( sr, Институт Михајло Пупин, Institut Mihajlo Pupin) is an institute based in Belgrade, Serbia. It is named after Mihajlo Idvorski Pupin and is part of the University of Belgrade. It is notable for ma ...
in Yugoslavia by a team led by Prof.
Miomir Vukobratović Miomir Vukobratović ( sr-cyr, Миомир Вукобратовић) (December 24, 1931 – March 11, 2012) was a Serbian mechanical engineer and pioneer in humanoid robots. His major interest were in the development of efficient modeling an ...
. Legged locomotion systems were developed first, with the goal of assisting in the rehabilitation of paraplegics. In the course of developing active exoskeletons, the Institute also developed theory to aid in the analysis and control of the human gait. Some of this work informed the development of modern high-performance humanoid robots. In 1972, an active exoskeleton for rehabilitation of paraplegics that was pneumatically powered and electronically programmed was tested at Belgrade Orthopedic Clinic. In 1985, an engineer at
Los Alamos National Laboratory Los Alamos National Laboratory (often shortened as Los Alamos and LANL) is one of the sixteen research and development laboratories of the United States Department of Energy (DOE), located a short distance northwest of Santa Fe, New Mexico, ...
(LANL) proposed an exoskeleton called Pitman, a powered suit of armor for infantrymen. The design included brain-scanning sensors in the helmet and was considered too futuristic; it was never built. In 1986, an exoskeleton called the Lifesuit was designed by Monty Reed, a US Army Ranger who had broken his back in a parachute accident. While recovering in the hospital, he read Robert Heinlein's science fiction novel ''
Starship Troopers ''Starship Troopers'' is a military science fiction novel by American writer Robert A. Heinlein. Written in a few weeks in reaction to the US suspending nuclear tests, the story was first published as a two-part serial in ''The Magazine of F ...
'', and Heinlein's description of mobile infantry power suits inspired Reed to design a supportive exoskeleton. In 2001, Reed began working full-time on the project, and in 2005 he wore the 12th prototype in the Saint Patrick's Day Dash foot race in Seattle, Washington. Reed claims to have set the
speed record A speed record is a world record for speed by a person, animal, or vehicle. The function of speed record is to record the speed of moving animate objects such as humans, animals or vehicles. Overall speed record Overall speed record is the recor ...
for walking in robot suits by completing the race at an average speed of . The Lifesuit prototype 14 can walk on a full charge and lift for the wearer. Član tima sa aktivnim egzoskeletom, 1972. godine.jpg Exoskeleton (3368708126).jpg LG CLOi, IFA 2018, Berlin (P1070245).jpg


Classification

The general categorization suggests several feasible exoskeleton categories. Such categories have general classes, due to the wide quantity of exoskeletons in existence, and are the structure, the body part focused on, the action, the power technology, the purpose, and the application area varying from one to another. Exoskeletons are not only designed for specific body parts; the exoskeletons may be designed more generally for only one hand, a leg, or even the complete body. Thus, the separation of the classes demonstrates the most common body parts exoskeletons can be built for. The full-body class refers to the exoskeletons made to assist all the limbs, or most of the body. The upper body refers to the exoskeletons made for the upper limbs, and involving the chest, head, back, and/or shoulders. The lower body category refers to the exoskeletons made for the lower limbs: thighs, lower legs, and/or hips. Moreover, there are classes for specific limbs and specific joints. These classes include exoskeletons designed for the knee, ankle, hand, arm, foot, etc. Additionally, there is a special class for any other exoskeleton that is not included in the previous classes. Rigid exoskeletons are those whose structural components attached to the user’s body are made with hard materials. Such materials include metals, plastics, fibers, etc. On the other hand, soft exoskeletons, also called exo-suits, are made with materials that allow free movement of the structural components. Exo-suits are often made with, yet not restricted to, textiles. The action category describes the type of help the exoskeleton gives the user, dividing exoskeletons into active and passive action. The active class comprises exoskeletons that give “active” aid to the user; in other words, these exoskeletons perform the movements without the need for the user to apply energy. The energy needed to perform the movement is supplied by an external source. On the other hand, the passive class comprises exoskeletons that need the user to perform the movement to work; these exoskeletons do not have power sources. Thus, the user has to perform the movement, and while doing it, the exoskeleton facilitates the movement. The powered technologies are separated into four main classes, with one specific class for hybrid and one for any other non-common power technology. The four main classes comprise the electric, hydraulic, and pneumatic actuators as the active action, and the mechanical systems as the passive action. The exoskeleton’s purpose defines what the exoskeleton will be used for. This category has only two classes: recovery and performance. The recovery exoskeletons are used for rehabilitation; the performance exoskeletons are used for assistance. The last category comprises the application area for which the exoskeleton was made. Each exoskeleton may belong to one or more class. The military class comprises any exoskeleton used for any activity involving an army, navy, airforce, or any other military branch. The medical class comprises the exoskeletons involved in clinical activities, or in general, used in any hospital/clinic. Additionally, the recovery exoskeletons are normally classified in the medical class. Furthermore, the research class comprises the exoskeletons that are nowadays in their research development phase. The industrial class, as its name suggests, encompasses those exoskeletons made specifically for industrial activities. These exoskeletons are characterized for being used by people without any pathology seeking the avoidance of long-term physical damages. This description also applies to military exoskeletons. The civilian class is for the recovery or performance exoskeletons made for people to use in their homes or public spaces, aiding in tasks that people cannot perform as easily alone. Finally, there is a class for exoskeletons in which the applications do not fit into any of the previous classes.


Applications


Medical

In medical application, e.g. with complete paraplegia after
spinal cord injury A spinal cord injury (SCI) is damage to the spinal cord that causes temporary or permanent changes in its function. Symptoms may include loss of muscle function, sensation, or autonomic function in the parts of the body served by the spinal cor ...
, an exoskeleton can be an additional option for the supply of aids if the structural and functional properties of the neuromuscular and skeletal system are too limited to be able to achieve mobilization with an
orthosis Orthotics ( el, Ορθός, translit=ortho, lit=to straighten, to align) is a medical specialty that focuses on the design and application of orthoses, or braces. An is "an externally applied device used to influence the structural and functio ...
. In patients with complete paraplegia (ASIA A), exoskeletons are interesting as an alternative to an orthosis under this criterion for lesion heights above the thoracic vertebra (T12). In patients with incomplete paraplegia (ASIA B-D),
orthotics Orthotics ( el, Ορθός, translit=ortho, lit=to straighten, to align) is a medical specialty that focuses on the design and application of orthoses, or braces. An is "an externally applied device used to influence the structural and functio ...
are even suitable for lesion heights above T12 in order to promote the patient's own activity to such an extent that the therapeutical mobilization can be successful. In contrast to an orthosis, an exoskeleton takes over a large part of the active muscle work, while an
orthosis Orthotics ( el, Ορθός, translit=ortho, lit=to straighten, to align) is a medical specialty that focuses on the design and application of orthoses, or braces. An is "an externally applied device used to influence the structural and functio ...
is intended to activate the recovery of muscle work. In addition powered exoskeletons can improve the quality of life of individuals who have lost the use of their legs by enabling system-assisted walking. Exoskeletons—that may be called "step rehabilitation robots"—may also help with the rehabilitation from
stroke A stroke is a medical condition in which poor blood flow to the brain causes cell death. There are two main types of stroke: ischemic, due to lack of blood flow, and hemorrhagic, due to bleeding. Both cause parts of the brain to stop functionin ...
,
spinal cord injury A spinal cord injury (SCI) is damage to the spinal cord that causes temporary or permanent changes in its function. Symptoms may include loss of muscle function, sensation, or autonomic function in the parts of the body served by the spinal cor ...
or during aging. Several prototype exoskeletons are under development. The Ekso GT, made by Ekso Bionics, is the first exoskeleton to be approved by the US Food and Drug Administration (FDA) for stroke patients. The
German Research Centre for Artificial Intelligence The German Research Center for Artificial Intelligence (German: ''Deutsches Forschungszentrum für Künstliche Intelligenz'', DFKI) is one of the world's largest nonprofit contract research institutes for software technology based on artificial in ...
has developed two general purpose powered exoskeletons, CAPIO and VI-Bot. These are primarily being used for teleoperation. Exoskeleton technology is also being developed to enhance precision during surgery, and to help nurses move and carry heavy patients.


Military

Developing a full-body suit that meets the needs of soldiers has proven challenging. The Defense Advanced Research Projects Agency (
DARPA The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the Adv ...
) launched the Warrior Web program in September 2011 and has developed and funded several prototypes, including a "soft exosuit" developed by
Harvard University Harvard University is a private Ivy League research university in Cambridge, Massachusetts. Founded in 1636 as Harvard College and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of higher le ...
's Wyss Institute. In the early 2000s, DARPA funded the first
Sarcos Sarcos Technology and Robotics Corporation (NASDAQ: STRC) is an American developer of robotics and microelectromechanical systems and related technologies. It was founded in the early 1980s when it was spun out from the University of Utah. Th ...
full-body, powered exoskeleton prototype, which was hydraulically actuated and consumed 6,800 watts of power. By 2010, DARPA and Sarcos had more than halved that, to 3,000 watts, but still required the exoskeleton to be tethered to the power source. Nowadays, the Sarcos Guardian XO is powered by lithium ion batteries and is applicable for military logistics applications. In 2019, the US Army's
TALOS In Greek mythology, Talos — also spelled Talus (; el, Τάλως, ''Tálōs'') or Talon (; el, Τάλων, ''Tálōn'') — was a giant automaton made of bronze to protect Europa in Crete from pirates and invaders. He circled the island's sh ...
exoskeleton project was put on hold. A variety of "slimmed-down" exoskeletons have been developed for use on the battlefield, aimed at decreasing fatigue and increasing productivity. For example,
Lockheed Martin The Lockheed Martin Corporation is an American aerospace, arms, defense, information security, and technology corporation with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995. It ...
's ONYX suit aims to support soldiers in performing tasks that are "knee-intensive", such as crossing difficult terrain.
Leia Stirling Leia Abigail Stirling (''née'' Blumenthal) (born 1981) 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 Ass ...
's group has identified that exoskeletons can reduce a soldier's response times.


Civilian

Exoskeletons are being developed to help firefighters and other rescue workers to climb stairs while carrying heavy equipment.


Industry

Passive exoskeleton technology is increasingly being used in the automotive industry, with the goal of reducing worker injury (especially in the shoulders and spine) and reducing errors due to fatigue. They are also being examined for use in
logistics Logistics is generally the detailed organization and implementation of a complex operation. In a general business sense, logistics manages the flow of goods between the point of origin and the point of consumption to meet the requirements of ...
. These systems can be divided into two categories: * exoskeletons for upper-limb for assisting shoulder flexion-extension movements; * exoskeletons for lumbar support for assisting manual lifting tasks. For broadest application, industrial exoskeletons must be lightweight, comfortable, safe, and minimally disruptive to the environment. For some applications, single-joint exoskeletons (i.e. intended to assist only the limb involved in specific tasks) are more appropriate than full-body powered suits. Full-body powered exoskeletons have been developed to assist with heavy loads in the industrial setting, and for specialized applications such as nuclear power plant maintenance. The biomechanical efficacy of exoskeletons in industrial applications is however still largely unknown. Companies have to conduct a risk assessment for workplaces at which exoskeletons are to be used. The
Institute for Occupational Safety and Health of the German Social Accident Insurance The Institute for Occupational Safety and Health of the German Social Accident Insurance (German: ''Institut für Arbeitsschutz der Deutschen Gesetzlichen Unfallversicherung'', ''IFA'') is a German institute located in Sankt Augustin near Bonn and ...
has developed a draft risk assessment for exoskeletons and their use. The safety assessment is based on diverse experience including machine safety, personal protective equipment and risk analysis of physical stresses at work. The exoskeletons available on the market often fail to give adequate consideration to safety aspects, in some cases despite claims to the contrary by their manufacturers.


Products


Powered

*Japet Exoskeleton is a powered lower-back exoskeleton for work and industry based on established passive braces. It is intended to reduce lumbar pressure. *
Parker Hannifin Parker Hannifin Corporation, originally Parker Appliance Company, usually referred to as just Parker, is an American corporation specializing in motion and control technologies. Its corporate headquarters are in Mayfield Heights, Ohio, in Greater ...
's Indego Exoskeleton is an FDA-Cleared, electrically powered support system for legs that helps spinal cord injury patients and stroke patients walk. *
ReWalk ReWalk is a commercial bionic walking assistance system that uses powered leg attachments to enable paraplegics to stand upright, walk and climb stairs. ReStore, a simpler system by the same manufacturer, attaches to a single leg to assist with gait retraining, and was approved by the FDA in 2019. *
Ekso Bionics 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 pa ...
's EskoGT is a hydraulically powered exoskeleton system allowing paraplegics to stand and walk with crutches or a walker. It was approved by the FDA in 2019. *SuitX's Phoenix is a modular, light and cheap exoskeleton, powered by a battery backpack that allows paraplegics to walk at up to . * Cyberdyne's HAL is a wearable robot that comes in multiple configurations. HAL is currently in use in Japanese and US hospitals and was given global safety certification in 2013. *
Honda is a Japanese public multinational conglomerate manufacturer of automobiles, motorcycles, and power equipment, headquartered in Minato, Tokyo, Japan. Honda has been the world's largest motorcycle manufacturer since 1959, reaching a product ...
's Walking Assist Device is a partial exoskeleton to help those with difficulties walking unsupported. It was given pre-market notification by the FDA in 2019. * The
European Space Agency , owners = , headquarters = Paris, Île-de-France, France , coordinates = , spaceport = Guiana Space Centre , seal = File:ESA emblem seal.png , seal_size = 130px , image = Views in the Main Control Room (1205 ...
has developed a series of ergonomic exoskeletons for robotic teleoperation, including the EXARM, X-Arm-2 and SAM exoskeletons. The target application is telemanipulation of astronaut-like robots, operating in a remote harsh environment. *In 2018, Spanish exoskeleton provider Gogoa Mobility was the first European company to get a CE approval for their powered lower body HANK exoskeleton for medical use. The CE approval covered the use of HANK for rehabilitation due to Spinal Cord Injury (SCI), Acquired Brain Damage (ABD) & Neurodegenerative Illnesses. In Feb 2020, their knee specific exoskeleton called Belk also received a CE approval. *Roam Robotics produces a soft exoskeleton for skiers and snowboarders. *Wandercraft produces Atalante, the first powered exoskeleton to allow users to walk hands-free, unlike most powered medical exoskeleton that require the simultaneous use of crutches. *
Sarcos Sarcos Technology and Robotics Corporation (NASDAQ: STRC) is an American developer of robotics and microelectromechanical systems and related technologies. It was founded in the early 1980s when it was spun out from the University of Utah. Th ...
has unveiled a full-body, powered exoskeleton, the Guardian XO, which can lift up to . Their "Alpha" version was demonstrated at the 2020 Consumer Electronics Show with
Delta Air Lines Delta Air Lines, Inc., typically referred to as Delta, is one of the major airlines of the United States and a legacy carrier. One of the List of airlines by foundation date, world's oldest airlines in operation, Delta is headquartered in Atla ...
. *ExoMed's ExoHeaver is electrically powered exoskeleton, designed for Russian
nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...
and
palladium Palladium is a chemical element with the symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by the English chemist William Hyde Wollaston. He named it after the asteroid Pallas, which was itself na ...
mining Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the economic via ...
and
smelting Smelting is a process of applying heat to ore, to extract a base metal. It is a form of extractive metallurgy. It is used to extract many metals from their ores, including silver, iron, copper, and other base metals. Smelting uses heat and a ch ...
company in 2018. Designed for lifting and holding loads weighing up to 60 kg and collecting information about the environment using sensors. More than 20 exoskeletons have been tested and are used at the enterprise.


Projects on hold/abandoned

* Lockheed Martin's Human Universal Load Carrier (HULC) was abandoned after tests showed that wearing the suit caused users to expend significantly more energy during controlled treadmill walks. * The Berkeley Lower Extremity Exoskeleton (BLEEX) consisted of mechanical metal leg braces, a power unit, and a backpack-like frame to carry a heavy load. The technology developed for BLEEX led to SuitX's Phoenix. *A project from
Ghent University Ghent University ( nl, Universiteit Gent, abbreviated as UGent) is a public research university located in Ghent, Belgium. Established before the state of Belgium itself, the university was founded by the Dutch King William I in 1817, when the ...
, WALL-X was shown in 2013 to reduce the metabolic cost of normal walking. This result was achieved by optimizing the controls based on the study of the
biomechanics Biomechanics is the study of the structure, function and motion of the mechanical aspects of biological systems, at any level from whole organisms to organs, cells and cell organelles, using the methods of mechanics. Biomechanics is a branch of ...
of the human-exoskeleton interaction.


Limitations and design issues

Mobility aids are frequently abandoned for lack of usability. Major measures of usability include whether the device reduces the energy consumed during motion, and whether it is safe to use. Some design issues faced by engineers are listed below.


Power supply

One of the biggest problems facing engineers and designers of powered exoskeletons is the
power supply A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As a r ...
. This is a particular issue if the exoskeleton is intended to be worn "in the field", i.e. outside a context in which the exoskeleton can be tethered to a power source. Batteries require frequent replacement or recharging, and may risk explosion due to thermal runaway. According to Sarcos, the company has solved some of these issues related to battery technology, particularly consumption, reducing the amount of power required to operate its Guardian XO to under 500 watts and enabling its batteries to be “hot-swapped” without powering down the unit. 
Internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combus ...
power supplies offer high energy output, but problems include exhaust fumes, heat and inability to modulate power smoothly. Hydrogen cells have been used in some prototypes but also suffer from several problems.


Skeleton

Early exoskeletons used inexpensive and easy-to-mold materials, such as steel and aluminium. However, steel is heavy and the powered exoskeleton must work harder to overcome its own weight, reducing efficiency. Aluminium alloys are lightweight, but fail through fatigue quickly. Fiberglass, carbon fiber and carbon nanotubes have considerably higher strength per weight. "Soft" exoskeletons that attach motors and control devices to flexible clothing are also under development.


Actuators

Joint
actuator An actuator is a component of a machine that is responsible for moving and controlling a mechanism or system, for example by opening a valve. In simple terms, it is a "mover". An actuator requires a control device (controlled by control signal) a ...
s also face the challenge of being lightweight, yet powerful. Technologies used include pneumatic activators, hydraulic cylinders, and electronic
servomotor A servomotor (or servo motor) is a rotary actuator or linear actuator that allows for precise control of angular or linear position, velocity and acceleration. It consists of a suitable motor coupled to a sensor for position feedback. It also r ...
s. Elastic actuators are being investigated to simulate control of stiffness in human limbs and provide touch perception. The air muscle, braided pneumatic actuator or McKibben air muscle, is also used to enhance tactile feedback.


Joint flexibility

The flexibility of human anatomy is a design issue for traditional "hard" robots. Several human joints such as the hips and shoulders are
ball and socket joint The ball-and-socket joint (or spheroid joint) is a type of synovial joint in which the ball-shaped surface of one rounded bone fits into the cup-like depression of another bone. The distal bone is capable of motion around an indefinite number o ...
s, with the center of rotation inside the body. Since no two individuals are exactly alike, fully mimicking the degrees of freedom of a joint is not possible. Instead, the exoskeleton joint is commonly modeled as a series of hinges with one degree of freedom for each of the dominant rotations. Spinal flexibility is another challenge since the spine is effectively a stack of limited-motion ball joints. There is no simple combination of external single-axis hinges that can easily match the full range of motion of the human spine. Because accurate alignment is challenging, devices often include the ability to compensate for misalignment with additional degrees of freedom. Soft exoskeletons bend with the body and address some of these issues.


Power control and modulation

A successful exoskeleton should assist its user, for example by reducing the energy required to perform a task. Individual variations in the nature, range and force of movements make it difficult for a standardized device to provide the appropriate amount of assistance at the right time. Algorithms to tune control parameters to automatically optimize the energy cost of walking are under development. Direct feedback between the human nervous system and motorized prosthetics ("neuro-embodied design") has also been implemented in a few high-profile cases.


Adaptation to user size variations

Humans exhibit a wide range of physical size differences in both skeletal bone lengths and limb and torso girth, so exoskeletons must either be adaptable or fitted to individual users. In military applications, it may be possible to address this by requiring the user to be of an approved physical size in order to be issued an exoskeleton. Physical body size restrictions already occur in the military for jobs such as aircraft pilots, due to the problems of fitting seats and controls to very large and very small people. For soft exoskeletons, this is less of a problem.


Health and safety

While exoskeletons can reduce the stress of manual labor, they may also pose dangers. The US
Centers for Disease Control and Prevention The Centers for Disease Control and Prevention (CDC) is the national public health agency of the United States. It is a United States federal agency, under the Department of Health and Human Services, and is headquartered in Atlanta, Georgi ...
(CDC) has called for research to address the potential dangers and benefits of the technology, noting potential new risk factors for workers such as lack of mobility to avoid a falling object, and potential falls due to a shift in center of gravity. As of 2018, the US
Occupational Safety and Health Administration The Occupational Safety and Health Administration'' (OSHA ) is a large regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. Congress established the agenc ...
was not preparing any safety standards for exoskeletons. The
International Organization for Standardization The International Organization for Standardization (ISO ) is an international standard development organization composed of representatives from the national standards organizations of member countries. Membership requirements are given in Ar ...
published a safety standard in 2014, and
ASTM International ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, an ...
was working on standards to be released beginning in 2019.


Major events

*
Cybathlon Moving People and Technology 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 be ...
- an international competition in which people with physical disabilities compete against each other to complete everyday tasks using state-of-the-art technical assistance systems.


Fictional depictions

Powered exoskeletons are featured in
science fiction Science fiction (sometimes shortened to Sci-Fi or SF) is a genre of speculative fiction which typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel unive ...
books and media as the standard equipment for
space marine The space marine, an archetype of military science fiction, is a kind of soldier who operates in outer space or on alien worlds. Historical marines fulfill multiple roles: ship defence, boarding actions, landing parties, and general-purpose hi ...
s, miners, astronauts and colonists. The science fiction novel ''
Starship Troopers ''Starship Troopers'' is a military science fiction novel by American writer Robert A. Heinlein. Written in a few weeks in reaction to the US suspending nuclear tests, the story was first published as a two-part serial in ''The Magazine of F ...
'' by
Robert A. Heinlein Robert Anson Heinlein (; July 7, 1907 – May 8, 1988) was an American science fiction author, aeronautical engineer, and naval officer. Sometimes called the "dean of science fiction writers", he was among the first to emphasize scientific accu ...
(1959) is credited with introducing the concept of futuristic military armor. Other examples include
Tony Stark Iron Man is a superhero appearing in American comic books published by Marvel Comics. The character was co-created by writer and editor Stan Lee, developed by scripter Larry Lieber, and designed by artists Don Heck and Jack Kirby. The charac ...
's
Iron Man Iron Man is a superhero appearing in American comic books published by Marvel Comics. The character was co-created by writer and editor Stan Lee, developed by scripter Larry Lieber, and designed by artists Don Heck and Jack Kirby. The charact ...
suit, the robot exoskeleton used by
Ellen Ripley Ellen Louise Ripley, often referred to simply as Ripley, is a fictional Character (arts), character and protagonist of the Alien (franchise), ''Alien'' film series, played by American actress Sigourney Weaver. The character earned Weaver worldwide ...
to fight the
Xenomorph The Alien (also known as a ''Xenomorph XX121'' or ''Internecivus raptus'', or simply a xenomorph)Alien: The Weyland-Yutani Report is a fictional parasitoid, endoparasitoid Extraterrestrials in fiction, extraterrestrial species that serves as the ...
queen in ''
Alien Alien primarily refers to: * Alien (law), a person in a country who is not a national of that country ** Enemy alien, the above in times of war * Extraterrestrial life, life which does not originate from Earth ** Specifically, intelligent extrater ...
s'' and the
Power Armor A powered exoskeleton, also known as power armor, powered armor, powered suit, cybernetic suit, cybernetic armor, exosuit, hardsuit, exoframe or augmented mobility, is a mobile machine that is wearable over all or part of the human body, pro ...
used in the ''
Fallout Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and the shock wave has passed. It commonly refers to the radioac ...
''
video game Video games, also known as computer games, are electronic games that involves interaction with a user interface or input device such as a joystick, controller, keyboard, or motion sensing device to generate visual feedback. This fee ...
franchise.


See also

*
Back brace A back brace is a device designed to limit the motion of the spine in cases of bone fracture or in post-operative spinal fusiona, as well as a preventative measure against some progressive conditions or to correct patient posture. Common back b ...
: somewhat similar devices as passive exoskeletons *
Bionics Bionics or biologically inspired engineering is the application of biological methods and systems found in nature to the study and design of engineering systems and modern technology. The word ''bionic'', coined by Jack E. Steele in August 1 ...
*
Future Force Warrior Future Force Warrior was a United States military advanced technology demonstration project that was part of the Future Combat Systems project. The FFW project sought to create a lightweight, fully integrated infantryman combat system. It was one ...
*
List of emerging technologies This is a list of emerging technologies, in-development technical innovations with significant potential in their applications. The criteria for this list is that the technology must: # Exist in some way; purely hypothetical technologies can ...
*
Mecha In science fiction, or mechs are giant robots or machines controlled by people, typically depicted as humanoid walking vehicles. The term was first used in Japanese (language), Japanese after shortening the English loanword or , but the mean ...
* Walking truck, also known as the "cybernetic anthropomorphous machine"


References


External links


Video, images and articles about the Bleex exoskeleton project


* ''
Wired ''Wired'' (stylized as ''WIRED'') is a monthly American magazine, published in print and online editions, that focuses on how emerging technologies affect culture, the economy, and politics. Owned by Condé Nast, it is headquartered in San Fra ...
'' Issue 13.01, January 2005
Ironmen
the world's first exoskeleton weight-lifting competition
Video and abstract about the GAIT Robotic Orthosis (via IEEE Xplore)

SARCOS Military Humanoid Exoskeleton (YouTube)
{{Robotics 1890 introductions Body armor Emerging technologies Industrial robotics Medical robotics Military robotics Prosthetics Robotic exoskeletons Russian inventions