Passive Exoskeleton

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, 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.

A powered exoskeleton differs from a passive exoskeleton, as the latter has no intrinsic actuator and relies completely on the user's own muscles for movements, adding more stress and making the user more prone to fatigue, although it does provide mechanical benefits and protection to the user. This also explains the difference of an exoskeleton to orthotics, as orthosis mainly aims to promote the progressively increased muscle work and, in the best case, regain 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 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 was co-developed by General Electric and the US Armed Forces. 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 in Yugoslavia by a team led by Prof. Miomir Vukobratović. 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 (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'', 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 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
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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, 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. 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 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 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, spinal cord injury 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 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) launched the Warrior Web program in September 2011 and has developed and funded several prototypes, including a "soft exosuit" developed by Harvard University's Wyss Institute. In the early 2000s, DARPA funded the first Sarcos 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 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's ONYX suit aims to support soldiers in performing tasks that are "knee-intensive", such as crossing difficult terrain. Leia Stirling'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.

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 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's Indego Exoskeleton is an FDA-Cleared, electrically powered support system for legs that helps spinal cord injury patients and stroke patients walk.
* ReWalk

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