Like the history of war, the history of military exoskeletons is filled with hardship and disappointment. \u00a0The 1959 book \u201cStarship Troopers\u201d by\u00a0Robert Heinlein is regarded as the first widely circulated work of fiction to feature military powered armor. \u00a0While there were some early patents and drawings outlining what a military exoskeleton should\u00a0look like, researchers in the field realized that the technology is a long way from being put in an active combat zone. \u00a0The relatively controlled and structured environments of hospitals, rehabilitation centers and factories provided a more fertile ground for wearable robotics implementation.<\/p>\n
Around\u00a02010, two major exoskeleton projects for the military were brought to the public\u2019s attention: the HULC (Human Universal Load Carrier) by Ekso Bionics and Lockheed Martin and the XOS and XOS2 by Sarcos\/Raytheon. \u00a0Both were full body suits for solider mobility augmentation. \u00a0Both projects captivated the public\u2019s imagination. \u00a0But with each article and newscast the capabilities and success of the two exos were becoming more and more exaggerated. \u00a0So it came with a great shock when the US Military stopped expressing interest in both projects. \u00a0In just a few months, it seemed that exoskeleton technology had gone from seemingly being months away from full deployment in the military to something useless and not worth pursuing.<\/p>\n The downfall of the first military exoskeletons was their size and power consumption. \u00a0Since both the HULC and the XOS were full body suits, they had large metal frames and multiple actuators. \u00a0Measuring and characterizing what all of these individual actuators actually did for a soldier was hard enough, but powering them proved impossible. \u00a0The XOS project emphasized on the development of the motors and control system first, with the idea that battery technology will catch up. \u00a0The XOS 2 was a tethered exoskeleton that needed to be connected to a power source at all times. \u00a0When it became clear that no batteries are capable of powering the suit for a long time, the development was cancelled.<\/p>\n The HULC project ran into similar power supply issues as the XOS but the Ekso Bionics and Lockheed Martin teams fought very hard to make it work. \u00a0The HULC was redesigned repeatedly to consume less power. \u00a0At one point, a small gas powered engine was brought in. \u00a0But as Boston Dynamics has now found out, the US Military did not appreciate the idea of a loud high pitch engine announcing the position of its troops.<\/p>\n Eventually, the HULC was able to move under its own power for several hours and it demonstrated reduced metabolic cost for the soldiers wearing it but the project ran into a new obstacle. \u00a0The US Military increased the number of hours the HULC should be able to operate without recharging. \u00a0The project then ran into an infinite loop, to increase the battery life a heavier battery was required, which then required more power to the suit which then required a larger battery and so on.<\/p>\n While the\u00a0HULC was not successful, a stripped down version with no motors and electronics called the iHAS\u00a0became one of the first passive exoskeletons to show promise for use at work and industry<\/a>. \u00a0The iHAS\u00a0morphed into the Mantis which eventually inspired the Ekso Works and FORTIS passive exoskeletons. \u00a0Sarcos\u00a0separated from Raytheon but it is still an active company and is\u00a0surely working on something interesting.<\/p>\n Over the years, military exoskeletons have evolved into smaller, lighter and more specialized devices. \u00a0For comparison, some of the initial versions of the HULC weighed 53 lb. (24 kg) compared to 11 lb. (5 kg) for many of the new military exos.<\/p>\n Challenges for Military Exoskeletons<\/strong><\/p>\n Military exoskeletons face many of the same challenges as their industrial counterparts: being comfortable to wear for many hours and integration with already established equipment and standards. \u00a0Military exoskeletons have to work with what is already accepted military equipment. \u00a0For example, if an infantry armored vest interferes with the fit of a military exoskeleton, the exoskeleton has to go. \u00a0Military exoskeletons have to be universal, yet comfortable and fully integrated with the soldier\u00a0while not getting in the way of weapons or the ability to take cover.<\/p>\n This is why many of the latest military exoskeletons have their motors and actuators at the front or the back of the user. \u00a0This is in sharp contrast to the vast majority of exoskeletons that have the bulk of the device at the hips or the side of the legs.<\/p>\n Furthermore, the exoskeletons have to be reliable and very durable. \u00a0If a paratrooper needs to jump off a plane, parachute into a lake, crawl through mud and then run for cover to engage the enemy that exoskeleton has to work and not become a liability.<\/p>\n Opportunities for military exoskeletons<\/strong><\/p>\n There is a real opportunity for the adoption of exoskeletons in the military. \u00a0As a rule of thumb, the more equipment a soldier has to wear, the less distance they can cover in a day. \u00a0In terms of safety, the distance a military unit is expected to cover is inversely proportional to how much armor the soldiers can wear. \u00a0An exoskeleton that can demonstrate a reduction of the metabolic cost of a loaded with equipment infantry can translate to soldiers that can cover more ground, have more supplies, become more independent and have additional armor.<\/p>\n All military exoskeletons with the notable exception of the Mojo series by 20KTS+ aim to reduce the metabolic cost of a soldier in one way or another. \u00a0The exoskeleton may apply direct power assistance to the soldier while walking, attempt to transfer some of the equipment weight into the ground or reduce the weight of batteries by recharging smaller ones. \u00a0The major exception to this rule are the Terra\u00a0Mojo and Marine\u00a0Mojo by 20KTS+<\/a> which reduce the vibrations on standing soldiers while on small boats or vehicles.<\/p>\n Categories and Examples:<\/strong><\/p>\n Just like the other three exoskeleton subfields (medical, work\/industry, consumer\/civilian) the military exoskeletons can be divided into categories based on function.<\/p>\n Full Body Military Exoskeletons<\/strong><\/p>\n These are wearable robots that cover the legs and the arms. \u00a0Outside of science fiction (movies, books and computer games) there have been few actual prototypes in development. \u00a0All full body suits share the same weaknesses as the HULC and XOS 2. \u00a0 They are large, have too many actuators and are difficult to power and control. \u00a0As a result, many later full body projects have been split in half into separate or modular lower body and upper body wearable robots.<\/p>\n The full body powered exoskeletons for the military\u00a0that have reached a prototype stage remain:<\/p>\n Lower Body Powered Military Exoskeletons<\/strong><\/p>\n Lower extremities (or just leg) exoskeletons\u00a0provide assistance to the legs. \u00a0If the wearable extends all the way down to the\u00a0ground, it can also be used to transfer loads. \u00a0Because a military exoskeleton always has to be flexible and compliant, the amount of load that it can carry while still moving quickly will always be limited. \u00a0These devices can also be classical with a hard metal frame or be made entirely out of soft materials. \u00a0This allows for powered leg exoskeletons to be merged into one category based on their main purpose: provide mobility assist and decrease the metabolic cost of movement (a soldier \u00a0that carriers the weight of their gear and the exoskeleton should expend less energy than carrying just the gear).<\/p>\n Examples of powered lower body military exoskeletons:<\/p>\n Passive Military Exoskeletons<\/strong><\/p>\n Passive exoskeletons do not have any actuators, batteries or electronics. \u00a0Two good examples of what a passive exoskeleton can do for a military are the Marine Mojo\u00a0and\u00a0DSTO Operations Exoskeleton. \u00a0The Marine Mojo by 20KTS+ is designed to absorb shock and vibrations for military personal on small, fast patrol boats. \u00a0It is a small light dampener system. \u00a0The\u00a0Operations Exoskeleton by the Australian Government Department of Defense Science and Technology (DSTO) is a system of Bowden cables designed to transfer a percentage of the weight of a soldier\u2019s heavy backpack directly into the ground.<\/p>\n Examples of passive exoskeletons:<\/p>\n Energy Scavenging\u00a0Military Exoskeletons<\/strong><\/p>\n Energy\u00a0scavenging\u00a0exoskeletons purposely hinder the soldier in an attempt to collect energy. \u00a0The collected energy can be turned into electricity to recharge a battery or directly power a device (such as a communication device). \u00a0Some lower body exoskeletons supposedly can be turned from assistive to energy collective, but that will make them permanently heavier. \u00a0For an idea of what a rough prototype of an energy collecting knee exoskeleton looks like refer to this article: Exoskeletons Extracting Energy For the User<\/a>.<\/p>\n Usually energy extraction from walking happens at the heel. \u00a0A compliant element is compressed at heel strike providing a small amount of energy. \u00a0Historically, energy extraction devices end up producing less energy than the cost of wearing them. \u00a0The best example of a scavenging\u00a0military exoskeleton is the PowerWalk by Bionic Power. \u00a0In May of 2016 the company acquired an additional contract for $1.25 million for initial low volume production of the PowerWalk for the US Army.<\/p>\n![\"XOS](\"http:\/\/exoskeletonreport.com\/wp-content\/uploads\/2016\/07\/XOS_Steel-Plate-Back-Cleaned.jpg\")
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