The widespread usage of exoskeletal robotics to augment human beings moved a step closer this week when Raytheon demonstrated its second generation Exoskeleton, the XOS 2. The new robotic suit (think of it as wearable robot guided by a human brain) is lighter, faster and stronger than the original proof-of-concept XOS 1, yet uses half the power. While Raytheon's development is primarily focused on military usage, exoskeletons for the mobility-impaired are already at market and industrial exoskeletons from Japan, Korea and Isreal are not far behind. One day in the not-too-distant future, one of these suits will enable us all to have superhuman strength, speed and endurance.

The XOS 2 enables its wearer to easily lift 200 pounds several hundred times without tiring and repeatedly punch through three inches of wood. Yet, the suit, which was developed for the U.S. Army, is also agile and graceful enough to let its wearer kick a soccer ball, punch a speed bag or climb stairs and ramps with ease.


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The XOS 2 robotics suit is being designed to help with the many logistics challenges faced by the military both on and off the battlefield. The US Defense Advanced Research Projects Agency (DARPA) has long harboured a desire to extend the human capabilities of soldiers through wearable robot exoskeletons to create superhuman strength, speed and stamina.

DARPA funded exoskeleton developments

A decade ago, DARPA funded a US$50 million project known as "Exoskeletons for Human Performance Augmentation" which spawned a number of exoskeleton projects. The scope of the program included the development of actively controlled exoskeletons that not only increased strength and speed, but enable larger weapons to be carried, provided a higher level of protection from enemy fire or chemical attack, allowed wearers to stay active longer and carry more food, ammunition etc.

One of the most promising of the projects which emanated from the DARPA funding was the Wearable Energetically Autonomous Robot (WEAR) from SARCOS Research Corporation.

In 2007, SARCOS was purchased by Raytheon and WEAR became the basis for the initial proof-of-concept Raytheon XOS 1.

Most of the original participants in the DARPA funding have now dropped away for one reason or another, leaving only two bipedal exoskeletons in contention for United States military usage: Raytheon's XOS series and Lockheed Martin's HULC which had its origins in the Berkeley Lower Extremity Exoskeleton (BLEEX) from UC Berkeley's Robotics and Human Engineering Laboratory.

The technology was spun out into Berkeley Bionics which has now begun working with defense contractor, Lockheed Martin, culminating in the announcement of HULC in 2009.

Earlier this year it was announced that HULC was to be updated to run on fuel-cell power. So clearly the race is hotting up, because Berkeley Bionics is getting set to unveil a new web site in just over a week from now, and with nine months development work on fuel cell power, Lockheed Martin's HULC will not have the limitations of tethering to contend with.

The Springtail/XFV Exo-skeletor Flying Vehicle

One other noteworthy exoskeleton resulting from the DARPA funding was Millennium Jet's Solo Trek XFV (eXoskeletor Flying Vehicle) which promised vertical take-off and landing, a range of 125 miles, a cruising speed of 70 knots and the ability to hover dead still at any altitude up to a maximum of 8000 meters.

Delivery of a working unit for field testing by the US military was expected in late 2003 but it never quite met its schedules and has since morphed into the Springtail Exoskeleton Flying Vehicle, built by Trek Aerospace, which purchased the technology from Millenium Jet.

Clearly the advantages of the Springtail/XFV make it suitable for an array of potential non-military applications too, but the project is still a work-in-progress.

The Raytheon XOS 2 in detail

In a common manual labour task, such as lifting or carrying, Raytheon claims the XOS 2 suit would multiply the amount of work done by one person by between two and three times. Hence a human can do two or three times as much work, but with no extra effort – the robot is doing the heavy lifting, and is simply being directed by the human inside it. Given the high cost of human labour, and the potential for injury in such a physically stressful environment, the XOS 2 and similar powered exoskeleton devices are logical tools of industry.

Currently, the suit is tethered to its power supply, significantly limiting the potential for usage. Raytheon expects that the power consumption will need to reduce a further 60% from that of the XOS 2 for the suit to be viable in untethered form.

The XOS 2 is powered by an internal combustion engine and power to the “limbs” is by high-pressure hydraulics rather than electrics and high energy density lithium ion batteries because the production XOS will eventually see service on the battlefield and in the words of Dr. Fraser Smith, vice president of Operation for Raytheon Sarcos, "we believe they (lithium ion batteries ) are extremely dangerous. If one gets breached, it can explode and cause a fireball that's similar to a magnesium flare.”

Just when we're likely to see the EXO 2's successor in commercial readiness is a difficult question for Raytheon, as an exoskeleton has som many different potential uses, that it depends on the requirements of the user.

“If you think of an exoskeleton like a car, the combat variant needs to be built to handle rugged terrain, yet it has to still be agile and light, and it needs to operate on its own power. Think of a hybrid Land Rover”, said Smith.

“The logistics variant is about amplifying brute force and enhancing a soldier's ability to lift and carry. It's more like a hard-working Ford truck. These are two very different missions, and right now different people want the exoskeleton to do different things.”

“In the nearer term we see the exoskeleton working on logistics applications where it can be tethered to an external power supply. With a tethered power source, you could likely see it within five years. For a suit that operates on its own power, it's probably more like a decade away.”

Hence the XOS is unlikely to see combat for some time, as the first XOS variant is focussed on assisting to overcome logistics challenges faced by the military.

According to Raytheon, logistic and support military personnel have to lift up to 16,000 pounds over the course of a typical day. With increasing pressure to reduce costs, the XOS suit's ability to enable one man to do the work of three is likely to be very enticing.

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