Have you ever met an alien queen and wanted to shout “Get away from her, you b*tch!”? Well, probably not, but if you’ve seen the movie, at some point you’ve probably been curious about how an exoskeleton would feel.
In fact, exoskeletons are already a (semi)functional reality, mostly because they attracted the attention of the most powerful public investor in the world: the military. Equipping soldiers with an all powerful exoskeleton is not new: Heinlen already introduced the idea in 1959 in his novel Starship Troopers and mechas became an instant classic in japanese manga and anime. The latest one would obviously be Tony Stark’s super-cool (and flying!) Iron Man suit. These suits allowed the soldiers to lift major weights and jump long distances and this is basically what DARPA requested a decade ago in one of their (well funded) robotic challenges: an exoskeleton to allow lifting of up to 400 pounds (180 kg) without a sweat.
XOS roughly solved all the initial problems related to building an exoskeleton up to a point.
-Power feeding: if your (motorless) smartphone battery goes dead after a day, how many of those would take to move a (multimotor) metal structure with you inside? Don’t think too big, because all those batteries add to the weight of your suit. It wouldn’t do to need a supersuit to actually lift the weight of your … supersuit, right? The goal of these suits is to have juice for at least 24 hours, but thus far most of them last for a few hours only.
-Human/Suit interface: do you find it hard to achieve those pesky combos using your XBox 360 controller? well, just imagine doing that with a dozen motors and joint at the time, knowing full well that meeting the ground face first firmly depends on your driving skills. Even if you are a combo master, you are not supposed to be paying attention to a joystick when you are in the middle of a battlefield, right? so everything should be more intuitive. And, also, the lag between the command and the reaction should be minimized, otherwise you would feel like you are trying to run through water.
-Safety is the most important issue, both for the suit user and the people around. If you want to lift 190 kg, it’s right to be superstrong, but if you unwillingly collide with a fellow nearby, you don’t want him reduced to a bloody pulp, right? Besides, if there’s a glitch in motion control in your suit, you don’t want powerful motors to rip your arm off because the suit doesn’t know that the human elbow does not bend the other way. These problems are basically solved using force feedback (haptics), inverse kinematics (telling the robot how a human moves) and proper sensors but everything needs to be super-tuned if we are actually wearing it.
The XOS had 30 actuators to control its 30 different joints and used hydraulic cylinders (like our car brakes) to power them. Feedback was based on keeping a number of contact points with the joints and mimic whatever the user does (improved force sensors), like when we try to teach a kid to dance by balancing their feet on our own. A computer was in charge of translating the user input into motory output.
Later, Raytheon bought Sarcos and produced the XOS 2, a suit powered by an internal combustion hydraulics engine with electrical systems that uses lighter material and is about 50% more energy efficient than the XOS 1. It has processors on every joint and its actuators are reported to deliver about 200kg of force per square centimetre using pressurised hydraulics.
There are two other major potential investors in this field: space and health.
NASA, for example, believes that exoskeletons might be just the thing to keep a fit muscular tone in space, where things don’t weight anything and one hardly exercises at all. In this sense, their 57-pound X1 robotic exoskeleton is meant to inhibit movement in leg joints, although it can also assist it in case some angry, giant spider-bug crawls into the space station (or we want to use it for assistance on Earth, which is more boring, but also way more likely). X1 has 10 degrees of freedom, or joints 4 at hips and knees and six passive ones for sidestepping, turning and pointing, and flexing a foot)
If someone fancies an Iron Man suit instead, Trek Aerospace is developing the Springtail Exoskeleton Flying Vehicle, an exoskeleton frame with a jetpack expected to fly up to 70 miles per hour (112.6 kilometers per hour) and hovering motionlessly thousands of feet above the ground as well.
The most down-to-earth application of exoskeletons is, however, assisted motion. If your limbs or back won’t support you, these thingies could free you from the wheelchair and preserve your autonomy (at least as long as the batteries last).
Cyberdine -unrelated to the infamous company that created evil Skynet- is a japanese company that commercializes the Hybrid Assistive Limb, or HAL (also unrelated to the also evil HAL computer in 2001, A Space Odyssey; these guys have a gift with names). HAL is a power-assisted pair of legs, and the company also developed similar robot arms.
Unlike the previous designs, HAL is meant to help the elderly with mobility or help hospital or nursing carers to lift patients (nowadays you need a fairly bulky mobile minicrane to do this if the patient can’t help at all). HAL is operating at 150 hospitals nowadays and suits are leased at $1,950 per unit per year approximately.
However, the most novel feature in HAL is not its purpose, but its user interface: Cyberdine claims that HAL can be operated with the brain. In fact, according to their website, they do not detect EEG signals, but bio-electrical signals that appear in the limbs when the brain decides it’s time to move them (actually, this approach is closer to electromyography, but without the needles and the pain). Given a large enough number of sensors to detect the appropriate number of currents, each combination of readings is associated to a different motion, that is fed to the actuators (e.g. if all fours sensors at hip, shoulder, elbow and wrist are in motion, maybe you’re throwing a punch, if the hip sensor is off, maybe you’re simply trying to reach something). Since it is highly unlikely that sensors work correctly all the time, incomplete information is filled by onboard computers, in a similar way that isolated words can be concatenated to form a meaningful sentence.