July 2004

Demo: Wearable Robots

Continued from page 1

By Gregory T. Huang

3-4. Strong and sensitive. Once the basic exoskeleton design is in place, the researchers turn their attention to the details of building it. At a fabrication test station, for example, an engineer tunes a force sensor that goes in the exoskeleton's pelvis (top). The robotic suit must sense what the user is doing and help him or her to do it without restricting movement. A bit like power steering, the control system is what Jacobsen calls "get-out-of-the-way control." To make it work, sophisticated sensors like this one are needed at every leg joint and in the platforms beneath the user's feet. At an actuator test station, Jacobsen shows how researchers power up one such joint with hydraulics, the stuff that drives construction equipment and car brakes (bottom). Using a bank of hydraulic valves, researchers test how the joint behaves when driven by different fluid pressures and speeds. One of Sarcos's big advances, says Jacobsen, is building machines that can be strong, fast, and dexterous.

5. I, Robot. In a large room next to the hangar, Jacobsen unveils the end result of all this tinkering: a prototype lower-body exoskeleton, standing on a treadmill behind a blue curtain. Each leg has powered joints at the hip, knee, and ankle and about 20 sensors, all coordinated by an onboard PC in a backpack attached to the frame. Strap it on, go for a walk on the treadmill or up and down stairs while carrying a 90-kilogram load on your back, and it feels as if you're carrying nothing, says Jacobsen. You can even balance on one foot with a person on your back and barely feel any more fatigued than if you were standing by yourself, he adds. The exoskeleton adds strength because it stays in parallel with the user's legs and pushes on the ground. But this is just a test unit, says Jacobsen. "When you start building systems of elements, all of which are complex, and you put them together," he says, "you have to test if they work together in a combined way."

6. Power pack. For now, the exoskeleton's power comes from hydraulic pumps in the wall or from a backpack-size internal-combustion engine with a fuel tank that generates hydraulic power. Jacobsen points out this portable engine in the hangar and explains that Sarcos is working on a smaller, more efficient power source for its next-generation exoskeleton, which will be lighter, stronger, and more user friendly. Ease of use is important, says Jacobsen, because in the end this project is about "saving lives and going further distances." Indeed, with powered exoskeletons, Sarcos hopes to take the field of wearable robots further than it has ever gone before.