Stories about superhuman strength permeate popular culture from Atlas to Zeus, Superman to Schwarzenegger. But now, says University of Utah robotics expert Stephen Jacobsen, it’s time to deliver in the real world. With funding from the U.S. Department of Defense, Jacobsen’s Salt Lake City-based company, Sarcos, has built a robotic suit that does just that. A person wearing this powered “exoskeleton” on his or her legs can carry massive loads without getting tired. Exoskeletons could enable soldiers to haul heavier equipment over greater distances, allow rescue workers to carry survivors more safely, and eventually help disabled people get around. It’s a daring vision-and Sarcos is hardly the first group to pursue it-but Jacobsen seems a good bet to do it right. Over the course of his career, the prolific inventor has developed standout devices that include the world’s leading powered prosthetic arm and the dancing fountains of the Bellagio hotel in Las Vegas-all using the most advanced robotics technologies available. And while it may take years to make exoskeletons practical for widespread use, Jacobsen says, “before you do it right, you have to do it at all.” This spring, he gave TR associate editor Gregory T. Huang an exclusive tour of Sarcos and showed how the company goes about building a wearable robot.

1. Sensor suit. Jacobsen walks into a bustling hangar-like hall and points out a yellow contraption the size of a person. The first step in designing the exoskeleton, he explains, was building this plastic mock-up of the device that designers could use to gather data about how the human body moves. Volunteers donned the suit, and its 30 position sensors measured the range of motion and timing of each joint as they walked, ran, jumped, twisted, and squatted. The data were used to help create a computer model of the exoskeleton.

2. Mini model. But to see how various designs will work, it helps to build physical models too. In an equipment room down the hall, designer Jon Price positions a miniature wooden model of the exoskeleton next to a quarter-scale clay sculpture of a person. This setup, he says, allows researchers to see whether the machinery around a joint will bump into itself, for instance. “You build and you analyze, hand in hand,” says Jacobsen. And it’s a lot easier to make changes to the design at this scale.

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.