SAFFiR provides Hong’s team with a clear head start. Because the two programs have overlapping goals, research that has gone into SAFFiR will apply to THOR and vice versa. The same basic engineering, specialized with different tools and capabilities, could wind up doing both jobs. That’s the advantage, in theory, of a humanoid: the ability to adapt and accomplish a wide range of tasks, whether it’s stepping over the high “knee-knocker” doorsills found on vessels or crawling across shifting rubble at a disaster site on shore.
Up to this point, Team THOR has focused almost entirely on mobility. Manipulation—the ability to hold steering wheels and power tools and ladder rungs—will be important down the line, but getting around quickly, and with stability, is the most pressing problem. After all, if a humanoid can’t reliably reach its mission, who cares how well it handles an air hammer?
Bipedal movement has always been the great promise and peril of humanoid robotics. It would allow machines to better maneuver through a range of environments, particularly those built for people. But it’s damn hard. It’s also damn risky—nearly any fall can be catastrophic. That’s why bots like CHARLI-2 take such tentative steps, carefully modulating the exact location of each foot, using a system generally referred to as position control.
A robot such as CHARLI-2 or Honda’s Asimo—a humanoid “helper” that walks, hops, and dances around its own show at Disneyland’s Tomorrowland—typically has actuators embedded in its joints that can rotate to bend or straighten each leg. As its walking pace increases, those motors spin faster, but the robot hits a functional speed limit; it can’t allow momentum to take over, the way humans do as we break into a run. Their joints are too stiff, and their algorithms require a constant reckoning of the limbs’ whereabouts. They don’t move like people, with our moment-to-moment oscillation between imbalance and recovery. Robots that use only position control have to know the exact geometry of the terrain beneath them.
RoMeLa’s new robot, by comparison, incorporates force control. It is far more biological in design and function. “The main difference is linear series elastic actuators,” Hong says. “Ours is inspired by human anatomy. Our actuators extend and contract like a human muscle.”
Long and cylindrical, the actuators are placed roughly where muscles would go; they act like them too, with titanium springs that provide shock absorption for each step and the elasticity to bounce from one stride to the next. These qualities enable the robot to also use force control: It can turn up the speed of its actuation, working those simulated muscles harder and overriding the algorithmic panic that sets in when position-control software can’t perfectly predict each footfall. As a result, it also has more opportunities to recover its balance. Where CHARLI-2 might instantly topple over on stiff legs, this design might try to turn a stumble into a squat. By balancing force and position control, the robot can move with something closer to the loose, improvisational—ultimately more efficient and powerful—manner of a person.
The benefits of musclelike actuators and a more adaptable control scheme should be greater speed and stability and an end to the old guard of timid bipedal bots. This robot will take long, terrain-devouring strides, with a literal spring in each step. It will move boldly—because it needs to.
When he first read DARPA’s broad agency announcement for the DRC, Nicolaus Radford balked. As the deputy project manager for NASA’s Robonaut, a humanoid currently being tested on the International Space Station, he was familiar with what humanoids can and can’t do. “It sounded like a six-year-old wrote it,” he says. “And then we’ll have it drive a car, and then we’ll have it climb a ladder and then operate a pump!”
The DRC is hyperbolic by design, easily the hardest robotics competition in history. That audacity has proved irresistible to engineers. With the glaring exception of Honda—and Asimo could still show up in the unfunded Track D, which has later deadlines—the DRC has attracted the best humanoid robotics labs on the planet. Along with Team THOR, Track A includes two teams from NASA, one from Carnegie Mellon University (the institution that won DARPA’s last robotic challenge, a self-driving car race), a company spun out of the University of Tokyo, and a wild-card entry from defense contractor Raytheon.
Teams in Tracks B and C design only software, but they’ll be competing to use robots built by Boston Dynamics (best known for the four-legged BigDog system). This government-provided bot, which Boston Dynamics has based on its PETMAN and Atlas prototypes, is shaping up to be one of the most capable humanoids to date; powerful hydraulic actuators allow it to leap across gaps. The 2014 finals will feature eight robots reflecting the highest overall scores from all tracks, so a showdown between the Boston Dynamics robot and the best of Track A is practically inevitable.single page