On a woodland hill covered with autumn leaves, a thing with four legs walks purposefully along a gradual incline, loaded with four equipment packs, its black, double-jointed legs carefully picking their way.
Later, the thing strolls across a parking lot and a technician kicks it, causing it to stagger sideways a few steps before righting itself exactly the way you’d imagine a horse or mule might under the same circumstances. In winter, the thing traverses a patch of ice on the same parking lot, slipping and sliding but — amazingly — never losing its balance and toppling over on the slick surface. We then watch it plow its way through a snow drift… up a hillside slippery with mud… up a stacked pile of concrete blocks and, finally, running — running — across a stretch of highway.
The thing’s movements are considered, almost instinctual in their appearance. From a distance, it might look to be an animal — a very large dog or very small horse, except it has no head. And nestled between the equipment packs strapped over each of its four legs is an aluminum box full of cables and electrical components — the equivalent of its heart and brain. Is this the pack animal of the future?
BigDog is a robot built by Boston Dynamics, an engineering firm specializing in dynamic robots and human-simulation software. Marc Raibert founded the company after developing some of the first self-balancing robots himself. “In the early 1990s, I was a professor at MIT where I ran the Leg Laboratory as part of the A.I. Lab, where we developed dynamic robots that balanced actively,” Raibert explains. “Rob Playter, Nancy Cornelius and I spun out of there to start Boston Dynamics in 1992. At the time, we planned to focus on simulators for robots and people, but after a while we were building robots again. Now we’re focused on robots that work in rough terrain, such as BigDog, AlphaDog, Atlas, RHex and others.”
BigDog senses its environment and its own position with internal instruments measuring joint position, joint force, ground contact and ground load, while a gyroscope helps keep it stable, and a light detection and ranging system (LIDAR) monitor the robot’s surroundings. Other sensors monitor hydraulic pressure, oil temperature, engine functions, battery charge and other factors. BigDog can run up to 4 mph; climb slopes up to 35 degrees; navigate rubble and mud, snow and water; and carry a 340-pound load. In doing so, it set a world record for legged vehicles by traveling 12.8 miles nonstop without refueling.
Like BigDog, AlphaDog scrambles on four legs. Almost horse-sized, it clatters through a Boston Dynamics testing facility in one online video. RHex runs on six flexible, spinning, “C”-shaped legs that allow it to traverse all kinds of terrain, scamper through mud, paddle through water and, with its sealed body, submerge and operate like a miniature submarine. All of these robots walk on legs, but why not just use wheels? “Wheels are more efficient than legs when operating on roads,” Raibert points out. “But the whole point of legged robots is to have vehicles that can go off-road on rough terrain. Eventually, legged robots will operate anywhere people and animals can go, which is pretty much the entire landmass of the Earth.”
In order to create robots that can operate in such a wide range of environments, Raibert and his associates look at things that already move around easily in those environments: animals. “We take broad inspiration from animals, but we don’t try to directly copy them. We work from the function we would like the robot to perform and go backwards toward the design. For example, AlphaDog [a.k.a. the Defense Advanced Research Projects Agency’s Legged Squad Support System, or LS3] needs to be able to get up from the ground when it falls over. So we looked at dozens of hip/body arrangements to get one that would support that type of behavior.
“Another example is our work building a ‘cheetah’ robot for the M3 program at DARPA. We worked with a cheetah expert to understand some of the details of how a cheetah works, but in the end we design a machine based on the physics, mechanical engineering constraints, energetics and controls.” In March the Cheetah robot broke a 22-year-old speed record when it was clocked running at 18 mph on a treadmill. The Boston Dynamics team plans to get the robot off its treadmill and out into the wild for free-running exercises soon.
PETMAN may be the company’s most intriguing robo product. For anyone who’s seen the Terminator movies, the machine looks disturbingly like a Cyberdyne Systems Model T-101: human-shaped, but with pistons and cables where skin and muscle would be — yet topped by a flashing red warning light instead of a head. The automaton walks, does knee-bends, crouches and pushups in a startling re-creation of human movement. While PETMAN was designed to test the tolerances of military chemical protection clothing for use in biological warfare, it seems so lifelike that it’s enough to make you wonder how long it will be before robots like this will march alongside humans soldiers on the battlefield. But Raibert says that’s not even a consideration: “For the time being, robots will be developed for specific purposes and used by humans who are responsible for operating them and giving them instructions or limited assignments.”
PETMAN’s control system has a posture algorithm that constantly calculates how to keep the robot’s balance, regardless of whether it’s simply walking or being pushed in order to intentionally knock it off balance. “Lifelike walking gaits are naturally unstable,” Raibert says, “so the posture algorithm always needs to make adjustments. During normal walking on smooth terrain, the adjustments are small; when there is a disturbance or the terrain is irregular, the adjustments are larger. The posture algorithm works by adjusting the timing of the next footfall and the placement of the next footfall, as well as the force each foot exerts on the ground once it touches. To do that, the posture algorithm always measures the motion of the system, which it does with various sensors in the system and the control computer.”
Fortunately, PETMAN can’t escape from its treadmill proving ground inside Boston Dynamics, but the company is developing another robot that will: ATLAS. “In keeping with our company focus, ATLAS will operate on rough terrain,” Raibert says. “In addition to its legs, it will use its arms to aid in climbing, as a person would. We anticipate many applications for ATLAS, especially where one needs a robot to fit where a person fits or to do tasks that require human ergonomics.”
In watching a video of these machines in operation, there’s a sense that you are watching a living creature in motion, something that goes far beyond the obvious fact that the robots are designed to mimic human and animal locomotion for specific purposes. With PETMAN, there’s the impression of a human body that’s not quite all there — missing a head or hands, for example — yet still moving with confidence and strength. The four-legged BigDog and AlphaDog robots move — and even sound — like real animals, their spindly black bodies and machined legs creating the impression of something halfway between the dogs and mules they are meant to mimic and some huge, scuttling insect. You might think there might be a sizable psychological impact to be explored in utilizing these machines in warfare, but Boston Dynamics seems to have limited that to a joke YouTube video of a “weaponized” BigDog, with a bull’s horns mounted to its front, facing off against a would-be matador while bullfighting music plays on the soundtrack.
Raibert says he’s not privy to any plan to exploit his company’s mechanical minions as psychological weapons. “I don’t find them disturbing at all,” he says with all seriousness. “In the end, the design of the robots is an engineering task where we work from analysis of the set of tasks we want the robot to do and develop structures, actuators, sensors and controllers that achieve those tasks. Broadly speaking, the most unexpected result has been how rapidly robotics is progressing at Boston Dynamics but also at other labs around the country and around the world. It’s really a sweet time to be working in this field.”
An outsider might view the company as something out of science fiction itself — building the C-3POs of the future — but Raibert and his colleagues see the work in purely practical terms: “The motivation for us is the engineering challenge of developing advanced machines with behavior that no machine has ever shown before. When you do that, you also make machines that have more practical value.”
Boston Dynamics also develops software tools for human simulation, including DI-Guy, which is used for simulation-based training, UAV training, law-enforcement training and mission-planning; and Digital Biomechanics, a physics-based human simulation product designed to test and evaluate equipment such as backpacks, helmets and body armor. But when it comes down to it, the company makes robots — and Raibert can trace that back to his childhood. “My father had a pretty good shop in the basement when I was a kid, so I spent a lot of time down there building things: catapults, sling guns, gadgets and contraptions. I became a roboticist one day during grad school when I followed a teacher back from class to his lab. One of the technicians had a robot arm taken apart for repair, with parts strewn everywhere. I was immediately hooked and I never looked back.”