A Giant Among Robots

Virtual life-forms get more impressive all the time

By Fenella Saunders|Thursday, March 01, 2001
RELATED TAGS: ROBOTS


Like a turn-of-the-century hunter returning from safari, Frank Mezzatesta stands next to a huge wooden crate he gleefully says contains something wild, a beast never before known to man. And he can hardly wait to show it off. With the click of a mouse, the front of the crate crashes to the floor, revealing an enormous metal monster 13 feet tall, 18 feet long, and weighing 11,000 pounds— the basic statistics of a loaded delivery truck. The creature seems to hesitate for a moment, then moves forward. With deliberate but surprisingly lithe steps, it strides across the floor, shifting its weight with the grace of a cat as it lifts each foot in turn. Nearing a small group of people, it leans toward them, then sways from side to side as if trying to decide whether to charge them, eat them, or ignore them. "At this point in a previous demonstration, one woman got up and ran," says Mezzatesta. The beast then takes a few steps backward, turns slightly, and begins to dance. Swiveling left and right as much as 7 degrees, it keeps its feet in place, making large undulations and 15-inch-deep knee bends. Before it is sent back to its box, some brave observers amble over for a better look.


To understand what Dino's inventors are attempting, imagine this behemoth covered with a shell that makes it look like a dinosaur. Then imagine it roaming freely on its own— the world's first truly autonomous robot.
Photo by Jan Staller

Mezzatesta is no big-game hunter; he's an engineer, and his beast is a robot dubbed Dino. It is the largest robot ever built that has legs and doesn't have a human inside. It contains its own power and moves autonomously after receiving basic instructions like "move forward." Ultimately, a version of Dino may be covered with a skin to make it look more like a triceratops. If challenging problems are solved, it could be let loose in theme parks to roam on its own. A machine that knows where it is, can make its own decisions, and can move around as easily as a living animal has long been the Holy Grail of roboticists. No one has yet been able to achieve this feat, even with small, wheeled robots.


Many robots have motors at each joint, especially at the knees. Dino's knees simply transfer power from the robot's hips, keeping the legs light and their inertia low.
Photo by Jan Staller
Birthed by Walt Disney Imagineering Research and Development, Dino was dreamed up by Danny Hillis, the man who invented massively parallel supercomputers in the 1980s. "I always wanted to build a robot dinosaur," says Hillis, who, as a Disney Fellow, ran the Dino project from 1998 until 2000, when he cofounded Applied Minds, Inc. His team of engineers and scientists was recruited from universities like the Massachusetts Institute of Technology and the University of California at Los Angeles. They went to work in a walled-off area of a large warehouse near the airport in Burbank. To one side of the robot sits a bank of computers where they created much of Dino's software and one console that wirelessly sends the robot simple commands like "walk backward."

Beyond those commands, Dino carries everything aboard needed to control itself— power from a bank of 55 sealed lead-acid batteries, three electric motors to move each leg, a Pentium 700 megahertz processor for each leg, and a central computer that receives commands, loads appropriate software from the onboard memory, and coordinates each leg's response. A gyroscope tells the robot how much it is leaning, and lasers at each ankle measure the distance to the ground to help calculate how a step should be taken. Sensors tell Dino how far each motor has rotated and the distance the robot has actually moved. The robot constantly compares feedback readings to make sure the multiple measurements make sense. It also monitors motors for current spikes or high temperatures to determine whether too much force is being applied, and it tracks velocity and acceleration limits.

Dino is impressive, but it is still a work in progress. Hillis originally wanted to power the robot with a Corvette V-8 engine that pressurized oil-filled hydraulic actuators. A test of that setup turned out to be far too noisy and cumbersome. Now smooth, quiet electric motors and batteries have replaced gasoline engines and hoses.


Age: 3 years
Total number of creators: 25
Height: 12 feet 11 inches
Length: 18 feet 2 inches
Width: 8 feet
Weight: 11,384 pounds
Motors: 12
Processors on board: 5
Memory: 5.1 GB
Batteries: 55 sealed lead-acid
Battery life
for walking: 90 minutes
Sensors: 45
Step length: 39 inches
Maximum leg-lift height: 19 inches
Force on one leg
during walking: 5,500 pounds
Amount body flexes when
a foot is raised: 2 inches
Photo by Jan Staller

Creating a full-scale Dino from simulations was an engineering challenge. "If you just scaled up a grasshopper to the size of an elephant, it would crush itself," says Hillis, because increases in scale create geometrically larger increases in weight. Make anything twice as big and it gets eight times heavier, so all its supports have to be thicker— which makes it even heavier. That extra mass, in turn, shoots up the forces of momentum and therefore the power necessary to get the robot moving and to stop it once it is moving. "The heavier and larger you scale an object, the more dynamic it becomes," says Gill Pratt, head of the Leg Lab group at MIT's Artificial Intelligence Laboratory, which is building its own, but much smaller, walking dinosaur (see "Walking on Two Legs," below). The more dynamic the robot, the more difficult it is to keep balanced when walking.


Each of Dino's leg linkages looks like a parallelogram. "If you move one of the angles of the parallelogram, all of the other angles move," says Alexis Wieland. But in the final application, using two connected parallelograms "is much more tricky."
Photo by Jan Staller
Small robots with legs are also easier to build because they can fall over without causing much damage— they don't have as far to fall or as much mass. "We'd be in a whole lot of trouble if this thing fell over," says Akhil Madhani, a mechanical engineer on the project. Madhani and other designers kept Dino's legs light by putting all the motors in the shoulders and then using a series of aluminum linkages and steel ball screws to transfer power through the knees to the ankles. Still, when Dino raises a foot, its body flexes about two inches, which sends vibrations through the whole chassis. "If you have ten thousand pounds vibrating a few inches, the forces are dramatic, maybe a thousand pounds back and forth," says Alexis Wieland, an applied mathematician who worked on the robot's software. "So all the walks are smoother than you'd really think is necessary, because any jarring of the body can produce enormous forces." Worse, when Dino lifts a foot, frame-flexing changes the distance between the three feet still on the ground, trying to pull them apart. By monitoring its motor currents, which shoot up due to the increased forces, Dino can compensate. "It's another level of intelligence that says: 'I'm exactly where I want to be, but, gosh, I'm fighting myself. Let me just move a few millimeters here and, oh, there it goes; the currents are lower,' " says Mezzatesta.

When Dino's sensors don't agree with its software or one another, it stops. "It is truly autonomous; there's no preplanned trajectory," says Wieland. Without any human input, Dino can shift its weight and move its feet until the motor sensors tell it that it has reached its original starting stance. Still, the team has had to learn to trust Dino. "When you're watching something generate trajectories on the fly and you don't know up front what it's going to do and the whole thing could fall over if it does the wrong thing, it's very nice to see it do the right thing," says Madhani. "But it gets your heart rate up."

Right now Dino should be able to handle uneven ground or walk up hills, and engineers plan to take it outside for a test run soon. Dino doesn't yet have sensors to tell it where it is on the planet or how to navigate around obstacles like people. All of that would be necessary before it could run around on its own. "But I wouldn't be that concerned about it, because much of that has been developed for wheeled mobile robots," says Martin Buehler, who's built small, running quadruped machines at the Ambulatory Robotics Lab of McGill University in Montreal. He is impressed by the work done on Dino. "The hard problem with all these robots is just to get the basic mechanics, dynamics, and control right."

Dino has laser gyroscopes that give it a balancing mechanism "sort of like an inner ear," Hillis says. "But right now it's not smart enough to take advantage of that. Once it starts being able to do that, feels itself start to trip and catches itself, I think it will start looking more and more natural. But that's a big software job and nobody's ever done it before, so it's going to take a long time. I think eventually you'll have lots of things like this walking around. Some of them will look like robots, and some of them will look like dragons, and some of them will look like big animals like rhinoceroses or woolly mammoths or imaginary animals, all kinds of things." Buehler notes that legged robots like Dino also would be able to perform extraordinary services like fire fighting, containing nuclear and chemical hazards, defusing bombs, searching for land mines, even exploring outer space. The key to all these activities, Buehler points out, is the superior mobility of legs that work as well as Dino's.


Photo by Jan Staller
Before the gigantic robot can go anywhere, though, it must be able to make its own decisions about where it should put its foot next without stepping on someone. Eric Haseltine, who heads research and development for Disney, says his team of Imagineers is already working on such artificial-intelligence technology for virtual-reality beings, and those programs might be reusable in actual machines like Dino. "This is a test bed that puts us on a road map toward intelligent, self-directed characters," he says. "We want them to be able to move around, react, learn, and behave on their own."

Autonomous dinosaurs roaming at will are likely to amaze and amuse us, but they will still be machines run by computers, and thus unlikely to operate perfectly. So as independent as they may become, Haseltine thinks, there will always have to be someone nearby watching— with a finger on a kill switch.



Walking on Two Legs

Not all ancient reptiles were giants. Troödon, for example, was a late Cretaceous dinosaur that grew up to six feet long and four feet tall. Over the past four years, Peter Dilworth, a robotics researcher at MIT's Leg Lab, has built a 10-pound version of that dinosaur called Troody, the first two-legged dinosaur robot. Dilworth consulted with paleontologist Gregory S. Paul to ensure that the dimensions are as true to the real thing as possible, based on fossils. Troody has 16 electric motors distributed among its hips, knees, ankles, feet, and tail. There are two sensors on each motor to feed joint angle and force readings to an onboard computer and a gyroscope to sense which way is up and in which direction the robot is moving. When Dilworth turns the robot on, it starts from a crouch like that of a nesting bird, then rises and rocks slightly before getting its balance. Although Dilworth gives Troody commands like "move forward" from a joystick, the robot plans its own movements. "Seven hundred times a second, an onboard computer reads all the sensors, does a bunch of math to figure out where all its joints are positioned, where its mass is, all its physical properties," says Dilworth. "Then a control algorithm decides whether it should be swinging a leg or how it should be moving." Dilworth hopes to eventually have Troodys running around museums so that visitors can get a more realistic sense of what dinosaurs may have been like.
F.S.







See photos and video of Troody walking at www.ai.mit.edu/projects/leglab.

For images of Martin Buehler's small running quadruped, SCOUT II, and of RHex, the cockroach robot he created with the University of Michigan and the University of California at Berkeley, go to the McGill Ambulatory Robotics Laboratory site: www.cim.mcgill.ca/~arlweb.


Comment on this article
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

ADVERTISEMENT
ADVERTISEMENT
Collapse bottom bar
DSCJulyAugCover
+

Log in to your account

X
Email address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it emailed to you.

Not registered yet?

Register now for FREE. It takes only a few seconds to complete. Register now »