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High-End Seals Have ''BigDog'' Robot Up and Running

January 12, 2011
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Trelleborg Sealing Solutions provides high-end o-ring seals for the hydraulic actuators that power the legs of Boston Dynamics'' BigDog robot.
Founded by former MIT professor Marc Raibert as a university spin-off in 1992, Boston Dynamics began building robots in 2003. The company, situated in Waltham, Mass., outside Boston, is dedicated to the “science and art of how things move.” It employs a team of 70 technicians, engineers and scientists specializing in building robotic systems that possess the mobility, agility, dexterity and speed normally seen in animals and humans. Robots made in Waltham combine advanced dynamic control systems with sophisticated mechanical designs. Trelleborg Sealing Solutions provides high-end hydraulic seals for Boston Dynamics'' robotics project.

Imagine a mechanized pack mule that can trudge through rocky terrain, wade across mud puddles, skid over ice sheets, wiggle through underbrush and climb steep hills. It can see and avoid obstacles, withstand blows and falls, follow a human leader on cue or autonomously stick to a preset course, all the while carrying upwards of 50 kilograms of payload. It sounds like a creature from a science fiction novel, but in actuality this is a sophisticated four-legged robot called BigDog that has already been put through its paces in the Massachusetts countryside in the United States.

Boston Dynamics
BigDog and its second-generation successor LS3 (short for Legged Squad Support System) were developed and built by a small but cutting-edge outfit called Boston Dynamics with funding from the Pentagon’s research arm DARPA.

The company’s founder, former MIT professor Marc Raibert, sees a wide range of applications for his agile robots, from carrying supplies to scouting, rescue and firefighting missions in rugged environments. In a decade or so, he believes, smart pack robots might be as commonplace as jeeps.

“About half the Earth’s landmass is inaccessible to wheeled and tracked vehicles,” Raibert says, explaining the motivation behind the creation of BigDog. “But people and animals can go almost anywhere on foot.”

Intelligent Movement
Boston Dynamics'' BigDog robot moves like a living creature, senses its surroundings, and can run, walk and even hop over obstacles.
Hence the idea was born to build a robot that moves like a living creature, senses its surroundings, and can run, walk and even hop over obstacles. Such a dynamically self-balancing robot requires a combination of advanced computer controls and sophisticated structural and mechanical designs, Raibert explains. “There have been a few legged robots in the past, but BigDog and LS3 are way out in front with regard to performance on rough terrain in all sorts of real-world conditions,” he says.

LS3, which is scheduled to enter its test phase in mid-2012, will be an upgraded version of BigDog, with more load-carrying capacity and a walking range of up to 20 miles before it needs to refuel. It will be able to obey simple commands from humans, such as “follow me” or “wait,” which can be given through a handheld device. While BigDog has sensors in its legs to feel the terrain, its successor will also be able to see and get a location fix thanks to GPS.

One key component to make sure Boston Dynamics’ robots can maneuver through almost any environment for hours on end is the hydraulic actuators that power the legs. That’s partially thanks to Trelleborg Sealing Solutions, which provided Raibert’s team with compact high-end seals for BigDog’s joints.

High Performance O-Rings
“Simple O-Rings fail and leak after a short period of time, so we gave them a durable, high-performance seal that met their requirements,” explains Dan Esterly, one of the technical managers at Trelleborg Sealing Solutions. Making a mechanical dog walk and run was an unusual project, he admits, since these types of seals are most commonly used for airplane landing gear and industrial equipment.

The unique project has already led to closer collaboration between both companies. Trelleborg is supplying high-end seals for the forthcoming LS3 and for the company’s latest robot, a humanoid creature dubbed PETMAN. It will be used by the U.S. Army to test chemical-protection clothing.

“We developed PETMAN from a clean sheet of paper to a walking robot in just eight months,” says Raibert. On a lab treadmill, the company’s latest creation is literally up and running, heel to toe like a human.

High-End Seals
Trelleborg’s seals are designed to take abuse, and they show minimal wear and will not leak under adverse conditions. Made from polytetrafluoroethylene (PTFE)-based sealing compounds, the high-end seals are usually used for industrial and aerospace applications. They operate reliably at temperatures ranging from –70 C to 260 C and remain functional even in a debris-filled environment at high speeds and pressures. These characteristics make Trelleborg seals a good fit for hydraulic actuators in robotic legs.

Check Out BigDog In Action:

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