Boston Dynamics has unveiled the latest in combat escorts: the AlphaDog.

AlphaDog is a robot that unlike most can walk and keep its balance. While walking robots have made the rounds for some time — Honda's ASIMO is one example — the big challenge has been getting them to keep their balance and move at a reasonable speed.

Most military escorts are vehicles. But vehicles don't work without roads, and in many parts of the world there aren't any. In a country such as Afghanistan, the pack mule is still a common method of carrying things — the U.S. military even trains soldiers in how to handle them. But mules need food and can be difficult to handle for people who don't have experience with animals. They also might run away when they hear gunfire.

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So the Department of Defense, through the Defense Advanced Research Projects Agency, sought alternatives. Waltham, Mass.-based Boston Dynamics, started by a group of MIT grads that were interested in robotics, used DARPA funding to experiment. The group came up with a method of using an array of gyroscopes, range finders and shock absorbers designed to help the robot "see" its environment and mimic the way an actual four-legged animal walks.

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The big advance was in understanding that animals (and people) are not perfectly stable when they walk. It's actually more of a controlled fall. Also, it turns out to be unnecessary to try and calculate exactly where a foot has to go for each step ahead of time. Far easier is to look at regions where the next step might have to be and calculate an approximation. That approximation can be fed back into the robot's "brain" and used to recalculate balance.

One of the early prototypes was BigDog, a quadruped robot powered by a two-stroke engine. It is loud (a two-stroke is the same type that powers a chainsaw) but it worked, able to travel a dozen miles and carry 340 pounds. AlphaDog expands on that — it carries larger loads and can move about the same distance. It will also be considerably quieter. (The demonstration model in the company's videos is powered by electricity, but this would not likely be practical in a real-world situation).

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Both AlphaDog and BigDog can also do something few robots can: regain their balance after getting pushed and get up after being knocked over. They can also negotiate rough terrain. Most walking robots lose balance easily (and can't get up).

AlphaDog isn't the only kind of robot Boston Dynamics is experimenting with; other models the company makes walk on two legs and climb.

Image: Youtube Screen grab/Boston Dynamics