Will a future Mars rover walk like a robot lizard?

Traversing slippery terrain can be a tricky game for a Martian rover -- or any wheeled robot, for that matter. Now, Georgia Tech researchers have built a biologically inspired robot that can speedily navigate slippery, sandy terrain.

The 2004 Mars rover Spirit discovered the disadvantages of wheeled travel the hard way when it became stuck in loose soil after six years of navigating all types of terrain. The six-legged robot, described in Friday’s edition of the journal Science, could provide a solution for such exploratory vehicles while navigating “flowable” ground.

Animals have developed fins to swim and legs to walk, but flowable terrain -- think dry sand or dead leaves -- presents particular challenges. Lizards and other critters, however, seem to navigate such terrain with relative ease.

So the scientists built a small robot -- just about 5 inches long and weighing 150 grams -- and used a 3-D printer to make legs in different shapes and see which one worked best.

The researchers found that a convex, C-shaped leg performed far better than a straight leg or a concave C-shaped leg. In fact, they achieved speeds of about 28 inches per second -- not half bad for a robot being forced to traverse slippery testing ground, like poppy seeds or glass beads.

The robots did face some scientific roadblocks. If the grain sizes were about as long as their legs -- relative “boulders,” from their perspective -- their peculiar stride lost its edge.

Still, the researchers say the findings -- and increasing understanding of what they call terradynamics, or how ground moves -- could offer insight into the physical principles behind how lizards and other critters walk as well.

“We envision that, in concert with aero- and hydrodynamics, a general terradynamics of complex ground will not only advance understanding of how animals move at present and in the past, but also facilitate the development of robots with locomotor capabilities approaching those of organisms,” the authors wrote.

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