The Bug (with no name yet)

As described elsewhere, I've always wanted to have a legged robot. Somehow, it's just a bit cooler than a box that rolls around. I want to build a robot that can handle real outdoor terrain, and until recently, I had resigned myself to building another robot with wheels, because all the walking robots seem to have significant problems: slow, energy inefficient, and just don't work too well in rough terrain, or on stairs. The real challenge, I have decided, is whether it can go up (and down!) a spiral staircase.

I had been researching NOMAD, SHRIMP, and the various Mars Rovers, as well as some other novel designs (balls, wheeled snakes, etc.), and came across a description of a legged robot called Rhex. Unlike other legged robots that have many degrees of freedom for each leg, and do all sorts of clever kinematic calculations to determine foot placement, etc., Rhex just had 1 degree of freedom for each leg, and flexible (compliant) legs. In the videos, it just sort of thrashes its way along, and most amazing, it can run, flip, and pronk, as well as climbing stairs. A walking robot that can go two body lengths per second (1 m/sec) is quite a feat.

There are two "hotbeds" of development for RHex: University of Michigan ( )and McGill ( and ). There is a sourceforge project for the Rhex software ( which includes SimSect, a simulator developed Uluc Saranli at UofM.

Rhex is about 50 cm long, with 17 cm long legs. The one I am building is about twice that size, largely because I have some suitable motors (which I had actually bought for the wheeled robots).

I haven't come up with a name yet...

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robot/bug.htm - 4 March 2002 - Jim Lux
robot home page - Jim's home page