This robot based on the Klann linkage technique. This is a mechanism designed to simulate the gait of a legged animal and replace the wheel. The mechanism consists of a "leg" that comes into contact with the ground, a crank, two rocker arms, and two connecting rods, all connected together.See : http://robotix.ah-oui.org/site/main.php?found=200607-kl-204-klann-linkage