The robot moves by propagation of square wave. It's quite different from the way real snakes move. The motion is also not that fast, in fact it's the slowest of all the motions I performed with the robot. However, it can be made to go a bit faster by tweaking the motion. The foam pads on the robot provide friction & help the robot move. The way this motion works is by folding-unfolding configurations. The robot goes through a series of configurations (10 in total) that involve the robot attain square wave like form (fig. 1) & then unfold & refold to attain the inverse square wave (fig. 6). Then the robot again unfolds & refolds into initial configuration (fig. 11 & 1). The robot moves forward during the unfolding states (fig. 2-6 & 7-11) i.e when it changes from square wave configuration to inverse square wave.

 

The  during motion can be seen in the figures below. Note that last step (fig. 11) is same as first step (fig. 1), hence the motion sequence repeats after 10th step. The motors which are responsible for the motion are labelled in odd numbers. These are the motors whose axes are vertical (axes perpendicular to plane of the pictures; 8 motors in total).