ACM-R5 is the name of this awesome, and quite scary, amphibious robot snake – developed by the people at the Hirose Fukushima Lab in Japan.
ACM-R5 is equipped with paddles and passive wheels around the body. To generate propulsive force by undulation, the robot need a resistance property as it glides freely in tangential direction but cannot in normal direction. Due to the paddles and passive wheels, ACM-R5 obtains that character both in water and on ground.
Here’s a video demonstration of the robot snake in the water (Update: The old video is no longer available, so here is a new video of ACM-R5H.)
The control system of ACM-R5 is an advanced one. Each joint unit has CPU, battery, motors, so they can operate independently. Through communication lines each unit exchanges signals and automatically recognizes its number from the head, and how many units join the system. Thanks to this system operators can remove, add, and exchange units freely and they can operate ACM-R5 flexibly according to situations.
Read more about the ACM-R5 robot snake over at Hirose Fukushima Lab. (Update: Link removed, because the page is gone.)