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James Bruton is giving legs their snakes back

Arduino TeamOctober 7th, 2022

James Bruton gave that title to his most recent video as a good-natured jab at Allen Pan’s project about “giving snakes there legs back.” In Pan’s video, he built a robotic exoskeleton to let snakes walk around on motorized legs. But as Bruton noted in his video intro, those legs didn’t look very snakelike. So Bruton created his own robot that walks around on more serpentine limbs.

This robot’s six limbs each have three degrees of freedom (DoF), all of which are motor-driven. But unlike most robotic limb designs, these use “oblique swivel joint mechanisms.” That mouthful of a term means that each joint rotates on a plane offset at an angle relative to the preceding joint. While that arrangement isn’t suitable for many applications, the kinematics are interesting and the resulting movement does resemble the wriggling of a snake’s body as it slithers along.

Beefy servo motors rotate the joints and an Arduino Mega 2560 board controls them. The servos don’t allow for continuous rotation, but that wasn’t necessary for this robot’s gait. Power comes from a hobby LiPo battery pack and Bruton pilots the robot using the custom universal remote that makes an appearance in most of his videos. All of the leg segments were 3D-printed and attached to a frame made from a couple pieces of aluminum extrusion.

While it is easy for the Arduino to control the position of each servo motor, Bruton had to do a lot of work to figure out how to coordinate their movement. He figured out the basics through trial-and-error, but sophisticated control would require trigonometry and the implementation of inverse kinematics. Bruton decided not to bother with those, since he had already accomplished his goal of building robotic legs that look like they would belong to a snake.