The tail is an appendage that is found throughout the animal kingdom and serves a variety of functions depending on the species. It can be used for everything from signaling to locomotion, but for a team of researchers at the University of Pennsylvania, the most relevant use of the tail is how it can be use for stabilizing a body while it's in motion.
In particular, this team was interested in stabilizing the body of its Jeroba robot, a bipedal machine which hops like a frog. Previously, the team had used the Jeroba's tail as a mechanism to energize its spring legs, but in order for the bot to move around in this manner, the team had to figure out a way to stabilize the robot while it pitched and rolled in the air from jumping.
To allow the tail to have the range of freedom it would need to offset the in-air rolling motion, the researchers connected the tail pole to two of the tail motors to "effectively create a spherical joint." When the spherical joint, which functions as a roll controller, is combined with the tail's function as a spring energizer, it offsets the rolling motion enough to allow the robot to maintain an acceptable degree of stability while hopping.
The future is adorable, the future is terrifying.