A Tail Lets Carnegie's Cat-Like Robot Jump With Surprising Dexterity

Nature can be incredibly useful when it comes to solving complex human problems. In this case, a cheetah's lightweight furry tail, which is known as an aerodynamic drag tail, might have enabled scientists to overcome a problem in robotics, according to a study published in IEEE Transactions on Robotics.

If you're surprised that cats can be so helpful to engineers, you shouldn't be. 

Many big cats move with high precision and maneuverability, even at excessively high speeds. Partly, it's thanks to their tails. Until now, the same thing couldn't have been said about robots. Adding a tail to a robot can mean disadvantages such as increased mass, high inertia — an object's resistance to any changes in its velocity — and higher energy cost.

But now, it seems that things have changed. 

A problem of inertia

While most robotic tails have high inertia, the cheetah's tail uses aerodynamic drag to achieve high forces with low inertia. According to the researchers at Carnegie Mellon University's Robomechanics Lab, who were working in collaboration with the University of Cape Town, an aerodynamic drag tail (much like the cheetah's) could help with robotic mobility. 

"Robotic tails have historically relied on high inertia tails because of their simplicity, but nature has already figured out that there are better ways to stabilize agile motions," explains Ph.D. student Joseph Norby.

In the paper, the researchers compared aerodynamic and inertial tails to construct a tail with maximum effectiveness and minimum inertia. "This research suggests that following nature's inspiration results in equally capable tails for a fraction of the weight cost."

Emphasizing the tail's effectiveness for improving robot agility and giving it better control over its movements, the researchers saw that while both can allow the robot to rotate in the air, the aerodynamic tail has the advantage of being much lighter.

Even though the mass increased because of the tail, the researchers found that the robot with a tail can accelerate faster than a robot without one. "Tails help to stabilize the robot, which is critical when it is performing difficult maneuvers. We believe that improving robot agility will make our robots better at aiding people outside the lab," said Norby.

You can watch the robot in action below: