| Summary: | From lizards to kangaroos, many animals with tails possess an agility that allows them to turn or self-right after a foot slip. Cheetahs demonstrate tremendous precision and maneuverability at high speeds due, in part, to their tails. Translating this performance to robots would allow them to move more easily through natural terrain. However, adding a tail to a robot carries disadvantages like increased mass, high inertia, and a higher energy cost. Researchers at Carnegie Mellon University's Robomechanics Lab, in collaboration with the University of Cape Town, have found ways to overcome these challenges inspired by the cheetah's tail. The findings were published in IEEE Transactions on Robotics. The cheetah's lightweight furry tail is known as an aerodynamic drag tail; that is, it acts sort of like a parachute. Most robotic tails have high inertia, but the cheetah manages to retain low inertia. Inertia is a physical quality that describes an object's resistance to changes in motion - high tail inertia means the tail can apply high forces. Aerodynamic tails instead use a different principle - aerodynamic drag - to achieve high forces without a large inertia. In nature, aerodynamic drag tails are often used in reorientation tasks, such as turning and recovering after a foot slip, so researchers believe an aerodynamic drag tail will help solve problems of robotic mobility. The researchers compare aerodynamic and inertial tails in their paper, eventually constructing a tail to maximize effectiveness while minimizing inertia. "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," said Ph.D. student Joseph Norby, who works with Aaron Johnson, an assistant professor of mechanical engineering. "This research suggests that following nature's inspiration results in equally capable tails for a fraction of the weight... |