On the Conical Motion of a Two-Degree-of-Freedom Tail Inspired by the Cheetah

An actuated tail can impart large angular impulse over short time spans, but swinging in a plane results in inevitable tail angle saturation. Cheetahs (Acinonyx jubatus) are observed swinging the tail in a cone during turns [1], and this paper develops a simplified two-degree-of-freedom (pitch and roll) rigid tail model to investigate this motion. Trajectory optimization and experiments on a robotic platform confirm the observed cone motion as a useful solution to roll stabilization. These results are relevant to the understanding of tail motions in biomechanics and bioinspired tailed robots.