Elucidation of Twisting Motion of a Falling Cat and its Realization by a Robot

Postural control of a falling cat was investigated analytically and experimentally. The authors intended to develop such a robot as a cat that could restore her attitude at free fall by twisting and controlling the body. There are still contradictory and ambiguous explanations among the text books of physics or dynamics which deal twisting motion of a cat. Firstly, the principle of the twisting motion of a robot cat was analysed using a jointed double column model. And it was made clear analytically that a cat could restore her attitude by bending and twisting the body in the air. Then, the authors developed the robot cat which had vertebrate-type backbones and twisting mechanisms. It was confirmed experimentally that the robot cat could control its attitude by 180 degrees' rotation within 0.6 second when it was released upside-down at about 1.8m height in the air.