A robotic catapult based on the closed elastica with a high stiffness endpoint and its application to swimming tasks

In this paper, we propose a new robotic catapult with a high stiffness endpoint. The conventional robotic catapults based on the closed elastica are robotic elements for generating impulsive motions by utilizing the snap-through buckling. In a typical robotic catapult, the two ends of an elastic strip are fixed to a free joint and an active joint, respectively. Here we found that by adding only the high stiffness at the free joint, compared to the conventional type, more elastic energy can be stored and release surely without loss of a characteristic of generating impulsive motion repeatedly. By utilizing the high stiffness endpoint, we develop a faster impulsive swimming robot than the conventional one.