An impulsive force generator based on closed elastica with bending and distortion and its application to swimming tasks

In this paper, we propose a novel closed loop elastic structure which can generate snap-through buckling with bending and distortion. The proposed mechanical closed loop structure consists of two rotary shafts and a belt-shaped elastic material which two ends are connected to one active rotary shaft and one free joint type shaft, respectively. Driving the active rotary shaft continuously, we can obtain impulsive motion by using snap-through buckling repeatedly. The change of the driving torque and the angular momentum generated snap-through buckling are shown by numerical simulations. From these results, it is shown that an offset parameter of the proposed structure is useful for generating impulsive turning motions of the compact swimming robot. The proposed mechanism is applied to a compact swimming robot which can turn impulsively at a maximum rate of 135 deg/s underwater.