  This paper presents aims at mobility improvement of flexible underwater
robots. For this purpose, a novel propulsion method using planar structural
vibration pattern is proposed, and tested on two kinds of prototypes. The
result of experiments showed the possibility of the movements for multiple
directions: forward, backward, turn, rotation, drift, and their combination.
These movements are achieved by only one structure with two actuators. The
results also indicated the possibility of driving using eigenmodes since
movements were concentrated on low driving frequency area. To investigate the
relation between movement and structural vibration pattern, we established a
simulation model.
