Thrust improvement of an fish robot actuated by compressed unimorph piezoelectric composite actuator

In this work, we have presented a fish robot actuated by four compressed light-weight piezo-composite actuators. Swimming speed, thrust, and drag of the fish robot were experimentally examined to verify effect of the applied compressive force on force actuation, consequently on swimming speed of fish robot. The swimming speed of the fish robot was measured for four different tail fin areas. The drag of the fish robot was estimated by experiment and computational fluid dynamics (CFD) simulation. For drag measurement, we have presented an apparatus to measure relatively small drag by using a high speed camera. The measured drag agreed well with the calculated one by the CFD. We have also suggested a thrust measurement apparatus, where we can ignore effect of vibratory motion of the system. The thrust of the fish robot was increased about 11% due to the applied compressive force on the piezoceramic actuators. However, the drag of the fish robot was also increased due to increment of the cross section area.