A dynamic model for robotic fish with flexible pectoral fins

This paper presents the dynamic modeling, design and fabrication of a free-swimming robotic fish with flexible pectoral fins. To capture the flexibility of the fins, a multi-segment model with torsional springs and viscous dampers is introduced and the hydrodynamic force on each segment is calculated based on the blade element theory. Other forces such as added mass, quasi-static lift, and drag are also considered in modeling the dynamics of the robot. A robotic fish has been prototyped, which has a 3D-printed body and a pair of servo-actuated flexible pectoral fins. The proposed dynamic model is validated with experiments done on the robotic fish, where the model predictions of forward swimming speeds and steady turning periods and radii are found to match closely the experimental measurements when the pectoral fins are actuated at different frequencies.