The design and prototyping of a wire-driven robot fish with pectoral fins

This paper presents a wire-driven robot fish with a pair of pectoral fins. The fish tail is a wire-driven flapping caudal fin. It is made of 7 vertebras, an elastic backbone and a fin plate. The tail is actuated by two servomotors via two pairs of wires. The wires control the tail flapping like a real fish. The pectoral fin can make two Degrees-Of-Freedom (DOF) motions, i.e. flapping (roll) and feathering (pitch). The pectoral fins can be controlled to move in labriform mode for propulsion, or for other purposes such as turning and diving. Experiment results show that under the tail propulsion, the robot fish can swim up to 0.66 BL/s (Body Length / second); under the pectoral fin propulsion, the robot fish can swim up to 0.26 BL/s. The pectoral fin can significantly improve the maneuverability of the robot fish. Without the pectoral fins, the turning radius is 0.6 BL, with the help of pectoral fins, the turning radius is reduced to 0.25 BL.