A novel underactuated wire-driven robot fish with vector propulsion

This paper presents a novel robot fish with vector propulsion. It can swim like a shark and/or a dolphin. The propulsor (tail) of the robot has an underactuated serpentine backbone and the actuation is done by two sets of orthogonally distributed wires. The backbone is composed of seven vertebras and an elastic rod. The vertebras are articulated by the rod and spherical joints. The horizontal flapping and vertical flapping are independently actuated by two motors. This enables the propulsor providing thrust in all directions. Propulsion model of the propulsor is developed by integrating the kinematic model and Lighthill´s elongated body theory. A prototype is built. Tests show that the robot fish could flap its tail like the shark or the dolphin effectively. In the swimming tests, the maximum swimming speed of the robot is 0.35 BL/s.