Robot fish with a novel biomimetic wire-driven flapping propulsor

Abstract

This paper presents a robot fish actuated by a novel biomimetic wire-driven flapping propulsor. The propulsor is composed by a flexible backbone and two sets of controlling wires. The backbone has 13 vertebras. They are articulated by cylindrical joints and an elastic fin plate. These vertebras are divided into two groups. Each group is controlled by one pair of wires and one actuator. By controlling the two sets of wires, the propulsor can generate oscillatory motion (C-Motion) and undulatory motion (S-Motion). The motions well resemble the fish swimming body curve. A prototype is developed and four swimming tests were conducted, i.e. ‘Big-C-Motion’ forward, ‘Small-C-Motion’ forward, ‘S-Motion’ forward and turning. Only two actuators are used in this prototype. Experimental results validated the effectiveness of the wire-driven design. Results show that the robot fish’s swimming performance is satisfactory. The forward swimming speed is influenced by the flapping amplitudes, waving frequency, the phase lag of the two segments and the swimming stability. In the experiments, the maximum cruise speed is 300.75 mm/s (0.608 BL/s) (BL/s is Body Length/s) in ‘C-Motion’ and 333.33 mm/s (0.673 BL/s) in ‘S-Motion’. The turning radius of the robot fish is around 0.7 BL, and the truning speed is 51.4 °/s.