Development and initial investigation of NTU robotic fish with modular flexible fins

Abstract

This paper presents an environment-friendly robotic system mimicking undulating fins of fish. To mimic the actual flexible fin of real fish, we model a fin-like mechanism with a series of connecting linkages and attached it to the robotic fish. By virtue of a specially designed strip, each link is able to turn and slide with respect to the adjacent link. The driving linkages are used to form a mechanical fin consisting of several fin segments, which are able to produce undulations, similar to those produced by the actual fins. Owing to the modular design and the flexible structure of the mechanical fin, we were able to construct various biomimetic robots of fish swimming by fin undulations. Two robotic fish have been designed, constructed, and initially tested in NTU: the first is swimming by undulations of a long anal fin, and the second is swimming by undulations of a pair of lateral fins. The modeling technique of the first designed robotic fish in Singapore is presented. Some qualitative observations obtained by experiments with the robotic fish are also shown and discussed.