Development and initial experiment of modular undulating fin for untethered biorobotic AUVs

An environment-friendly propulsion system mimicking undulating fins of cuttlefish or stingray has been built. A nonconventional method was considered to model the flexibility of the fins of cuttlefish or stingray. A two-degree-of-freedom mechanism comprises several linkages was designed and constructed to mimic the actual flexible fin. 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 modularity of the design of the mechanical fin, we were able to construct various biomimetic robots of fish swimming by fin(s) undulations. Two variants are shown in this paper: the first is a biomimetic robot of a South American electric fish swimming by undulations of a long anal fin, and the second is a biomimetic robot of a cuttlefish swimming by undulations of its lateral fins. Some qualitative observations, obtained by experiments, predicted several factors affecting the thrust produced by the mechanical fins. Future work may include development other variants of biomimetic undulating fin robot and further development of the cuttlefish robot for autonomous deployment