Mechatronics and buoyancy implementation of robotic fish swimming with modular fin mechanisms

This paper presents an underwater vehicle mimicking the undulating fins of fish. To mimic the actual flexible fins of real fish, a fin-like mechanism is modelled with a series of connecting linkages. 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, it is possible to model different types of fin and to construct various biomimetic robots of fish swimming by fin undulations. On the other hand, a buoyancy tank has been designed and attached to the modular fin mechanisms for the complete fish swimming capability. The workspace of the fin mechanism is derived and applied in locomotion implementation. The mechatronics design and locomotion control of the integrated robotic fish are presented. Some qualitative and workspace observations by experiments with the robotic fish are also shown and discussed.