Abstract: One problem of biomimetic propulsion underwater vehicles is mechanism design and motion control. And how to reduce the volume of propulsion mechanism and accurately simulate typical motions of natural fish tail fin is the key factor. A parallel two joint tail fin mechanism (Parallel-TJTFM) is proposed, and motion analysis of each links is brought forward, based on a simplified model of the propulsion mechanism. Effects of turning capability and singularity positions on Parallel-TJTFM are also investigated. The relationship between middle angle of flapping motion and links length is given. Comparison result shows that parallel-TJTFM can reduce volume of the propulsion part of biomimetic underwater fish-like robot. Simulation of parallel-TJTFM gives a reasonable motion illustration and shows that the design is an alternative scheme of propulsion mechanism.

Key words: Mechanism design, Motion analysis, Motion control, Tail fin propulsion, Underwater biomimetic robot