Abstract:

We present a dynamic model of a fish robot with a Non-uniform Flexible Tail (NFT). We investigate the tendencies of the thrust and swimming speed when the input driving moment changes. Based on the proposed dynamic model of the NFT, we derive the thrust estimation, equation of motion, and performance evaluation of a fish robot with a NFT. By defining the optimal stiffness of the NFT in simulation, a fish robot prototype is then designed and fabricated. A series of experiments are performed to verify the proposed model. Experiment results are in good agreement with simulation data. The results show that the thrust and swimming speed of the fish robot are proportional to the amplitude of the driving moment. There are two resonant fre-quencies (f = 1.4 Hz and 2.2 Hz), the maximum thrust and swimming speed (about 0.7 BL•s−1) are found to be around
f  = 1.4 Hz. The above results inidicate the proposed model is suitable for predicting the behavior, thrust and swimming speed of a fish robot with a NFT.

Key words: fish robot, flexible tail, dynamic modeling, swimming speed, thrust, Froude efficiency