Pectoral Fin Structural Design and Experiments on Robotic Cow-Nosed Ray with Backward Swimming Performance

Abstract

Robotic fish with pectoral fin swing have many outstanding features, especially forward swimming stability, but the research on their backward swimming performance is insufficient. Therefore, this article specifically discussed the hydrodynamic performance of the robotic cow-nosed ray with backward swimming in pectoral fin swing propulsion mode. Complete pectoral fin and split pectoral fin were designed, and the superiority of split pectoral fin structure over complete pectoral fin structure in terms of backward thrust was verified through experimental testing. The energy conversion efficiency was analyzed through the ratio of thrust to current. According to the collected current data, the equivalent thrust efficiency and amplitude and frequency variation curves of the two pectoral fin structures under forward and backward swimming conditions were drawn. The reasons for the thrust generation and equivalent thrust efficiency of two types of pectoral fin structures were analyzed. The experimental results show that under the forward swimming condition, the two types of pectoral fins have similar thrust values. Under the backward swimming condition, with the increase in amplitude and frequency, the thrust of the split pectoral fin structure increases significantly, reaching a maximum of 0.22 N. Under the forward swimming condition, the split pectoral fin structure is slightly worse than that of a complete pectoral fin. Under the backward swimming condition, with the increase in amplitude and frequency, the equivalent thrust efficiency of the split pectoral fin structure is significantly improved. The design of the split pectoral fin structure in the article provides a reference for exploring the backward swimming performance of robotic fish based on the swing mechanism.

Keywords

• cow-nosed ray
• robotic fish
• pectoral fin design
• backward swimming performance