Motion modeling and hydrodynamic analysis of pectoral fin

The motion of pectoral fin is highly complex, and accurately describing it is essential to guide the development of bionic pectoral fin mechanisms or ray-inspired robots. Although many researchers have proposed motion equations to express its motion, most of them have limitations, such as limited displacement degrees of freedom, indistinct topology, and empirically set coefficients values, which make it difficult to develop corresponding bionic pectoral fin mechanisms. To overcome these limitations, this paper proposes a new motion equation, whose coefficients values were strictly derived from observed pectoral fin information. The motion equation accurately describes three-dimensional motion of the pectoral fin and has a distinct topology. A geometric model is drawn from the shape of the real pectoral fin, and the motion simulation of the pectoral fin is completed by combining the motion equation. The result shows that the motion equation can achieve large amplitude and large bending motion characteristics of the real pectoral fin, which indicates a favorable imitation. The validity of the motion equation is verified by computational fluid dynamics simulation method. The established motion equation and the homogeneous coordinate transformation method for establishing it are useful for the development of the bionic pectoral fin mechanisms.