Effect of Active–Passive Deformation on the Thrust by the Pectoral Fins of Bionic Manta Robot

Bionic manta underwater vehicles will play an essential role in future oceans and can perform tasks, such as long-duration reconnaissance and exploration, due to their efficient propulsion. The manta wings’ deformation is evident during the swimming process. To improve the propulsion performance of the unmanned submersible, the study of the deformation into the bionic pectoral fin is necessary. In this research, we designed and fabricated a flexible bionic pectoral fin, which is based on the Fin Ray^® effect with active and passive deformation (APD) capability. The APD fin was actively controlled by two servo motors and could be passively deformed to variable degrees. The APD fin was moved at 0.5 Hz beat frequency, and the propulsive performance was experimentally verified of the bionic pectoral fins equipped with different extents of deformation. These results showed that the pectoral fin with active–passive deformed capabilities could achieve similar natural biological deformation in the wingspan direction. The average thrust (T) under the optimal wingspan deformation is 61.5% higher than the traditional passive deformed pectoral fins. The obtained results shed light on the design and optimization of the bionic pectoral fins to improve the propulsive performance of unmanned underwater vehicles (UUV).