Seal-Inspired Underwater Glider With a Rigid-Flexible Composite Hull

It is difficult for traditional underwater gliders (UGs) equipped with rigid hulls to compensate for the buoyancy loss caused by seawater density variation and reduce the vibration noise. Inspired by the streamlined shape and soft body of seals, this article develops a bionic UG with appropriate buoyancy compensation and vibration and noise reduction. The seal-inspired underwater glider (SIUG) contains a rigid-flexible composite hull, with the outer flexible silicone rubber shell completely covering the inner rigid hull. A vibration experiment is performed, and the results verify that the proposed hull can obviously suppress the propagation of vibration noise, especially the high-frequency ones. Further, the dynamic models of the SIUG and the traditional rigid UG are established, respectively, to compare their dynamic behaviors. The dynamic simulation results show that the net buoyancy of the SIUG remains almost unchanged in deep water, with obviously smaller fluctuations of pitch angle and velocity. A sea trial in the South China Sea also proves that the SIUG has a good capability of buoyancy compensation in maintaining its net buoyancy. Overall, the SIUG provides a two-in-one solution of buoyancy compensation as well as vibration and noise reduction.