Development of a New Buoyancy Control Device for Underwater Vehicles Inspired by the Sperm Whale Hypothesis

Abstract

This paper proposes a new buoyancy control device inspired by a hypothesis about the buoyancy control mechanism of sperm whales that claims that sperm whales control their buoyancy by melting or coagulating spermaceti oil in their heads to induce volume change. We have previously proposed a buoyancy control mechanism using a syringe and a piston inspired by this hypothesis. Since that system had problems, we built a new buoyancy control device with a mechanism that utilizes the elasticity of rubber to handle the volume change. In the new device, peltier elements and a nichrome wire were installed to heat and cool the paraffin wax and induce volume change. We conducted experiments to assess the buoyancy change and confirmed that the device works well. Then, we built a prototype of an underwater vehicle with four of the devices and confirmed that this robot benefited from 1.3-times higher buoyancy change per unit mass of paraffin wax than with the previous mechanism. Based on the above results, we discuss the feasibility of this method.