Low Energy Buoyancy Actuator for Vertical Underwater Motion

Abstract

This thesis presents the physical and technical premise for implementing and designing an underwater vehicle capable of moving vertically using the unit s own buoyancy force, and how this principle benefit in energy efficiency. The goal is to create a prototype unit that makes experimental testing and documentation of this principle possible.

An electrical linear actuator with a piston was used to manipulate the unit s volume. Depth control was achieved using a PID controller combined with a pressure sensor, and the control parameters tuned by implementing simulations of the unit s dynamical behavior. By combining two power saving methods, it was estimated (using simulations) to reduce the power consumption to 12.6% of maximum power consumption. A 3D model of the unit was made to determine the vertical stability, mass properties, and to create drawings of a prototype.

A functional prototype was successfully implemented, and two physical experiments were carried out. The physical experiments were not sufficient to determine the unit s energy efficiency using buoyancy as a principle of vertical movement underwater. But the work here suggest there is a promising potential for the unit being energy efficient.