Variable buoyancy system metric

Abstract

Over the past 20 years, underwater vehicle technology has undergone drastic improvements, and vehicles are quickly gaining popularity as a tool for numerous oceanographic tasks. Systems used on the vehicle to alter buoyancy, or variable buoyancy (VB) systems, have seen only minor improvements during the same time period. Though current VB systems are extremely robust, their lack of performance has become a hinderance to the advancement of vehicle capabilities.This thesis first explores the current status of VB systems, then creates a model of each system to determine performance. Second, in order to quantitatively compare fundamentally different VB systems, two metrics, β m and β vol , are developed and applied to current systems. By determining the ratio of performance to size, these metrics give engineers a tool to aid VB system development. Finally, the fundamental challenges in developing more advanced VB systems are explored, and a couple of technologies are investigated for their potential use in new systems.

Variable buoyancy control for a bottom skimming autonomous underwater vehicle

“…A number of different approaches to variable buoyancy control have been used to successfully regulate the buoyancy of AUVs [1]. A review of the literature shows that classic PI control, sliding mode control, and fuzzy logic control have all been applied to the control of underwater vehicle buoyancy and depth regulating systems.…”

“…A VBS will usually fall into one of three categories: pumped water, oil displacement, and mass discharge systems [1]. The pumped water VBS utilizes a rigid fixed volume buoyancy chamber which water can be pumped in to reduce buoyancy.…”

SeaDog: A rugged mobile robot for surf-zone applications

“…For this reason the tail will be used to aid in propulsion. The third method of locomotion combines the previous two by including a variable buoyancy mechanism, examples of which are described in [14]. In this manner, the robot is free to explore the three dimensional space under the surface of the water and can locomote using either of the previously described methods.…”

Design, Simulation, Fabrication and Testing of a Bio-Inspired Amphibious Robot with Multiple Modes of Mobility

“…A multifunction tail will provide increased stability on land and will prevent high centering during climbing, similar to the function of the body joint in the American cockroach. In surf-zone environments, the tail can be used to convert constantly changing currents into downward force, thus increasing stability and keeping the robot on the seabed in the same way that lobsters use their tails (as shown by Ayers et al and implemented RoboLobster [20]). The tail can also be used as a propulsion method while under water, similar to a flipper.…”