The Development Of An Unmanned, Self-Controlled, Free-Swimming Vehicle
D. Richard Blidberg, E. Eugene Allmendinger, Nicholas Richard Sideris · Offshore Technology Conference · 1978
ABSTRACT This paper reviews the design, construction, testing and evaluation of an unmanned, self controlled (as opposed to remote-controlled), free-swimming vehicle whose mission is to fallow exposed pipelines serving as a platform for instruments surveying and monitoring them. The vehicle is of open space frame construction with on-board systems including the energy source, sensors and a microcomputer system for controlling the vehicle in five degrees of freedom while following a pipeline at a fixed height above it. Its design utilizes minimum cost components, this practice forcing some compromises in the sensor development. However, the software design is made flexible in order that future changes in sensor design would cause minimal hardware changes. The computer program's design provides for three modes of operation:override,auto-altitude andauto-track modes. The operator has complete control in selecting a particular operating mode through use of a lightweight cable linking the vehicle with this station, a feature to be employed only during the vehicle's developmental stage. The microcomputer itself is a very low power emulation of the proven PDP 8 mini-computer. A development system was created to facilitate the software design, this system solving complex changes in the computer program with minimal effort. The paper discusses all aspects of the vehicle but emphasizes the design philosophy and development of the on-board sensor-microcomputer and associated software. Laboratory and field test results are discussed. INTRODUCTION The paper focuses on a project undertaken at the University of New Hampshire having both broad and specific objectives:the upgrading of unmanned submersibles' capabilities as compared with those of manned submersibles and divers andthe demonstration of this upgrading it an unmanned submersible designed for a specific mission task - that of following an exposed seafloor pipeline at a predetermined height above it for inspection purposes. An appreciation of these objectives requires a brief review of unmanned submersible vehicle development pertinent to this paper. Since ancient times, man has had two basic options in accomplishing underwater work:the has chosen to remain on the surface from whence he controlled underwater equipment to do the work orhe has elected to go below the surface and directly control equipment, including his limbs, at the work site. Fishermen and shallow water divers first used these options while, in modern times, surface-based operators of unmanned submersibles and occupants of one-atmosphere and ambient-pressure submersibles or surface based divers continue to exercise them. The virtues and shortcomings of these two options in performing modern-day, underwater work has been debated in numerous papers and articles has been generally recognized that, most likely, neither option will completely replace the other that there will remain areas of underwater work activity which can best be accomplished by one option or the other or, perhaps, by systems combining both options.