Design Concepts for an Energy-Efficient Amphibious Unmanned Underwater Vehicle

Abstract

This paper describes the conceptual design and operating principles of an oscillating-foil propulsion system for an unmanned underwater vehicle called TURTLE (‘Tele-operated Unmanned Robot for Telemetry and Legged Exploration’), currently under development. This UUV (‘Unmanned Underwater Vehicle) will be designed to be a 6-legged swimming and walking amphibious robot, fitted with foils (or flat fins) which can be manipulated with several degrees of freedom to produce highly efficient underwater propulsion forces. The legs will each have four degrees of freedom, of which the fourth is rotation of a foil that is fitted to the ’shin’ to provide propulsion for swimming. By manipulating the movements and rotations of this foil, propulsion forces can be generated to implement a variety of swimming modes, each with its own advantages and disadvantages. The foils attached to the fins allow the main body to be controlled in all six degrees of freedom. It will also be an amphibious robot that will be able to transition between swimming mode and walking mode, for walking on an underwater surface or over dry land if power considerations permit. It must be powerful and strong enough to support itself and light payloads while walking over rough or undulating surfaces commonly found on a beach. The mechanical design will allow the absolute position and orientation of the body to be accurately controlled relative to the ground surface, whether above or below water, for the purpose of precision control of onboard tools and sensors. The space frame construction method keeps water drag low and allows large scale, strong, rigid structures and manipulator limbs (or links) to be built. Space frames also keep material cost, weight and actuator energy usage to very low levels. Such lightweight and energy efficient robots will be useful in many practical applications, such as oil and gas exploration, drilling, mining, construction, automated agriculture, military transport and space exploration.