Design of a Modular, Compact, Multi-Role Remotely Operated Vehicle for Sheltered Water Operations

Since its founding in 2003, the MIT ROV Team has been participating in the Marine Advanced Technology Education (MATE) Center's International ROV Competition. This year's challenges, in recognition of the International Polar Year, include operations in environments made to resemble those found in the Polar Regions. This includes working in currents, under ice sheets and in simulated open ocean environments. The three missions, each approximately 15 minutes long and in depths of up to 20 feet, include recovery and deployment of science packages and related support structures, the collection of faunal samples and repair and maintenance work at stations under water. In keeping with its vision to look beyond the competition and push the envelope, the MIT ROV Team built on the lessons learnt during the design, construction and operation of its fourth generation ROV, MTHR, to design MIT ROV 5.0, a compact, powerful, highly maneuverable and modular robot capable of not only participating in the competition, but also performing a variety of tasks in the open environment. MIT ROV 5.0 was primarily designed to be an exploration robot meant to operate in sheltered waters, that is, with currents below one knot, lack of powerful localized turbulent flow and the absence of highly corrosive materials. The major design requirements included ease of operation, including setup, maintenance, dives and recovery, modularity, to allow quick reconfiguration to suit a variety of missions, robustness, so that it would stand up to the rigors of the open environment, small size, for greater maneuverability and low cost, for ease of reproduction. We came up with a robot that was slightly bigger than MTHR with two modular payload bays with standard connectors that could accommodate mission-specific packages. The control box contains custom designed PC-104 size circuit boards that can support a number of different actuators and thrusters and adequate space for NiMH or LiON battery packs, which can both be used. Each board can be switched easily due to extensive use of standard sizes and connection interfaces. The frame uses high strength ABS plastic side plates with LEXAN cross-struts. The tether is a single strand Kevlar-jacketed fiber-optic cable with a Kevlar support string for added security. This tether can be replaced by a regular Ethernet or CAT-V cable is the need arises. Thus the vehicle is truly modular in every way. The MIT ROV 5.0 system as designed is very easy to use. The control software can be run off virtually any computer, using the keyboard or a standard USB joystick. The vehicle itself connects to the computer using a USB-serial interface. The entire system can be setup and ready to go in under five minutes. An on-board guidance system consisting of an inertial navigation unit and a magnetic compass provide heading, attitude and position data, as well as performing station-keeping functions, allowing effective operation in currents and low-visibility conditions. MIT ROV 5.0 can also carry several different types of sensors, such as temperature, pressure and salinity, not to mention a combination of infra-red and color cameras. Payloads currently being prototyped include precision deployment and recovery modules, a sample collection package, instrument bays and an articulated manipulator arm. This capability coupled with a production cost as low as $3,000 makes MIT ROV 5.0 an extremely valuable platform for exploration, research, education, environmental monitoring and small scale repair and recovery work.