I've been a bit busy lately, working on an underwater remotely operated vehicle as part of my university's entrance into the MATE rover competition. The goal of the particular competition this year was to install mock-up research equipment at the bottom of a 17 foot deep pool.

My own contribution focused on the electrical systems, which I designed as a single module to fit inside a waterproof enclosure welded together by one of my classmates.

The propulsion system was made from six waterproof bilge pump motors fitted with propellers; two for depth control and four arranged to give vectored thrust for increased mobility. We also had control over several waterproofed servo motors to operate a robotic claw which we never ended up actually using during the event. Electrical connections through the drybox were made with specialized waterproof marine connectors we got at great discount from SeaCon. The larger one carries all motor connections as well as power to our camera, and the smaller connects to our tether, carrying command data and 48 volt electrical power.

Our internal computer was made from a slightly modified Stellaris Launchpad (several 0-ohm resistors were removed to reroute output ports) connected to a daughterboard with a power regulator, breakout headers for servo and motor control (with current protection) and a TTL to RS232 converter to communicate through a 50 foot long tether back to a laptop on the surface.

Controller boards sat between the microcontroller and the motors, which I designed based around an L6203 H-bridge chip. A small amount of logic circuitry allowed us direct control over motor polarity and duty cycle. Each module was removable and replaceable in the event of failure.

Our microcontroller acted as a gateway between these motor drivers and the surface computer, which did all the heavy calculation for our vectored thrust system. The actual drive interface was an X-box controller communicating with a C# application.

The other board inside the drybox is a switching regulator, bringing the 48 volt power supply from our tether down to 12 volts that ran all the internal systems. Finally a waterproof camera was mounted to the side of the main body with a coaxial cable running up the side of the tether.

Most of the construction of the ROV took place in the week before the competition with about seven of us working 14-hour days amongst our classes.

Unfortunately we did not pass from regional to the international level competition due to buoyancy control issues. The foam you can see attached to the wings in the first image worked well in our local pool (6 feet), but below 9 feet the pressure crushed it. We replaced this with used gatorade bottles while at the competition, which in turn crushed at 17 feet. We eventually were able to use bits of a cut apart fishing float designed to work at depths of up to several hundred feet, but without time to properly calibrate float placement we weren't able to balance the ROV in the water, or successfully reach neutral buoyancy. Our underpowered thrusters were unable to cope with either our positive or negative buoyancy and ultimately we were only able to scoot around at the bottom.

The two other teams in our bracket at the regional competition did not fair much better; the other university present was unable to complete their ROV in time and the local 4-H club (which qualified for the international level) only completed half of the mission objectives (despite operating with a budget 16x larger than ours). If other regional competitions end up having a similar level of success, I think we can expect a relaxation of mission objectives next year.

Our plan for next year's competition is to lighten our frame and replace our motors with a more powerful variety. We'll also be able to do extensive buoyancy testing in both our university's pool and our local lake.

Personally, I am interested in independently constructing a smaller ROV as part of my senior electrical engineering project before graduation.