Student-built submarines vie for bragging rights in this year’s international robotics competition.
Stephen J. Mraz
Forty- four teams from high schools and colleges around the world journeyed to the Institute for Ocean Technology in St. John’s Newfoundland, Canada, to pit their robot-building skills against one another in the sixth annual remotely operated vehicle (ROV) competition. And in keeping with the designation of 2007 as the International Polar Year, the competition sponsor, the Marine Advanced Technology Education Center at Monterey Peninsula College, Monterey, Calif., the robots were judged on how they perform three missions that might take place underwater and under the ice.
There were two classes, Rangers and the more-experienced Explorers. The Ranger class was open to high schools, middle schools, and home schools, while Explorers was open to community and technical colleges and universities. High schools could apply to compete in the Explorer class, as well.
Ranger subs had to operate on a maximum of 13 Vdc and 25 A, and the only onboard power could be batteries with 9 V or less to run dive lights. Explorer vehicles could have up to 51 Vdc and 40 A, along with 13 Vdc, 25 A of onboard power. They could also have 9-V batteries for dive lights. All the subs this year relied on power and controls delivered vie a tether. Both classes could also use hydraulics (up to 150 psi) or pneumatics (inert gases at up to 40 psi).
The tasks were all the same regardless of class, But there were different environmental conditions, with the Explorers getting the harsher ones.
The 13th Hour
The winner in the Explorer class was the 17-member team from Jesuit High School in Carmichael, Calif. They didn’t start on their remotely operated vehicle, The 13th Hour, until December while other teams began in September. Still, their ingenuity and clear-headed planning won the day. For example, each team member was given tasks, along with a title, such as chief engineer, chief electrician, or cocaptain. For the competition, there were two operators, two students responsible for putting the sub in and taking it out of the water, and a safety director who orchestrated the rest of the team. They practiced their teamwork prior to the actual event to make sure everyone knew their roles.
Key to the team’s success was the design of their dual claws, which would be used in all three missions. “At first, we tried using servos to operate the grippers,” says Eric Guess, cocaptain. “But waterproofing them by filling them with mineral oil didn’t work. Next we tried stepper motors, but quickly discovered we lacked the expertise to properly program and run them, and there was no easy way to waterproof them. So we finally went with dc linear actuators.”
“And they worked flawlessly,” says Chief Engineer Jason Isaacs modestly. “One of our biggest challenges was coming up with a way to insert the hot stab into the well head.” (A hot stab is a device used to move fluid, often hydraulic fluid, from one device to another.)
Eventually, with much help from Steve Larsen, a freshman and designated design intern, the team developed a bracket and rope technique that, together with one of the grippers, managed to do the job.
The team’s ROV used two IR cameras for navigation and carrying out missions. This let them get away without lights, which would have eaten up some power. But they didn’t work perfectly in the ice tank where the fluid is a glycol mixture. It made images on the IR camera milky. Next year they plan to add a wide-angle high-definition camera that will scan vertically using a servo.
They also want their next ROV to have all power onboard, hopefully as lithium-ion batteries. It would, among other things, let them go to a lighter, simpler fiber-optic tether. Their current tether consists of three camerasignal wires, along with power and control lines. To make it neutrally buoyant, students wrapped foam-pipe insulation around it at selected points. The team also wants to use more-efficient motors for the next sub. Although their design won, it never quite had enough power for precise control. Another key part of the team’s win was its technical presentation. E. J. Borg, the team’s CAD intern and historian explained the team’s ROV and efforts to a panel made up of three NASA engineers.
As part of their prize, the team earned a $2,300 grant to attend the Underwater Intervention Conference in January to demonstrate their sub. And Veolia Environmental Services, a large environmental management company, will fly seven team members to any of its far-flung facilities for a tour and to interview students for internships.
Students at the Long Beach Community College in California spent the first half of the 2006-07 school year designing Ormhildur, (Old Norse for “female battle serpent”). Then they were supposed to spend the second semester building it. “But we spent much of that second semester redesigning parts, as well as building,” says Emily Morrow, an anthropology student and member of the Long Beach Explorer-class team. (She took the course at her advisor’s urging who said the experience could prove valuable if she pursues a career in underwater archeology.) “We quickly discovered that just because you are happy with a design, that doesn’t mean it will stay the same and end up on the sub. Our gripper, for example, had to be redesigned after our first try didn’t work out.”
“The gripper started as an electromechanical subsystem driven by a motor,” recalls Ian Jasper, an electrical technology student and team leader. “Then we switched to hydraulics, but still ran into some snags. So we ended up going with pneumatics.”
One of the key tools the Long Beach team relied on to design (and redesign) their entry was CAD modeling software (Solid-Works). “It was essential,” says Jasper. “It let us design the entire sub before building anything, and let us ensure everything would fit. It also helped us make parts as small as possible with the tightest tolerances. For example, we shortened some bolts so there were no interference issues inside the frame. And making the vehicle small was important because the it had to fit through an 80 80-cm hole cut the ice for a mission.”
The Long Beach team’s biggest engineering setback wasn’t a contentious design issue or a seemingly insurmountable task. It was the people manning airport security the day they flew to St. John’s, Newfoundland, the site of the competition. “We had decided not to ship the robot, but to take it on the plane as checked luggage,” explains Morrow. “We even made an appointment with TSA to check that all was packed correctly. And we had packed it quite well. Later TSA opened up almost every box and didn’t repack them. So when we got to Newfoundland and started putting the sub together, we found parts missing and broken. We had to go out and buy parts, then spend time in a hotel room putting it all back together.”
“When we opened the boxes, the stuff inside look like TSA had put it through a rock tumbler,” says Jasper. “It was a mess.”
“And we never did get our cameras recalibrated after being shaken around by TSA,” says Jasper. “They wouldn’t focus as well as they should have. Next year, we’ll probably have hardpoint mounts to simplify calibration, maybe different ones for each task, and we won’t have a servo turning them.
Another minor catastrophe, one the team also traces to TSA, was a 6-V battery that blew out 5 min into the first mission. “We visually inspected it before the event started and there was no apparent damage, but we couldn’t test it before the actual competition,” says Jasper. “When it failed in the tank, it meant we had no chance of completing the first mission, the wellhead task, which should have been easy for us. That killed us on points.”
Losing the battery meant the sub had to maneuver on 24 V rather than 30. “And we could’ve used that extra power, especially for the task that had us battling currents,” recalls Jasper.
To ensure these setbacks don’t happen at the next competition, the Long Beach team plans to use a more-comprehensive checklist and, if the budget allows, a better- stocked spare-parts locker. And with the next competition set for San Diego, they won’t have to put their vehicle in TSA’s hands; they’ll drive to the competition.
The Eastern Edge Robotics team, a collection of 17 students from schools in Newfoundland, Canada, (College of the North Atlantic, the Marine Institute, and Memorial University), fielded Bartlett, a submarine that earned second place in the Explorer class. The remote-controlled vehicle was built specifically for this past competition, unlike many others that were modified from last year’s competition. It was named for Capt. Robert Bartlett, an Arctic explorer from Newfoundland. After deciding that the task involving underwater currents would be the most difficult, the team designed a small, streamlined sub and made sure the thrusters were not obstructed in any way, which gave them a high power-to-drag ratio.
The sub’s frame, made of 12.25-mm-thick polycarbonate, was also designed to minimize drag, thanks to SolidWorks 3D CAD. The team mounted six 9-W off-the-shelf thrusters from Inuktun Services Ltd., Canada. Each thruster had six degrees of freedom, and were hooked up so operators could control each one and the direction it was pointing. Three cameras, one mounted on the front to monitor mission tasks, another mounted aft but facing forward for navigation, and an upward-pointing camera helped in the under-the-ice sampling mission.
The tether, a donated but teamdesigned component, contains six fiber-optic strands for control and video signals, five backup strands, and three 12-gauge copper wires to deliver dc power. It was covered with a low-drag, high-visibility yellow polyurethane coating at various points to make it neutrally buoyant in fresh water.
A team of students at the Massachusetts Institute of Technology worked on WiiBot I, an ambitious sub that can be controlled through a wireless Wii interface (hence its name). But without enough practice time, the team pilots didn’t feel comfortable with the remote controls, so it is being tweaked for next year’s event.
The MIT team’s major challenge was the lack of testing. One mission, for example, was carried out under the ice, an environmental condition the MIT team could not replicate. “So we were unaware that our extremely small tolerances were still too big,” says Franz Hoover, one of the team’s mentors, “The cold water caused screws in our thrusters to contract, causing two to fail during a mission. Our battery seal was also damaged by the cold. We did not detect the damage until in the middle of another mission when the battery box started leaking.”
While testing might have been the MIT team’s Achilles heel, design was their strong suit. They kept the sub simple and easy to manufacture. That way, if they ran into problems, they could devise an easy fix. For example, two magnets were supposed to stay aligned during the anchor recovery mission. So the team built a strap of sorts to hold the magnets together. When this didn’t solve the problem, the team added notches to the magnets so they would self-align. Then the strap had to be redesigned out of a sturdier material. This called for an adhesive that would secure the strap to the magnets. After testing they selected an adhesive that worked well in the competition.
“Troubleshooting most problems was successful because the team took the time to build several prototypes and refine their design,” says Hover. ”It let the team build a vehicle they could take pride in.”
(Sidebar) Your missions, should you decide to accept
The three simulated missions in the competition included:
The anchor recovery mission gave students and their remotely operated subs 5 min to set up and deploy the sub, 15 min to thread a messenger line through the ring on an anchor sitting on the bottom of the flume tank, and 5 more min to get the sub out of the water. Temperatures in that tank were between 15 and 18°C, the subs would operate at about 4-m deep, and there would be a current. Officials at first had the current set at 0.5 knots. But that was too strong, so they lowered it to 0.25 knots.
The wellhead-preparation mission requires subs take a gasket to a simulated wellhead, remove the well’s cover, install the gasket, and replace the cover. The sub must then transport a hot stab (a device used to transfer hydraulic fluid to another tool) to the well, insert and remove it from the wellhead’s port, and return it to the surface. The teams have one attempt and 20 min, with 5 min for set up and 5 min to take the sub out of the water. The subs had to work 2.8 m below the surface in a 7-m deep tank with water between 8 and 15°C. Ten or 15-cm waves with periods on the order of 1.2 or 1.3 sec covered the surface of the water.
The biologic sampling mission simulates underwater collection of samples, with ping-pong balls (which float) representing algae and hollow balls made of interconnected rings (which sink) representing jellyfish. The water was covered with a sheet of ice, except for a precut hole through which the subs entered the tank. The teams had 5 min for set up and 20 min to recover one of 10 rings and one of 50 balls, drop a simulated acoustic sensor, and return samples to the surface through the precut, but possibly slushy square hole. Water in this ice tank had a slightly different specific gravity than in the other two tanks so buoyancy for each sub was different and teams had to adjust. The water was also colder, 1C, and up to 3 m deep.