Timothy Wong, a third-year student at Northeastern University in Boston, was doing an internship at Fleet Robotics. There he took part in developing a robot that cleans ship hulls of marine organisms. This is reported by Tech Xplore.
The robot looks like an enlarged version of the household Roomba robot vacuum cleaner. It has two platforms with brushes, connected by a bridge. Each platform has "legs" with switchable magnets that stick to the steel side. Instead of rolling over the surface, the robot steps: it lifts one leg, turns it, then the other. The device is about a meter long and 60 centimeters wide. For a container ship this is a tiny size, but for a Roomba it is very large.
The problem the robot solves is called biofouling. First algae appear on the bottom, then barnacles, mollusks and other organisms. The layer of slime and shells increases water resistance, and the ship has to burn more fuel to maintain speed. According to an estimate by the Sofar ocean sensor network, in the US additional fuel and paint costs due to fouling reach 36 billion dollars a year.
In addition, along with fouling, ships transport invasive species - foreign organisms that displace local ones. The International Maritime Organization (IMO) gives examples: the Asian shore crab brought white spot virus to New Zealand, and the North Pacific sea star is devastating mollusk populations in the northeastern Pacific. White spot virus causes mass mortality of shrimp and crabs, and the star eats mussels, scallops and other commercial mollusks.
The IMO is now preparing new rules. So far, keeping hulls clean remains voluntary, but requirements are expected to become mandatory soon. Fleets that are laid up, for example off the coast of Iran, are especially vulnerable: organisms accumulate on hulls, and when the ships go to sea, they will spread alien species around the world.
Cleaning the bottom is a difficult task. The fouling layer can weigh several tons, and the work has to be done in moving water. "We get tossed around a lot, the forces from the current and waves are very great," Wong says. The robot must navigate underwater on its own without Wi-Fi or a cable, overcome obstacles and not stray off course. The electronics have to be sealed so that they do not corroded - are not destroyed by corrosion. Tests were conducted at depths of up to 40 meters, where the pressure changes cyclically.
Unlike other systems that clean ships in port, Fleet Robotics proposes installing the robot on the ship permanently. It will make regular autonomous passes and return to a docking station between them. "It's like brushing your teeth every day instead of going to the dentist," explains Joshua Batra, an engineer at the company. However, too frequent cleaning can damage the paint and cause corrosion, so it is important to maintain a balance.
Wong began with testing the robot on different types of paint, then designed a motion coordination system and led tests on a real ship at the Woods Hole Oceanographic Institution. After a six-month internship, he returned to his studies and a part-time job as a climbing instructor. Batra noted that Wong worked as a full-fledged employee and called his departure a big loss for the team.
Wong himself says he cares about the oceans and wants to create tools that help scientists protect coral reefs and track whale migration, reducing the burden on the environment.