Jellyfish-shredding robots dispatched to clean Korea's coast
October 8, 2013
Over the past few years, jellyfish populations along South Korea's coastline have risen to the point where they are adversely affecting the fish populations and marine industries in the area, costing the country over 3 billion won (about US$2.8 million) each year. A team led by Associate Professor Hyun Myung of the Korea Advanced Institute of Science and Technology however may have a solution with the JEROS (Jellyfish Elimination RObotic Swarm), a series of autonomous robots that work together to track down jellyfish in the ocean and grind them into a pulp.
It may sound like a harsh method for getting rid of them, but in South Korea, jellyfish are becoming a serious pest, and in some cases a fatal hazard. Over 2,000 people were treated for jellyfish stings in the country last year, including one child who later died from the injuries. In recent years, officials with the National Fisheries Research & Development Institute have attempted to tackle the problem by trawling the southern coast with nets and releasing natural jellyfish predators into the area, but these methods have proven to be either too costly or ineffective.
Myung and his team have been working on a robotic method for dealing with the problem since 2009 and completed their first successful field test last year. More recently, the group upgraded its invention's speed and programming so it can work at a much faster rate.
Each JEROS robot is held afloat by two pontoons fitted with motorized propellers, which keep the bot stable on the water while controlling its speed and direction. A square net is suspended underwater along the bot's width and pulls nearby jellyfish into it using its own propulsion. Any jellyfish that get scooped up are guided straight into a separate propeller, which instantly grinds them into a pulp that disperses in the water.
The robot uses a combination of GPS and INS (inertial navigation system) to accurately determine its location and orientation in the ocean within 1.5 m (4.9 ft). Researchers can wirelessly upload data on current jellyfish hot spots to the JEROS's onboard computer and microprocessor to have it plot a course to these areas on its own. A camera also scans the surface of the water, while the built-in computer processes the images to identify any jellyfish within range by their shape. Using all these features, a controller can either have the JEROS steer itself autonomously towards higher concentrations of jellyfish or manually issue commands from a distance.
But one lone robot would take far too long to deplete the jellyfish's numbers, which is why a large portion of the project has focused on developing an algorithm to have several robots coordinate their efforts. A single robot can be designated the leader and will determine a path to follow, while other JEROS bots trawl alongside it in formation, covering a much larger area. While traveling in a "swarm," as the developers are calling it, the robots will wirelessly exchange information about their locations to ensure they remain spaced apart evenly. This also makes the removal process easier on the controllers, since they only have to focus on the leader bot's course.
Myung's team recently ran a series of test in Gyeongnam Masan Bay with three JEROS bots moving at a speed of 4 knots (7.2 km/h or 4.6 mph) and found they were able to eradicate 900 kg (1,984 lbs) of jellyfish per hour. To put that into perspective, the most common species appearing on Korea's shores is the moon jellyfish, which has been found to weigh upwards of 150 grams. At that weight, the JEROS would be able to eliminate a total of 6,000 jellies in the same time frame. However, it might have some difficulty with the Nomura's jellyfish, which are also commonly found in Korea's waters and have been found to grow up to 200 kg (440 lb).
Myung and his team are still conducting further tests to determine the JEROS's efficiency under various conditions and whether any further improvements need to be made. Aside from handling Korea's jellyfish problem, they also foresee the project being adapted to other aquatic missions, such as ocean cleanup, marine surveillance, and oil spill prevention.
The video below shows how the JEROS captures jellyfish from an underwater viewpoint, however our more sensitive readers should be warned that it also shows the grisly process of disposing of them.