Robotics Diving Robot Cleans Mussels and Algae from the Boat Hull

Italian engineers have developed a remotely operated diving robot that cleans boat hulls of algae, mussels, and barnacles. To ensure the robot can operate underwater permanently, the developers use lubrication-free polymer plain bearings from Igus.

The nightmare of every boat owner: algae, mussels, and barnacles that have to be removed from the hull before each season begins. The remote-controlled underwater robot called Keel Crab, developed by the Italian company Aeffe, is designed to handle this task quickly in the future. To do this, the Keel Crab is simply placed in the water and then guided over the boat hull using a joystick and camera support, while the two brushes of the underwater robot effortlessly remove the deposits.

The construction of the Keel Crab, on the other hand, was less effortless, especially concerning underwater and upside-down movement. The engineers had to develop an underwater-compatible drive system that met these requirements. They opted for a vacuum pump that allows the robot to adhere to the hull, along with two caterpillar tracks. "The bearing of the four drive rollers was a real problem," recalls Mattia Pagani, development engineer at Aeffe. "We were looking for a solution for underwater use that was as fail-safe and low-maintenance as possible, while also not increasing the robot's weight too much." The solution for the bearing of the four drive rollers was ultimately found in plain bearings made from the high-performance plastic Iglidur X by Igus.

A Challenge for Conventional Bearings

Underwater use poses a challenge for many conventional bearings. "Classic lubricated rolling bearings were out of the question due to the risk of corrosion," explains Mattia Pagani. Bearings made from high-performance polymers by Igus, on the other hand, are corrosion-free. Another advantage: unlike many standard plastics, the Iglidur X material absorbs very little moisture. The bearings remain dimensionally stable, even in continuous contact with fresh or salt water. "This is a key prerequisite for the long-term reliable underwater use of our robot."

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Mars Technology in the Stress Test

But it wasn’t just the risk of corrosion that played a role in selecting the plain bearings for the robot's drive. The engineers also focused on low weight and operating costs. "We briefly considered single-row radial bearings made of stainless Ionox steel with seals, but they would have been too heavy and too expensive," says Mattia Pagani. "The polymer bearings from Igus weigh about 80 percent less than comparable metal bearings due to their low material density." At the same time, they work permanently dry thanks to integrated solid lubricants. Lubricants, and the associated maintenance work, are no longer necessary. Mattia Pagani: "This reduces operating costs over the entire service life, an advantage that ultimately also benefits the operators of the robots."