A robot boat with four legs could one day help rescuers reach a person in distress more quickly. Named QuadBoat, this prototype is inspired by the dolomedes, spiders that move across water. It was designed to detect, track and retrieve floating objects.
The device was developed by researchers from the Shenzhen Institute of Artificial Intelligence and Robotics for Society, in China, and the Stevens Institute of Technology, in the United States. Unlike a conventional boat, its central hull is surrounded by four articulated limbs that act as floats. Their position can be changed to steer the robot, stabilize its trajectory or grasp a target.
The QuadBoat robot boat
The dolomedes move across water thanks to their long hydrophobic legs and surface tension. QuadBoat does not reproduce this mechanism: it floats by Archimedes' buoyancy, like a boat. Its architecture instead draws on these animals' ability to quickly adjust their support points and posture on a moving surface.
To coordinate its movements, the system combines several control methods. An inverse kinematics calculation determines the required positions for each joint. A predictive controller then anticipates the vehicle's trajectory, and a PID system corrects deviations. This combination aims to maintain precise navigation despite the simultaneous movements of the four limbs.
The researchers tested the prototype in a pool, then in outdoor experiments. QuadBoat had to follow set routes, reproduce different postures and detect a target using a camera. The demonstrations show that it can approach a floating object, hold it between its front legs and bring it back to a designated area.
Dolomedes fimbriatus walking on water
Image Wikimedia
These results do not yet prove that the machine can rescue a person. The trials involved objects, in conditions simpler than a rough sea. The craft will have to withstand waves, wind, currents, reduced visibility and a much larger load.
A finished version could complement motorized buoys and surface vehicles already used by some rescue services. Its legs would provide direct grip on a target, rather than simply a way to approach it. Next steps should include trials with mannequins, reinforced sensors and scenarios representative of real interventions.