A spider-inspired robotic boat could track and rescue people in water

Researchers at the Shenzhen Institute of Artificial Intelligence and Robotics for Society in China and Stevens Institute of Technology in the United States have developed QuadBoat, a four-legged unmanned surface vehicle intended to support water rescue operations. The project addresses a limitation of many existing surface rescue robots, which can locate or approach people in distress but are not designed to physically retrieve them from the water.

QuadBoat was inspired by fishing spiders, which use long, water-repellent legs to distribute their weight and move across calm water using surface tension. Rather than duplicating that mechanism, the robotic vessel uses conventional buoyancy to remain afloat while seeking to reproduce the spiders' agile movements. It has a central body and four legs whose motions are planned and coordinated by an inverse kinematics controller. Additional control methods, including cascaded model predictive control and PID control, steer the vehicle, manage its posture, and stabilize it during movement.

The researchers evaluated the system in pool experiments. They tested whether it could perform planned motions and follow predetermined routes, then examined its capacity to detect, follow, and retrieve designated floating targets. The reported demonstrations showed agile maneuvering, accurate leg-action and trajectory tracking, and visual-based target tracking. Object-pickup trials indoors and outdoors also indicated that the vehicle could retrieve floating objects.

The work was presented in an arXiv paper. The researchers suggest that QuadBoat could be further refined and tested in more demanding conditions resembling real rescue environments. If developed further, it could help search-and-rescue teams locate, track, and extract people from water after boat crashes or other water-based accidents more quickly.