Spider-inspired robot boat could help rescue people from water

A four-legged robotic boat inspired by fishing spiders could help rescue people from drowning by tracking and retrieving victims directly from the water.

Developed by researchers at the Shenzhen Institute of Artificial Intelligence and Robotics for Society (AIRS) in China and Stevens Institute of Technology in the US, the robot, called QuadBoat, is designed to move across the water while actively tracking floating targets.

The researchers say most existing unmanned surface vehicles (USVs) used in search-and-rescue missions are built mainly to locate or approach people in distress. QuadBoat is designed to go a step further by physically retrieving targets from the water.

The robot has a central body and four independently controlled legs. Its design takes inspiration from fishing spiders, which use their long, water-repellent legs to move across the surface of calm water.

Four legs take water

Unlike fishing spiders, QuadBoat does not rely on surface tension to stay afloat. Instead, the robot uses conventional buoyancy while its four legs provide propulsion and maneuverability.

An inverse kinematics controller coordinates the movements of the legs, allowing the robot to adjust its posture and move in different directions. The researchers also developed control systems combining model predictive control and proportional-integral-derivative control to steer and stabilize the robot.

“QuadBoat features a quadrupedal robot configuration, enabling it with highly adaptable and agile maneuverability through its actively adjustable posture,” wrote the authors. “Employing an inverse kinematics-based controller and cascaded model predictive control (MPC)-PID controller for overall movement, QuadBoat can accurately track and retrieve objects on the water surface.”

The team tested the robotic boat in a pool, first examining how accurately it could follow planned routes and execute specific movements. Further experiments focused on its ability to identify, track and retrieve floating targets.

The tests also included visual tracking and object pickup experiments conducted in indoor and outdoor settings. The researchers said these trials demonstrated that QuadBoat could follow targets on the water and carry out retrieval tasks relevant to rescue operations.

Robot tracks victims, retrieves

The system is aimed at a critical gap in maritime search and rescue. Finding a person in the water is only part of the challenge. Rescue teams must also reach the victim and remove them from the water quickly, particularly when exhaustion, cold or rough conditions could make survival more difficult.

“The prompt extraction of victims from water is crucial in water surface rescue missions,” wrote Lianxin Zhang, Yihan Huang and Huihuan Qian in their paper. “However, previous research on rescue robots has seldom addressed this issue. This paper presents QuadBoat, a bio-inspired USV designed to track and retrieve victims from water.”

The researchers believe the robot could eventually assist emergency teams responding to boat crashes and other maritime accidents. Its ability to move and adjust its posture could also make it useful in situations where conventional USVs may struggle to maneuver close to a person.

However, QuadBoat is still at the research stage. The initial demonstrations were conducted in controlled environments, and further work will be needed to determine how the robot performs in waves, currents, and other conditions encountered during real rescue missions.

The researchers say future development could help turn the spider-inspired design into a practical tool for search-and-rescue teams, giving responders another way to locate, track and retrieve people from the water.

The study was published on the arXiv preprint server.