Robust Underwater Positioning System Using LED Markers and Perspective-n-Point Solver

Swarm operations of underwater robots are gaining attention as a means of performing more complex and efficient tasks underwater. For successful operation, each underwater robot must know its position and pose. Traditional underwater acoustic positioning using ultrasonic waves has the advantage of providing wide-area coverage. However, the large size of those systems makes them difficult to mount on smaller robots such as those used in underwater robot swarms. This paper proposes a new simultaneous position and pose measurement system suitable for underwater robot swarm operations. In this system, a camera is mounted on each robot, and the relative position and pose of the light-emitting diodes (LEDs) are based on the coordinates of several known LEDs and the images captured by the camera. The effectiveness of the proposed positioning system using LEDs and cameras is verified through experiments in a test tank.