수중 가시광 통신을 이용한 UUV의 제어 연구

Abstract

Aged port facilities and water tanks require inspection and diagnosis to check for damage. Previously, A diver dived underwater and inspected offshore structures, but recently, the inspection of offshore structures using UUV is increasing. ROV(Remotely Operated underwater Vehicle), one of the types of UUV(Unmanned Undersea Vehicle), can be controlled and inspected in real time using tether cable, but the tethered cable may be twisted or bent when used in an environment with complex and dense offshore structures. This limits the behavior of the ROV. In this paper, to solve the problems caused by tether cables, we propose a system equipped with an underwater visible light communication module in UUV. UUV used a transparent acrylic housing to attach the underwater visible light communication module, and placed two vertical thrusters and two horizontal thrusters. UUV is equipped with AHRS(Attitude Heading Reference System) and Depth sensors inside to enable attitude and water depth control. The underwater visible light communication module is divided into a transmitter and a receiver, and the PCB(Printed Circuit Board) is designed to enable bidirectional communication. For the light source of the transmitter, LED(light-emitting diode) are arranged in a circle to expand the range of UUV activity, and the LED driver is designed for power supply and stable switching of LEDs. For communication stability between the transmitter and the receiver, data waveforms were compared using OOK(On-off keying) and RZ(Return to Zero) modulation, and RZ modulation was used in consideration of high-speed communication. There are PIN and APD(Avalanche Photo Diode) photodiodes constituting the receiver, and the PIN photodiode was selected in consideration of UUV internal space and driving voltage. A signal processor was designed to convert the current of the photodiode sensing the light of the transmitter into data. Finally, a UUV equipped with a visible light communication module was tested in a water tank, and the results are shown in communication performance and attitude control.