Introduction to operations of a high-resolution acoustic camera on crabster CR200 and applications

Abstract

This paper describes operations of a high-resolution multi-beam acoustic camera installed on Crabster200 (shortened to CR200) and application researches. The CR200 is a new type of ROVs having six artificial legs driven by BLDC motors. The robot thrusts itself using the legs on seafloor and controls its body posture and attitude. Each leg has four degrees of freedom. And the robot is supposed to inspect and work in fast current flow and turbid water where visibility is very low. The name of “Crabster” came from a combination of crab and lobster because the CR200 imitates behaviors of the two creatures to keep its position against water current flow. In turbid water, performance of typical optical cameras is limited and fails. Therefore, in this case, the acoustic camera can be a good alternative to image objects of interest using acoustic beams. The CR200 is equipped with high-resolution acoustic camera using 3M Hz frequency obtaining maximum 2.9 mm resolution with a rotation which provides two degrees of freedom; roll motion and pitch motion. Yaw motion cannot be provided by the rotator. Then, the CR200 have to rotate its body in place to obtain yaw motion. From these roll motion, pitch motion and yaw motion with image processing, we extract and derive depth perception, 3-dimensional reconstruction and mosaicking, respectively. In this paper, we introduce practical uses of the acoustic camera in offshore and water basin and its application researches. The authors have tried to verify the performance of CR200 as an actively adaptable underwater mobile observant platform. ？ 2015 Penerbit UTM Press. All rights reserved.