Roll Control of an Autonomous Underwater Vehicle Using an Internal Rolling Mass

A stable autonomous underwater vehicle (AUV) is essential for underwater survey activities. Previous studies have associated poor results in bathymetry survey and side-scan imaging with the vehicle’s unwanted roll motion. The problem is becoming more prominent as AUVs are smaller nowadays. This causes reduction in the metacentric height of the AUVs which affects the inherent self-stabilization in the roll-axis. In this paper, we demonstrate the use of an internal rolling mass (IRM) mechanism to actively stabilize the roll motion of an AUV. We rotate the whole electronics tray, which has an off-centric center of gravity, to produce the required torque to stabilize the roll motion. The mechanical design of such mechanism and its dynamics modeling are discussed in detail. A Proportional-Integral (PI) controller is synthesized using the identified linear model. Results from tank tests and open-field tests demonstrate the effectiveness of the mechanism in regulating the roll motion of the AUV.