Fully automatic visual servoing control for underwater vehiclemanipulator systems based on a heuristic inverse kinematics

The use of underwater vehicle manipulator systems (UVMS) equipped with cameras has gained significant attention due to their capacity to perform underwater tasks autonomously. However, controlling both the manipulator and the remotely operated vehicle (ROV) based on the vision system information is not an easy task, especially in situations where the vehicle cannot be parked/held stationary. Most of the existing approaches work based on complex matrix calculations for the inverse kinematics (IK), which can lead to high computational costs and the need to deal with singularity problems. A problem arises when the amount of time needed to calculate the UVMS configuration can result in reduced frequency of target pose estimation, beyond the point where the target has moved out of the camera field of view. Therefore, this paper proposes an autonomous visual servoing approach for UVMS, including an extension of a heuristic technique named M-FABRIK (Mobile - Forward and Backward Reaching IK) to calculate the UVMS inverse kinematics in a simple and fast way. This approach aims to control both the configuration of the manipulator and ROV position in order to allow underwater intervention in situations where the ROV cannot be parked/held stationary. This solution allows the vehicle to be positioned according to additional criteria, besides avoiding matrix inversion and being robust to singularities. Trials have been performed with a manipulator mounted on a work-class ROV for an autonomous underwater monitoring task and results demonstrate a simple and fast approach, which is able to set the configuration of the manipulator as well as the ROV for visual servoing applications in real-time, such as for monitoring, tracking and intervention tasks underwater.