Robust Ship-to-Ship Object Pick-Up With a 6-DoF Robotic Arm Based on Force/Torque Measurement and Gripper Design

Abstract

In this paper, we present a method for the manipulation of objects in maritime environments, in particular, for the transportation of objects between two docked ships using a 6-DoF robotic arm. The presented method uses an RGBD camera mounted on the robotic arm end effector to localize the object relative to the robotic arm base. The design of a gripper and a control method based on force and torque measurements provides a robust means of picking up an object and compensating for the influence of relative ship motion due to waves and localization error. The components of the proposed method and the entire manipulation procedure have been tested both in a laboratory environment and in a real-world maritime scenario, demonstrating reliable performance. Laboratory experiments have demonstrated that the gripper design allows for picking up objects with an allowable positioning error of up to 20 cm in the $x$ direction, 4 cm in the $y$ direction, and $15^{\circ }$ in the yaw angle. For the entire pick-up procedure, a 98.3% success rate in laboratory tests demonstrates the repeatability and resilience of the proposed system. The experiment conducted in a real maritime scenario showed successful pick-up of objects using a robotic arm mounted on an autonomous catamaran, both on calm seas and in conditions with small waves.