Development of DP System for Merlin WR200 ROV

Abstract

This thesis presents and documents the efforts to model, develop and implement a full six-degree-of-freedom dynamic positioning system for IKM Subsea's Merlin WR200 ROV. It also documents the performance of the system during full-scale sea trials. The aim of the system is to ease the burden on human pilots and increase the efficiency, reliability and endurance of both pilot and ROV. A dynamic positioning system allows a pilot to concentrate on more important tasks than keeping the ROV at a fixed position and orientation. It also introduces the possibility of low speed maneuverability as part of the system as well as an intuitive user interface that will simplify the challenge of conducting complicated maneuvers, thus possibly reducing the necessary training time for the user of the system. Several large modules were created through the development of a complete control system for Merlin, including a mathematical six-degree-of-freedom model of ROV based on data from unique hydrodynamic experiments and CAD modeling. This is the basis for the implemented controller design that uses the ROV?s inverted dynamics. Furthermore, development, implementation and validation of a comprehensive state estimator that uses raw data available from Merlin's existing sensors were done to enable local dynamic positioning. Development and implementation of the reference model and a reference frame for control input to the system have also been performed. Results from part-tests and sea trials where the total system was tested are included. The results of this thesis show a system that works and performs very well with few shortcomings considering the scope and complexity of the undertaking. However, more work around completion and testing of the system is necessary before it could be installed as a control system for operational use by Merlin