Backstepping Control of Heavy Lift Operations with Crane Vessels

Offshore structures with large mass are installed and removed by heavy lift vessels. During offshore constructions, two safety-critical interconnected operations take place, the dynamic positioning of the vessel and the lifting of the heavy structure by an immovable boom crane on the vessel. Existing studies on offshore boom crane control either neglect the structure (load) dynamics in sway and the vessel movement, or consider the boom angle of the crane controllable. In this paper, we present a control scheme for underactuated offshore structure, taking into consideration the impact of the dynamic positioning of the vessel on the physical load model. The proposed control scheme is designed following a backstepping control approach using command filtering to generate virtual control signals and their derivatives avoiding the analytic differentiation. Simulation results are obtained by applying the control scheme in a dynamic positioned vessel-load model showing that the controller is able to stablize the load position during the vessel dynamic positioning.