SETPOINT CHASING FOR THRUSTER-ASSISTED POSITION MOORING

摘要

This paper presents a new concept for control of thruster-assisted position moored vessel using setpoint chasing. The mooring system is designed to compensate the mean environmental loads up to a certain limit of the environmental conditions. In the present industrial position mooring (PM) system, the thrusters are used to damp the vessel's dynamical motions and to provide compensation of any line break. The main contribution in this paper is to extend the damping control used in industrial PM system with improved restoring and mean force control. In order to avoid conflicting control action with the mooring system, the equilibrium position of the uncontrolled vessel will be found using setpoint chasing. The setpoint chasing with proportional control will be developed to prevent a possible resonance situation by shifting the natural frequency of the moored vessel out of the bandwidth of the excitation loads. The setpoint chasing with integral control will improve the ability to prevent line break in extreme conditions by compensating the mean drift loads together with the mooring system. Simulation and experiment will be carried out to verify the advantages of the setpoint chasing strategies.