This paper proposes the study and the set-up of a real-time control system for offshore cranes in order to compensate the unwinding of the rope during the handling of loads between the ships and the floating platforms during adverse sea conditions. The control system must compensate the effects of the sea wave (three elementary movements of rotation: roll, pitch and yaw; three elementary movements of translation: surge, sway and heave) on the ships and the floating platforms in order to prevent any damage of the loads. The dual system of compensation can be also applied to the offshore gangways used to transfer the crew to floating platforms. A typical case is that of offshore wind generators.
The proposed study is an evolution of the current state of the art that provides only the compensation of the movements of the ship caused by sea wave. The handling of a load from the ship to the floating platform presents several scientific and technical problems because the oscillators phenomena that occur are complex. Due to the effect of the sea wave, all these movements, related to a fixed reference frame, can have different amplitudes and phases being affected by the hull geometries of the ship of the platform.
The main objective of the proposed control system is the compensation of the unwinding of the rope of the crane so that, at the instant of the contact, the relative speed between the load and the surface of the platform is below a preset limit.
An architecture of sensors will be studied in order to detect the position of the load in relation to the movement of the platform.
The effectiveness of the sensors and the control system will be tested by means of a stochastic models of the sea state.