Crane feedback control in offshore moonpool operations

A novel controller for cranes employed in heavy-lift offshore marine operations is proposed. The control objective is to reduce the hydrodynamic slamming load acting on a product at water-entry of moonpool operations; at the same time the values of the wire tension must be kept within acceptable bounds. The control design is based on an extension of classical SISO feedback design to the case of not measurable controlled output. The effectiveness of the proposed design is shown experimentally. The experiments are carried out using a scale-model of a crane vessel with a moonpool. Experimental results show improvements with respect to a previous feedforward controller.