Modelling and Control of J-Lay Vessel during Positioning Operation

Nonlinear mathematical vessel model and environmental model are developed for a semi-submersible pipelay and crane vessel during J-lay operation.The natural catenary method is adopted to calculate the quasi-dynamic horizontal force that the pipe acts on the ship.Change of force acting on the pipe and the pipe shape are given.The controller is designed for the constant tension between tensioner and pipeline.It indicates that the controller can limit the pipe tension in a slowly varying state,so that the pipe won't glide relative to the tensioner and ensure the security of pipelay operation.