The exploitations in the Chinese offshore oil and gas projects need the supply ofoffshore facilities. Chinese marine industry began in the last century, at present, a lotof equipment has expired. The two kinds of factors lead to the demand of crane ship.The crane vessel is one of the special operation vessel, which is responsible forthe installation and construction of the offshore construction. It is an indispensablepart of the process in the marine engineering. Safety is the key issue of heavy liftoperations. Such operations require the involvement of a lot of people and a majorincident could endanger lives. A better dynamic positioning control system not onlycan improve positioning accuracy and operational efficiency, but also can ensure thestationeriness and safety of the crane vessel during the crane operation.In this paper, we can establish the crane ship motion mathematical model basedon the model of the marine environmental disturbances. The crane operation isdivided into four parts. Firstly, the crane vessel moves towards the offshoreinstallation. Then, the topside is lifted off the cargo barge. After, the topside is rotatedto the target point. Lastly, the topside is set down to the offshore installation. Becauseof the specificity of the crane vessel’s operation, we must study the effect of the pitchand heave movement for the crane vessel. Simplify, we ignore the couple with theother three degrees of freedom.Passive nonlinear observer is adopted to estimate the low-frequency part of thevessel movement, and the estimated variables are used as control inputs to decreaseoscillations in control output.Large load lifting operation will change some parameters of the model of thecrane vessel. As a result, the accuracy of the dynamic positioning will be affected. Tosolve this problem, we design the self-tuning controller based on Lyapunov theoryand. We use the feedforward control to reduce the oscillations caused by heavemovements. The pitch movements are as the external disturbance. The aim is to getgood performance and improve accuracy.The Matlab software is used to simulate the controller. We focus on the dynamicpositioning of the crane vessel. Simulation results demonstrate the performance of thecontrol method with crane DP system. |