Research On Path Following Control Method Of A Working Cable Laying Vessel

Cable laying vessel is used to lay or repair underwater cables. Track keeping control, which means sailing according set path, is needed during working. In order to regulate the vessel to a desired location based on the plough's desired position, a Dynamic Positioning control system is the key part. Mathematical models of, an offshore cable laying operation have been derived. And the track keeping control method has been studied for the offshore cable laying vessel.First of all, the cable laying system was introduced, and some reasonable assumption of operation environment, on which the later modeling based, was made. Then the plough's friction force was studied and the mathematic model of it was derived. Meanwhile, the model of the towline was simply introduced and analyzed. All of these laid the foundation for cable laying vessel's modeling and the research of the control method.Second, based on actual offshore supply vessel, the final low-speed model of the cable laying vessel was derived by combining the effect of the plough during working with the vessel. The vessel's mathematical model was validated in respect of correctness by simulation. Meanwhile for the closely related with the dynamic positioning ship, the propulsion systems were studied, and thruster power constraints has been derived. And also, the mathematic models of wind, current and wave were researched.Finally, for researching the path following control method, a reference model was used to convert input signals of the plough's desired path into a smooth tracking signal for the cable laying vessel's control system. The LOS method was used to calculate the track error. The direct control method was selected for the good precision of it. Path following controller was designed with a force saturation element, in order to bound the speed of the cable laying operation. The two modes of path following were tracking pause and tracking keeping, control arithmetic of both were designed. PID control parameters and self-tuning fuzzy PID controller were derived, and provided good position tracking quality by simulation.