Research On Towline’s Mathematic Model And Track Control Method Of A Cable Laying Ship

During the burial operation of a submarine cable, a plough is driven by a cable laying shipthough a towline, so as to burry the cable in a scheduled path. The towline’s tension, togetherwith the ocean environment, is an important factor infuluencing the cable laying ship’s motion.The significance obviously is there to analyse the towline’s motion and design a contrail trackerfor improving the control precision of the ship’s speed and track.The towline and ship’s mathematic model are built in the first place. Then the towline andship’s couple system’s motion is analysed, and the couple system mathematic model is built.Aiming at the coupling system model, a contrail tracker controller is designed for the ship. Thecable laying ship’s path is obtained form the plough’s path by using simplified method. The shipand plough’s path obtained from simulation are compared with the expected path.(1) Considering the characteristics of water surface operation and low speed, the cablelaying ship ship’s3-dof mathematic model can be obtained from the6-dof mathematic model ofthe common ship. And the environment distance mathematic model is built.(2) The towline’s motion mathematical model is obtained by analyzing the steady statemotion and the dynamic motion. For the steady state motion, the mathematical mode isdeveloped by analyzing the motion of the towline mico-unit as the study object. Future more,the steady state motion is resolved into initial value problem by using known state values, andthen the4th runge-kutta can be used as numerical solution. The relation between the steady statemotion and the attitude angle of the towline’s lower end, and the way how the current influencesthe steady state motion are simulated.For the dynamic motion, the lumped mass method isemployed to obtain the mathematical model. The status value of the steady state motion is usedas initial value. The towline’s dynamic motion is simulated in two conditions：the towline’supper end moves in a straight line at a variable speed or moves in a circular line at a constantspeed.(3) The towline and cable laying ship’s coupling system’s motion model is built bycombining the towline and cable laying ship’s model using the coupling conditions, which laysa foundation for the cable laying ship’s contrail tracker. At the meantime, the influences due totowline for a cable laying ship are analysed, by comparing the motion situation, containinggyration radius and headway speed, of the ship with or without the towline.(4) The cable laying ship’s path is obtained form the plough’s path by using simplifiedmethod. (5) Aiming at the coupling system model, employing the sliding mode control method,using the exponential law, a sliding mode contrail tracker controller is designed for the ship. Thecontroller’s performance is upgraded effectively by using a cloud controller, which is designedthough the cloud model theory.(6) The coupling system’s motion, under the control of contrail tracker controller designedby employing the sliding mode and cloud model theory, is simulated and analysed.