Research On Path Tracking Control Method Of Dynamic Positioning Ships At High Speed

With the advancement of marine exploration and development to the deep ocean and the open ocean,Dynamic Positioning(DP)vessels are increasingly used in offshore operations.Tracking operations,as the main task function of DP ships,are divided into low-speed tracking and high-speed tracking.Both require the ship to be able to follow the planned path under the influence of marine environmental interference.This paper mainly studies the high-speed tracking control problem of DP ships.Based on the research results at home and abroad,a dynamic surface linear adaptive disturbance rejection controller and an adaptive neural backstepping controller are designed for the uncertain and unknown disturbance of the ship’s model.This article mainly completes the following tasks:First,a three-degree-of-freedom horizontal plane model of the ship is given for the motion characteristics of the dynamic positioning ship in the horizontal plane.At the same time,mathematical models of environmental disturbances such as sea wind,waves and currents have been established.And three-degree-of-freedom mathematical model of the horizontal plane considering sea current interference is given.The validity of the model is verified by numerical simulation.Then,the guidance system of high-speed tracking controller of the dynamic positioning ship is studied.Based on the traditional line-of-sight(LOS)guidance method,the Serret-Frenet framework is introduced to address the limitations of the linear path,and a SFLOS guidance method that is not limited by the path geometry is derived.Facing that the SFLOS guidance method is susceptible to the influence of ocean current disturbances,an adaptive line-of-sight(ALOS)guidance method using ocean current observers to suppress ocean current interference is designed.Simulation experiments show that the ALOS guidance method presented in this paper has better guidance performance in the presence of ocean current interference.Then,to solve the ship’s model uncertain and unknown disturbances,a dynamic surface linear active disturbance rejection high-speed tracking controller is proposed,which is composed of heading controller and longitudinal speed controller.Dynamic surface control(DSC)technology has a better control effect when solving nonlinear control problems,and at the same time avoids the "differential explosion" problem of traditional backstepping methods.The linear active disturbance rejection control(LADRC)technology is introduced to solve the problem that DSC relies on accurate mathematical models of ships.LADRC solves the problem that traditional ADRC parameters are difficult to adjust.The linear extend observer(LESO)in LADRC estimates and compensates the uncertainties and unknown disturbances of the system model in real time.It has strong robustness.Combined with the SFLOS guidance method,the stability of the system was verified.Compared with other methods,the dynamic surface linear ADRC controller presented in this paper has better tracking performance.Finally,for the high-speed tracking control problem of a dynamic positioning ship with uncertainty and input saturation,the heading controller and longitudinal speed controller which use the filtering backstepping method as the control method,combining the adaptive radial basis neural network(RBFNN)and the auxiliary system are designed,solving heading tracking and speed control problems of dynamic positioning ship.RBFNN compensates for uncertainties in ship dynamics.For the saturation of the thruster,an auxiliary system was designed.Combined with the ALOS guidance method,the boundedness of the closed-loop system is theoretically proved.Comparative simulation experiments show that the adaptive neural backstepping tracking controller presented in this paper has higher tracking accuracy.