Research On The Control Technology For Dynamic Positioning System Of Floating Cranes

With the continuous development of the marine industry and the exploration of the ocean gradually expanding to the deep sea,floating crane has become an indispensable part of the marine engineering facilities.The operating environment of floating crane is complex,which increased likelihood of danger.In order to ensure the safety and stability of the floating crane operation,the demand of dynamic positioning system has become more and more accurate.In this paper,we regard 1000 t crane vessel as the research object.According to the operation characteristics of the floating crane,respectively,designing a new type of ADRC and adaptive back-stepping sliding mode controller based on extended state observer to achieve the stable control of floating crane.In order to reduce the floating crane model complexity,only considering the influence of the suspension system,the floating crane mathematical model with three degrees of freedom is established based on the movement model of ship dynamic positioning system proposed by Thor I.Fossen.Then environmental disturbance force mathematical model is established.Describing the working principle and the components of the active disturbance rejection controller(ADRC).Aiming at the difficulty of adjusting the parameters of ADRC in practical engineering,the linear active disturbance rejection controller(LADRC)is studied.In order to further improve the dynamic performance of LADRC,combining the advantages of linear and nonlinear tracking differentiator,the improved tracking differentiator is designed which can track the differential signal preferably.Which constitutes a new LADRC.The simulation results show that the LADRC based on the improved tracking differentiator has strong robustness and disturbance rejection compared with the traditional LADRC.Aiming at the problem that the dynamic positioning system of floating crane is vulnerable to external environment disturbance and the ship model parameters can not be determined,the adaptive back-stepping sliding mode controller based on extended observer is designed.The system is divided into inner observer and outer loop controller,first make extended state observer estimate the unknown state and uncertainty of system,and compensate them in the adaptive back-stepping sliding mode controller in the outer loop.Last using Lyapunov approach to prove the stability of the system.The ship position controlsimulation experiments show that the adaptive back-stepping sliding mode controller based on extended state observer has strong robustness and controllability.Which can effectively restrain chattering problem of traditional sliding mode control and is beneficial to marine engineering application.