Elegant Anti-disturbance Control For Dynamic Positioning System Of Ships Under Different Sea Condition

Dynamically-positioned(DP)ship need to be fixed on the sea surface or sail along a fixed track according to different operating requirements when sailing in the deep sea.The DP systems are widely applyed because they can remain anchored to the surface and perform a range of operations,even in harsh Marine environments.Marine disturbances such as wind,wave and current will greatly affect the system performance of the DP ships,resulting in inaccurate positioning and inaccurate operation.Therefore,how to effectively deal with the disturbance on the sea surface and improve the positioning accuracy of the DP system has become a research hotspot.The main research contents of this paper are as follows:The first part considers the elegant anti-disturbance control(EADC)under the slow changing environment disturbance and the long peak wave disturbance in mature stage when the DP ship is traveling on the sea.The stochastic disturbance observer(SDO)was constructed by using the known information of the slow changing environment disturbance and the long peak wave disturbance in mature stage.At the same time,stochastic control theory is applied to design EADC strategy,which can keep high control accuracy of the DP ship.The second part considers the non-harmonic disturbance with unknown nonlinear function and the EADC under white noise when the DP ship is sailing on the sea.The adaptive disturbance observer(ADO)is constructed.At the same time,the stochastic control theory is applied to construct the EADC strategy,so that the state of the DP ship can still realize asymptotically bounded according to the mean square under the influence of the disturbance.The third part considers the EADC of the DP ships under the condition of its own actuator saturation.At the same time,two ocean disturbances are considered,one is additional stochastic disturbance,the other is slow changing environment disturbance.The stochastic disturbance observer(SDO)is constructed to observe slow-changing environmental disturbances,and additional stochastic disturbances are suppressed by stochastic control method.In addition,for the actuator saturation problem of the DP ship,the polytopic bounding analysis method is adopted to deal with it.At the same time,lagrange multiplier algorithm is considered in the control design of the DP ships to distribute control commands to each actuator to achieve the optimal control command distribution.Under the EADC strategy,the DP ships can still maintain its desired trajectory and heading.