The Ship Motion Identification Modelling And Path Following Control Under Engineering Constraits

To solve the problem that the existing ship motion modeling and control methods are not applicable or have unsatisfactory application effects in the engineering application,this thesis takes " The Ship Motion Identification Modeling and Path Following Control Uunder Engineering Constraints" as the theme to conduct systematic theoretical exploration and experimental verification,with the aim of making innovative exploration and practice in the theoretical completeness,navigational practicality,and engineering applicability of ship motion modeling and control.In the field of ship motion control,modeling and control are the two most important core issues.From the perspective of engineering application,the main problems currently include the model uncertainty caused by external environmental disturbances and changes in the ship’s own situation,insufficient navigational practicality caused by excessive emphasis on theory,optimal control based on constraints,and energy-saving control,which can all be collectively referred to as "engineering constraints" in this thesis.For this topic of " The Ship Motion Identification Modeling and Path Following Control under Engineering Constraints",a nonlinear innovation-based identification modeling strategy is used to solve the uncertainty problem of the model.A global course constraint guidance strategy is proposed,and a comprehensive control algorithm is constructed to consider optimal control and energy-saving control under constraints.Specifically:Firstly,for ship motion modeling,a nonlinear(multi)innovation-based identification modeling strategy is adopted.Innovation refers to useful information used to correct the identification parameters at the previous moment in the identification modeling.By nonlinear processing of the innovation,the effect of identification modeling is improved.Specifically,a stochastic gradient algorithm based on nonlinear innovation is proposed to identify the parameters of the ship motion response-type model,which has the advantages of high identification accuracy,fast speed,and less required identification data.In addition,a nonlinear multi-innovation least squares identification algorithm is constructed to identify the parameters of the multi-degree-of-freedom model,which improves data utilization,ensures identification accuracy,and can achieve online identification.The former is mainly used for ship motion controller design,and the latter is mainly used for ship motion simulation experiments.Secondly,for the guidance problem in ship path following,a novel global course constraint guidance strategy is proposed to make it more in line with navigational practice.Currently,Line-of-Sight(LOS)is a commonly used guidance algorithm,which mimics the operating habits of seameans and has clear physical meaning.In fact,the ship’s path following problem can generally be divided into two parts: straight-line segments and waypoint segments.The former is relatively simple,while the latter is more complex.However,LOS,as a comprehensive guidance algorithm,is too complex compared to the straight-line segment,which wastes computational resources,and is relatively simple in the waypoint segment,which may lead to significant course change due to lack of tracking signals,which does not conform to navigational practice.Based on the above considerations,the global course constraint guidance strategy proposed in this thesis adopts a segmented guidance method in the straight-line segment to simplify the algorithm.In the waypoint segment,a plan-then-follow method is used to avoid the situation of jumping tracking signals and make the course change during the turning process smoother.Finally,with regard to the control problem in ship path following,the inevitable constraint problem in engineering practice is mainly considered,such as the actuator constraint problem and the control energy saving problem under the current "dual-carbon" background.This study adopts Model Predictive Control(MPC)algorithm to solve the optimization control problem under actuator constraint conditions.In addition,nonlinear feedback technology is introduced to fully utilize its energy-saving advantages in the control process,which can achieve the same control effect with smaller rudder angle.Meanwhile,event-triggered mechanism is applied to optimize the control algorithm,reducing the wear and energy consumption of the rudder and improving its engineering usability.In summary,this thesis conducts research on ship motion modeling and path following control from the perspective of engineering applicability.In the research on ship motion identification and modeling,the characteristics of high efficiency,accuracy,simplicity,and practicality are highlighted,which lay the foundation for ship path following control.In the research on path following,the practicality and engineering usability of navigation are emphasized,which lays the groundwork for more complex research on ship motion control.The above research has a good engineering application background,making a beneficial attempt to combine ship motion control theory research with engineering practice.