Research On Robust Adaptive Formation Control Of Multiple Dynamic Positioning Vessels

With the gradualimprovement of control strategy forsingle Dynamic Positioning(DP)vessel and the formation of multipleDPships work collectively in practical more widely used,the research on formation control of multiple DP vessels has attracted widespread attention from domestic and foreign scholars.Compared with the single DP vessel's limited working time and poor robustness,the formationof multipleDPvessels can not only significantly improve the operating efficiency,but also has the advantages of self-adaptability and fault tolerance.In this paper,we mainly study the problem of formation control of multiple DP vesselsin the presence of time-varying disturbances and uncertain dynamics parameters.The main research content includes the following severalparts:Firstly,two reference coordinate framesare established,the kinematics model of vessel is deduced according to the relationship between the two reference coordinate frames.According to the momentum theorem and moment of momentum theorem of the rigid,we derived thedynamics model of vessel.Sowe get the DP vessel's horizontal motion mathematical model.Then,we discussenvironmental load models of wind,wave,and current in the mathematical model.Finally,to verify direct and steady rotation of the established horizontal motion mathematical model of vessel,simulations have been carried out,which demonstrates the stability and the turning ability of vessel as well as the effectiveness of the established vessel mode.Secondly,considering the unknown disturbance in the ocean environment,an extended state observeris designed to observe and estimate the disturbance of time-varying disturbance on line.In order to improve the performance of the formation control,based on the control strategyof virtual leader,the desired trajectory is input to the virtual leader,and then the expected trajectory of each vessel in the formation is determined by the relative distance with the virtual leader.Then,based on the output of extended state observer and the dynamic surface control method,a robust formation controller is designed for each vessel in the formation.Finally,the effectiveness of the robust cooperative formation controller is proved by simulation experiments.Finally,considering in the presence of unknown time-varying disturbance and the uncertainty of kinetic parameters,the multiplesurface vessels work collectively toperform trajectory tracking task with a certain formation while avoiding collision withall vessels inthe formation.Based on the control theory of artificial potential function,defining the attractive potential function between vessel and expected trajectory and the mutual potential function between ships to avoid collision,and then combined with variable structure based design technique to deal with the time-varying disturbance by ensuring astable formation.And then combining with the adaptive backstepping sliding mode control approachand Lyapunov synthesis method to design a coordinated tracking controller for each vessel in the formation,which makesthe multiplesurface vesselsformation move along a desired trajectory with a desired formation shape while avoiding collision with each other.Finally,the simulation experiment is carried out to prove the effictiveness of the proposed robust adaptive formation algorithm.