Research On Scheme Optimization Of Stabilizing Fin And Longitudinal Motion Control Of SWATH

SWATH is a kind of new high performance ship with the excel seaworthiness.Compared with the general single hull,it's natural period is longer,motionamplitude is smaller,speed lose in waves is little,probability of slams,deckwetness and nausea is lower.Because of the small waterplane area the restoringmoment of the longitudinal motion of SWATH is also small.However,the MUNKmoment added on the lower hulls is increased quickly with the square of the speedand the longitudinal motion of SWATH will be unstable when the speed exceedsthe critical value.Now the main way that solves this problem is to install thestabilizing fin inside the lower hulls.Therefore,the design of the stabilizing finbecomes the important part of the SWATH building.The stabilizing fin not only is the important tool that balances the MUNKmoment for ensuring the stability of the longitudinal motion of SWATH,but alsocan bring the biggish influence to the longitudinal motion maneuverability,thelongitudinal motion performance in waves and resistance performance.So it isnecessary for getting excel stabilizing fin to involve all of the influence factorswhich are mentioned before.Therefore,this paper establishes the multi-objectiveoptimization mathematical model of the stabilizing fin scheme of SWATH afteranalyzing the longitudinal motion performance of SWATH in waves and theinfluence of the longitudinal motion stability and maneuverability from theparameters change of the stabilizing fin and solves this problem by themulti-objective genetic algorithm.Then,this paper establishes the evaluatingindex system of the stabilizing fin scheme and uses the fuzzy multilevelcomprehensive evaluation method to get the satisfying stabilizing fin scheme fromPareto set.Though the SWATH that is installed the stabilizing fin designed in reason can work with the excel motion performance in waves,it is necessary to control thestabilizing fin for improving the motion performance further.In view of theuncertainty of the actual longitudinal motion control system of SWATH,this paperuses the robust control theory to control the stabilizing fin for improving thelongitudinal motion performance of SWATH.And this paper presents a newcontroller design method based on the linear matrix inequality theory and theprobabilistic robustness analysis method for the parameter uncertainty system.This method can not only satisfy the robust performance requirement of thesystem but also assign the pole of the closed system to the given region.And thesynthesis process of this method is simple,the conservation is little and it is notlimited by the way that the parameters enter into the system.Finally,this paperuses the new control method andμ-synthesis method respectively to control thelongitudinal motion system of SWATH with the parameter uncertainty and themixed uncertainty,the effect is excel.