Application Of D-S Evidence Theory In Ocean Environment Safety Situation Evaluation

The ocean is the important resource for human survival in the future.As human explore and utilize the ocean constantly,the underwater vehicle provides a very suitable platform for the people.To obtain more maritime interests,a large number of underwater vehicles are constantly applied in ocean surveys,scientific experiments,resource explorations and other fields.As we all know,the ocean is considered to be one of the most difficult environment for the underwater vehicle to achieve autonomous navigation and collaborative mobility.Because the underwater application environment is very complex,and it varies with time,which makes the underwater vehicle face many challenges to solve key technologies such as precision navigation,autonomous hedging and collaborative control.No matter what kind of the underwater vehicle,the navigation safety is the foundation for it to successfully complete the mission.Therefore,to evaluate the ocean environment safety situation can provide the effective reference for the underwater vehicle to navigate safely and to carry out the tasks successfully.However,the current studies on the ocean environment safety situation evaluation is still in the exploratory stage.Therefore,around the common basic scientific issues that the underwater vehicle navigates safely and evades risk independently in the complex ocean environment,this paper considers the underwater vehicle as the research object,and establishes a cognitive model for complex ocean environment factors and reveales the general laws of threat features contained in multiple heterogeneous dynamic environment factors.This paper evaluates the ocean environment safety situation with Dempster-Shafer(D-S)evidence theory to solve multi-scale safety situation field generation evolution problem in the complex ocean spatial,which can provide theoretical basis and technical support for the underwater vehicle navigating safely and evading risk independently in the complex ocean environment.The main works can be summarized as follows:Aimming at the non-structural polymorphism of the ocean environment,this paper analyzes the important ocean environment factors that affect the navigation safety of the underwater vehicle.Based on the relevant characteristics of the ocean environment factors,this paper studies the mapping relation between the ocean environment factors and the parameters such as position,attitude,speed,and heave of the underwater vehicle,and discusses the influence mechanism between the ocean environment factors and the underwater vehicle.According to the characteristics distribution law of the physics,geometry,behavior of the ocean environment factors,this paper discusses the connotation(attributes,space,position,rank,etc.)of the ocean environment factors and their roles in the relationship between them.And for their effect on the navigation safety of the underwater vehicle,this paper proposes a construction method of basic probability assignment based on the interval center value to describe and characterize the threat characteristics of multiple heterogeneous ocean environment factors in the complex ocean.At the same time,this paper also gives the reasonable analysis and quantitative description of the uncertainty information caused by the uncertainty factors.In order to solve the uncertainty information problem caused by the uncertainty factors,this paper makes full use of the known information and presents a transformation method of decision-making probability based on the certainty degree.The new transformation method can effectively transfer the uncertainty information into the certainty information and reduce the risk of decision-making.Since the multi-elements proposition is an expression that the multi-elements proposition supports the sole-element proposition,and the transformation of decision-making probability quantizes this performance.So this paper takes advantage of this intrinsic link between them,and uses the correlation coefficient as the evaluation criterion to evaluate the performances of various transformation methods.In order to improve the drawbacks of the conflict measurement method in D-S evidence theory,this paper proposes a conflict measurement method based on the decision-making probability.The novel method utilizes the new transformation method of decision-making probability to transfer the initial evidence,and uses the decision-making probability difference to define the conflict coefficient according to the relationship between the evidence.The new conflict coefficient can measure the conflict between the evidence reasonablely and accurately.Aiming at the shortcomings of fusion method in D-S evidence theory,this paper proposes a new fusion method based on the conflict measurement.The method impoves the Dempster’s combination rule by making use of new conflict coefficient,which better solves the problem that Dempster’s combination rule is unreasonable.This paper establishes the evaluation factor index of the ocean environment safety situation according to the determination principles of evaluation index and the characteristics of various ocean environment factors,and divides the evaluation level into five levels.This paper deals with the ocean environment data by the unification according to the actual needs.This paper determines the weight of each ocean environment factor with the super-standard weight method based on the basic probability assignment,and processes the ocean environment data in weighted way.This paper evaluates the ocean environment safety situation by using the improved combination rule to fuse the processed ocean environment data.Finally,this paper does the experiments with the method proposed to evaluate the ocean environment safety situation in a certain area,and generates the safety situation fields,which provide the decision support for the safety navigation and independent hedge of the underwater vehicle.