Research On Availability Modeling And Evaluation For Maritime Autonomous Surface Ships Maintenance Decision-Making

With the rapid development of communication technology,artificial intelligence and other related technologies,Maritime Autonomous Surface Ships(MASS)will gradually become an important vehicle for waterway transportation.At the same time,with the frequent occurrence of autonomous system accidents in recent years,how to ensure the safety of MASS has become a current research focus.At present,many researches focus on the autonomous navigation safety of MASS,and there are few studies on the safety of its mechanical system.The ship’s mechanical system has the characteristics of complex structure,numerous equipment,and harsh operating environment.MASS don’t have crew onboard to check,maintain and urgently handle the mechanical system failure,and its safety problems are becoming more and more prominent.Aiming at the safety issue of the availability of MASS mechanical system,this paper takes the cooling water system as an example,and analyzes failure mode effects and its critical,and identifies the failure mode with higher risk in the cooling water system;Based on the Dynamic Bayesian Networks(DBN),established a multi-state DBN availability model for ship mechanical systems considering maintenance strategies,and calculated the availability of conventional ship cooling water systems;Taking the availability of conventional ship cooling water systems as the benchmark,the optimization problem of MASS redundant structure and planned maintenance strategy is discussed.The specific research contents are as follows:(1)Failure mode and effect analysis of MASS cooling water system.Taking the cooling water system as an example,based on the structure of the conventional ship cooling water system,historical data and expert investigation,the failure modes of the conventional ship and MASS cooling water system were identified,and they were ranked according to the risk priority number.From the perspectives of occurrence,detection and severity,methods to improve the safety of MASS mechanical system are discussed.(2)Availability model of ship mechanical system based on DBN.On the basis of the multi-state DBN availability model,a DBN availability model of the ship’s mechanical system considering the maintenance strategy is developed.Under the current planned maintenance strategy,the availability of conventional ship cooling water system with on-board maintenance is calculated,and it is used as a benchmark.The redundant structure and the longest planned maintenance interval of the MASS mechanical system without on-board maintenance are studied,which provides a model basis for the optimization of the MASS planned maintenance strategy.(3)Optimization of planned maintenance strategy of MASS mechanical system based on availability threshold.Taking the availability of the conventional ship cooling water system as the benchmark,the calculation method of the planned maintenance budget of the MASS mechanical system is proposed,and the maintenance budget of the periodic planned maintenance and non-periodic planned maintenance of different redundant structures is optimized based on the DBN availability model.It has certain reference significance for formulating the planned maintenance strategy of MASS mechanical system.