Risk Assessment For Mooring Control System On Unmanned Cargo Ships

For conventional ships,during mooring operations,various adverse factors including equipment failure,human error and rough environment may lead to frequent occurrence of accidents causing personal injury and property damage.To reduce the risks and improve safety of berthing and un-berthing operations,auto-mooring systems have been developed and applied to more efficient unmanned ships.However,new risks to ships and shore facilities emerge because mooring unmanned ships is different from mooring unmanned ships in terms of operation procedures.Therefore,it is necessary to conduct risk analysis and management of auto-mooring equipment to ensure that unmanned ships can be at least as safe as conventional ships,particularly in terms of mooring operations.In this paper a relatively comprehensive risk analysis procedure is conducted regarding potential failures involving unmanned ship mooring system.Firstly,the potential failures are identified using Failure Mode and Effects Analysis(FMEA).Based on review of relevant guidelines adopted by different nations and design requirements for unmanned ship mooring system as well as international authoritative research findings concerning unmanned ship risk factor analysis,this paper identifies the potential failures in software and hardware system in unmanned cargo ship mooring operations and these failures are further confirmed and supplemented through expert panel discussions.Secondly,the risks are ranked.On the basis of risk index standards in FSA guideline,and in combination with FMEA and ship risk features,this paper establishes a complex risk assessment index system(O,Sh,Ss,Se,D),which includes five index,namely,failure occurrence frequency,severity of consequence to human,ship and environment and difficulty in failure detection.Then risk analysis is conducted through expert panel decisions and fuzzy linguistic variables and Technique for Order of Preference by Similarity to Ideal Solution(TOPSIS)are used to rank the risks.For higher accuracy,index weight and hesitance extent are included.Finally,risk control measures are implemented.This paper finds risk control measures to target several high-ranking risks and FSA cost-benefit analysis procedure is also optimized.Cost-efficiency rate for each control measure is calculated using experts’ evaluation of the cost of each risk control measure to ascertain their cost-efficiency type.This paper identifies 19 major failure modes,ranks them and clarifies those failure of high priority as well as the risk control measure implementation and cost efficiency analysis.The findings of the paper indicate that such failures as failure of real-time detection and receiving signals and data,failure of switching between the onboard automatic control system and the remote control system,damage of bollards,failure of the closed guide control device and failure of bollard work load monitoring,are high on the list to be controlled firstly.The risk control measures selected in the paper are mostly of high benefit to prevent and mitigate the above-mentioned failures.The methodology employed by this paper may contribute to solving the problem facing unmanned ships—lack of historical data to conduct risk analysis,and it also can be applied to analysis of failures on unmanned ships and also to risk analysis of unmanned ships of different types with different levels of autonomy.