Analysis of functional systems of MASS based on STPA-FCM model

doi:10.16265/j.cnki.issn1003-3033.2023.08.1571

Abstract

Abstract:

In order to analyze the failure mechanism among the functional systems of MASS and improve its navigational safety, STPA and FCM methods were combined to establish a failure analysis model of the functional systems of MASS. The control/feedback relationships of functional systems were modeled using the STPA method. 27 control relationships and 43 feedback relationships were identified. Potential unsafe control action(UCA) and their key causes were analyzed. Then, the FCM method was used to further construct the cognitive map of interaction relationships among functional systems. Finally, the relative failure probability of each functional system would be determined when the FCM reaches its steady state. The results indicate that the core functional systems are the power system, virtual captain system, dynamic positioning system and collision avoidance system, and their stability values account for 7.66%, 7.62%, 7.47% and 7.14%, respectively. Priority should be given to ensuring its reliability, stability, and safety.

Key words: systematic theory process analysis (STPA), fuzzy cognitive map (FCM), maritime autonomous surface ships(MASS), functional system, failure probability, control/feedback relationships

QIN Tingrong, ZHOU Xinjie, HE Xingjie, CHEN Weijiong. Analysis of functional systems of MASS based on STPA-FCM model[J]. China Safety Science Journal, 2023, 33(8): 8-14.

Figures/Tables 9

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等级	影响(在UCA-1下的受影响程度)	概率(功能系统的失效频率)	三角模糊数
极小	功能系统受到干扰,但能完全恢复正常	几艘船在总生命周期里可能发生1次	(0,0.2,0.4)
小	主要功能正常运行,但整体功能下降	1艘船在其生命周期内可能发生1次	(0.2,0.4,0.6)
中	部分功能失效,但能维持基本使用功能	1艘船在其生命周期内可能发生几次	(0.4,0.6,0.8)
大	大部分功能失效,影响到可靠度或精度	1艘船每年可能发生1次	(0.6,0.8,1)
极大	导致功能系统完全失效	1艘船每月可能发生1次	(0.8,1,1)

UCA-1	需要避让时,未下达推进与转向控制行动	UCA-1下的关键致因分析:① 动力定位系统出现物理故障;②动力定位系统的控制算法存在缺陷;③ 动力定位系统未收到或不充分收到虚拟船长的指令;④动力定位系统未收到或错误收到环境感知系统的反馈;⑤动力定位系统未收到或过晚收到避碰系统的反馈;⑥推进及转向系统出现物理故障;⑦推进及转向系统的控制算法存在缺陷;⑧外部环境干扰
UCA-2	在不需要避让时,下达推进与转向控制行动
UCA-3	需要避让时,下达推进与转向控制过晚
UCA-4	需要避让时,下达推进与转向时间过长或停止过早

编号	功能系统	初始值	稳态值	占比/%
H₁	虚拟船长	0.34	0.959	7.64
H₂	航线规划	0.34	0.853	6.79
H₃	避碰	0.37	0.897	7.14
H₄	动力定位	0.29	0.938	7.47
H₅	自感知	0.40	0.770	6.13
H₆	环境感知	0.43	0.771	6.14
H₇	船岸通信	0.37	0.739	5.89
H₈	船船通信	0.31	0.766	6.10
H₉	电力	0.54	0.962	7.66
H₁₀	推进及转向	0.51	0.772	6.15
H₁₁	数据存储	0.23	0.769	6.13
H₁₂	声光号型	0.29	0.834	6.64
H₁₃	系泊锚泊	0.29	0.852	6.79
H₁₄	压载水	0.26	0.814	6.48
H₁₅	货物装卸与监控	0.31	0.859	6.84