Quantitative Analysis And Evaluation Of System-of-Systems Resilience Based On Functional Dependency Network

System-of-systems(SoS)is an integrated large-scale system,in which a collection of heterogeneous component systems can interact with each other to achieve capabilities that are unachievable by single systems.Due to the diversity of elements,large scale,and complex connectivity,SoS is faced with a variety of uncertainties.Resilience is a key feature for responding to uncertainties.In the face of task changes,sudden disturbances,attacks,and even failures,a resilient SoS can predict,respond to,resist,absorb,and recover from failures with certain strategies,so as to maintain the original effectiveness or exhibit positive emergent behaviors.However,the analysis,evaluation and design of SoS resilience are facing many challenges.It is necessary to carry out in-depth research from the aspects of connotation,metrics,and mitigation strategies,to provide effective technical support for constructing a resilient SoS.The evaluation of resilience needs a set of metrics and appropriate models to calculate the metrics.Based on the understanding of resilience and the interdependency feature of SoS,this thesis analyzes the cascading impact of internal and external disruptions on the SoS effectiveness.Considering both the situations with and without mitigation strategies,two system importance measures are proposed based on functional dependency network analysis(FDNA)to identify systems crucial to overall resilience.Building upon the two metrics,we further adopt a visualized resilience map analysis to help decision-makers identify the critical systems and evaluate the usefulness of proposed mitigation strategies.Considering the cost of achieving resilience,we bring in the concept of order degree in ecological network analysis(ENA)to capture the relationship between redundancy and resilience.This thesis develops a method for calculating the SoS order degree based on functional dependent network,and constructs a framework for conducting trade-off analysis between resilience and cost and verifying the effectiveness of SoS order degree.Through the process of SoS architecture design,effectiveness calculation,redundancy cost calculation,and order degree calculation,we can identify a proper range of order degree that indicates a balance between resilience and cost and provides guidance for resilient architecture design.In the end,the proposed methods are applied to a combat ship centered anti-sea warfare SoS.The FDNA method and the system importance measures help to calculate the importance of each component system and evaluate the effectiveness of the mitigation strategies.The resilience map provides visual support to identify the critical systems and strategies.On this basis,this case study further puts forward architecture upgrading alternatives for improving resilience,and uses the proposed framework to select the resilience-cost balanced architecture,while determining the range of order degree.