A resilience metric and its calculation for ship automation systems

Resilient systems maintain state awareness and an accepted level of operational normalcy in response to disturbances, including threats of an unexpected and malicious nature [1]. In this paper we present a resilience metric for a large scale multi-physics system. We summarize the resilience metric calculations methods from different domains and analyze the fundamental challenges for case-by-case resilience metric calculation methods. We propose to decompose complex systems into subsystems and calculate multiple performance metrics, which are then combined to determine the resilience metric. Based on the context of ship automation system, we define a normalized resilience metric, which can be estimated by the system decomposition approach. The value of the resilience metric is between 0 and 1, where 1 is the best possible resilience. In a case study presented in this paper, we consider a ship chiller system that is partially damaged due to an external event. The control strategy takes proper action to determine new configuration that maximizes the resilience metric.