Development of functional architectures for cyber-physical systems using interconnectable models

Cyber-physical Systems (CPSs) are characterized by entities in both the physical and the virtual space, thus enabling an immersion of the physical world into the cyberspace. Connectivity via the cyberspace allows CPS cooperation for new services in product service systems (PSS). In consequence, cooperating CPSs act as actors with interest in the CPS in focus. Considering the needs of human actors and cooperating CPSs is a challenging task in CPS development because of many actors, interdepending CPS functions, and multiple CPS interfaces. For systems, the known Functional Architectures for Systems (FAS) method offers a solution approach for deriving functional system architectures from system use cases originating from human actors. For CPS development, this publication presents an expansion of the FAS method for developing functional architectures based on use cases originating from human actors as well as from cooperating CPSs and offers a model-based approach based on the method description. In the authors' opinion, interconnectable CPSs and models of cooperating CPSs can be integrated and interconnected with each other into a unifying aggregated model to represent the joint behavior of CPSs in an aggregated system. The paper explains this novel approach through a CPS functional architecture development example related to the prediction of remaining boarding time in an aircraft. The result is an approach that allows the consideration of initial CPS functions and new aggregated system functions, that pays special attention to the interconnectivity of CPSs and the required interfaces, and enables the systematic analysis of functions for the identification of redundancies.