Preparing Cyber-Physical Systems Functional Models for Implementation

The design process of Cyber-Physical Systems (CPS) normally starts with the development of a functional model, used for simulation purposes. This model is composed of the control algorithms and a mathematical representation of the physical system to be controlled. The approach, called Assisted Transformation of Models (AST), provides a means to transform the functional model into an architectural model, which is intended to detail how the computing system should be implemented on a real (typically embedded) platform. Up to now, AST only focused on the transformation of the control part. It is assumed that the mathematical model will be treated as a device, i.e., that it will be seen as an external element to the system under development. The consequence of this assumption is that there will be work left to be done by the designers, since the control application running on a real platform requires sensing and actuation instead of the mathematical model. This paper describes how to extend the AST approach in order to transform a CPS functional model into an architectural model that also takes into consideration the sensing and actuation subsystems. For instance, it addresses how designers should modify the functional model to consider a set of sensors and actuators, the possibility to express their dynamic characteristics (like sampling frequency, time response, and period) and technological details (like communication protocol and power supply). The outcome of this proposal is not only a proper generation of the architectural model, but also an adaptation of the functional model to be used with Hardware-In-the-Loop (HIL) simulations.