**3. Preliminary Activities and Simulation Environment**

Prior to the definition of the PHM system, a number of preliminary activities were performed to better assess the perimeter of the research program, define the architecture and the type of the simulation models to be employed (e.g., physics-based, black-box, surrogate), and how to translate such simulation models to make them suitable for deployment in the real-time environment of the iron bird. This section is intended as a summary of such preliminary activities, highlighting the most significant considerations for each passage and referring to the literature for additional details.
