Human Digital Twin in Industry 4.0: Concept and Preliminary Model

: Digital Twins originally concern technical systems and do not yet integrate human elements properly. This limits their quality and usefulness when we consider systems where machines and human workers still cohabit. This paper presents the concept of Human Digital Twin (HDT), the human equivalent of a Digital Twin (DT), which aim at being coupled with DTs of technical elements in systems where humans play a role. We detail the state of the art on the subject, propose a definition for HDT and a preliminary human model, bringing foundations for handling the human factor in industry with digital twins.