Figure 6 shows the holistic approach of a cyber-physical system connected to the
DT according to the automation pyramid of Siepmann [15, 16]. On the left, 0–5
describe the automation pyramid separated into strictly hierarchical company levels:
0 is the sensor/actuator level, characterized by simple and rapid data sampling; 1 is
the field level, the interface to the production process; 2 is the control level; 3 is the
process control level; 4 and 5 are the plant management and company levels,
respectively, where production planning, production data acquisition, and order
processing are conducted. The pyramid of the DT is illustrated on the right. Levels
0–1 contain the physical assets, where level 0 includes actuators, sensors, and
equipment and level 1 provides additional functionality such as HMIs for the
DT. Level 2 contains communication and data servers. Level 3 is the gateway
between the physical assets and the DT, and all the other structures connected to
the system. Levels 2 and 4 communicate over the gateway, whereby level 4 supports
cloud-based databases with information from the physical assets and DT. Levels 0–4
allocate the required infrastructure for the DT. Level 5 consists of the digital core
asset, the DT with all necessary apps such as simulation, emulation, and modeling.
With increasing levels in the automation pyramid, the data flow increases. This
correlation offers extensive networking, thus enabling the full capability of the DT.
The connection of levels 1–3 in the DT pyramid is achieved in production lines
through hierarchy, whereby three levels of networking are distinguished: unit,
system, and system of system (SoS) level [18]. The unit level is the smallest element
and can comprise machine equipment, materials, or sensors. The system level is a
combination of multiple unit levels, which can communicate and control each other
by field bus, Ethernet, or 5G. SoS is composed of multiple system levels as in the
collaboration of multiple production lines and combines all data of the production
lifecycle.
3.4 Process Characterization
Process characterization requires a detailed analysis of all physical production
equipment (including sensors) and the procedures to identify all the production
parts that are linked with the product, or relevant for the supply of utilities (e.g.,
electricity, steam, and gases), or affect the process quality indirectly (e.g., cooling
systems and logistics). The production departments and floors relevant for implementation into the DTMS must be defined. Within these individual sections, identification of equipment and defining of the process borders ensure the assignment of
the process to the most appropriate subsections. Moreover, the defined process
borders help to model the correct process sequence in the DTMS and reduce its
overall complexity (Fig. 7).
In process engineering, a process consists of a sequence of several chemical,
physical, or biological unit operations [19, 20]. Each unit operation aimed to convert,
transport, or store raw materials or intermediates. Combining all process steps
ensures the production of the desired good and its packaging. Industrial production
The Challenge of Implementing Digital Twins in Operating Value Chains
139
DT according to the automation pyramid of Siepmann [15, 16]. On the left, 0–5
describe the automation pyramid separated into strictly hierarchical company levels:
0 is the sensor/actuator level, characterized by simple and rapid data sampling; 1 is
the field level, the interface to the production process; 2 is the control level; 3 is the
process control level; 4 and 5 are the plant management and company levels,
respectively, where production planning, production data acquisition, and order
processing are conducted. The pyramid of the DT is illustrated on the right. Levels
0–1 contain the physical assets, where level 0 includes actuators, sensors, and
equipment and level 1 provides additional functionality such as HMIs for the
DT. Level 2 contains communication and data servers. Level 3 is the gateway
between the physical assets and the DT, and all the other structures connected to
the system. Levels 2 and 4 communicate over the gateway, whereby level 4 supports
cloud-based databases with information from the physical assets and DT. Levels 0–4
allocate the required infrastructure for the DT. Level 5 consists of the digital core
asset, the DT with all necessary apps such as simulation, emulation, and modeling.
With increasing levels in the automation pyramid, the data flow increases. This
correlation offers extensive networking, thus enabling the full capability of the DT.
The connection of levels 1–3 in the DT pyramid is achieved in production lines
through hierarchy, whereby three levels of networking are distinguished: unit,
system, and system of system (SoS) level [18]. The unit level is the smallest element
and can comprise machine equipment, materials, or sensors. The system level is a
combination of multiple unit levels, which can communicate and control each other
by field bus, Ethernet, or 5G. SoS is composed of multiple system levels as in the
collaboration of multiple production lines and combines all data of the production
lifecycle.
3.4 Process Characterization
Process characterization requires a detailed analysis of all physical production
equipment (including sensors) and the procedures to identify all the production
parts that are linked with the product, or relevant for the supply of utilities (e.g.,
electricity, steam, and gases), or affect the process quality indirectly (e.g., cooling
systems and logistics). The production departments and floors relevant for implementation into the DTMS must be defined. Within these individual sections, identification of equipment and defining of the process borders ensure the assignment of
the process to the most appropriate subsections. Moreover, the defined process
borders help to model the correct process sequence in the DTMS and reduce its
overall complexity (Fig. 7).
In process engineering, a process consists of a sequence of several chemical,
physical, or biological unit operations [19, 20]. Each unit operation aimed to convert,
transport, or store raw materials or intermediates. Combining all process steps
ensures the production of the desired good and its packaging. Industrial production
The Challenge of Implementing Digital Twins in Operating Value Chains
139