This research aims to develop a reference architecture for the Digital Twin of a manufacturing cell, which provides a service-based and real-time enabled infrastructure for vertical and horizontal integration. We have thus developed a Six-Layer Architecture for Digital Twins (SLADT).

SLADT facilitates the communication of the Digital Twin with the physical entity and the outside world, and embeds value-adding functionality, in six layers:

• Connecting to smart sensors and actuators.
• Connecting to low level controllers.
• Connecting to local data repositories.
• Accessing the internet through an IoT Gateway.
• Accessing cloud-based data repositories.
• Interfacing with emulation and simulation tools.

The Industry 4.0 vision considers the integration of humans in the industries of the future—this is critically important to the South African context. Our research thus considers the issue of effectively integrating human workers through Human Digital Twins.

We are developing a generic architecture for Human Digital Twins that will connect human workers with the digital infrastructure of different application domains. The architecture incorporates the following core components:

• Biography—manage all historical data of human task execution.
• Attributes—represent and utilize the attributes of individual human workers.
• Scheduling—manage the scheduling of human worker tasks.
• Execution—control and monitor the execution of tasks.