A PLC Variable Identification Method by Manual Declaration of Time-Stamped Events

The fourth industrial era, the digitisation of production and the emergence of digital twin involve the hyper-connection of all industrial equipment and especially Automated Production Systems (APSs). Nevertheless, the acquisition of data within these machines remains complicated. APS is an expensive invest, composed of many heterogeneous equipments, they are made for having a long lifespan. So, industries rely on old equipment and it is not possible to wait new Industry 4.0-compatible APSs to follow the digital evolution. A solution is to retrieve data from the APSs through their Programmable Logic Controller (PLC), with industrial networks, like the Modbus. The PLC knows the APS state with sensors and pilots the APS with actuators; all this information is stored into variables is the PLC memory, referenced with addresses. Due to several factors, such as heterogeneous data, lack of PLC program documentation or no automation specialist, the data collection is a complicated and time-consuming task. There are difficulties in linking the desired information and the memory addresses. The aim of this contribution is to propose a method for identifying addresses, through photos of APS, a history of memory values and an a posteriori declaration of viewed events with photos. This method must be suitable for non-specialists.