Skip to main content Link Menu Expand (external link) Document Search Copy Copied

Dual-way synchronization between the physical lab and the virtual lab

Table of contents

MQTT architecture

The dual-way synchronization between the physical lab and the virtual lab helps complete the full digital twin architecture, going beyond the unidirectional monitoring [1].

The dual-way synchronization can be realized by exploiting the MQTT architecture, as shown in the following figure. Both the Physical Lab (PL) and the Virtual Lab (VL) can play the role of publisher and subscriber, depending on the intended communication flow:

  1. The physical lab subscribes to the VL topic and publishes to the PL topic

  2. The virtual lab subscribes to the PL topic and publishes to the VL topic

The controller on the side of the physical lab and the software tools on the virtual lab side will take care of generating the outcoming messages and elaborating the incoming messages.

MQTT-based architecture for dual-way synchronization

MQTT messages can adopt the proposed data formalization, but it may happen that the raw message is serialized according to a different schema, thus needing a preliminary elaboration and conversion.

MQTT functionalities of VEB.js

Most of the VR environments enable interactions and animations that can be exploited to visualize the current monitoring of assets. After the visualization and navigation of the virtual labs, the VEB.js web application can be exploited also to support the dual-way synchronization thanks to the modularity of the project and the flexibility of JavaScript language. Therefore, during the VirLaDEE project a novel VEB.js module was designed and implemented, taking advantage of the JavaScript library MQTT.js, to provide an MQTT client that is able to publish and subscribe.

Specifically, the Animation panel of VEB.js has been upgraded with the following commands:

  • “MQTT Sub” to subscribe to topics and receive messages containing the updated position and state of the assets. The topic name is defined based on the input configuration and scene id.

  • “MQTT Unsub” to unsubscribe from all topics

  • “MQTT Pub” to publish a message that contains the snapshot of the assets in terms of position and state. The topic name is defined based on the input configuration and scene id.

Animation panel of VEB.js

The “show” event (cf. data formalization) is typically enough to support the implementation of the dual-way synchronization, but more advanced event type can be employed as well.

An example of dual-way synchronization is provided for the PERFORM Lab use case.

References

  1. Modoni GE, Caldarola EG, Sacco M, Terkaj W (2019) Synchronizing physical and digital factory: benefits and technical challenges. Procedia CIRP, 79:472-477