MQTT gateways

On the way to Industry 4.0, tools like the MQTT gateway can be used to expand access to and transformation of industrial data for the increased benefit of users.

MQTT is a release/subscription protocol that supports a message-oriented middleware architecture. This is not a novel idea in IT; Enterprise Service Buses (ESBs) have long been used to integrate applications using a similar bus architecture. When an exception occurs, MQTT sends device data to the MQTT gateway. The application orders information from the MQTT gateway, which means it does not need to be connected to an endpoint device.

The advantages of the MQTT gateway are
1. Open standards/ interoperability (OASIS standards and Eclipse Open Standards (TAHU)).
2. Separation of devices from applications.
3. Event-triggered reporting.
4. Minimal bandwidth required.
5. Transport layer security.
6. Remotely initiated connections (outbound only; no inbound firewall rules).
7. State-awareness.
8. Single source of data.
9. Automatic tag identification.
10. Data buffering (store and forward).
11. Plug-and-play functionality.

Assume that there are 10 Modbus devices connected to the SCADA system. The user can configure an edge computing gateway between Modbus and MQTT, which allows polling closer to the PLC. In this way, users can query more information quickly and send data to the central MQTT server when it changes. You can also connect to the MQTT server through SCADA and get the data through the MQTT server. This is of paramount importance to ensure that the SCADA system will grow in the future. After the user purchases a sensor or updates a device with MQTT capabilities, SCADA can acquire data without the need to know the end device.

The user must not only access the data, but also ensure that the data is valid and contextually informed, and must be a member of the general architecture. This is a very critical step before using analytics and machine learning. Only when this data is available can the system make reasonable use of it. New sensors and devices generally have this capability. But this does not apply to older devices. There are hundreds of polling protocols that require mapping and expansion. The address design of most PLC address systems is not well understood. Such mappings are often found in SCADA, but they still lack relevant information, contain invalid data, or do not have a standard data structure.

The most efficient way to do this is to connect to an edge computing gateway. It requires software with data cleansing, data rounding, and data structure support.