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Process Automation Device Information Model

digital fieldbus connections, process automation, device information model
Liaison agreement encompasses Process Automation Device Information Model (PA-DIM) and development of function blocks and FDI technology within OPAF “standard of standards.”

Worldwide initiatives and ongoing work to achieve digital transformation are focused on connectivity options that will enable replacement of process automation field device interfaces that communicate with host systems over either analog 4-20mA connections or two-wire digital fieldbus connections.

System diagram shows an FDI server offering combined information models, and the ability for the PA-DIM information to be embedded in native OPC-UA devices. (Source: FieldComm Group)

FieldComm Group and The Open Group Process Automation™ Forum recently announced that they have completed a liaison agreement to leverage FieldComm specifications within the OPAF ‘standard of standards.’ Earlier, the group announced endorsement of its process automation device information model specification (PA-DIM) based on NAMUR requirements by the OPC Foundation (OPCF) and PROFIBUS & PROFINET International (PI).

At the 2018 ARC Forum, FieldComm and OPC Foundation presented their joint vision for creating a protocol-independent, process automation device information model specification to implement requirements of the NAMUR Open Architecture.

Technology Trends

Active development is underway in the IEEE 802.3 committee to create a two-wire Ethernet standard. When complete, the new APL (Advanced Physical Layer) standard will allow for high-speed (10 Mbit/s) communications for process automation devices. Current projections expect availability of process automation devices supporting APL around 2020.

The goal of APL is to allow the implementation of Ethernet-based field communication protocols such as PROFINET and HART IP at the device level. This new technology will also allow the implementation of OPC-UA and its information models directly at the device level. The potential is that this would help create simplified system architectures and allow for seamless communication from devices to the cloud without the need for specific protocol gateways.

According to a white paper released by FieldComm, initiatives all over the world such as Industrie 4.0, Industrial Internet of Things (IIoT), Open Process Automation Forum and the NAMUR Open Architecture are working on concepts for digital transformation and new automation system architectures. Information models are key in all of these approaches to make device information available to any kind of application in a well-structured and transparent way.  “To ensure interoperability and seamless access to device information it is necessary to standardize on the form and basic contents of the information models for certain device classes independent of a specific communication protocol,” the white paper states.

Development of the PA-DIM information model is part of the work being performed in the working group structure of FCG with dedicated representatives from OPCF and PNOPI. PA-DIM is based on a combination of the NAMUR requirements for Open Architecture that is in development along with Self-Monitoring and Diagnosis of Field Devices (NE107) and NAMUR standard device-field devices for standard applications (NE 131).

 PA-DIM use cases include:

  • Provide/receive information to/from HMIs, information and reporting applications
  • Information for inventory management and remote monitoring applications
  • Information for real time control applications
  • Device configuration and parameterization
  • Interfaces for configuring the security of a device, and for monitoring its current hardening status
  • Information for device dashboards

Another important input for PA-DIM is an Asset Administration Shell (AAS) concept being defined by the I4.0 consortium. The idea behind the shell is a standardized digital representation of assets between applications managing manufacturing systems.

Ongoing PA-DIM Development

According to the group, PA-DIM will be extended in the future with new sub models and goals to standardize security, for example, or user interface information for comprehensive device configuration.

According to the white paper, there are moves to implement the OPC-UA information model server on field device level, and the PA-DIM will be also embedded on native OPC-UA devices. The mapping of protocol specific formats on the FDI server level also will not be required; information from individual native OPC-UA devices would be accessed by OPC-UA clients directly or indirectly through aggregated OPC-UA servers. For an OPC-UA client there will no difference whether it accesses information from existing field devices mapped through an FDI server or if it accesses information directly from a native OPC-UA field device. The PA-DIM structure will be the same.

For more technical information on these developments, take a look at the white paper that is available on the FieldComm Group website.

Al Presher is a veteran contributing writer for Design News, covering automation and control, motion control, power transmission, robotics, and fluid power.

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