OPC is a widely adopted interoperability standard for secure, reliable and platform-independent information exchange in the industrial automation space and other industries like automotive and building automation.

Mapping of EtherNet/IP (CIP) objects like Identity, Assembly to OPC UA Information Model will enable standard OPC UA Services to access the objects of EtherNet/IP devices in a vendor-neutral way. This article focuses on various ways of supporting OPC UA standard for EtherNet/IP devices – Deployment Scenarios, some specific use cases relevant for Process Automation Industries, and mapping and comparing use cases with various OPC UA Information models.

Supporting OPC UA standard

The access of EtherNet/IP object via OPC UA Service is possible in three different scenarios:

• Scenario 1: OPC supported Host/DCS system (FDT/FDI/PA-DIM)
• Scenario 2: EtherNet/IP OPC UA Server using EDS file embedded in Industrial Gateway or in any HMI/Industrial Software application
• Scenario 3: OPC UA Server directly embedded in EtherNet/IP device

Process automation use cases

Some of the process automation industry specific use cases relevant for EtherNet/IP device listed below.

• Use Case 1: Device Identification
• Use Case 2: Device Health Status (NAMUR NE107)
• Use Case 3: Monitoring Process Variable
• Use Case 4: Parameterization
• Use Case 5: Calibrating the field device

For Scenario 1: Map and compare the Process Automation Industry specific use cases listed above to:

• FDT OPC UA Information Model
• FDI Information Model
• PA-DIM

For Scenario 2: Possible mapping of EDS Information to OPC UA Information model for above listed use cases.

For Scenario 3: High level understanding of supporting OPC UA in EtherNet/IP device.

Mapping to OPC UA Model

This section covers the mapping of EtherNet/IP (CIP) object to the standard OPC UA Information model for above three scenarios and process automation industry specific use cases.

Scenario 1: OPC supported Host/DCS system (FDT/FDI/PA-DIM)

OPC UA supported FDT/FDI Host or DCS system can expose the EtherNet/ IP (CIP) object via any of the below three information model

• FDT OPC UA Information Model
• FDI Information Model
• Process Automation – Device Information Model (PA-DIM)

EtherNet/IP objects mapped to FDT OPC UA Information Model

As part of IIoT/Industrie 4.0 strategy, FDT Group and OPC Foundation have jointly worked on FDT OPC UA Information model specification document.EtherNet/IP devices connected to OPC enabled FDT Host/Frame allows access to the EtherNet/IP object via OPC UA Services. No additional implementation is necessary for exposing EtherNet/IP (CIP) via OPC UA services in FDT Host/Frame system.

Use Cases Supported by FDT OPC UA Information Model

Below are the set of use cases supported by FDT OPC UA Information Model:

• List Topology
• Device Identification
• Browse Parameters and its attributes
• Get Device Status
• Get Device Diagnostics
• Read Offline Parameters
• Read Online Data
• Write Device Parameters
• Audit Trail

EtherNet/IP field device is represented by EtherNet/IP Device DTM in the FDT Host/Frame application. FDT Host application exposes the FDT OPC UA Information model and enables the access to the EtherNet/IP device object via OPC UA Services. Any generic or FDT aware OPC UA Client can access the EtherNet/IP device by connecting to FDT OPC UA Server.
Components required for supporting EtherNet/IP field device in FDT OPC UA Information Model listed below:

• FDT Host supporting OPC UA Server
• EtherNet/IP Communication DTM
• FDT EtherNet/IP (CIP) Annex Specification Document
• FDT EtherNet/IP Device DTM

EtherNet/IP objects mapped to FDI (Field Device Integration) Information Model

FDI specification can support EtherNet/IP devices using FDI generic protocol extension specification. EtherNet/IP devices connected to FDI Host supporting FDI Information model allows access to the EtherNet/IP device object via OPC UA Services.

Use Cases Supported by FDI Information Model

• Asset Management
• Supporting all the methods defined in the EtherNet/IP FDI Device Package (For example: Calibration, Device Setup, and Echo Curve for Level Transmitter etc.).
• Supporting all functionalities defined in the EtherNet/IP Device Package like Configuration, Alarms, Diagnostics, Trends etc.
• UIP Hosting for supporting complex device functionalities
• Upload/Download for Offline Configuration
• Audit Trail

EtherNet/IP FDI Device Package represents the EtherNet/IP device in FDI host system. FDI Server communicates with EtherNet/IP device using EtherNet/IP FDI Communication Server. It exposes the EtherNet/IP device object in the FDI Information Model. Any generic OPC UA Client or FDI Client application can access the EtherNet/IP device by connecting to the FDI Server (OPC UA Server).

Components required for supporting EtherNet/IP field device in FDI Information Model listed below:

• FDI Server supporting generic protocol extension
• EtherNet/IP FDI Communication Server
• EtherNet/IP FDI PSD Annex specification document
• EtherNet/IP FDI Device Package

EtherNet/IP objects mapped to PA-DIM

Devices mainly used in the process industries like chemical, oil & gas, pharmaceutical, food & beverage, power generations, water and waste water are known as process automation devices. They include measurement devices like flow, density, level, temperature and controlling devices like valves, actuators and positioners.

It is necessary to access the common set of parameters and functions from these devices for effective commissioning, operation and maintenance of these devices. This may be necessary to have this information even during procurement stage of these devices.

IEC standards like Common Data Dictionary (CDD) – IEC 61987 and eCl@ass have a unique way to identify the device parameters using the standard unique identifier. However, it is necessary to have the Information Model to manage the entire life cycle of device independent of the communication protocol.

OPC Foundation and FieldComm Group is jointly working on PA-DIM specification document.

PA-DIM use cases

The first release of PA-DIM focus mainly on the NAMUR Device Core Parameter NE131 and NAMUR OPEN Architecture (NOA) use cases for Pressure, Temperature, Flow, Level, Density, Control Actuator/Positioner devices.

• Identification
• Diagnostics
• Process Values
• Configuration

EtherNet/IP device connects to FDI Server using EtherNet/IP FDI Communication Server. FDI Server exposes the PA-DIM Server. EtherNet/IP FDI Device Package representing the EtherNet/IP field device supports the SEMANTIC_MAP information. PA-DIM Server exposes the EtherNet/IP device information. Any generic OPC UA client can access it by connecting to PA-DIM Server.

Components required for supporting EtherNet/IP field device in PA-DIM server listed below:

• FDI Server supporting generic protocol extension
• EtherNet/IP FDI Communication Server
• EtherNet/IP FDI PSD Annex specification document
• EtherNet/IP Device Package supporting the SEMANTIC_MAP

Use Case Mapping for FDT OPC UA, FDI Information Model and PA-DIM

Section maps below compare process specific use cases with the OPC UA Information model.

Use Case 1: Device Identification
Goal: Uniquely identify an EtherNet/IP field device in the network.

Use Case 2: Device Health Status (NAMUR NE107)
Goal: DeviceHealth indicates the status of a device as defined by NAMUR Recommendation NE107.

Use Case 3: Monitoring Process Variable
Goal: Remotely monitor the process variables read from the EtherNet/IP device using any OPC UA client application.

Use Case 4: Parameterization
Goal: Remotely configure the EtherNet/IP adapter device via OPC UA client application

Use Case 5: Calibrating the field Instruments
Goal: Calibrating the field instrument remotely via OPC UA Client

Scenario 2: EtherNet/IP OPC UA Server using EDS file embedded in Industrial Gateway or in any HMI/Industrial Software application

EDS File is a plain text file created and distributed by EtherNet/IP device vendors. The EDS file provides detailed information related to the device identification, configuration parameters, process variables, composition of assemblies etc. EtherNet/IP Configuration tool uses the EDS file to configure the device.

The EtherNet/IP OPC UA Server derives the information model from EDS file. EtherNet/IP OPC UA Server can be implemented in existing EtherNet/IP configuration tool or any Industrial IoT gateway supporting EtherNet/IP communication protocol. ‘OPC UA for Devices – Part 100’ specification is considered as base for mapping the EDS information to OPC UA. Below section maps information derived from EDS file to the process industry specific use cases are listed.

Use Case 1: Device Identification

Goal: Uniquely identify an EtherNet/IP field device in the network.

Use Case 2: Device Health Status (NAMUR NE107)

Goal: Device Health indicates the status of a device as defined by NAMUR Recommendation NE107. The EDS file does not have any standardized way to identify the device health. EtherNet/IP device health can be derived by reading the status attribute of Identity Object. However, values of Status attribute are not as per NAMUR Recommendation NE107.
As a future possibility/workaround, below are the options to map the Device Health Status to OPC UA DeviceHealth enumeration based on NAMUR Recommendation NE107.

Option #1: Process Device Diagnostic Object (Class Code 0x108) defined in CIP specification document follows the NAMUR Recommendation NE107. The EtherNet/IP device shall implement this object. Note: It is not mandatory to implement the Process Device Diagnostic Object.

EDS file shall specify the details in the Public Object Class Sections to indicate the presence of Process Device Diagnostic Object.

Option #2: Standardization of a new Diagnostic Assembly as part of Predefined Diagnostics Assembly Instances of the EtherNet/IP spec as per NAMUR Recommendation NE107.
Note: As per the EtherNet/IP specification, for most of the objects it is not mandatory to specify the details in the Public Object Class Sections of EDS file.

Use Case 3: Monitoring Process Variable

Goal: Remotely monitoring the critical process variables read from the EtherNet/IP device using any OPC UA client application.

In the OPC UA for Device Information Model, the ParameterSet object of DeviceType instance can be mapped to device parameter information that is available from the EDS file as listed below for monitoring the process values.

Option #1: Parameters of EtherNet/IP devices are listed in the [Params] section of EDS file. Each parameter may contain the possible enumeration details associated with it. This parameter can be mapped to OPC UA Information Model.

Link Path in the EDS file allows access to parameter. However, as per EDS specification Link Path is optional. Hence, OPC UA Information model mapping will not be possible for parameter without Link Path information.

Option #2: Another possibility to map the Parameter would be to use the [Assembly] section of the EDS file. Parameter Members of the each Assembly section can be mapped to OPC UA Information Model.

Note: Read/Subscription can be performed on ParameterSet in OPC UA Information Model for monitoring the process values.

Use Case 4: Parameterization

Goal: Remotely configuring EtherNet/IP adapter device parameters using OPC UA client. Parameterization use case is similar to Option #1 and Option #2 of Use Case 3.
Note: Write operation can be performed on ParameterSet in the OPC UA Information Model.

Use Case 5: Calibration

Goal: Calibrating the field instrument remotely via OPC UA Client

Device profiles implementing S-Sensor Calibration Object can be calibrated from OPC UA Client. However, this requires the EDS file to specify the object details in the Public Object Class Sections. The instance services can be mapped to method call nodes of the OPC UA Information Model.

For Scenario 3: OPC UA Server directly embedded in EtherNet/IP device

Apart from fetching the information from OPC supported host system, it is possible to have the OPC UA embedded in EtherNet/IP adapter devices, drives, PLCs and Controllers.

This enables the vertical communication between the EtherNet/IP device and higher-level systems like MES, Visualization Tools for diagnostics, Asset monitoring, Configuration use cases.

Conclusion

Exposing EtherNet/IP object via OPC UA Information model will accelerate the adoption of EtherNet/IP devices in the process automation industry.

FDT OPC UA Information Model: EtherNet/IP Device DTM can take an advantage of FDT OPC UA Information model without any additional implementation. However, FDT2 CIP Annex specification document is necessary. FDT OPC UA Information model supports the network topology and other use cases listed in this document.

Even though EtherNet/IP DTM supports Complex methods/functionalities, it cannot executed from OPC UA client via FDT OPC UA Information model. For example, calibration methods which require user feedback during method execution using this approach are not supported.

FDI Information Model: FDI Information Model is very elaborate and it allows the distributed deployment of FDI Client and Server module. It is possible to support any complex methods remotely using FDI Client.

Some sections of FDI Information Model has been validated with the tools (reference FDI Host). FDI Client application is thick client application and requires complex UI Engine module. EtherNet/IP FDI PSD specification document is necessary to support FDI Information model for EtherNet/IP device.

PA-DIM: PA-DIM is limited, but highly focused on NAMUR use cases applicable for process automation industry. Using the Semantic ID, PA-DIM can fetch information from the field device without knowledge of the device or parameter specific details. PA-DIM supported Industrial IoT gateway can push the data to the cloud.

Semantic Map of the parameter is necessary to support PA-DIM Server. PA-DIM may require additional update to the Common Data Dictionary (IEC document) to support more use cases. Supporting complex method is not in scope of PA-DIM yet.

Information model using EDS file

EDS file is mandatory for the EtherNet/IP device. Use Cases like Device Identification, Monitoring Process Values and Parameterization can be supported in EDS driven OPC UA Information model. Due to the flexible nature of EDS file, OPC UA Information model may have interoperability issues. Supporting the complex methods, user interfaces, etc. is not possible using the EDS file.

EtherNet/IP OPC UA Companion Specification Document

This companion specification document provides the flexibility to map any EtherNet/IP object to OPC UA Information Model. Apart from supporting the common use cases like Device Identification, Parameterization, Monitoring process Values; Companion Specification should focus on Industry focused use cases like Diagnostic Information and other applications. An appropriate OPC UA information model should be chosen based on the specific business need.

GV Chatrapathi, Director – Embedded; G Sivansethu, Director – Technology; Bhanu Prakash Technical Lead; and Smitha Rao, Co-founder, Director, Utthunga Technologies Pvt. Ltd.