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PMS 3 - Episode 4 : Application modeling in practice

This fourth episode of our series on the benefits of modeling for a SCADA/IoT platform showcases a concrete example of use.

Application modeling tools

The PcVue supervision platform offers, for example, an advanced configuration tool for application modeling: the application architect.

The Application Architect lets you use high-level facilities to template and reuse of components.
 It enables you to create reusable objects to integrate not only graphics, symbols and tables but also all the frequent configuration elements such as variables, alarms and their associated behaviors: events, archiving, thresholds, commands, scripts etc.

The Application Architect...

  • Reduce development time
  • Enhance application description reliability
  • Reduce the risk of errors
  • Does not require scripting
  • Help applying existing good design practices 
    • Branch and leaves
    • Generic graphic objects

The interest of such a tool also lies in its flexibility and in particular the possibility of adapting the models according to the context and synchronizing the project according to changes over time. Build the applications in 4 steps: templating, differentiation, instantiation, and customization.

The design and maintenance of a project using the Application Architect are possible by following 5 main steps:

Modeling

Differentiation

Instantiation

Customization

Generation / Synchronization 

These steps are described through the example of modeling a pump described below.

Example of modeling a pump

Take the example of a pumping station, to which we would like to add an additional pump:

Modeling

Modeling is the step of defining object models that can always be modified throughout the life of the project.  

Modeling is:

  • Identify Inputs / Outputs
  • Define the necessary internal variables
  • Identify behaviors (trend, archiving, etc.)
  • Specify the graphic appearance

It is also possible to define higher level models by inheritance and / or inclusion.

For our pump the model is as follows:

Figure 1 - Application Architect : modeling

Differentiation

This step lets you identify and specify the differences between the processes of a model in three ways:

  • Parameters
  • Manual input
  • Evaluated expression: by calculation
  • Values of preset parameters  

For our pump, for example, the OPC item is defined by an expression. Other properties are defined by parameters:

Figure 2 – Application Architect : differentiation

Figure 3 - Application Architect : parameters 

Instanciation

Instantiation is the step that allows to:

  • Define the structure of the process to be modeled by creating instances of models
  • Represent physical objects such as installations (motor, conveyor, production line, fan, air handling unit, soil, etc.)
  • Enter any value required to differentiate instances

In the case of our pump a copy / paste of the instance of a similar pump is possible:

Figure 4 - Application Architect : Instantiation

Note that it is also possible to make copies of multiple instances:

Customization

A component can be very similar to another without justifying a supplementary model, so the Application Architect enables you to customize processes to take account of their particular features.

Unit modifications of instances : 

  • Add or remove elements on a particular instance
  • Only if an additional template is not worthwhile

In our example, the additional pump does not have a discrepancy alarm. It is possible to remove it in the instance:

Generation / synchronization

The generation is the step that creates all the elements from the models in the project. If elements were previously generated they will be synchronized according to the changes:

The added pump appears in the synoptic and is operational:

The display of discrepency doesn’t appear for this pump

To go further:

Learn more on Advanced Configuration Environment and all its features here

Watch our videos on Project Modeling Tools

Don't miss the final episode of this third series, we will tackle importing configuration !

PMS 3 - Episode 5 : Importing configuration
PMS 3 - Episode 3: The benefits of modeling
 

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Monday, 28 September 2020

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