Object Modelling Quick Start

For high-end System Integrators and OEMs, the holy grail of SCADA has been the dream of creating your own fully-fledged, custom, industry-specific SCADA database types along with graphical user interface representations to visualize and interact with them. Because, at its heart, Adroit Smart SCADA is an extensible object model, we show how this dream is now a reality

In this Object Modelling quick start guide, we create aCustom SCADA data type which, in keeping with conventional object oriented paradigms, has a distict set of properties and methods. Aftertesting to verify its successful operation, we go on to develop a re-usable graphical representation that can be deployed tovisualize instances of the object type. Finally, becausealarming and alarm management are so vital to SCADA applications, we demonstrate firstly how to create custom alarm types, and then how to smoothly integrate these with the Adroit alarming subsystem

This is the fifth in the series of Adroit Smart SCADA quick start guides. It follows on from Quick Start Guide 1 – the initial Adroit Smart SCADAQuick Start Guide Quick Start Guide 2 –Logging & Trending Quick Start Guide 3 –Alarming & Alarm Management and Quick Start Guide 4 –Smart UI Re-use Techniques There are some parts of these earlier guides that are essential to understanding this latest guide, and so in that respect they are all, to some extent, essential prerequisites

PRV Custom Agent Type

To keep it all relatively understandable and yet fairly meaningful, we create a hypothetical agent type that models a Pressure Relief Valve (PRV). The characteristics of our PRV are that for pressures higher than some configurable limit the valve opens, but for lower pressures it remains closed. In addition, a count of every open operation is maintained so that essential maintenance can be indicated after a configurable number of operations. Our valve can raise two kinds of alarms: one when it is open, i.e. excess pressure, and a second when essential maintenance is due

As shown in the screenshot of the Adroit 8.4 program group, a special tool for developing custom agent types ships with Adroit: Custom Agent Designer

This tool has its own, comprehensive, in-built Help repository, so run the tool, click on the Help button, and familiarize yourself to some level of detail with its features and operations before continuing any further

The screenshot below shows the design for our Pressure Relief Valve custom agent type:

Because some of the slots such as Open and Operations as well as the two type-specific status bits need to be controlled by the agent itself in response to value changes in various other slots, it is necessary to make sure each agent has a script engine for this purpose. This is indicated in Custom Agent Designer by selecting the Has script engine radio button top right of the above screenshot

The PRV Custom Agent Script

Our VBScript implementing the PRV agent logic is shown below. The screenshot shows the VBS script file loaded into MS Visual Studio – hence the nice colour-coding. Just clicking the Edit script button in Custom Agent Designer will, however, invoke a much simpler script editor that does not have the same colour-coding

Starting at the top of the script:
  • Option Explicit is a Visual Basic statement which forces variables to be declared before they can be used and is regarded as a way of reducing the likelihood of producing code that will generate compile errors
  • As described in the Custom Agent Designer Help, it is necessary to assign unique values starting from zero and incrementing for each different slot defined in the agent. So, by means a Const statements, we create six different constants – one for each slot
  • Similarly, we define two different constants – one for each type-specific status bit. Type-specific status bits need to be given indices starting from 16 up to a maximum of 31. This is because status bits 0 through 15 have predefined functions common to all agent types, whereas status bits 16 through 31 are free to be defined for any purpose the design of an agent type needs
  • A handful of Script Procedures are described in the Help. To implement the PRV agent we need only override two of these: OnCompiled and OnChange
  • OnCompiled is really there only so that compilation errors can easily be detected. All we do is call the Custom.LogEvent script method (cf. Help) and write the string “Compiled OK” to the Windows event log. When first developing the script if you see this message in an event view, then you can be sure the script has compiled OK. Otherwise there should be some other message in the event log describing any compilation error(s)
  • OnChange is the real workhorse procedure of the PRV agent and is called whenever one of its slot values is modified, for example whenever the valve pressure changes. The only two slots we need to be concerned about in the PRV script engine are the Pressure slot and the Reset slot. So we code a Select case statement with cases idx_Pressure and idx_Reset

Running the PRV Custom Agent

Before being able to try out our new custom agent type, we need to publish it by clicking the Publish button on the Custom Agent Designer screen, which will have the effect of copying all T_PRV.* files into the Adroit installation folder as shown

The CSV file contains the various slot and status bit definitions, etc. The VBS file contains the Visual Basic Script described above, and the DLL file is the actual custom agent DLL loaded into the agent server at start up. A further message box is displayed, explaining that these custom agent files will need to be manually copied to any other network computers that are part of the solution

At this point we can run up the agent server application. Just use the configuration left over from the last Quick Start 4 - Smart UI Re-use

As you can see, the new PRV custom agent type is shown along with all the other built-in Adroit agent types

The PRV agent type is also visible as a Type along with others. You can Add, Edit, Scan, Alarm, Log and otherwise configure PRV agents just like any other agent

The right-hand screenshot above shows we have added PRV agent VALVE_01 and edited Pressure, Limit, MaxOperations, and Reset slots to be 8.0 psi, 10.0 psi, 5, and 0 respectively. Note that because Open and Operations slots are not editable, these are shown in a darker grey background

Testing the PRV Custom Agent

The reason we have included so many Custom.LogEvent method calls in the PRV agent script engine is so that we can relatively easily see what’s going on at run time. When you are satisfied everything works as expected, you can take these statements out of the script if you want to

In the meantime, in Smart UI Designer, create a Graphic Form and drop an Adroit EventViewer control onto the graphic form

To avoid getting all sorts of Adroit events displayed, set the FilterString property of the control as shown. This will mean only event messages originating in a custom agent will be displayed

Next, use the Ellipsis […] button at the right of the Columns property to select and order a sub-set of columns to be displayed. All we really need to see are the Time, Object, and Message columns, after which the event viewer should look something like the screenshot below when the form is run either in Smart UI Designer or Operator

From the Time column we can see that events are ordered in reverse chronological order. The earliest event we see is a pressure value change to 17 psi which is above limit and should cause the valve to open. Next we see a pressure value change to 7 psi which, being less than 10 psi, is within limit and should cause the valve to close. Finally we see another, above limit pressure value change, and in this case because the total number of open operations has exceeded 5, a Service alarm is raised as indicated by the Maintenance Required event message

Note: There are only two open operations visible on the event viewer shown, but if we were to page up and down using the Page Up and Page Down buttons on the event viewer, we would see earlier open events

All this will be a lot clearer when we develop and show different PRV instances using a Smart UI wizard and alarm view, but for now we need to be sure the custom agent is functioning correctly and to test this we can simply modify slot values in the Configurator and observe the effect on other slots

The screenshot below left shows the initial situation, i.e. valve open due to pressure above limit at 17 psi. The right-hand screenshot shows when we bring the pressure back down to within limit (5 psi), the valve closes again (Open = 0)

Next if we set the Reset slot On three things happen: The Status_MaintenanceReqd bit in the agent header is reset (right-hand screenshot below), the Operations slot is reset to zero, and the Reset slot itself reverts to Off

Continue experimenting for yourself with various slot value changes until you are happy from observing the event view and other slots in the agent that everything is as it should be

Visualizing the PRV Custom Agent

Our goal in this section is to create a comprehensive Smart UI wizard that can be used to succinctly visualize all salient aspects of PRV agent instances. As we learned in the previous quick start guide on Smart UI Re-use techniques, the best way to go about creating a wizard is first to create a graphic form for a single agent or known group of agents and then later on, turn this into a substitutable wizard

So the following table lists the type and usage of graphical elements we would like when visualizing PRV agent instances on a graphic form, after which we will drill down in some detail on how each different element is configured

Element Description of use
Picture - Show valve in two different positions: Closed and Open
- Display a tool-tip when the mouse hovers over the picture
Text - Display current pressure value
- Display a description for PRV agent instance
- Display text Open when valve is open
- Display text Service Due when maintenance is required
- Display alarm priority of Open alarm
- Display alarm priority of Service alarm
Ellipse - In line withhigh-performance HMI situation awareness guidelines (ISA 101), a circle element in Orange to indicate Normal priority Open alarm
Polyline - Similarly, a triangle element in Yellow to indicate High priority Service alarm
Button - Set Reset slot On after maintenance has been carried out
Trackbar - Slide up and down to simulate the process by varying the pressure up and down as required

Open/Closed Picture Display

Under the Vector group in the Smart UI Designer Toolbox is a Picture element which, amongst other things, supports the anachronistically-named Flip Bitmap behaviour that can show any one of a number of different pictures based on a tag value

The two images alongside show our PRV in the Closed and Open positions respectively, and so by editing the Pictures property of a Picture element we add the two pictures for picture indices 0 and 1 as shown

So copy and paste the two images above left from your Web Browser into the QuickStart Smart UI project folder1 as ValveClosed.png, ValveOpen.png, and add the two pictures to the Pictures collection as described above. All that is then necessary to animate the picture in response to changes in valve position is to apply a Flip Bitmap behaviour driven by the Open slot as shown in the screenshot alongside

1C:\ProgramData\Adroit Technologies\Adroit\SmartUI\Configurations\QuickStart\Projects\Quick Start

Another useful behaviour that can be applied to our valve picture is Tooltip

The screenshot alongside shows a Tooltip behaviour with multi-line text displaying Current pressure, Pressure limit, Operations since service, and Maximum operations. The grid at the bottom defines the Pressure, Limit, Operations, and MaxOperations (not visible) slots to drive these

At the top-right we are stipulating that the Tooltip position is middle-centre of the picture

Clicking the Advanced View button allows you to specify a hover delay before the tool-tip shows up, and another delay (usually longer) before the tool-tip disappears

The screenshot below shows hovering over the picture with our valve in the closed position..

Text Displays

Text elements above and below the picture are used to display the current pressure value and PRV description respectively…

Open Alarm Indication

Towards the top-right of our valve picture a number of graphical elements are used to indicate a Normal priority Open alarm situation

Firstly we Group an Ellipse (circle) to indicate alarm colour and a Text element to display alarm priority. When looking at the group in the Contents pane we see that the ellipse has Colour behaviour, the Text has a Visibility behaviour, and the overall group also has a Visibility behaviour

All behaviours are driven from the Open slot of our PRV agent, the colour behaviour being background Orange for Open and Transparent for Closed. Both visibility behaviours are configured as visible when the Open slot is True and invisible when the Open slot is False...

Finally to the right of the ellipse we display a Text element Open, visible when the valve is open

Service Due Alarm Indication

This is considered to be a higher priority alarm than an Open alarm - priority 3 (High) as opposed to priority 2 (Normal)

Just below the Open alarm indications we similarly show several graphical elements that indicate a High priority Service Due alarm situation

According toISA 101 situation awareness guidelines this should be indicated by a yellow inverted triangle

Firstly, a group comprising, this time, a closed PolyLine (triangle) to indicate alarm colour and a Text element to display alarm priority. In the Contents pane we see that the ellipse has Colour behaviour, the Text has a Visibility behaviour, and the overall group has a Visibility behaviour

All the behaviours are driven from the Status_MaintenanceReqd status bit of our PRV agent. The colour behaviour is background Yellow for ON and Transparent for OFF. Both visibility behaviours are configured as visible when the status bit is ON and invisible when it is OFF...

Finally to the right of the ellipse we display a Text element Service Due, visible when the status bit is ON

Reset Button

Below the Open and Service Due alarm indications, we locate a Button element captioned Reset, the purpose of which is to allow the operator to set a PRV agent’s Reset slot to ON after maintenance has been successfully completed

This button need only be visible when maintenance is actually required, so the initial behaviour we configure is a Visibility behaviour, driven in the same way as the previous behaviours by the Status_MaintenanceReqd status bit of the PRV agent

The other behaviour we need to configure for this button is an Operator Action behaviour to carry out the actual reset action. This is shown alongside as a Control Action, Set Boolean True, Operator Action, operating on the Reset slot of the PRV agent

TrackBar Windows Forms Control

In a real-world application, the current pressure value would in all probability be acquired as a process variable by scanning some or other PLC register. But in our case, to avoid this complexity, and to be able easily to execute various scenarios, we drop a TrackBar Windows Forms Control to the left of our PRV picture. Be sure to set its Orientation property to Vertical since, by default, trackbar controls are horizontally orientated

Because we want the TrackBar to both indicate as well as manipulate current pressure value, we apply a Bind Value behaviour to this control. As shown, we choose our PRV agent’s Pressure slot as the Data Element to bind in a bi-directional sense with the control’s Value property

This bi-directional binding is specified by the Both (To/From Control Property) radio button being selected as indicated near the top-right of the right-hand screenshot below...

Putting it all together

The three screenshots above show our form, with all the graphical elements previously described, configured for a single PRV agent instance VALVE_01

The leftmost screenshot shows the valve operating normally in the closed position at a pressure of 8.0 psi which is below the 10.0 psi pressure limit

The middle screenshot shows the valve in the open position at 16.0 psi which is above the 10.0 psi pressure limit. A normal priority Open alarm is indicated by the orange circle showing alarm priority 2

The rightmost screenshot shows the valve in the open position at 17.0 psi which is above the 10.0 psi pressure limit. A normal priority Open alarm is indicated by the orange circle showing alarm priority 2, but in addition because we have reached the maximum of 5 operations before maintenance is required, a high priority Service Due alarm is indicated by the yellow inverted triangle showing alarm priority 3

Note that in keeping with theISA 101 situation awareness guidelines, the screenshots are mostly low-impact colours which will not distract an operator. The eye is definitely drawn to the high priority Service Due alarm, and to a lesser extent to the normal priority Open alarm

The next step is to transform this hard-coded graphic form into a wizard, but before doing so convince yourself that all the graphic elements and behaviours work as they should do

Transforming our form into a wizard

The next step is to transform our graphic form, hard-coded to show only VALVE_01, into a wizard that can potentially be used to visualize any PRV agent

To do this we click the Save As Wizard toolbar button as shown. Accept the Optimise graphic form size option, and the suggested wzdPressureReliefValve wizard form name

At this point you will presented with a Substitutions Overview dialog as shown below. On this dialog you need meticulously to go through every graphic object behaviour, double-clicking and replacing the hard-coded ‘VALVE_01’ string with a string of the form ‘{Valve}’

The curly braces are very important because they are substitution delimiters recognized by Smart UI Designer to replace the placeholder Valve string with actual PRV agent names when the wizard is pasted onto a graphic form. It is strongly recommended you copy the ‘{Valve}’ string to the clipboard (Ctrl-C) before carrying out the replacements, and then paste the string back from the clipboard (Ctrl-V) so as to minimize the likelihood of any errors

If, at any time after saving your form as a wizard, you’d like to go back to the Substitutions Overview dialog again, for example to verify that everything has been replaced correctly, you can do so by clicking the Substitutions toolbar button as shown below...

Once you are satisfied that all VALVE_01 replacements have been successfully carried out, drag wzdPressureReliefValve across from Enterprise Manager on the left to the Favourites pane on the right in readiness for pasting the wizard onto a graphic form

You may need to enable display of the Favourites pane on the right by selecting it from the relevant View tab toolbar in Smart UI Designer as shown

Making use of the wizard

In order to make use of and demonstrate the capabilities of our wizard, in the Configurator window create two more PRV agents named, say, VALVE_02 and VALVE_03. Make sure they have different Limit slot and MaxOperations slot values as shown below...

Next create a graphic form Form_05, and drag the wizard across from the Favourites pane on the right, drop it onto Form_05 somewhere, and select the Paste Wizard context menu item. This will invoke the Substitution Assignment dialog shown below, where you can, for example, select VALVE_03 to replace the ‘{Valve}’ placeholder string...

Pasting three instances of our wizard onto Form_05, one for each PRV agent should result in something like the screenshot below. Note that VALVE_01 has an Open and Service Due alarm, VALVE_02 is operating normally (closed) with its tool-tip displayed, and VALVE_03 has an Open alarm but does not yet require maintenance

Alarming the PRV Custom Agent

From the graphic form above we can see that VALVE_01 has both an Open and Service Due alarm and VALVE_03 has just an Open alarm. This can also be seen by looking at each agent’s header (just click the Header button with the required agent selected in the Configurator window) as shown in the screenshots below...

Note the state of the checkboxes in the Specific Status section. This is precisely where custom agent development integrates neatly with the Adroit alarming subsystem

To see this, with all the Agent filter checkboxes unchecked in the Configurator window, select Alarm agent type, and edit the defaultAlarmAgent as shown in the screenshot alongside

Navigate to the Types tab and you will see in the Agent Type drop down there is an entry for our newly created PRV agent type

Select PRV agent type, and click the Add an entry button above the list of Available Alarm Types which will initially be empty

The screenshots below show the two alarm types we create for our PRV agent type

On the left we create an alarm type called Open that is raised whenever the Status_Open status bit transitions to ON. At the bottom we designate that it’s the Pressure slot we show in the alarm list’s Reported Data column for this alarm type, by moving this slot over from the list of Available to Current slots using the left chevron button

On the right we create a Service alarm type that is raised whenever the Status_MaintenanceReqd status bit transitions to ON. In the Reported Data section at the bottom we designate the Operations slot to be shown in the alarm list’s Reported Data column for this alarm type

The final part to alarming our three PRV agents is to multiply select all three of them in the Configurator window, and click the Alarm button on the right. This will display a dialog listing the alarm types available to alarm the PRV agents: Open and Service as we created previously

Select the Open type and move it across from Available to Current by clicking the left chevron button

Choose route 3 to avoid the system beeper sounding when an alarm occurs, and choose Priority 2 – Normal for this alarm type

Next, since we want to see both Open and Service alarms, select the Service alarm type as well, and move it across in the same way from the list of Available to Current alarm types. We also use route 3, but we choose Priority 3 – High for this alarm type

Configuration of both alarm types for all PRV agents is shown in the screenshots below...

In order to visualize our PRV agents and at the same time see alarms in the alarm list, we adapt the Navigation Template used in earlier quick start guides by adding a button to display our new Form_05. The result running in Smart UI Operator is shown below...

In Conclusion

So, we have created our own custom SCADA database object type and integrated it seamlessly along with all the existing in-built database types. We have proved that it operates in the way that we want it to and gone on to create a comprehensive graphical representation for it. Finally we have accessed the custom alarm indications designed into the new type and smoothly integrated them into the existing Adroit alarm subsystem

By virtue of this capability, System Integrators and OEMs building their own solutions on top of Adroit are able to create whole libraries of data types and corresponding graphical representations, effectively encapsulating their specialized knowledge and know-how of a particular industry sector. These libraries are usable across countless different project and product configurations, providing significant competitive advantage in terms of both productivity and functionality


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