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Create a Reference Profile from multiple signals

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  • Seeq Team


Often times two (or more) units that the same products and unit procedures. This is common in continuous processes that are running a specific "grade"; also in batch processes that are manufacturing the same product ID.  Since they are identical pieces of equipment or units, the “profiles” of critical process parameters are similar and we want to use profiles from multiple units for our reference profile.  In this example we will create a profile from 2 units - the same process can be applied for additional units ad infinitum.  Then we will apply this profile to a running batch to look for deviations in near real-time.


Step 1: Add Signals and Conditions to Display

Add the signals for profiling.  Then specify the modes of operation, or unit procedures, using Seeq's Condition logic to create capsules - there are various ways to do this using Seeq's Capsule logic Formula, Value Search, Custom Condition, Composite Condition, etc.  Shown below are temperature signals for two units R-401 and R-402, along with their corresponding unit operations.  Note that some capsules are overlapping in time, but don't worry, Seeq will handle this just fine.

20191008_reference profile from multiple signals 1.png


Step 2: View the signals in Capsule Time

Here we use the Seeq trending tools to examine the profiles.  Capsule Time is a great way to do this. The 'Group' button in the menu can select the appropriate capsules to overlay the signals - and handle those pesky overlapping capsules on the different units.  We can filter out additional capsules if we want; but let's use them all in this example. Here are the profiles we’ll use to make our reference profile:

20191008_reference profile from multiple signals 2.png


Step 3: Build the Reference Profiles

The key to building a reference profile with multiple signals and conditions is to use the Formula Tool.  The Reference Profile Tool in the Tools Pane provides a nice user experience for a single signal with a single condition - that approach won't work for us here.  We will create two unique profiles, upper and lower, but we’ll need 4 formulas so we can repeat the profile over both the R-401 unit procedures and the R-402 unit procedures.

We “selected” each capsule in the formula by creating a bunch of capsule groups that just contained a single capsule.  This approach works in all cases including overlapped capsules. Here’s the formula for the upper profile, +3 Standard Deviation, repeated over R-401 and we plotted the reference profile in capsule view.

20191008_reference profile from multiple signals 3.png

Below is the Formula that we used, for easy cutting/pasting.  *Pro Tip* - Use the Start and End times from the Capsules Pane to define the capsule() times in the toGroup() function.  The times do not have to match the exact times of the capsule - they only need to fully enclose the single capsule.  Usually this gives us a little wiggle-room on the times.

This formula uses the referenceTable() function to build the profile across the 2 units and 2 signals.  We specified each capsule and each corresponding signal in each capsule then added them using addRows() to the referenceTable().  Then we told Seeq which condition to draw the reference profile using repeatOver() along with the statistic to calculate, +3 StdDev, in this case.

Important!  The referenceTable() function must include Bounded Capsules, i.e. those with specified maxDurations, otherwise you will get an error suggesting to use the removeLongerThan() function.  Make sure that the $c401 and $c402 conditions are either bounded or were created with the removeLongerThan() function.

$R401_1 = $c401.toGroup(capsule('2019-10-07T05:00-06:00', '2019-10-07T07:00-06:00'))
$R401_2 = $c401.toGroup(capsule('2019-10-07T09:00-06:00', '2019-10-07T11:00-06:00'))
$R401_3 = $c401.toGroup(capsule('2019-10-07T15:00-06:00', '2019-10-07T16:30-06:00'))
$R401_4 = $c401.toGroup(capsule('2019-10-07T16:30-06:00', '2019-10-07T18:00-06:00'))
$R401_5 = $c401.toGroup(capsule('2019-10-08T00:00-06:00', '2019-10-08T02:00-06:00'))
$R402_1 = $c402.toGroup(capsule('2019-10-07T05:30-06:00', '2019-10-07T07:30-06:00'))
$R402_2 = $c402.toGroup(capsule('2019-10-07T11:00-06:00', '2019-10-07T13:30-06:00'))
$R402_3 = $c402.toGroup(capsule('2019-10-07T14:00-06:00', '2019-10-07T15:15-06:00'))
$R402_4 = $c402.toGroup(capsule('2019-10-07T15:20-06:00', '2019-10-07T16:40-06:00'))
$R402_5 = $c402.toGroup(capsule('2019-10-08T00:30-06:00', '2019-10-08T02:30-06:00'))

$rt = referenceTable (2min)
   .addRows ($t401, $R401_1)
   .addRows ($t401, $R401_2)
   .addRows ($t401, $R401_3)
   .addRows ($t401, $R401_4)
   .addRows ($t401, $R401_5)
   .addRows($t402, $R402_1)
   .addRows($t402, $R402_2)
   .addRows($t402, $R402_3)
   .addRows($t402, $R402_4)
   .addRows($t402, $R402_5)
   .repeatOver($c401 , ReferenceTableStat.StdDev, 3 )

Repeat the above process for the R-401 lower profile.  *Pro Tip* - Use the 'Duplicate' functionality by clicking on the 'Item Properties' i-icon in the Details Pane.  Then we only need to change the "3" to a "-3" at toward the end of the formula to do a -3 Standard Deviation.

20191008_reference profile from multiple signals 4.png

Repeat this process 2 more times for the R-402 upper and lower profiles.  We only need to change the parameter in the repeatOver() function from $c401 to $c402.  Here is everything plotted in Calendar Time as Reference Profiles and then as Boundaries after using the Boundary Tool.

20191008_reference profile from multiple signals 5.png

And now with Boundaries:

20191008_reference profile from multiple signals 6.png


Step 4: Apply Boundary to Running Unit

Lastly, let's apply this boundary to a currently running mode of operation or batch.  Let's focus on unit R-401 at the moment.  All that we need to do is add the currently running capsule to the existing 'R-401 Unit Procedure - Product X' Condition.  This can be done in a variety of ways using Seeq's Formula functions for modifying conditions.  Here I'll simply add a Capsule by drawing it using the Custom Condition tool.  Note, the result is a capsule that shows the boundary of the running batch, projected into the future.  This same approach can be applied to unit R-402.

20191008_reference profile from multiple signals 7.png

Seeq is able to handle any arbitrary amount of units, signals, overlapping or not to create your reference/golden profiles.

Edited by Brian Crandall
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