Curve matching functionality

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1

Do we have any curve matching functionality to match the reference curve with the actual curves on products through optical sensor analog feedback on AI2632 ?
Please share some sample task/ reference / guidance / logic if any ?

2

Hi,

I’m not aware of a dedicated function for curve matching / envelope.
But it’s more or less the comparison of an actual value with a reference value on the curve, if the actual value is inside the envelope by checking the allowed +/- tolerance.

To create / share ideas about how to implement such a functionality, some more information would be helpful (at least for my own understanding :wink: ):

  • How your reference curve is created?
    • Is it done by “doing a reference run at the machine and saving the measured data”?
    • Or is there a known mathematical function describing the reference curve?
  • How long the process creating the curve is running, and how often a measurement value is created? (I’m asking to get an impression of the needed number of measurement points for the reference curve, and the needed interpolation in between two points)
  • what is the x-axis value of the curve? Time, or position, or …?
  • is the “duration” (means: the x-axis value range) of the process always the same? Or is it changing (for example “conveyor speed can change, but reference curve is position-oriented and still the same”, which would lead to a compressed or stretched curve)?

I’m asking those details to get an idea, if for example the following way to implement could be used:

  • measurement or definition of some interpolation points of the reference curve
  • generating the reference curve by using MTLookUpTable function block
  • comparing measurement value with curve value and check, it measurement value minus curve value is inside the +/- tolerance wanted

Best regards!

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6

Thanks for the reply, Alexander

Please find answers below

  1. Yes, reference curve can be created by doing a reference run and saving the analog feedback data received on X20AI2632 via optical sensor.
  2. The process creating curve may run for 0.2 s to 1.2 s.
  3. X axis is real axis position
  4. yes, the duration may change depending upon the machine speed and reference position on x axis remains limited.

Feedback is received by reading the complete 360 deg. of a bottle and finding the bulged numbers on a glass bottle e.g. 2 6 8 1 and generate the unique feedback on number 2.
Current status:

  1. We are able to get the analog values and stop at position as per the feedback.
    But the req. feedback received varies between number 2 & 8.

  2. We need support on understanding that how most efficiently we can use this module to detect the value 2 every time, related to configuration parameters?

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7

Hi,

I’m sorry that I can’t dig more into detail at the moment.
But it sounds like I’ve misunderstood your curve matching use-case a bit, hopefully not leading you into the wrong direction.
I know such curve envelope use-cases from checking if a sensor value “is and stays within a band”, because this band is a quality criteria for the produced product (for example temperature or pressure values of an injection molding process).

As I understood now, you have to detect the start position of this bulged number (I assume for do some alignment of the bottles for the following process).
In general, it sounds a bit like that the sampling time for the analogue signal is not fast enough to get every time the “full information”. But unfortunately, I’ve no practical knowledge in that direction, nor special knowledge about the AI2632 module settings.

I hope someone here in the community has more experience in that direction then me,
best regards!

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