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Entry type: FAQ Entry ID: 109751227, Entry date: 04/06/2018

Which controllers can you use for an actual value extrapolation?

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In the case of an actual-value coupling of axes, the extrapolation of master values is usually required and is supported only by a S7-1500T CPU.

In the case of an actual-value coupling, delays occur through the processing of the actual values. To compensate these delays the actual value is extrapolated on the master value side. This means that the master value is calculated based on already known values. You can use the extrapolation in conjunction with the "Motion Control" technology instructions (V3.0 and higher). The following requirements have to be fulfilled here:

  • You need at least STEP 7 V14 for configuring.
  • The extrapolation is supported only in the case of an actual-value coupling in conjunction with gearing and camming.
  • The extrapolation does not affect the technology objects measuring probe ("TO_MeasuringInput"), cam ("TO_OutputCam") and cam track ("TO_CamTrack").
  • The actual-value coupling and therefore also the extrapolation are only possible with an S7-1500T CPU (firmware V2.0 or higher).

The Motion Control function "Extrapolation" is only supported by S71500T and S7-1500TF CPUs.
For the sake of compatibility however the structures of technology data blocks are all identical (independend you have a standard S7-1500 or a S7-1500T).
The variable structure ".Extrapolation." is also described in the manual in conjunction with the S7-1500 Standard CPU. But you cannot use the variable structure ".Extrapolation." with an S7-1500 Standard CPU, it has there no function.

Further Information
More information is available in the function manuals

SIMATIC S7-1500 S7-1500T Motion Control V4.0 in TIA Portal V15 
SIMATIC S7-1500 S7-1500T Motion Control V3.0 in TIA Portal V14  

In this chapters:

  • Extrapolation of the leading values for actual value coupling
  • Actual value extrapolation
  • Configuration - Actual value extrapolation
  • Extrapolation tag (positioning axis/synchronous axis)
  • Extrapolation tag (external encoder)
  • StatusExtrapolation tag (positioning axis/synchronous axis)
  • Variable StatusExtrapolation (External encoder)

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