Modifications in the Heavac PI controller between PG5 1.1 and PG5 1.2

FAQ #100374

The PI controllers of the Heavac library was modified in the version step from PG5 1.1 to PG5 1.2. This seems a bit disturbing on the first sight. This FAQ explains the changes and their reasons.

 

Explanation
For historical reasons, the "old" PI controller from PG5 version 1.1 and before didn't have the same parameters as the rest of the controllers of the Heavac library. Among others, the only way to set the ampification factor was the option "Amplification Fp" whle the option "Xp range" was absent. This didn't really fit into a library dedicated to the building automatisation, where the "Xp range" is the common specification for the proportional factor of a P controller.
An additional weakness of the old PI controller from PG5 1.1 was the missing dead range of the FBox. There was also a rather complicated specification of the minimal- and maximal percentage of the I-portion of the controller output.
In order to increase the functionality and to reduce the complexity of the PI controller, its implementation got changed.

 

Points to be considered when updating the FBox
Since not only the interface but also some default values were changed, the following points are to be considered when applying the new version of the PI controller:

  • The new default value for the proportional factor is "Xprange" and not any more the "Amplification Fp"
    (formula for conversion: Xp = ( Ymax - Ymin ) / Fp).

  • The new FBox does have a default dead range of 1% (in order to have the same behaviour as the old FBox had, choose 0%).

  • The default value for the integration time Ti is 999.9 seconds in the new FBox while it was only 60 second for in the old FBox (in order to avoid a too agressive controller behaviour with default values, the default value was increased).

Are all existing FBoxes in the existing Fupla programs to be modified?
No, Fupla will leave already existing FBoxes as they are; they will work as before (also after an update of PG5 the old file can be compiled and the old FBox implementation will be used).
Note that PG5 will not insert the old FBox any more. Once an (old) FBox is deleted, the only possibility is using the new version.

 

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Last update: 01.06.2015 03:17

First release: 30.05.2005 14:31

Views: 2649

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