Rockwell-automation DeviceLogix System User Manual Manuale Utente Scaricare il pdf (Pagina 33)

Publication RA-UM003B-EN-P - February 2010 33

Navigate the Function Block Editor Interface Chapter 2

The above discussion outlined the general process of low-pass

filtering. Specifically, the filter discussed order 1 LPF and order 2 LPF.

Order 1 LPF

The target analog filter is as follows.

When bilinear transformation is applied, we take the w

as the actual

cutoff frequency. That is, the target transform function is as follows.

Then we apply the bilinear transformation.

Therefore, the corresponding difference equation is as follows.

Order 2 LPF

The target analog filter is as follows.

This is the same derivation process that is in order 1 LPF. Finally, the

corresponding difference equation is as follows.

where

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Rockwell-automation DeviceLogix System User Manual Manuale Utente Pagina 33