Allen-Bradley LOGIX 5000 Reference Manual page 340

Chapter 3 Filter
Example
The NTCH instruction attenuates a specific resonance frequency. Typically, these
resonance frequencies are directly in the range of response being regulated by the
closed loop control system. Often, they are generated by loose mechanical linkages
that cause backlash and vibration in the system. Although the best solution is to
correct the mechanical compliance in the machinery, the notch filter can be used
to soften the effects of these signals in the closed loop regulating scheme.
The following diagram shows the ideal gain curve over a frequency range for a
specific center frequency and Q factor. As increases, the notch becomes wider and
shallower. As decreases; the notch becomes deeper and narrower. The instruction
may be set for an order of 2 or an order of 4. Higher orders take more execution
time.
This example is the minimal legal programming of the NTCH function block and
is only used to show the neutral text and generated code for this instruction. This
is for internal purposes only and is not a testable case.
Function Block
340 Rockwell Automation Publication 1756-RM006K-EN-P - November 2018