Yaskawa SMC–4000 User Manual
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SMC–4000 User Manual
Resonance shows up as a pair of complex poles with a real part. A notch filter attempts to cancel the
unwanted poles by placing zeroes on top of them and placing new poles in a more desirable location. The
following diagram shows the pole-zero configuration of a general system with resonance and a notch
filter:
A notch filter can be extremely helpful when used properly, however it is not right for every system.
Incorrect placement of the Notch can cause system instability, and a notch filter puts extra overhead on
the CPU of the controller. A general rule of thumb is to only use a notch when resonance has been found
that cannot be eliminated with the controller’s standard PID filter of the controller. Also, the notch filter
is only effective with a single resonant frequency.