Lite-On Technology Corp.
Industrial Automation
180
If the user knows the resonance frequency, set the notch filter parameter directly for resonance
suppression. Set the frequency of the notch filter to 50~1000Hz. If the resonance frequency falls out of
this range, it is suggested to use the resonant low-pass filter (PB-17) to reduce the resonance effect.
Next, we want to find out effect of the notch and low-pass filters in the resonance system.
First, let's explore the effect created by applying the notch filter to the resonance system. In the
following Bode plot, the resonance system suppresses the resonance point effectively after the notch
filter is added to the system. The system bandwidth is not much affected.
Next, we can see that the system broadband is smaller when using the resonant low-pass filter to increase the
NLP (PB-17). According to the graph below, the resonant low-pass filter can solve the resonance problem
but the phase margin of system is lower, as well as the system stability.
System resonance point
Addition of NLP low-pass filter
System resonance point
Addition of notch filter
System broadband
