A doubt on notch Filters

Hi all
I have some doubts on fundementals
As mentioned in tuning process instructions we normally set the INS_GYRO_FILT and INS_ACCEL_FILT to a value of 15 or 20 Hz. That means vibrations beyond this value will not have any affect on the control of the aircraft.
In that case why do we need Notch Filters.? As we have already filtered out vibrations beyond 15 or 20 Hz, why do we even need to worry about vibrations levels of motors.

Same doubt here. I think notch filter works because a lot of people posts seems that they makes the flying better, but I was wondering the same question. Maybe @andyp1per could solve us the doubt.

The low pass filters reduce the noise gradualy after the configured cut-off frequency. They do not eliminate the noise completely. The notch filters attenuate the noise a lot more, but they are very narrow band. Hence you need both filters and both need to be properly tuned.


Also, aggressive low pass filters also filter the control bandwidth meaning that the vehicle reacts more sluggishly to change and thus is not capable of either crisp control or good disturbance rejection. The notch filters allow you to set your low pass filters higher and thus avoid this problem.