hi. folks.
I am a machine designer
i design a 3 aixs motion system , every aix use linear motor to drive and Grating rulers to feedback
This is a question confused me. in my system, the closed loop bandwidth is about 200 Hz. so how much mechanical resonant freq should be?
someone telled me the mechanical resonant freq should be a least 3 times over closed loop bandwidth
so he mechanical resonant freq means First-order modal frequency of all structure or just the Direction of movement RESONACE？

 

I hope you told about velocity loop bandwidth 200Hz. And position loop bandwidth must be 2...3 times lower. As a rule an axis with linear motor has resonances frequencies higher than 100Hz. But for some cases velocity loop bandwidth maybe even >100Hz using some filters.
The mechanical resonance frequency means first (i.e. lowest) modal frequency. But real axis mechanics has up to 2 frequencies or even more.
You can review my researches in LinkedIn - find Leonid Gannel papers