How to Interpret Multiple Peaks in a Bode Plot?

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The discussion centers on interpreting multiple peaks in a Bode plot, particularly identifying the first peak as a resonance frequency. Subsequent peaks may represent other system modes rather than noise. The x-axis frequency response is measured for both nominal and payload conditions, with the first peak shifting lower under maximum load, indicating expected behavior in a loaded resonant system. The importance of staying below the first peak for effective closed-loop control is emphasized. Understanding these peaks is crucial for analyzing the system's open-loop response and planning its application.
skyhj105
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I think that first peak of the graph represent a resonance frequeny but i don`t know some peaks which are located after first peak.
Is it a just noise? or some other?
 

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The measurement is what it is regardless of the names you assign to the peaks, so I'm not sure what you're really asking.

To determine if the plots are real or just measurement noise, one needs much more detail than you provided.
 
anorlunda said:
To determine if the plots are real or just measurement noise, one needs much more detail than you provided.

Thank you for your answer.
I `ll tell you more detail. The value what this plot measure is x-axis frequency response for nominal and payload.(I don`t konw meanig of nominal load and payload exactly... what is this?)
x-axis is one axis of nanopositioning system.
 
Sorry, that is still not enough information to answer your question.
 
skyhj105 said:
I `ll tell you more detail. The value what this plot measure is x-axis frequency response for nominal and payload.
The graph text suggests nominal response when unloaded, compared to response with a maximum load.
Payload is not mentioned. I would expect it to be somewhere between the two.

It appears that when the load is increased to the maximum, the frequency of the first peak is lower, which is what is expected from a loaded resonant system. The fact that the phase cleanly changes by 180° degrees at that frequency confirms that it is a resonance.

Can you give a reference for the scanned figure.
 
skyhj105 said:
I think that first peak of the graph represent a resonance frequeny but i don`t know some peaks which are located after first peak.
Is it a just noise? or some other?
The simple answer is that you should stay well below the first peak if you want good closed loop control.

The other peaks are other system modes probably, transverse modes etc...
 
MRFMengineer said:
The simple answer is that you should stay well below the first peak if you want good closed loop control.

The other peaks are other system modes probably, transverse modes etc...

You are looking at the open loop response of the system, how are you planning to use it? Closed loop?
 

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