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How can i read this Bode plot?

  1. Sep 11, 2016 #1
    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?

    Attached Files:

  2. jcsd
  3. Sep 12, 2016 #2


    Staff: Mentor

    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.
  4. Sep 12, 2016 #3
    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.
  5. Sep 13, 2016 #4


    Staff: Mentor

    Sorry, that is still not enough information to answer your question.
  6. Sep 13, 2016 #5


    User Avatar
    Science Advisor

    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.
  7. Sep 14, 2016 #6
    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.....
  8. Sep 14, 2016 #7
    You are looking at the open loop response of the system, how are you planning to use it? Closed loop?
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