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Sketch the response of a system(bode plot given) to two inputs

  1. Jun 29, 2012 #1
    Hi all
    Please help me with this question, thanks a lot.
    7464930188_dbb23a915a_b.jpg
    7464930048_cb14610b6c_b.jpg



    My attempt on this question is that i can calculate the damping ratio from the magnitude diagram, approximately 0.16
    I can't do more than that, please help. I will be grateful even if you pointing me a direction solving this.
    cheers
     
    Last edited: Jun 29, 2012
  2. jcsd
  3. Jun 29, 2012 #2

    gneill

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    Staff: Mentor

    Hint: What type of signals (waveforms) are the inputs? What are the basic defining characteristics of such signals?
     
  4. Jun 29, 2012 #3

    rude man

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    Your two input plots are the same.
    Are they intended to be continuous or stop at t = 10? If continuous the answer should bite you on the nose. If truncated at 10 sec. then you have a bigger challenge. Tell us which, and what happened to the second input plot.
     
  5. Jul 1, 2012 #4
    thank you for the reply, the question asks to draw response on the input diagram.
     
  6. Jul 1, 2012 #5
    hi
    I'm not sure what information should i get from the bode plot and the input signal to sketch the response.

    to your question, the signal is sine wave form
    :smile:
     
  7. Jul 1, 2012 #6

    gneill

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    What parameters define a sinewave?
     
  8. Jul 1, 2012 #7
    Hi:smile:
    period, amplitude,
     
  9. Jul 2, 2012 #8

    NascentOxygen

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    I doubt that the question is asking for you to draw a waveform that is a composite of two. I'd say you are to first consider one of the inputs and plot the corresponding output on the same set of axes as that input. Then as a separate question, consider the other signal as input, and sketch the corresponding output, again on the same plot as the input so you can demonstrate the phase difference.

    There is no requirement to determine damping ratio, that I can see.

    Are you right to go now, legolegoyoyo?
     
  10. Jul 2, 2012 #9
    Hi, thanks for the reply, its very helpful
    there is an equation from my lecture notes,

    y(t)=AMsin(ω0t+∅)
    the 2 input signal graph are just 2 different input, and the question requires to sketch on them individually
    my understanding to this equation is,

    y(t) is the response wave
    A is the amplitude of the input signal
    M is the magnitude read from the bode diagram(magnitude diagram) at the frequency of ω0
    ω0 is the frequency(in rad/s) read from the input signal and convert to rad/s by multiply the frequency(in Hz) with 2[itex]\pi[/itex]
    ∅ is the angle read from bode diagram(phase diagram) at the frequency of ω0
    then i just substitute all the values i got into the equation y(t) to get the response wave plot

    Im i correct? Please comment
    cheers mate!
     
  11. Jul 2, 2012 #10

    gneill

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    Yup, it looks like you're on your way. One thing though, make sure that you understand precisely what the Bode plot "Magnitude" is...
     
  12. Jul 2, 2012 #11
    Thank to you for your hints:wink:

    for the quote, did you mean i need to anti log the reading from magnitude bode diagram
     
  13. Jul 2, 2012 #12

    gneill

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    When you're drawing a bode magnitude diagram, what expression are you plotting against angular frequency?
     
  14. Jul 3, 2012 #13
    20logK
     
  15. Jul 3, 2012 #14

    gneill

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    And what's K in this context?
     
  16. Jul 4, 2012 #15
    10m/20
     
  17. Jul 4, 2012 #16

    gneill

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    Perhaps I should have been more specific; I wasn't looking for you to isolate K but rather to state what K represents in the given formula.
     
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