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Current regulation

  1. Aug 18, 2008 #1
    Hi, I'm trying to do current regulation on a motor driven wagon running on a track.
    Instead of having a closed loop servo where the feedback is the speed or position the regulation is to use current. I'm struggling a bit with the theory.

    This is what I'm used to doing:
    Look at 1. Transfer function.
    Now, newton's law in this system is a 2nd order differential equation which can be solved.
    I thought that I need a transfer function I/V which I was able to obtain:
    Code (Text):

    I(s)                Js + b
    -----  = -----------------------
      V        (Js+b)(Ls+R)+K^2
    Ok so I have the transfer function, which is good. My problem however is that I have no idea of how to solve this equation it looks like it is third order? I might be incorrect.
    Sure this could be done numerically but I would prefer an algebraic way as I need to determine the time constant!

    Any help or input would be appreciated.

    wow that was stupid... just elminate (Js+b)/(Js+b) and then it can be solved...
    Last edited: Aug 18, 2008
  2. jcsd
  3. Aug 18, 2008 #2
    Ugh, now I can't edit it obviously my edit was wrong so the question still stands. Is this a third order differential equation? And if so how can I solve it.

    Not too sure about this but it looks like I should get:


    which reduces to:

    JLi'+(bL+JR)i +integral((bR+K^2-b)dt)=VJ+constant

    Now... what is the constant?
    This is a system where the wagon is suddenly given power so at t = 0, i = 0 but what's i'(0)?
    Last edited: Aug 18, 2008
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