Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How to find the transfer function (frequency response function) given the EOM

  1. Sep 30, 2011 #1
    for a given spring/damper system the equation of motion is:

    [PLAIN]http://img600.imageshack.us/img600/2140/equation1.png [Broken]

    where x is the displacement of a mass from a fixed point
    d is a damping constant
    L1 and L2 constant lengths
    k1 and k2 are 2 spring constants
    and Y(t) is a harmonic input fuction

    How can i find the transfer function of this system?
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Oct 1, 2011 #2
    Hi,

    You need to find x(t)/y(t). For this you can assume a harmonic forcing function, for example:

    Y(t) = Y0 sin(wt)

    and corresponding displacement function:

    X(t) = X0 sin(wt-phi), where phi is the phase lag between applied force and resultant displacement.

    You input these equations in your equation and solve (considering differential xdot and xdotdot). After substitution, replace X0sin(wt-phi) term with x(t).

    Then you will get left side of the equation in terms of x(t). x/y gives you FRF.

    Being a single dof, it should be easier for you to calculate by hand.

    You can refer any standard vibrations book for this.

    Best wishes
    Geoff
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: How to find the transfer function (frequency response function) given the EOM
Loading...