Finding mass, spring constant and damping constant from unit step response

Discussion in 'Homework Help' started by tinvan, May 21, 2011.

  1. tinvan

    Thread Starter New Member

    May 21, 2011
    1
    0
    I have to solve following question and am completely stuck. If you click on the link at the end of this post, you'll see a picture for the system. Im my question, the force is acting in opposit direction to that picture.

    I found the transfere functionto be : G(s)=1/(cs-k-ms^2) but I have no idea how to find those unknowns.I have to use MATLAB.

    Thank you for your help!

    Question:
    When a unit step function force P(t) is applied to the system, the displacement x(t) has overshoot of a bit less than 5% (indicating that the real part and imaginary part of poles are the same), reaches its final value of 2, at about 4 seconds. From this unit step response of the system, determine the values of m, k and c.

    Figure 1: http://wikis.controltheorypro.com/index.php?title=Forced_Vibration_in_Second_Order_Systems
     
  2. Georacer

    Moderator

    Nov 25, 2009
    5,142
    1,266
  3. littlefairy

    New Member

    Jul 18, 2012
    1
    0
    In M-FILE
    function
    u=unitstep(t)
    for i=1:length(t)
    if t(i)>=0
    u(i)=1
    else
    u(i)=0
    end
    end
    plot(t,u,'r')
    In COMMAND WINDOW
    >> t=-10:0.01:10;
    >> u=unitstep(t)
     
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