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How to solve this system of Differential equation

  1. Aug 4, 2012 #1
    I have equations as
    C1*y1' = F*C2*y2 - C3*y1
    y2' = C4 -B* C5*y3 - C6*y1

    X(t) is a known function
    where F = 0 when y3<y1
    1 when y3>y1
    B=0 when C7<y3
    1 when C7>y3

    C's are constants

    so what I am thinking is at time t1 i will get the values for F and B depending on previous values and X value will be known and I need the solution for the unknowns at time t1. I tried solving this by newton raphshon method but the solution is not converging. Are there any MATLAB commands for this like ODE 23 OR any new solution is welcomed

    Thanks a lot
  2. jcsd
  3. Aug 4, 2012 #2


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    Science Advisor

    Hey revooridinesh and welcome to the forums.

    This is definitely a non-linear system of DE's so you won't be able to use something like an integral transform as easily.

    What I recommend is if you use MATLAB, you use a scheme like say RK4 and then implement your F and B functions as Heaviside functions.

    The idea is that you have a function representing the derivative of all your functions (y1,y2,y3) as a function of the current values of each function. You then use a scheme (like RK4, but it could be any decent numerical scheme) to get the new values at some later step-size.

    If you are using MATLAB, maybe you should show us what your code is doing so people can make specific comments on it.
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