# How to solve this system of Differential equation

1. Aug 4, 2012

### revooridinesh

I have equations as
C1*y1' = F*C2*y2 - C3*y1
y2' = C4 -B* C5*y3 - C6*y1
y2-C7=x(t)*y3

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. Aug 4, 2012

### chiro

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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