nonlinear differential equations

[Zwingel, Reinhold]

Hi,

how can I create a m-file for nonlinear differential equations?

e.g:

dx1/dt =  b1*u1 - a1*x1 -a2*x2*x3
dx2/dt =  b2*u2 - a3*x2
dx3/dt = -b3*u3 + a4*a2*x1*x2

u1, u2 and u3 are the input variables.

Which A-matrix can I use?

The value of a2 is constant for the beginning of the simulation.

Unfortunately the value of a2 is a nonlinear function of x2: a2 = f(x2)
Is it possible to use Octave in this case? When yes: How?

Best regards

Reinhold Zwingel

P.S.: I am new at this group. Maybe these questions are too simple.



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