implant non linear model using matlab

may I ask how can I create a nonlinear functions manually using simulink or .m

Answer 1

[Hoai Tran Quoc]

You'd better give one example (one formula) which you want to create.

[mansour sabra]

it's very simple example

dx1=-x1+x1x2+u
dx2=2x1-3x2
y=(1 0)x

[Walter Roberson]

Is dx1 intended to represent the derivative of x1? If so then is part of the task to figure out what the function is? Something like

syms x1(t) x2(t) u
eqn = [diff(x1(t),t) == -x1(t) + x1(t)*x2(t) + u; diff(x2(t)) == 2*x1(t)-3*x2(t), x1(0) == 1, x2(0) == 0]
dsolve(eqn)

??

[mansour sabra]

thnak you

[Walter Roberson]

The above system has no general solution and runs into a singularity at about t = 1.33