I tried to convert odes to ss but i have problem//o​deToVector​Field

syms x(t) f(t) x3(t) g(t) t 
eqn1 = v == diff(x, t);
eqn2 = diff(v) == -3647.333890*x-99.48571587*v+3947.845868*x3+3947.845868*g+0.0002385211688*f;
eqn3 = diff(x3) == -0.004499581734*eqn2-0.71466948*v-28.3599*x+28.3599*g;
eqns = [eqn1 eqn2 eqn3];
V = odeToVectorField(eqns)

I want to solve this but it shows me error

i have 3 odes f and g are inputs x,v are outputs and x3 is state variable ?

[Star Strider]

You will probably end up using equationsToMatrix, however you will have to edit your system first to make it compatible (and linear).

[meng fowler]

Can you send me the matlab code for this equations please?

Answer 1

[Walter Roberson]

Your code had some problems.

You were not declaring v as a function.

Your definition of eqn3 involved multiplying eqn2 by a value, but eqn2 is an equality and multiplying it by a value as part of an expression is dubious.

I had to guess what you might possibly mean by multiplying by eqn2 there. I probably guessed wrong, so review your system.

syms x(t) f(t) x3(t) g(t) v(t)
eqn1 = v == diff(x, t);
eqn2 = diff(v) == -3647.333890*x-99.48571587*v+3947.845868*x3+3947.845868*g+0.0002385211688*f;
eqn3 = diff(x3) == -0.004499581734*rhs(eqn2)-0.71466948*v-28.3599*x+28.3599*g;
eqns = [eqn1; eqn2; eqn3]

eqns(t) = 

vars = [f(t), g(t), v(t), x(t), x3(t)]

vars = 

[V, S] = odeToVectorField(eqns)

V = 

S = 

[meng fowler]

Thank you very much !!!!!