MATLAB: How to solve system of 3 differential equations

differential equations

dx1/dt = r*x1 + p* (x2-x1) dx2/dt = r*x2 + p* (x1+x3-2*x2) dx3/dt = r*x3 + p* (x2-x3)

Best Answer

Hi , the following equations are solved symbolically and unknown constants arise because no initial conditions were provided:

syms x1(t) x2(t) x3(t) p r
eqn1 = diff(x1) == r*x1 + p* (x2-x1) 
eqn2 = diff(x2) == r*x2 + p* (x1+x3-2*x2) 
eqn3 = diff(x3) == r*x3 + p* (x2-x3)
eqns = [eqn1 eqn2 eqn3]
[x1, x2, x3] = dsolve(eqns)

Related Solutions

MATLAB: I tried to convert odes to ss but i have problem//odeToVectorField

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 =

MATLAB: I can’t plot 2nd order differential equation

I can!

Try this:

syms x(t);
Dx = diff(x);
Dx2 = diff(x,2);
x(t) = dsolve(Dx2+(5*Dx)+(6*x)==100,x(0)==0,Dx(0)==0)
figure(1)
fplot(x, [0 10])
axis([xlim    0  17])
grid

Best Answer

Related Solutions

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

MATLAB: I can’t plot 2nd order differential equation

Related Question

MATLAB: I tried to convert odes to ss but i have problem//odeToVectorField