how to solve differential equation when the derivative is in right and left side of the equation.

Hi guys,

I have a program that needs to solve a differential equation in it and I know that ode45 can solve it in matlab. But, the problem here is that some of our equations are like these:

dx(1) = -k_psi*x(1)+dx(23)

dx(12) = -dx(1)*x(12) + d1 + (1/m)*(sin(x(16))*cos(x(15))*K_T*f_t),....

because of the initial conditions that are not very simple, I cannot integrate it by hand and when I run the program, it says dx(23) is not defined yet. dx is the output of my function and x is input. I searched on web, though I couldnot find anything. Can anyone help?

Answer 1

[Torsten]

MATLAB solves ODE systems of the form

A(t,x)*dx = f(t,x)

So put all dx terms on the left-hand side, determine the matrix A and use the MASS MATRIX option of the ODE integrators.