fsolve not converging at F(x) = 0

Hello,

I have written the attached code for solving the equilibrium of a rigid-link torsional spring model using fsolve.

However, when I evaluate the function values using the output of fsolve, I don't get 0 -

x = Equilibrium_Position

Equation solved.

fsolve completed because the vector of function values is near zero
as measured by the value of the function tolerance, and
the problem appears regular as measured by the gradient.

<stopping criteria details>
   -0.4065    0.4065

x =

   -0.4065    0.4065

>> k * (x(1) - x(2)) - g * l * sin(x(1)) * (M + m * (n_links - 0.5))

ans =

  -8.6695e+04

>> k * (x(2) - x(1)) - g * l * sin(x(2)) * (M + m * 0.5)

ans =

   8.6695e+04

I am unable to understant why this is happening. Any help/recommendation is welcome. Thanks!

Answer 1

[Walter Roberson]

>> k * (x(1) - x(2)) - g * l * sin(x(1)) * (M + m * (n_links - 0.5))

You define most of those variables inside your function, and their values disappear when the function returns. You are not at a debug prompt.

We deduce that the visible values of some of the variables (in your base workspace) are not the same as the values in the code.

When I put in a breakpoint and ensure that I am using the values from the file, the calculates values are about 2E-13

[Neilabh Banzal]

Thanks a lot! Indeed, I have not updated the worksapce variables. Will keep this in mind in the future.