I have a second-order ODE with an unknown parameter $p$,
$$\frac{y''}{(1+y'^{2})^{\frac{3}{2}}} -p – A(x-B)^2 =0,$$
where $x$ is the independent variable, $y$ is the unknown function, $p$ is unknown parameter to be determined, and $A$ and $B$ are known constants.
I am given $y$ values at three $x$ points, $y_0(x=x_0)$, $y_1(x=x_1)$ and $y_2(x=x_2)$.
I have seen some boundary value problem examples from MATLAB (bvp4c) or Scipy (solve_bvp), where the boundary conditions must be on the boundary exactly such as $y(a)$, $y(b)$, $y'(a)$.
Solve BVP with Unknown Parameter
Is there a way to solve my above ODE equation given $y$ values not on two boundaries?
Currently I am using an optimizing method to search best solution of parameter p and $y'(x_0)$ by solving the IVP problem, but it is time consuming.
Could you kindly give me a more efficient way to solve it?
Thank you.
Best Answer
According to the suggestions from @AVK, I built the problem in MATLAB(but I have no MATLAB to test)
I have read that example and try to adapt it to my case .
$$ \frac{y''}{(1+y'^{2})^{\frac{3}{2}}} -p - A(x-B)^2 =0 $$
given
$$ \begin{equation} \begin{cases} y(x_a)=YA \\ y(x_c)=YC \\ y(x_b)=YB \end{cases}\, \end{equation} $$
where $ x_a \lt x_c \lt x_b$
Let $y_1=y,\quad y_2=y'$
$$ \begin{equation} \begin{cases} y_1'=y_2, \\ y_2'=(1+y_2^{2})^{\frac{3}{2}}\cdot (p + A(x-B)^2) =0 \end{cases}\, \end{equation} $$
I apply the following BCs.
initialization
solve
I don't know if it is correct. Because I have no MATLAB on hand, I just check it in mathworks online site. I want to try a Fortran solver COLNEW to do similar work. If someone has experience on this, please help me.
[ADD]
I also found a newer solver
BVP_SOLVER
. Though it is easier to use, it only supports two-point BVPs and separated BCs, it is not convenient to use on my problem.[Update]
Finally, I have solved the problem(MP-BVP with unknown parameters) using COLNEW, which is really a great solver.