Adding New interpolator to pybamm.Interpolant class.

[MartinFuentetaja]

Hello everyone! I am trying to use Akima1D interpolator to interpolate the OCPs of gr/LFP cell. I have tried to use pchip instead of cubic spline (due to the flatness of the OCP of LFP). However, the following error arises:

NotImplementedError: The interpolator 'pchip' is not supported by CasAdi. Use 'linear' or 'cubic' instead. Alternatively, set 'model.convert_to_format = 'python'' and use a non-CasADi solver.

Therefore, I have also tried to implement Akima1D interpolator from scratch. However, I did not success.

I have to mention that it works with linear interpolator, however I would prefer to use another one.

[martinjrobins]

This is possible, the main piece of work would be to implement the pchip interpolant in the file pybamm/expression_tree/operations/convert_to_casadi.py. There is an issue on the casadi repo that gives an example of how to do this: casadi/casadi#2489

[vipulramknovo]

Hello @MartinFuentetaja could you please share the code block you used as a interpolation function also how you updated in the parameter values.
I am have some trouble using the interpolation function as as a function of stoichiometry

[MartinFuentetaja]

Hello @vipulramknovo, I'm sorry, but I can't share the code block. However, if it helps, I used the Okane2022.py script as a reference to develop my own methods for an LFP/Graphite cell. You can check it out to see how it can be implemented.

I hope this is helpful!