adding arctan function in pybamm

[gyouhoc]

Hi,

I have a OCP function as

u_eq = (
    + 0.1493 + 0.8493*exp(-61.79*sto)
    + 0.3824*exp(-665.8*sto) - exp(-39.42*sto - 41.92)
- 0.03131*atan(25.59*sto - 4.099) 	
- 0.009434*atan(32.49*sto - 15.74)
)

And I just realize that there is no atan function defined in pybamm.
I tried to add an atan function as below but it doesn't work.
Would you let me know the proper way to add atan function in pybamm?

In the function file, I add following lines.

class Arctan(SpecificFunction):
""" Arctan function """

def __init__(self, child):
    super().__init__(np.arctan, child)

def _function_diff(self, children, idx):
    """ See :meth:`pybamm.Function._function_diff()`. """
    return 1 / (children[0] ** 2 + 1)

def atan(child):
" Returns hyperbolic tan function of child. "
return pybamm.simplify_if_constant(Arctan(child), keep_domains=True)

However, I still have a following error.

 18         + 0.3824*exp(-665.8*sto) - exp(-39.42*sto - 41.92)
 19         - 0.03131*atan(25.59*sto - 4.099)

---> 20 - 0.009434atan(32.49sto - 15.74)
21 )
22

NameError: name 'atan' is not defined

[valentinsulzer]

Did you import atan in the first line of your ocp function file? (from pybamm import exp, atan)

[gyouhoc]

Yes, I did.

Below is from my input file.

from pybamm import exp, atan

def graphite_ocp_NCM2020(sto):
"""
Graphite Open Circuit Potential (OCP) as a function of the stochiometry [1].

   References
   ----------
   .. [1] Kim, G. H., Smith, K., Lee, K. J., Santhanagopalan, S., & Pesaran, A.
   (2011). Multi-domain modeling of lithium-ion batteries encompassing
   multi-physics in varied length scales. Journal of The Electrochemical
   Society, 158(8), A955-A969.
   """

u_eq = (
    + 0.1493 + 0.8493*exp(-61.79*sto)
    + 0.3824*exp(-665.8*sto) - exp(-39.42*sto - 41.92)
- 0.03131*atan(25.59*sto - 4.099) 	
- 0.009434*atan(32.49*sto - 15.74)
)

return u_eq

[gyouhoc]

Nevermind. It is working after I restart the code.

thx

[valentinsulzer]

Great! When you're ready, it would be great if you could open a PR adding the atan function to the code