Problem with the code of EIS

[alirahdarian]

Hello,
i need to find to find the impedance at different frequencies with the fixed sampling frequency.
when set the frequencies as frequencies = [pow(10, -1), pow(10, 0), pow(10, 1), pow(10, 2), pow(10, 3)] it works well but when i increase the range as follows it returns an error. Here is the code:

import pybamm
import numpy as np
import matplotlib.pyplot as plt
from scipy.fft import fft
import pickle
import gc # Import garbage collection module

np.set_printoptions(threshold=np.inf)

#Set up
model = pybamm.lithium_ion.DFN(options={"surface form": "differential"}, name="DFN")
parameter_values = pybamm.ParameterValues("Prada2013")
frequencies = [pow(10, -2), pow(10, -1), pow(10, 0), pow(10, 1), pow(10, 2), pow(10, 3)]

#EIS parameters
I = 1 / 100

def current_function(t):
return I * pybamm.sin(2 * np.pi * pybamm.InputParameter("Frequency [Hz]") * t)

parameter_values["Current function [A]"] = current_function
sim = pybamm.Simulation(model, parameter_values=parameter_values, solver=pybamm.IDAKLUSolver())

impedances_time = []
for frequency in frequencies:
fs = 20 * np.max(frequencies)
dt = 1 / fs
print('dt', dt)

Tfinal = 10 * (1 / np.min(frequencies))
print('Tfinal', Tfinal)
t_eval = np.arange(0, Tfinal, dt)
#print(t_eval)

sol = sim.solve(t_eval, inputs={"Frequency [Hz]": frequency}, initial_soc=0.3)
samples_per_period = int((1 / frequency) / dt)
time = sol["Time [s]"].entries[-3 * samples_per_period:]
current = sol["Current [A]"].entries[-3 * samples_per_period:]
voltage = sol["Terminal voltage [V]"].entries[-3 * samples_per_period:]

#FFT
current_fft = fft(current)
voltage_fft = fft(voltage - np.mean(voltage))
idx = np.argmax(np.abs(current_fft))
impedance = -voltage_fft[idx] / current_fft[idx]
impedances_time.append(impedance)

#Clear variables to free up memory
del sol, time, current, voltage, current_fft, voltage_fft
gc.collect()  # Force garbage collection

#Save impedance data
data = 1000 * np.array(impedances_time)
#pickle.dump(data, open("data.dat", "wb"))

#Plot Nyquist Plot
plt.plot(data.real, -data.imag, linestyle='None', marker='o')
plt.xlabel(r"$Z_\mathrm{Re}$ [mOhm]")
plt.ylabel(r"$-Z_\mathrm{Im}$ [mOhm]")
plt.title('EIS')
plt.show()

And this is the error:

dt 5e-05
Tfinal 1000.0

[IDAS ERROR] IDASetStopTime
The value tstop = 0.360062 is behind current t = 46.7259, in the direction of integration.

Traceback (most recent call last):
File "/home/ali/.local/lib/python3.10/site-packages/pybamm/solvers/solution.py", line 252, in t
return self._t
AttributeError: 'Solution' object has no attribute '_t'. Did you mean: 't'?

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/home/ali/New_folder/cell/basic_calculations.py", line 37, in
time = sol["Time [s]"].entries[-3 * samples_per_period:]
File "/home/ali/.local/lib/python3.10/site-packages/pybamm/solvers/solution.py", line 543, in getitem
self.update(key)
File "/home/ali/.local/lib/python3.10/site-packages/pybamm/solvers/solution.py", line 503, in update
var = pybamm.ProcessedVariable(
File "/home/ali/.local/lib/python3.10/site-packages/pybamm/solvers/processed_variable.py", line 72, in init
self.t_pts = solution.t
File "/home/ali/.local/lib/python3.10/site-packages/pybamm/solvers/solution.py", line 254, in t
self.set_t()
File "/home/ali/.local/lib/python3.10/site-packages/pybamm/solvers/solution.py", line 260, in set_t
raise ValueError("Solution time vector must be strictly increasing")
ValueError: Solution time vector must be strictly increasing
double free

I guess that it might be a memory issue. please let me know how can i solve it Thanks in advance for your help.

[rtimms]

I haven't checked the code, but the error is because the times you are passing to the simulation are not increasing (ValueError: Solution time vector must be strictly increasing)

See here for an EIS example.