Add design optimisation example #149

NicolaCourtier · 2023-12-15T09:16:41Z

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into 38b-design-example

codecov · 2023-12-15T10:54:59Z

Codecov Report

Attention: 7 lines in your changes are missing coverage. Please review.

Comparison is base (3ba9a6a) 93.03% compared to head (2578c36) 94.10%.
Report is 11 commits behind head on develop.

❗ Current head 2578c36 differs from pull request most recent head 112139d. Consider uploading reports for the commit 112139d to get more accurate results

Files	Patch %	Lines
pybop/_problem.py	94.73%	2 Missing ⚠️
pybop/optimisers/scipy_optimisers.py	92.00%	2 Missing ⚠️
examples/scripts/spme_max_energy.py	98.27%	1 Missing ⚠️
pybop/optimisers/nlopt_optimize.py	66.66%	1 Missing ⚠️
pybop/plotting/quick_plot.py	88.88%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #149      +/-   ##
===========================================
+ Coverage    93.03%   94.10%   +1.06%     
===========================================
  Files           34       36       +2     
  Lines         1178     1323     +145     
===========================================
+ Hits          1096     1245     +149     
+ Misses          82       78       -4

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BradyPlanden

Hi @NicolaCourtier, I've start the review but have to cut it short. I'll try to continue to it later this afternoon. Great addition, I'm really excited for it to be merged! I've added comments around areas that I think can be improved or where I didn't follow the flow.

examples/scripts/spme_max_energy.py

BradyPlanden · 2023-12-15T13:43:51Z

examples/scripts/spme_max_energy.py

+
+
+# Define functions
+def nominal_capacity(x, model):


I think I would prefer to have this be within a pybop class. This example would be simpler with nominal_capacity(), cell_mass(), and GravimetricEnergyDensity() in a seperate pybop class.

For now, they need to be defined in the example - the definitions are not fixed and have been adjusted for the purpose of maximising the gravimetric energy density within the constraints of the model. Do you mean a class within the script?

More like the GravimetricEnergyDensity class would be within pybop.costs with the nominal_capacity and cell_mass methods inside something like a _utilities.py file. They could be then be called within this example via pybop.cell_mass() andpybop.nominal_capacity(), without needing to be defined.

As below, I don't think the definitions should be taken out of context at this stage, but I think this example is still worth having as we continue to test and develop!

BradyPlanden · 2023-12-15T13:45:50Z

examples/scripts/spme_max_energy.py

+    theoretical_energy = model._electrode_soh.calculate_theoretical_energy(
+        model._parameter_set
+    )
+    average_voltage = (


Should this be the mean of the output model voltage instead of the mean on the bounds? A mean value from the OCV function is an alternative if we don't have the model output at this point.

The nominal capacity is required to scale the C-rate used in the experiment, so it must be computed before the simulation. However, it is only a scaling factor on the current so, as long as the same average_voltage is used each time, I believe the energy density will be maximised.

Understood. This implementation would result in an optimal energy density for a given applied current (scaled by the calculated nom. capacity), but this applied current wouldn't be the correct C-rate, right? I think we can get the correct mean voltage via the OCV function though.

Something like this model._parameter_set["Positive electrode OCP [V]"](mean_sto) where themean_sto variable can be calculated by taking the mean ofmodel._esoh_solver.get_min_max_stoichiometries(). More information here.

As far as I understand, there's no feasible way to compute the "correct C-rate" - this is a challenge that comes with using C-rate instead of a defined current and one that we will probably have to address more explicitly in user guidance in the future. In practice, the measured charge/discharge capacity depends on the electrode balancing as well as the overpotential dynamics. So the question becomes: how accurate does the C-rate need to be for the optimisation results to hold and by how much do we want to prioritise accuracy over speed?

The approach you suggest will certainly give a more accurate "average_voltage" but it will also increase the computational load, which is already high due to the re-building. It may also disguise the fact that we need to use an approximation here to obtain a C-rate pre-experiment. We could calculate the realistic mean once at the beginning, using the starting parameter set and inputs, but this would change the cost values from run-to-run so reproducibility could be an issue.

A fixed, easy-to-compute value avoids these issues and, while a particular voltage use-case may be more helpful, I think an average of the voltage limits is a reasonable approximation for now.

examples/scripts/spme_max_energy.py

BradyPlanden · 2023-12-15T13:52:39Z

examples/scripts/spme_max_energy.py

+    """
+
+    # Approximations due to SPM(e) parameter set limitations
+    electrolyte_density = ps["Separator density [kg.m-3]"]


No electrolyte density variable for the SPMe, correct? Since it's just a scalar in this example, I would probably remove it instead of substituting with the separator density variable.

Alternatively, we could just pull from literature for a standard EMC/DMC elecrolyte at a given molarity.

BradyPlanden · 2023-12-15T13:59:05Z

examples/scripts/spme_max_energy.py

+
+
+# Define cost function as a subclass
+class GravimetricEnergyDensity(pybop.BaseCost):


Can this be within _costs.py?

I don't think it should be taken out of context at this stage.

examples/scripts/spme_max_energy.py

BradyPlanden · 2023-12-15T14:11:07Z

pybop/_problem.py

@@ -259,6 +259,12 @@ def __init__(
                init_soc=self.init_soc,
            )

+        # Add an example dataset for plotting comparison


I'm not sure I follow this addition. Could this be completed outside of the DesignProblem class, maybe by grabbing the first step in the optimiser?

Possibly? It could be left to the user to add these steps if desired. I added them here simply to ensure that there is a target dataset for the plotting comparisons.

pybop/_problem.py

into 38b-design-example

…t userwarning, reduce iterations for tests

BradyPlanden

Looks good @NicolaCourtier, nice job!

NicolaCourtier added 9 commits December 14, 2023 23:03

Lower parameter range

18c77d2

Lower test parameters

1cd6732

Add model-specific parameter checks

22526a9

Wrap cost functions for error checking

e55eb81

Add electrode SOH functionality to echem

985fc19

Use predict for evaluating a DesignProblem

40ec760

Update plotting bounds

d45463c

Add design optimisation example

5e5c85e

Merge branch 'develop' into 38b-design-example

30520f9

NicolaCourtier linked an issue Dec 15, 2023 that may be closed by this pull request

Add design optimisation example #38

Closed

pre-commit-ci bot and others added 7 commits December 15, 2023 09:17

style: pre-commit fixes

c444690

Set SciPy pop_size and relax two_signal assertion

b7d3125

Remove unused dependency

85ec240

Merge branch '38b-design-example' of https://github.com/pybop-team/PyBOP

546a1be

into 38b-design-example

Switch SciPy test

9384bc7

Reduce SciPy pop size

97606f0

Scale cost for SciPyMinimize

7c9bb44

NicolaCourtier marked this pull request as ready for review December 15, 2023 10:46

NicolaCourtier requested a review from BradyPlanden December 15, 2023 10:48

BradyPlanden reviewed Dec 15, 2023

View reviewed changes

NicolaCourtier and others added 9 commits December 15, 2023 14:29

Switch Adam to more resilient IRPropMin

5d0c60f

Change areal mass to area density

77a66d9

style: pre-commit fixes

f1ec4bc

Update ps to parameter_set

5b0335b

Merge branch '38b-design-example' of https://github.com/pybop-team/PyBOP

9247fa1

into 38b-design-example

Add Experiment class and unit test

a53b3e1

style: pre-commit fixes

b900110

Update comment

2578c36

Add calc nom. voltage from half-cell ocps, np.trapz dx variable, prin…

112139d

…t userwarning, reduce iterations for tests

BradyPlanden approved these changes Jan 2, 2024

View reviewed changes

BradyPlanden merged commit 24429ec into develop Jan 8, 2024
15 of 16 checks passed

BradyPlanden deleted the 38b-design-example branch January 8, 2024 10:06

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Add design optimisation example #149

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		# Define cost function as a subclass
		class GravimetricEnergyDensity(pybop.BaseCost):

Add design optimisation example #149

Add design optimisation example #149

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