#492 clean up setting external variables for potentials

pybamm/models/submodels/current_collector/base_current_collector.py

@@ -19,15 +19,6 @@ class BaseModel(pybamm.BaseSubModel):
     def __init__(self, param):
         super().__init__(param)
 
-    def get_coupled_variables(self, variables):
-
-        # 1D models determine phi_s_cp
-        phi_s_cn = variables["Negative current collector potential"]
-        phi_s_cp = variables["Positive current collector potential"]
-
-        variables = self._get_standard_potential_variables(phi_s_cn, phi_s_cp)
-        return variables
-
     def _get_standard_negative_potential_variables(self, phi_s_cn):
         """
         A private function to obtain the standard variables which
@@ -54,42 +45,6 @@ def _get_standard_negative_potential_variables(self, phi_s_cn):
 
         return variables
 
-    def _get_standard_potential_variables(self, phi_s_cn, phi_s_cp):
-        """
-        A private function to obtain the standard variables which
-        can be derived from the potentials in the current collector.
-
-        Parameters
-        ----------
-        phi_s_cn : :class:`pybamm.Symbol`
-            The potential in the negative current collector.
-        phi_s_cp : :class:`pybamm.Symbol`
-            The potential in the positive current collector.
-
-        Returns
-        -------
-        variables : dict
-            The variables which can be derived from the potential in the
-            current collector.
-        """
-
-        pot_scale = self.param.potential_scale
-        U_ref = self.param.U_p_ref - self.param.U_n_ref
-
-        # Local potential difference
-        V_cc = phi_s_cp - phi_s_cn
-
-        variables = {
-            "Positive current collector potential": phi_s_cp,
-            "Positive current collector potential [V]": U_ref + phi_s_cp * pot_scale,
-            "Local current collector potential difference": V_cc,
-            "Local current collector potential difference [V]": U_ref
-            + V_cc * pot_scale,
-        }
-        variables.update(self._get_standard_negative_potential_variables(phi_s_cn))
-
-        return variables
-
     def _get_standard_current_variables(self, i_cc, i_boundary_cc):
         """
         A private function to obtain the standard variables which

pybamm/models/submodels/current_collector/set_potential_single_particle.py

@@ -32,9 +32,8 @@ def __init__(self, param):
     def get_fundamental_variables(self):
 
         phi_s_cn = pybamm.standard_variables.phi_s_cn
-        phi_s_cp = pybamm.standard_variables.phi_s_cp
 
-        variables = self._get_standard_potential_variables(phi_s_cn, phi_s_cp)
+        variables = self._get_standard_negative_potential_variables(phi_s_cn)
 
         # TO DO: grad not implemented for 2D yet
         i_cc = pybamm.Scalar(0)
@@ -53,11 +52,10 @@ def get_fundamental_variables(self):
 
     def set_rhs(self, variables):
         phi_s_cn = variables["Negative current collector potential"]
-        phi_s_cp = variables["Positive current collector potential"]
 
         # Dummy equations so that PyBaMM doesn't change the potentials during solve
         # i.e. d_phi/d_t = 0. Potentials are set externally between steps.
-        self.rhs = {phi_s_cn: pybamm.Scalar(0), phi_s_cp: pybamm.Scalar(0)}
+        self.rhs = {phi_s_cn: pybamm.Scalar(0)}
 
     def set_algebraic(self, variables):
         ocp_p_av = variables["X-averaged positive electrode open circuit potential"]
@@ -84,17 +82,13 @@ def set_algebraic(self, variables):
 
     def set_initial_conditions(self, variables):
 
-        param = self.param
         applied_current = variables["Total current density"]
         cc_area = self._get_effective_current_collector_area()
         phi_s_cn = variables["Negative current collector potential"]
-        phi_s_cp = variables["Positive current collector potential"]
         i_boundary_cc = variables["Current collector current density"]
 
         self.initial_conditions = {
             phi_s_cn: pybamm.Scalar(0),
-            phi_s_cp: param.U_p(param.c_p_init, param.T_init)
-            - param.U_n(param.c_n_init, param.T_init),
             i_boundary_cc: applied_current / cc_area,
         }
 

pybamm/models/submodels/electrode/base_electrode.py

@@ -126,14 +126,18 @@ def _get_standard_current_collector_potential_variables(self, phi_s_cn, phi_s_cp
 
         pot_scale = self.param.potential_scale
         U_ref = self.param.U_p_ref - self.param.U_n_ref
+        phi_s_cp_dim = U_ref + phi_s_cp * pot_scale
 
         # Local potential difference
         V_cc = phi_s_cp - phi_s_cn
 
-        # terminal voltage (Note: phi_s_cn is zero at the negative tab)
+        # Terminal voltage
+        # Note phi_s_cn is always zero at the negative tab
+        V = pybamm.boundary_value(phi_s_cp, "positive tab")
+        V_dim = pybamm.boundary_value(phi_s_cp_dim, "positive tab")
+
         # Voltage is local current collector potential difference at the tabs, in 1D
         # this will be equal to the local current collector potential difference
-        phi_s_cp_dim = U_ref + phi_s_cp * pot_scale
 
         variables = {
             "Negative current collector potential": phi_s_cn,
@@ -142,6 +146,8 @@ def _get_standard_current_collector_potential_variables(self, phi_s_cn, phi_s_cp
             "Positive current collector potential [V]": phi_s_cp_dim,
             "Local voltage": V_cc,
             "Local voltage [V]": U_ref + V_cc * pot_scale,
+            "Terminal voltage": V,
+            "Terminal voltage [V]": V_dim,
         }
 
         return variables
@@ -170,18 +176,13 @@ def _get_standard_whole_cell_variables(self, variables):
         i_s = pybamm.Concatenation(i_s_n, i_s_s, i_s_p)
 
         variables.update({"Electrode current density": i_s})
+
         if self.set_positive_potential:
-            # don't overwrite current collector potentials
-            try:
-                phi_s_cn = variables["Negative current collector potential"]
-            except KeyError:
-                phi_s_n = variables["Negative electrode potential"]
-                phi_s_cn = pybamm.boundary_value(phi_s_n, "left")
-            try:
-                phi_s_cp = variables["Positive current collector potential"]
-            except KeyError:
-                phi_s_p = variables["Positive electrode potential"]
-                phi_s_cp = pybamm.boundary_value(phi_s_p, "right")
+            # Get phi_s_cn from the current collector submodel and phi_s_p from the
+            # electrode submodel
+            phi_s_cn = variables["Negative current collector potential"]
+            phi_s_p = variables["Positive electrode potential"]
+            phi_s_cp = pybamm.boundary_value(phi_s_p, "right")
             variables.update(
                 self._get_standard_current_collector_potential_variables(
                     phi_s_cn, phi_s_cp

pybamm/models/submodels/external_circuit/current_control_external_circuit.py

@@ -1,7 +1,6 @@
 #
 # External circuit with current control
 #
-import pybamm
 from .base_external_circuit import BaseModel, LeadingOrderBaseModel
 
 
@@ -29,18 +28,6 @@ def get_fundamental_variables(self):
 
         return variables
 
-    def get_coupled_variables(self, variables):
-        # Update terminal voltage
-        phi_s_cp_dim = variables["Positive current collector potential [V]"]
-        phi_s_cp = variables["Positive current collector potential"]
-
-        V = pybamm.boundary_value(phi_s_cp, "positive tab")
-        V_dim = pybamm.boundary_value(phi_s_cp_dim, "positive tab")
-        variables["Terminal voltage"] = V
-        variables["Terminal voltage [V]"] = V_dim
-
-        return variables
-
 
 class LeadingOrderCurrentControl(CurrentControl, LeadingOrderBaseModel):
     """External circuit with current control, for leading order models. """

pybamm/models/submodels/external_circuit/function_control_external_circuit.py

@@ -30,18 +30,6 @@ def get_fundamental_variables(self):
 
         return variables
 
-    def get_coupled_variables(self, variables):
-        # Update terminal voltage
-        phi_s_cp_dim = variables["Positive current collector potential [V]"]
-        phi_s_cp = variables["Positive current collector potential"]
-
-        V = pybamm.boundary_value(phi_s_cp, "positive tab")
-        V_dim = pybamm.boundary_value(phi_s_cp_dim, "positive tab")
-        variables["Terminal voltage"] = V
-        variables["Terminal voltage [V]"] = V_dim
-
-        return variables
-
     def set_initial_conditions(self, variables):
         super().set_initial_conditions(variables)
         # Initial condition as a guess for consistent initial conditions