Implicit Components: Set initial param values

Question

Using OpenMDAO v1.7.3 Alpha

I have a simple example OpenMDAO Problem consisting of 2 Implicit Components:

The first Component uses temperature to calculate voltage
and the second Component uses voltage to calculate temperature

(code at bottom of question)

Unfortunately, it's failing to converge when I run it in OpenMDAO. I think the problem is that I am not setting initial parameter values. as OpenMDAO is printing the following message to output:

The following params are connected to unknowns that are updated out of order, so their initial values may contain uninitialized unknown values: ['battery_temp_comp.volt']

I have been scouring the documentation but cannot figure out how to set this type of Problem (with Implicit Components) up properly. Any help is appreciated. Thank you!

Code:

from __future__ import print_function
import math as m
import numpy

from openmdao.api import Component, Group, Problem, Newton, ScipyGMRES


class BatteryVoltImplicitComp(Component):
    """ A Simple Implicit Component modelling a Battery's Voltage"""
    def __init__(self):
        super(BatteryVoltImplicitComp, self).__init__()

        # Params
        self.add_param('temp', 30.0)

        # Unknowns
        self.add_output('volt', 12.0)

        # States
        self.add_state('delta', 0.0)

    def calc_voltage(self, params, unknowns, resids):
        temp = params['temp']
        voltage_shift = (25.667 - temp) * 0.02933
        return 12.77 + voltage_shift

    def solve_nonlinear(self, params, unknowns, resids):
        pass

    def apply_nonlinear(self, params, unknowns, resids):
        print("Params:   BatteryVoltImplicitComp.temp: {}".format(params['temp']))
        print("Unknowns: BatteryVoltImplicitComp.volt: {}".format(unknowns['volt']))
        print("Resids: BatteryVoltImplicitComp.delta: {}".format(resids['delta']))
        calculated_voltage = self.calc_voltage(params, unknowns, resids)

        resids['delta'] = calculated_voltage - unknowns['volt']


class BatteryTempImplicitComp(Component):
    """ A Simple Implicit Component modelling a Battery's Temperature"""
    def __init__(self):
        super(BatteryTempImplicitComp, self).__init__()

        # Params
        self.add_param('volt', 12.0)
        # Unknowns
        self.add_output('temp', 30.0)

        # States
        self.add_state('delta', 0.0)

    def calc_temp(self, params, unknowns, resids):
        v = params['volt']
        room_temp = 23.0            # celsius
        batt_resist = 50e-3
        power = v**2 / batt_resist
        temp_increase = power / 50  # magic number
        return room_temp + temp_increase

    def solve_nonlinear(self, params, unknowns, resids):
        pass

    def apply_nonlinear(self, params, unknowns, resids):
        print("Params:   BatteryTempImplicitComp.volt: {}".format(params['volt']))
        print("Unknowns: BatteryTempImplicitComp.temp: {}".format(unknowns['temp']))
        print("Resids: BatteryTempImplicitComp.delta: {}".format(resids['delta']))
        calculated_temp = self.calc_temp(params, unknowns, resids)

        resids['delta'] = calculated_temp - unknowns['temp']


if __name__ == '__main__':

    top = Problem()
    root = top.root = Group()

    root.add('battery_temp_comp', BatteryTempImplicitComp())
    root.add('battery_volt_comp', BatteryVoltImplicitComp())

    root.connect('battery_volt_comp.volt', 'battery_temp_comp.volt')
    root.connect('battery_temp_comp.temp', 'battery_volt_comp.temp')
    root.battery_temp_comp.deriv_options['type'] = 'fd'
    root.battery_temp_comp.deriv_options['form'] = 'central'
    root.battery_temp_comp.deriv_options['step_size'] = 1.0e-1
    root.battery_volt_comp.deriv_options['type'] = 'fd'
    root.battery_volt_comp.deriv_options['form'] = 'central'
    root.battery_volt_comp.deriv_options['step_size'] = 1.0e-1

    root.nl_solver = Newton()
    root.ln_solver = ScipyGMRES()

    top.setup()
    top.run()

    print('Solution (battery_volt_comp): volt = {}, temp = {}, resid = {}'.format(top['battery_volt_comp.volt'], top['battery_volt_comp.temp'], top['battery_volt_comp.delta']))
    print('Solution (battery_temp_comp): volt = {}, temp = {}, resid = {}'.format(top['battery_temp_comp.volt'], top['battery_temp_comp.temp'], top['battery_temp_comp.delta']))

Output:

########################################
Setup: Checking root problem for potential issues...

No recorders have been specified, so no data will be saved. Group '' has the following cycles: [['battery_temp_comp', 'battery_volt_comp']]

The following params are connected to unknowns that are updated out of order, so their initial values may contain uninitialized unknown values: ['battery_temp_comp.volt']

Setup: Check of root problem complete.
########################################
Params: BatteryTempImplicitComp.volt: 12.0
Unknowns: BatteryTempImplicitComp.temp: 30.0
Resids: BatteryTempImplicitComp.delta: 0.0
Params: BatteryVoltImplicitComp.temp: 30.0
Unknowns: BatteryVoltImplicitComp.volt: 12.0
Resids: BatteryVoltImplicitComp.delta: 0.0
Params: BatteryTempImplicitComp.volt: 12.1
Unknowns: BatteryTempImplicitComp.temp: 30.0
Resids: BatteryTempImplicitComp.delta: 50.6
Params: BatteryTempImplicitComp.volt: 11.9
Unknowns: BatteryTempImplicitComp.temp: 30.0
Resids: BatteryTempImplicitComp.delta: 50.6
Params: BatteryTempImplicitComp.volt: 12.0
Unknowns: BatteryTempImplicitComp.temp: 30.0
Resids: BatteryTempImplicitComp.delta: 50.6
Params: BatteryTempImplicitComp.volt: 12.0
Unknowns: BatteryTempImplicitComp.temp: 30.0
Resids: BatteryTempImplicitComp.delta: 50.6
Params: BatteryVoltImplicitComp.temp: 30.1
Unknowns: BatteryVoltImplicitComp.volt: 12.0
Resids: BatteryVoltImplicitComp.delta: 0.64291311
Params: BatteryVoltImplicitComp.temp: 29.9
Unknowns: BatteryVoltImplicitComp.volt: 12.0
Resids: BatteryVoltImplicitComp.delta: 0.64291311

...

Params: BatteryVoltImplicitComp.temp: nan
Unknowns: BatteryVoltImplicitComp.volt: nan
Resids: BatteryVoltImplicitComp.delta: 0.64291311
[root] NL: NEWTON 1 | FAILED to converge after 1 iterations
Solution (battery_volt_comp): volt = nan, temp = nan, resid = -inf
Solution (battery_temp_comp): volt = nan, temp = nan, resid = -inf

Implicit Components: Set initial param values

Answers (1)

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