Source code for jmodelica.examples.vdp_minimum_time

#!/usr/bin/env python 
# -*- coding: utf-8 -*-

# Copyright (C) 2010 Modelon AB
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, version 3 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.

# Import library for path manipulations
import os.path

# Import numerical libraries
import numpy as N
import matplotlib.pyplot as plt

# Import the JModelica.org Python packages
from jmodelica.jmi import compile_jmu
from jmodelica.jmi import JMUModel

def run_demo(with_plots=True):
    """
    Demonstrate how to solve a minimum time dynamic optimization problem based 
    on a Van der Pol oscillator system.
    """

    curr_dir = os.path.dirname(os.path.abspath(__file__));
    model_name = 'VDP_pack.VDP_Opt_Min_Time'
    mo_file = curr_dir+'/files/VDP.mop'

    jmu_name = compile_jmu(model_name, mo_file)
    vdp = JMUModel(jmu_name)
    res = vdp.optimize()

    # Extract variable profiles
    x1=res['x1']
    x2=res['x2']
    u=res['u']
    tf=res['finalTime']
    t=res['time']

    assert N.abs(tf - 2.2811587) < 1e-3, \
            "Wrong value of cost function in cstr_minimum_time.py"
    
    if with_plots:
        # Plot
        plt.figure(1)
        plt.clf()
        plt.subplot(311)
        plt.plot(t,x1)
        plt.grid()
        plt.ylabel('x1')
        
        plt.subplot(312)
        plt.plot(t,x2)
        plt.grid()
        plt.ylabel('x2')
        
        plt.subplot(313)
        plt.plot(t,u)
        plt.grid()
        plt.ylabel('u')
        plt.xlabel('time')
        plt.show()

if __name__ == "__main__":
    run_demo()