def _make_model()

in local_dm_control_suite/lqr.py [0:0]

• 35 lines of code
• 8 McCabe index (conditional complexity)

def _make_model(n_bodies,
                n_actuators,
                random,
                stiffness_range=(15, 25),
                damping_range=(0, 0)):
  """Returns an MJCF XML string defining a model of springs and dampers.

  Args:
    n_bodies: An integer, the number of bodies (DoFs) in the system.
    n_actuators: An integer, the number of actuated bodies.
    random: A `numpy.random.RandomState` instance.
    stiffness_range: A tuple containing minimum and maximum stiffness. Each
      joint's stiffness is sampled uniformly from this interval.
    damping_range: A tuple containing minimum and maximum damping. Each joint's
      damping is sampled uniformly from this interval.

  Returns:
    An MJCF string describing the linear system.

  Raises:
    ValueError: If the number of bodies or actuators is erronous.
  """
  if n_bodies < 1 or n_actuators < 1:
    raise ValueError('At least 1 body and 1 actuator required.')
  if n_actuators > n_bodies:
    raise ValueError('At most 1 actuator per body.')

  file_path = os.path.join(os.path.dirname(__file__), 'lqr.xml')
  with resources.GetResourceAsFile(file_path) as xml_file:
    mjcf = xml_tools.parse(xml_file)
  parent = mjcf.find('./worldbody')
  actuator = etree.SubElement(mjcf.getroot(), 'actuator')
  tendon = etree.SubElement(mjcf.getroot(), 'tendon')

  for body in range(n_bodies):
    # Inserting body.
    child = _make_body(body, stiffness_range, damping_range, random)
    site_name = 'site_{}'.format(body)
    child.append(etree.Element('site', name=site_name))

    if body == 0:
      child.set('pos', '.25 0 .1')
    # Add actuators to the first n_actuators bodies.
    if body < n_actuators:
      # Adding actuator.
      joint_name = 'joint_{}'.format(body)
      motor_name = 'motor_{}'.format(body)
      child.find('joint').set('name', joint_name)
      actuator.append(etree.Element('motor', name=motor_name, joint=joint_name))

    # Add a tendon between consecutive bodies (for visualisation purposes only).
    if body < n_bodies - 1:
      child_site_name = 'site_{}'.format(body + 1)
      tendon_name = 'tendon_{}'.format(body)
      spatial = etree.SubElement(tendon, 'spatial', name=tendon_name)
      spatial.append(etree.Element('site', site=site_name))
      spatial.append(etree.Element('site', site=child_site_name))
    parent.append(child)
    parent = child

  return etree.tostring(mjcf, pretty_print=True)