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Gazebo proxy

Gazebo proxy

The Gazebo proxy is an implementation of interfaces with all services provided by the gazebo_ros_pkgs. It allows easy use and from of the simulation through Python.

It can be configured for different ROS_MASTER_URI and GAZEBO_MASTER_URI environment variables to access instances of Gazebo running in other hosts/ports.

The tutorial below will make use of the simulation manager to start instances of Gazebo.

# Importing the Gazebo proxy
from pcg_gazebo.task_manager import GazeboProxy

The Gazebo proxy may also work with an instance of Gazebo that has been started external to the scope of this package, for example by running

roslaunch gazebo_ros empty_world.launch

The only instance will be found by using the input hostname and ports for which they are running. Here we will use the simulation manager.

# If there is a Gazebo instance running, you can spawn the box into the simulation
from pcg_gazebo.task_manager import Server
# First create a simulation server
server = Server()
# Create a simulation manager named default
server.create_simulation('default')
simulation = server.get_simulation('default')
# Run an instance of the empty.world scenario
# This is equivalent to run
#      roslaunch gazebo_ros empty_world.launch
# with all default parameters
if not simulation.create_gazebo_empty_world_task():
    raise RuntimeError('Task for gazebo empty world could not be created')

# A task named 'gazebo' the added to the tasks list
print(simulation.get_task_list())
# But it is still not running
print('Is Gazebo running: {}'.format(simulation.is_task_running('gazebo')))

['gazebo']
Is Gazebo running: False

# Run Gazebo
simulation.run_all_tasks()

Adding some models to the simulation to demonstrate the Gazebo proxy methods. 

# Now create the Gazebo proxy with the default parameters. 
# If these input arguments are not provided, they will be used per default.
gazebo_proxy = simulation.get_gazebo_proxy()
# The timeout argument will be used raise an exception in case Gazebo 
# fails to start

from pcg_gazebo.simulation import create_object
from pcg_gazebo.generators import WorldGenerator

generator = WorldGenerator(gazebo_proxy)

box = create_object('box')
box.add_inertial(mass=20)
print(box.to_sdf('model'))

<model name="box">
  <static>0</static>
  <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
  <allow_auto_disable>0</allow_auto_disable>
  <link name="box">
    <visual name="visual">
      <geometry>
        <box>
          <size>1 1 1</size>
        </box>
      </geometry>
      <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
      <cast_shadows>1</cast_shadows>
      <transparency>0.0</transparency>
    </visual>
    <collision name="collision">
      <geometry>
        <box>
          <size>1 1 1</size>
        </box>
      </geometry>
      <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
      <max_contacts>10</max_contacts>
    </collision>
    <inertial>
      <mass>20.0</mass>
      <pose frame="">0 0 0 0.0 -0.0 0.0</pose>
      <inertia>
        <ixy>0.0</ixy>
        <ixz>0.0</ixz>
        <ixx>3.333333333333333</ixx>
        <iyy>3.333333333333333</iyy>
        <izz>3.333333333333333</izz>
        <iyz>0.0</iyz>
      </inertia>
    </inertial>
  </link>
</model>

generator.spawn_model(
    model=box, 
    robot_namespace='box_1',
    pos=[-2, -2, 3])

generator.spawn_model(
    model=box, 
    robot_namespace='box_2',
    pos=[2, 2, 3])

True
Pausing/unpausing the simulation
from time import time, sleep
pause_timeout = 10 # seconds
start_time = time()
# Pausing simulation
gazebo_proxy.pause()
print('Simulation time before pause={}'.format(gazebo_proxy.sim_time))
while time() - start_time < pause_timeout:
    print('Gazebo paused, simulation time={}'.format(gazebo_proxy.sim_time))
    sleep(1)
print('Unpausing simulation!')
gazebo_proxy.unpause()
sleep(2)
print('Simulation time after pause={}'.format(gazebo_proxy.sim_time))

Simulation time before pause=3.174
Gazebo paused, simulation time=3.174
Gazebo paused, simulation time=3.174
Gazebo paused, simulation time=3.174
Gazebo paused, simulation time=3.174
Gazebo paused, simulation time=3.174
Gazebo paused, simulation time=3.174
Gazebo paused, simulation time=3.174
Gazebo paused, simulation time=3.174
Gazebo paused, simulation time=3.174
Gazebo paused, simulation time=3.174
Unpausing simulation!
Simulation time after pause=5.173
Get world properties

The world properties return

  • Simulation time (sim_time)
  • List of names of models (model_names)
  • Is rendering enabled flag (rendering_enabled)

The return of this function is simply the service object GetWorldProperties.

# The world properties returns the following
gazebo_proxy.get_world_properties()

sim_time: 5.182
model_names: - ground_plane
- box_1
- box_2
rendering_enabled: True
success: True
status_message: "GetWorldProperties: got properties"
Model properties
# Get list of models
gazebo_proxy.get_model_names()

['ground_plane', 'box_1', 'box_2']

# Get model properties
for model in gazebo_proxy.get_model_names():
    print(model)
    print(gazebo_proxy.get_model_properties(model))
    print('-----------------')

ground_plane
parent_model_name: ''
canonical_body_name: ''
body_names: - link
geom_names: - collision
joint_names: []
child_model_names: []
is_static: True
success: True
status_message: "GetModelProperties: got properties"
-----------------
box_1
parent_model_name: ''
canonical_body_name: ''
body_names: - box
geom_names: - collision
joint_names: []
child_model_names: []
is_static: False
success: True
status_message: "GetModelProperties: got properties"
-----------------
box_2
parent_model_name: ''
canonical_body_name: ''
body_names: - box
geom_names: - collision
joint_names: []
child_model_names: []
is_static: False
success: True
status_message: "GetModelProperties: got properties"
-----------------

# Get model state
for model in gazebo_proxy.get_model_names():
    print(model)
    print(gazebo_proxy.get_model_state(model_name=model, reference_frame='world'))
    print('-----------------')

ground_plane
header: 
  seq: 1
  stamp: 
    secs: 5
    nsecs: 248000000
  frame_id: "world"
pose: 
  position: 
    x: 0.0
    y: 0.0
    z: 0.0
  orientation: 
    x: 0.0
    y: 0.0
    z: 0.0
    w: 1.0
twist: 
  linear: 
    x: 0.0
    y: 0.0
    z: 0.0
  angular: 
    x: 0.0
    y: 0.0
    z: 0.0
success: True
status_message: "GetModelState: got properties"
-----------------
box_1
header: 
  seq: 1
  stamp: 
    secs: 5
    nsecs: 256000000
  frame_id: "world"
pose: 
  position: 
    x: -1.9999999999998166
    y: -1.999999999999968
    z: 0.49999999990200894
  orientation: 
    x: -4.815307161304866e-14
    y: 1.8732345076863254e-13
    z: 1.3228445350203323e-15
    w: 1.0
twist: 
  linear: 
    x: 2.380877975645348e-10
    y: 2.3806985306445073e-10
    z: 9.800284425098838e-10
  angular: 
    x: -4.761370851283154e-10
    y: 4.761622511753355e-10
    z: -1.8285059128478188e-15
success: True
status_message: "GetModelState: got properties"
-----------------
box_2
header: 
  seq: 1
  stamp: 
    secs: 5
    nsecs: 263000000
  frame_id: "world"
pose: 
  position: 
    x: 1.9999999999999458
    y: 1.9999999999997948
    z: 0.4999999999020089
  orientation: 
    x: 1.8990912995643563e-13
    y: -5.0738730839988036e-14
    z: 1.4343436938640824e-15
    w: 1.0
twist: 
  linear: 
    x: -2.380700244227119e-10
    y: -2.380878770514427e-10
    z: 9.799262239290619e-10
  angular: 
    x: 4.761622850817339e-10
    y: -4.76137043576906e-10
    z: 1.383497449329015e-15
success: True
status_message: "GetModelState: got properties"
-----------------

# Check if model exists
print('Does ground_plane exist? {}'.format(gazebo_proxy.model_exists('ground_plane')))
print('Does my_model exist? {}'.format(gazebo_proxy.model_exists('my_model')))

Does ground_plane exist? True
Does my_model exist? False

# Get list of link names for a model
for model in gazebo_proxy.get_model_names():
    print(model)
    print(gazebo_proxy.get_link_names(model))
    print('-----------------')

ground_plane
['link']
-----------------
box_1
['box']
-----------------
box_2
['box']
-----------------

# Test if model has a link
print('Does ground_plane have a link named link? {}'.format(gazebo_proxy.has_link(model_name='ground_plane', link_name='link')))

Does ground_plane have a link named link? True

# Get link properties
for model in gazebo_proxy.get_model_names():
    print(model)
    for link in gazebo_proxy.get_link_names(model_name=model):
        print(' - ' + link)
        print(gazebo_proxy.get_link_properties(model_name=model, link_name=link))
        print('-----------------')
    print('==================')

ground_plane
 - link
com: 
  position: 
    x: 0.0
    y: 0.0
    z: 0.0
  orientation: 
    x: 0.0
    y: 0.0
    z: 0.0
    w: 1.0
gravity_mode: False
mass: 0.0
ixx: 0.0
ixy: 0.0
ixz: 0.0
iyy: 0.0
iyz: 0.0
izz: 0.0
success: True
status_message: "GetLinkProperties: got properties"
-----------------
==================
box_1
 - box
com: 
  position: 
    x: 0.0
    y: 0.0
    z: 0.0
  orientation: 
    x: 0.0
    y: 0.0
    z: 0.0
    w: 1.0
gravity_mode: True
mass: 20.0
ixx: 3.33333
ixy: 0.0
ixz: 0.0
iyy: 3.33333
iyz: 0.0
izz: 3.33333
success: True
status_message: "GetLinkProperties: got properties"
-----------------
==================
box_2
 - box
com: 
  position: 
    x: 0.0
    y: 0.0
    z: 0.0
  orientation: 
    x: 0.0
    y: 0.0
    z: 0.0
    w: 1.0
gravity_mode: True
mass: 20.0
ixx: 3.33333
ixy: 0.0
ixz: 0.0
iyy: 3.33333
iyz: 0.0
izz: 3.33333
success: True
status_message: "GetLinkProperties: got properties"
-----------------
==================

# Get link state
for model in gazebo_proxy.get_model_names():
    print(model)
    for link in gazebo_proxy.get_link_names(model_name=model):
        print(' - ' + link)
        print(gazebo_proxy.get_link_state(model_name=model, link_name=link))
        print('-----------------')
    print('==================')

ground_plane
 - link
link_state: 
  link_name: "ground_plane::link"
  pose: 
    position: 
      x: 0.0
      y: 0.0
      z: 0.0
    orientation: 
      x: 0.0
      y: 0.0
      z: 0.0
      w: 1.0
  twist: 
    linear: 
      x: 0.0
      y: 0.0
      z: 0.0
    angular: 
      x: 0.0
      y: 0.0
      z: 0.0
  reference_frame: ''
success: True
status_message: "GetLinkState: got state"
-----------------
==================
box_1
 - box
link_state: 
  link_name: "box_1::box"
  pose: 
    position: 
      x: -1.9999999999998166
      y: -1.999999999999968
      z: 0.49999999990200894
    orientation: 
      x: -4.815307093534131e-14
      y: 1.8732345086044444e-13
      z: 1.3094942447844376e-15
      w: 1.0
  twist: 
    linear: 
      x: 2.3808779732312217e-10
      y: 2.380698505717412e-10
      z: 9.800284459793307e-10
    angular: 
      x: -4.761370801428996e-10
      y: 4.761622506924893e-10
      z: -1.8285059159830147e-15
  reference_frame: ''
success: True
status_message: "GetLinkState: got state"
-----------------
==================
box_2
 - box
link_state: 
  link_name: "box_2::box"
  pose: 
    position: 
      x: 2.000000000000184
      y: 2.000000000000033
      z: 0.49999999990200894
    orientation: 
      x: -4.815307159875995e-14
      y: 1.8732345220793713e-13
      z: 1.42007914893501e-15
      w: 1.0
  twist: 
    linear: 
      x: 2.3808779822978176e-10
      y: 2.380698514289336e-10
      z: 9.800284459793307e-10
    angular: 
      x: -4.761370818572423e-10
      y: 4.761622525058307e-10
      z: -1.8285059111177573e-15
  reference_frame: ''
success: True
status_message: "GetLinkState: got state"
-----------------
==================
Get physics properties

The physics properties returns the GetPhysicsProperties response with the current parameters for the physics engine. Currently only the parameters for the ODE engine can be retrieved.

print(gazebo_proxy.get_physics_properties())

time_step: 0.001
pause: False
max_update_rate: 1000.0
gravity: 
  x: 0.0
  y: 0.0
  z: -9.8
ode_config: 
  auto_disable_bodies: False
  sor_pgs_precon_iters: 0
  sor_pgs_iters: 50
  sor_pgs_w: 1.3
  sor_pgs_rms_error_tol: 0.0
  contact_surface_layer: 0.001
  contact_max_correcting_vel: 100.0
  cfm: 0.0
  erp: 0.2
  max_contacts: 20
success: True
status_message: "GetPhysicsProperties: got properties"
Apply wrench
# Applying wrench to a link in the simulation
# The input arguments are
#  - model_name
#  - link_name
#  - force: force vector [x, y, z]
#  - torque: torque vector [x, y, z]
#  - start_time: in seconds, if it is a value lower than simulation time, the wrench will be applied as soon as possible
#  - duration: in seconds
#              if duration < 0, apply wrench continuously without end
#              if duration = 0, do nothing
#              if duration < step size, apply wrench for one step size
#  - reference_point: [x, y, z] coordinate point where wrench will be applied wrt the reference frame
#  - reference_frame: reference frame for the reference point, if None it will be set as the provided model_name::link_name
gazebo_proxy.apply_body_wrench(
    model_name='box_1',
    link_name='box',
    force=[100, 0, 0],
    torque=[0, 0, 100],
    start_time=0,
    duration=5,
    reference_point=[0, 0, 0],
    reference_frame=None)

gazebo_proxy.apply_body_wrench(
    model_name='box_2',
    link_name='box',
    force=[10, 0, 200],
    torque=[0, 0, 150],
    start_time=0,
    duration=4,
    reference_point=[0, 0, 0],
    reference_frame=None)

start_time = time()
while time() - start_time < 10:
    sleep(1)
Move models in the simulation
gazebo_proxy.move_model(
    model_name='box_1', 
    pos=[2, 2, 15],
    rot=[0, 0, 0],
    reference_frame='world')

gazebo_proxy.move_model(
    model_name='box_2', 
    pos=[-2, -1, 4],
    rot=[0, 0, 0],
    reference_frame='world')

True

# End the simulation by killing the Gazebo task
simulation.kill_all_tasks()