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Add an example with a passive joint (#172)
Co-authored-by: Alejandro Hernández Cordero <[email protected]> (cherry picked from commit 7d5ec5d) # Conflicts: # doc/index.rst
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‎doc/index.rst

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@@ -220,7 +220,12 @@ gazebo_ros2_control_demos
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This package contains the contents for testing gazebo_ros2_control. It is running Gazebo Classic and some other ROS 2 nodes.
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There are some examples in the *Gazebo_ros2_control_demos* package. These examples allow to launch a cart in a 30 meter rail.
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There are some examples in the *Gazebo_ros2_control_demos* package.
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Cart on rail
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-----------------------------------------------------------
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These examples allow to launch a cart in a 30 meter rail.
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.. image:: img/cart.gif
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:alt: Cart
@@ -232,9 +237,6 @@ You can run some of the configuration running the following commands:
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ros2 launch gazebo_ros2_control_demos cart_example_position.launch.py
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ros2 launch gazebo_ros2_control_demos cart_example_velocity.launch.py
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ros2 launch gazebo_ros2_control_demos cart_example_effort.launch.py
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ros2 launch gazebo_ros2_control_demos diff_drive.launch.py
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ros2 launch gazebo_ros2_control_demos tricycle_drive.launch.py
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When the Gazebo world is launched you can run some of the following commands to move the cart.
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@@ -243,11 +245,40 @@ When the Gazebo world is launched you can run some of the following commands to
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ros2 run gazebo_ros2_control_demos example_position
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ros2 run gazebo_ros2_control_demos example_velocity
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ros2 run gazebo_ros2_control_demos example_effort
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Mobile robots
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-----------------------------------------------------------
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You can run some of the mobile robots running the following commands:
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.. code-block:: shell
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ros2 launch gazebo_ros2_control_demos diff_drive.launch.py
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ros2 launch gazebo_ros2_control_demos tricycle_drive.launch.py
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When the Gazebo world is launched you can run some of the following commands to move the robots.
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.. code-block:: shell
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ros2 run gazebo_ros2_control_demos example_diff_drive
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ros2 run gazebo_ros2_control_demos example_tricycle_drive
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<<<<<<< HEAD
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The following example shows parallel gripper with mimic joint:
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=======
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Gripper
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-----------------------------------------------------------
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The following example shows a parallel gripper with a mimic joint:
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.. image:: img/gripper.gif
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:alt: Cart
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.. code-block:: shell
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ros2 launch gazebo_ros2_control_demos gripper_mimic_joint_example_position.launch.py
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>>>>>>> 7d5ec5d (Add an example with a passive joint (#172))
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.. image:: img/gripper.gif
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:alt: Cart
@@ -264,3 +295,23 @@ Send example commands:
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.. code-block:: shell
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ros2 run gazebo_ros2_control_demos example_gripper
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Pendulum with passive joints
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-----------------------------------------------------------
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The following example shows a cart with a pendulum arm. This uses the effort command interface for the cart's
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degree of freedom on the rail, and the physics of the passive joint of the pendulum is solved correctly.
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.. code-block:: shell
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ros2 launch gazebo_ros2_control_demos pendulum_example_effort.launch.py
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ros2 run gazebo_ros2_control_demos example_effort
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.. note::
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If the position command interface is used instead, the motion of the pendulum is not calculated correctly and does not move at all, see this `PR <https://github.com/ros-controls/gazebo_ros2_control/issues/240>`__. This also holds true if a mimicked joint with position interface is used. To demonstrate this, run
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.. code-block:: shell
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ros2 launch gazebo_ros2_control_demos pendulum_example_position.launch.py
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ros2 run gazebo_ros2_control_demos example_position

‎gazebo_ros2_control_demos/launch/pendulum_example_effort.launch.py

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# Copyright 2024 ros2_control Development Team
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import os
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from ament_index_python.packages import get_package_share_directory
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from launch import LaunchDescription
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from launch.actions import ExecuteProcess, IncludeLaunchDescription, RegisterEventHandler
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from launch.event_handlers import OnProcessExit
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from launch.launch_description_sources import PythonLaunchDescriptionSource
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from launch_ros.actions import Node
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import xacro
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def generate_launch_description():
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gazebo = IncludeLaunchDescription(
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PythonLaunchDescriptionSource([os.path.join(
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get_package_share_directory('gazebo_ros'), 'launch'), '/gazebo.launch.py']),
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)
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gazebo_ros2_control_demos_path = os.path.join(
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get_package_share_directory('gazebo_ros2_control_demos'))
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xacro_file = os.path.join(gazebo_ros2_control_demos_path,
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'urdf',
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'test_pendulum_effort.xacro.urdf')
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doc = xacro.parse(open(xacro_file))
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xacro.process_doc(doc)
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params = {'robot_description': doc.toxml()}
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node_robot_state_publisher = Node(
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package='robot_state_publisher',
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executable='robot_state_publisher',
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output='screen',
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parameters=[params]
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)
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spawn_entity = Node(package='gazebo_ros', executable='spawn_entity.py',
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arguments=['-topic', 'robot_description',
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'-entity', 'cartpole'],
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output='screen')
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load_joint_state_controller = ExecuteProcess(
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cmd=['ros2', 'control', 'load_controller', '--set-state', 'active',
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'joint_state_broadcaster'],
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output='screen'
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)
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load_joint_trajectory_controller = ExecuteProcess(
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cmd=['ros2', 'control', 'load_controller', '--set-state', 'active', 'effort_controller'],
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output='screen'
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)
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return LaunchDescription([
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RegisterEventHandler(
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event_handler=OnProcessExit(
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target_action=spawn_entity,
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on_exit=[load_joint_state_controller],
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)
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),
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RegisterEventHandler(
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event_handler=OnProcessExit(
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target_action=load_joint_state_controller,
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on_exit=[load_joint_trajectory_controller],
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)
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),
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gazebo,
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node_robot_state_publisher,
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spawn_entity,
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])

‎gazebo_ros2_control_demos/launch/pendulum_example_position.launch.py

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# Copyright 2024 ros2_control Development Team
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import os
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from ament_index_python.packages import get_package_share_directory
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from launch import LaunchDescription
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from launch.actions import ExecuteProcess, IncludeLaunchDescription, RegisterEventHandler
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from launch.event_handlers import OnProcessExit
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from launch.launch_description_sources import PythonLaunchDescriptionSource
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from launch_ros.actions import Node
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import xacro
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def generate_launch_description():
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gazebo = IncludeLaunchDescription(
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PythonLaunchDescriptionSource([os.path.join(
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get_package_share_directory('gazebo_ros'), 'launch'), '/gazebo.launch.py']),
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)
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gazebo_ros2_control_demos_path = os.path.join(
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get_package_share_directory('gazebo_ros2_control_demos'))
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xacro_file = os.path.join(gazebo_ros2_control_demos_path,
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'urdf',
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'test_pendulum_position.xacro.urdf')
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doc = xacro.parse(open(xacro_file))
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xacro.process_doc(doc)
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params = {'robot_description': doc.toxml()}
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node_robot_state_publisher = Node(
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package='robot_state_publisher',
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executable='robot_state_publisher',
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output='screen',
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parameters=[params]
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)
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spawn_entity = Node(package='gazebo_ros', executable='spawn_entity.py',
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arguments=['-topic', 'robot_description',
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'-entity', 'cartpole'],
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output='screen')
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load_joint_state_controller = ExecuteProcess(
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cmd=['ros2', 'control', 'load_controller', '--set-state', 'active',
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'joint_state_broadcaster'],
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output='screen'
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)
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load_joint_trajectory_controller = ExecuteProcess(
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cmd=['ros2', 'control', 'load_controller', '--set-state', 'active',
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'joint_trajectory_controller'],
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output='screen'
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)
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return LaunchDescription([
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RegisterEventHandler(
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event_handler=OnProcessExit(
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target_action=spawn_entity,
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on_exit=[load_joint_state_controller],
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)
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),
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RegisterEventHandler(
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event_handler=OnProcessExit(
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target_action=load_joint_state_controller,
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on_exit=[load_joint_trajectory_controller],
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)
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),
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gazebo,
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node_robot_state_publisher,
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spawn_entity,
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])

‎gazebo_ros2_control_demos/urdf/test_pendulum_effort.xacro.urdf

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<?xml version="1.0"?>
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<robot xmlns:xacro="http://www.ros.org/wiki/xacro" name="pendulum on cart">
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<xacro:macro name="quadr_block" params="mass width height name">
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<link name="${name}">
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<collision>
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<geometry>
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<box size="${width} ${width} ${height}"/>
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</geometry>
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<origin xyz="0 0 0"/>
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</collision>
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<visual>
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<geometry>
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<box size="${width} ${width} ${height}"/>
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</geometry>
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<origin xyz="0 0 ${height/2}"/>
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<material name="blue">
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<color rgba="0 0 .8 1"/>
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</material>
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</visual>
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<inertial>
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<origin xyz="0 0 ${height/2}" rpy="0 0 0"/>
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<mass value="${mass}"/>
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<inertia
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ixx="${mass / 12.0 * (width*width + height*height)}" ixy="0.0" ixz="0.0"
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iyy="${mass / 12.0 * (height*height + width*width)}" iyz="0.0"
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izz="${mass / 12.0 * (width*width + width*width)}"/>
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</inertial>
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</link>
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</xacro:macro>
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<link name="world"/>
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<link name="slideBar">
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<visual>
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<geometry>
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<box size="30 0.05 0.05"/>
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</geometry>
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<origin xyz="0 0 0"/>
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<material name="green">
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<color rgba="0 0.8 .8 1"/>
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</material>
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</visual>
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<inertial>
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<mass value="100"/>
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<inertia ixx="1.0" ixy="0.0" ixz="0.0" iyy="1.0" iyz="0.0" izz="1.0"/>
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</inertial>
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</link>
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<xacro:quadr_block name="cart" mass="10" width="0.5" height="0.2"/>
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<xacro:quadr_block name="pendulum" mass="1" width="0.2" height="1.0"/>
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<joint name="world_to_base" type="fixed">
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<origin rpy="0 0 0" xyz="0 0 1"/>
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<parent link="world"/>
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<child link="slideBar"/>
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</joint>
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<joint name="slider_to_cart" type="prismatic">
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<axis xyz="1 0 0"/>
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<origin xyz="0.0 0.0 0.0"/>
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<parent link="slideBar"/>
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<child link="cart"/>
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<limit effort="1000.0" lower="-15" upper="15" velocity="30"/>
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<dynamics damping="0.3" friction="0.0"/>
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</joint>
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<joint name="cart_to_pendulum" type="revolute">
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<axis xyz="0 1 0"/>
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<origin xyz="0.0 0.35 0.0" rpy="0 0.1 0"/>
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<parent link="cart"/>
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<child link="pendulum"/>
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<limit effort="10000.0" lower="-100000" upper="100000" velocity="100000"/>
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<dynamics damping="0.1" friction="0.0"/>
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</joint>
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<ros2_control name="GazeboSystem" type="system">
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<hardware>
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<plugin>gazebo_ros2_control/GazeboSystem</plugin>
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</hardware>
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<joint name="slider_to_cart">
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<command_interface name="effort">
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<param name="min">-1000</param>
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<param name="max">1000</param>
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</command_interface>
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<state_interface name="position">
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<param name="initial_value">1.0</param>
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</state_interface>
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<state_interface name="velocity"/>
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<state_interface name="effort"/>
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</joint>
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<joint name="cart_to_pendulum">
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<state_interface name="position">
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<!-- this does not work if no command interface is set -->
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<!-- <param name="initial_value">1.57</param> -->
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</state_interface>
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<state_interface name="velocity"/>
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<state_interface name="effort"/>
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</joint>
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</ros2_control>
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<gazebo>
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<plugin filename="libgazebo_ros2_control.so" name="gazebo_ros2_control">
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<parameters>$(find gazebo_ros2_control_demos)/config/cart_controller_effort.yaml</parameters>
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</plugin>
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</gazebo>
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</robot>

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