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Start the ur_robot_driver

In the last chapter we created a custom scene description containing our robot. In order to make that description usable to ros2_control and hence the ur_robot_driver, we need to add control information. We will also add a custom launchfile to startup our demonstrator.

We will generate a new package called my_robot_cell_control for that purpose.

Create a description with ros2_control tag

The first step is to create a description containing the control instructions:

.. literalinclude:: ../my_robot_cell_control/urdf/my_robot_cell_controlled.urdf.xacro
    :language: xml
    :linenos:
    :caption: my_robot_cell_control/urdf/my_robot_cell_controlled.urdf.xacro

This URDF is very similar to the one we have already assembled. We simply need to include the ros2_control macro,

.. literalinclude:: ../my_robot_cell_control/urdf/my_robot_cell_controlled.urdf.xacro
    :language: xml
    :start-at:   <xacro:include filename="$(find ur_robot_driver)/urdf/ur.ros2_control.xacro"/>
    :end-at:   <xacro:include filename="$(find ur_robot_driver)/urdf/ur.ros2_control.xacro"/>
    :caption: my_robot_cell_control/urdf/my_robot_cell_controlled.urdf.xacro

define the necessary arguments that need to be passed to the macro,

.. literalinclude:: ../my_robot_cell_control/urdf/my_robot_cell_controlled.urdf.xacro
    :language: xml
    :start-at: <xacro:arg name="robot_ip" default="0.0.0.0"/>
    :end-at: <xacro:arg name="mock_sensor_commands" default="false" />
    :caption: my_robot_cell_control/urdf/my_robot_cell_controlled.urdf.xacro

and then call the macro by providing all the specified arguments.

.. literalinclude:: ../my_robot_cell_control/urdf/my_robot_cell_controlled.urdf.xacro
    :language: xml
    :start-at:    <xacro:ur_ros2_control
    :end-at:   />
    :caption: my_robot_cell_control/urdf/my_robot_cell_controlled.urdf.xacro

Extract the calibration

One very important step is to extract the robot's specific calibration and save it to our workcell's startup package. For details, please refer to our documentation on extracting the calibration information. For now, we just copy the default one for the ur20.

cp $(ros2 pkg prefix ur_description)/share/ur_description/config/ur20/default_kinematics.yaml \
  my_robot_cell_control/config/my_robot_calibration.yaml

Create robot_state_publisher launchfile

To use the custom controlled description, we need to generate a launchfile loading that description (Since it contains less / potentially different) arguments than the "default" one. In that launchfile we need to start a robot_state_publisher (RSP) node that will get the description as a parameter and redistribute it via the robot_description topic:

.. literalinclude:: ../my_robot_cell_control/launch/rsp.launch.py
    :language: py
    :start-after: # Author: Felix Exner
    :linenos:
    :caption: my_robot_cell_control/launch/rsp.launch.py

With this we could start our workcell using

ros2 launch ur_robot_driver ur_control.launch.py \
  description_launchfile:=$(ros2 pkg prefix my_robot_cell_control)/share/my_robot_cell_control/launch/rsp.launch.py \
  use_mock_hardware:=true \
  robot_ip:=123 \
  ur_type:=ur20 \
  rviz_config_file:=$(ros2 pkg prefix my_robot_cell_description)/share/my_robot_cell_description/rviz/urdf.rviz \
  tf_prefix:=ur20_

Create start_robot launchfile

Since the command above is obviously not very convenient to start our robot, we wrap that into another launchfile that includes the ur_control.launch.py launchfile with the correct description launchfile and prefix:

.. literalinclude:: ../my_robot_cell_control/launch/start_robot.launch.py
    :language: py
    :linenos:
    :caption: my_robot_cell_control/launch/start_robot.launch.py

With that we can start the robot using

ros2 launch my_robot_cell_control start_robot.launch.py use_mock_hardware:=true

Testing everything

Before we can test our code, it's essential to build and source our Colcon workspace:

#cd to your colcon workspace root, e.g.
cd ~/colcon_ws

#source and build your workspace
colcon build
source install/setup.bash

We can start the system in a mocked simulation

#start the driver with mocked hardware
ros2 launch my_robot_cell_control start_robot.launch.py use_mock_hardware:=true

Or to use it with a real robot:

#start the driver with real hardware
ros2 launch my_robot_cell_control start_robot.launch.py