Popular tips 

What is a Xacro?

Kobe Glover

What is a Xacro?

Xacro is an XML macro language. With xacro, you can construct shorter and more readable XML files by using macros that expand to larger XML expressions.

What is URDF Xacro file?

As its name implies, xacro is a macro language. The xacro program runs all of the macros and outputs the result. Typical usage looks something like this: xacro –inorder model.xacro > model.urdf. On ROS distros melodic and later, you should omit the {–inorder} argument.

How do I change my URDF to Xacro?

When converting from a URDF to a xacro file, I did the following:

  1. Create properties for commonly-used constants.
  2. Create properties for variable components of your robot (Parts that will be constant over a run, but may change between runs)

How do you write URDF?

  1. So, just creating the structure is very simple!
  2. Update your file my_urdf.xml and run it through the parser:1 $ rosrun urdf_parser check_urdf my_urdf.xml.
  3. Update your file my_urdf.xml and run it through the parser:1 $ rosrun urdf_parser check_urdf my_urdf.xml.
  4. That’s it, you created your first URDF robot description!

What is macros in Ros?

Macros allow the insertion of system features into normal wiki pages; the only thing that makes those pages special is that they contain macros. If you edit pages like RecentChanges or SystemInfo, you’ll see what that means.

How do I open a ros file?

launch File. To actually start a node, the tags are used, the pkg, type and name argument are required. pkg/type/name: The argument pkg points to the package associated with the node that is to be launched, while “type” refers to the name of the node executable file.

How do you make a robot with URDF?

Learning URDF (including C++ API)

  1. Create your own urdf file. In this tutorial you start creating your own urdf robot description file.
  2. Parse a urdf file. This tutorial teaches you how to use the urdf parser.
  3. Using the robot state publisher on your own robot.
  4. Start using the KDL parser.
  5. Using urdf with robot_state_publisher.

What is ROS URDF?

The Unified Robotic Description Format (URDF) is an XML file format used in ROS to describe all elements of a robot. To use a URDF file in Gazebo, some additional simulation-specific tags must be added to work properly with Gazebo.

What is robot state publisher?

The robot state publisher is a tool that will do this job for you. The robot state publisher internally has a kinematic model of the robot; so given the joint positions of the robot, the robot state publisher can compute and broadcast the 3D pose of each link in the robot.

How do you read URDF?

Reading a URDF file

  1. Let’s first create a package with a dependency on the urdf parser: $ roscd sandbox $ roscreate-pkg learning_urdf urdf $ roscd learning_urdf $ rosmake.
  2. Now first copy your my_urdf.
  3. Now let’s try to run this code.
  4. build your package, and run it.

What is URDF Ros?

The URDF (Universal Robot Description Format) model is a collection of files that describe a robot’s physical description to ROS. These files are used by a program called ROS (Robot Operating System) to tell the computer what the robot actually looks like in real life.

What do you need to know about xacro in ROS?

As its name implies, xacro is a macro language. The xacro program runs all of the macros and outputs the result. Typical usage looks something like this: On ROS distros melodic and later, you should omit the {–inorder} argument.

Which is XML macro language does xacro use?

Xacro is an XML macro language. With xacro, you can construct shorter and more readable XML files by using macros that expand to larger XML expressions. actuator_array_examp…

How to see the model generated by xacro?

To see the model generated by a xacro file, run the same command as with previous tutorials: roslaunch urdf_tutorial display.launch model:=urdf/08-macroed.urdf.xacro (The launch file has been running the xacro command this whole time, but since there were no macros to expand, it didn’t matter)

How can I use xacro as a constant?

Fortunately, xacro allows you to specify properties which act as constants. Instead, of the above code, we can write this. The two values are specified in the first two lines. They can be defined just about anywhere (assuming valid XML), at any level, before or after they are used.