Universal_Robots_ROS2_Description

This repository contains description files and meshes for Universal Robots manipulators.

Build status

ROS2 Distro	Branch	Released packages
Galactic	`galactic`	ur_description
Humble	`ros2`	ur_description
Rolling	`ros2`	ur_description

Note that for ROS2 Foxy the description is in the driver's repository. Please do not clone this repository into a Foxy workspace.

Structure of the repository

The most relevant files are:

urdf/ur_macro.xacro - macro file with UR-manipulator description. This file is usually included into external projects to visualize and configure UR manipulators properly. An example how to use this macro is in urdf/ur.urdf.xacro file.
urdf/ur.ros2_control.xacro - definition of manipulator's joints and interfaces for ros2_control framework.

Testing description of a manipulator

To visualize the robot install this repository to you workspace and execute the following:

ros2 launch ur_description view_ur.launch.py ur_type:=ur5e

To test other descriptions change the ur_type argument.

Package / Description structure

This package uses one description for all robots. The different robot variants are configured using four configuration files. These files can also be changed for further customizing a description.

Basically, the description can be modified using configuration values stored in four files:

config/urXX/default_kinematics.yaml - This contains the calibration values as they can be extracted from the robot. Changing these values with the one extracted from a real robot will result in a description matching the real robot exactly (w.r.t the tool0 frame). It is highly recommended to use matching kinematic values in real-world applications.
config/urXX/joint_limits.yaml - If you'd like to further restrict the robot's joint limits, these limits can be modified there.
config/urXX/physical_parameters.yaml - Everything regarding physics simulation parameters (e.g. inertia poses and values) can be tuned here
config/urXX/visual_parameters.yaml - Some users change certain visual aspects, e.g. replacing the cap on the wrist_3_link. This config file specifies which meshes (both, visual and collision) should be used.

The four configuration files have to be passed to ur_macro.urdf (more specific to the macro defined in that file) which is done inside the ur.urdf.macro. Contents of the files are parsed inside ur_common.xacro.

Arguments that have to be passed to the main ur.urdf.xacro file are:

kinematics_params - Filename to the default_kinematics.yaml (or equivalent specific kinematics) file
joint_limit_params - Filename to the joint_limits.yaml file
physical_params - Filename to the physical_parameters.yaml file
visual_params - Filename to the visual_params.yaml file

The launchfile launch/view_ur.launch.py abstracts these four parameters to one ur_type argument which will basically replace the urXX part of the paths as shown in the picture above.

Creating your own description including this description

In real-world applications you will most probably have a more complex description consisting of more objects than just the robot. It is recommended to create a separate ROS package containing this particular description. Inside this description you could also store your robot-specific kinematics parameters file.