Author of this series of tutorials: Xiaoyu
Public account: Yuxiang ROS
QQ exchange group: 139707339
Teaching video address: Xiaoyu's B station
Full document address: Yuxiang ROS official website
Copyright statement: Reprinting and commercial use are prohibited unless permitted.

8.2 RVIZ2 Visualized Mobile Robot Model

Hello everyone, I'm Xiaoyu. After the joint and link in the previous section, let's display the simple URDF (including body and radar) we defined above with RVIZ2, and intuitively feel our robot model.

The steps of URDF visualization are as follows:

Create a robot description function package
Create urdfa folder to write a urdf file
Create launcha folder and write a launch file
Modify the setup.pyconfiguration, compile and test

1. Create a function package

Familiar with the road, first create a fishbot_wsworkspace, then create a function package, choose the type of packageament_python

ros2 pkg create fishbot_description --build-type ament_python

2. Create a URDF file

Create a folder, create a urdf file

cd fishbot_description && mkdir urdf 
touch fishbot_base.urdf

editfishbot_base.urdf

<?xml version="1.0"?>
<robot name="fishbot">
    
  <!-- base link -->
  <link name="base_link">
  	<visual>
      <origin xyz="0 0 0.0" rpy="0 0 0"/>
      <geometry>
		<cylinder length="0.12" radius="0.10"/>
      </geometry>
    </visual>
  </link>
    
  <!-- laser link -->
  <link name="laser_link">
  	<visual>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <geometry>
		<cylinder length="0.02" radius="0.02"/>
      </geometry>
      <material name="black">
      	<color rgba="0.0 0.0 0.0 0.8" /> 
      </material>
    </visual>
  </link>
    
  <!-- laser joint -->
    <joint name="laser_joint" type="fixed">
        <parent link="base_link" />
        <child link="laser_link" />
        <origin xyz="0 0 0.075" />
    </joint>

</robot>

3. Create a launch file

mkdir launch
touch display_rviz2.launch.py

import os
from launch import LaunchDescription
from launch.substitutions import LaunchConfiguration
from launch_ros.actions import Node
from launch_ros.substitutions import FindPackageShare


def generate_launch_description():
    package_name = 'fishbot_description'
    urdf_name = "fishbot_base.urdf"

    ld = LaunchDescription()
    pkg_share = FindPackageShare(package=package_name).find(package_name) 
    urdf_model_path = os.path.join(pkg_share, f'urdf/{
      
      urdf_name}')

    robot_state_publisher_node = Node(
        package='robot_state_publisher',
        executable='robot_state_publisher',
        arguments=[urdf_model_path]
        )

    joint_state_publisher_node = Node(
        package='joint_state_publisher_gui',
        executable='joint_state_publisher_gui',
        name='joint_state_publisher_gui',
        arguments=[urdf_model_path]
        )

    rviz2_node = Node(
        package='rviz2',
        executable='rviz2',
        name='rviz2',
        output='screen',
        )

    ld.add_action(robot_state_publisher_node)
    ld.add_action(joint_state_publisher_node)
    ld.add_action(rviz2_node)

    return ld

To visualize the model requires three nodes to participate

joint_state_publisher_guiResponsible for publishing robot joint data information through joint_statestopics
robot_state_publisher_nodeResponsible for publishing robot model information robot_descriptionand joint_statespublishing data conversion tf information
rviz2_nodeResponsible for displaying information about the robot

graph
A[joint_state_publisher]--joint_states-->B
B[robot_state_publisher]--robot_de-->C
C[rviz2]

Here we use joint_state_publisher_guiand robot_state_publishertwo packages, if your system does not have these two packages installed, you can install them manually:

sudo apt install ros-$ROS_DISTRO-joint-state-publisher-gui ros-$ROS_DISTRO-robot-state-publisher

joint_state_publisher_gui, and there is a brother called joint_state_publisherthe difference between the two . When joint_state_publisher_guirunning, an interface will pop up. Through the interface, you can operate the active joints in the URDF.

4. Modify setup.py

import header

from glob import glob
import os

add directory installation

('share/ament_index/resource_index/packages',
['resource/' + package_name]),
('share/' + package_name, ['package.xml']),

whole

from setuptools import setup
from glob import glob
import os

package_name = 'fishbot_description'

setup(
    name=package_name,
    version='0.0.0',
    packages=[package_name],
    data_files=[
        ('share/ament_index/resource_index/packages',
            ['resource/' + package_name]),
        ('share/' + package_name, ['package.xml']),
        (os.path.join('share', package_name, 'launch'), glob('launch/*.launch.py')),
        (os.path.join('share', package_name, 'urdf'), glob('urdf/**')),
    ],
    install_requires=['setuptools'],
    zip_safe=True,
    maintainer='root',
    maintainer_email='[email protected]',
    description='TODO: Package description',
    license='TODO: License declaration',
    tests_require=['pytest'],
    entry_points={
    
    
        'console_scripts': [
        ],
    },
)

5. Compile and test

compile

colcon build

run the test

source install/setup.bash
ros2 launch fishbot_description display_rviz2.launch.py

Add the robotmodel module, select the link name as follows, and you can see the model display of the robot

Now look at the node relationship diagram

Here you can refer to the relationship between the three nodes started in the Graph-Management launch file.

Then open the TF module and look at the coordinate system relationship of the robot

6. Exercise in this section

Exercise 1: Try changing the color of the modified robot body to blue and the opacity to 50%(0.1 0.1 1.0 0.5)

Exercise 2: Try to add imu_link in URDF and use imu_joint to fix it 2cm above the center of the car body. The geometry used by imu is box. Length, width and height are each 2cm

Results show:

Technical exchange && problem assistance:

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about the author:

I am Xiaoyu, a senior player in the field of robotics. I am currently a unipod robot algorithm engineer in Shenzhen,
learning programming in junior high school. I began to get in touch with robots in high school. During college, I played robot-related competitions and achieved a monthly income of 2W+ (competition bonus).
Currently, I am outputting robot learning guides , paper notes, work experience, welcome everyone to pay attention to Xiaoyu, exchange technology together, and learn robots

"Hands-on ROS2 Advanced" 8.2RVIZ2 Visualized Mobile Robot Model