The author of this series of tutorials ： Little fish
official account ： Fish fragrance ROS
QQ Communication group ：139707339
Teaching video address ： Small fish B standing
Full document address ： Fish fragrance ROS Official website
Copyright notice ： Reprint and commercial use are prohibited unless permitted .

8.2 RVIZ2 Visual mobile robot model

Hello everyone , I'm little fish , After the last section joint and link, Let's put the simple we defined above URDF( Including body and radar ) use RVIZ2 Show it , Under the intuitive feeling , Our robot model .

URDF The steps of visualization are as follows ：

1. Build robot description function package
2. establish urdf Folder authoring urdf file
3. establish launch Folder , To write launch file
4. modify setup.py To configure , Compile testing

1. Create a feature pack

Get familiar , So let's create one fishbot_ws working space , Then build the function package , Select the type of package ament_python

ros2 pkg create fishbot_description --build-type ament_python

2. establish URDF file

establish URDF Folder , establish urdf file

cd fishbot_description && mkdir urdf 
touch fishbot_base.urdf

The completed directory structure ：

├── fishbot_description
│   ├── __init__.py
├── package.xml
├── setup.cfg
├── setup.py
└── urdf
    └── fishbot_base.urdf

edit fishbot_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. establish launch file

In the catalog src/fishbot_description Create launch Folder and create a new display_rviz2.launch.py file .

mkdir launch
touch display_rviz2.launch.py

The completed directory structure ：

├── fishbot_description
│   ├── __init__.py
├── launch
│   └── display_rviz2.launch.py
├── package.xml
├── setup.cfg
├── setup.py
└── urdf
    └── fishbot_base.urdf

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, you need three nodes to participate

• joint_state_publisher_gui Responsible for publishing robot joint data information , adopt joint_states Topic Publishing
• robot_state_publisher_node Responsible for publishing robot model information robot_description, And will joint_states Data conversion tf Information Delivery
• rviz2_node Responsible for displaying the information of the robot

Here we use joint_state_publisher_gui and robot_state_publisher Two bags , If your system does not have these two packages installed , It can be installed by hand :

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

joint_state_publisher_gui, There is also a brother called joint_state_publisher The difference between the two lies in joint_state_publisher_gui When running, an interface will pop up , It can be operated through the interface URDF Active joints in

4. modify setup.py

Import head

from glob import glob
import os

Add directory installation

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

complete

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 testing

compile

colcon build

Run the test

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

add to robotmodel modular , Choose... Separately link The name is as follows , You can see the model display of the robot

Now look at the node diagram

Here you can refer to graph theory launch The relationship between the three nodes started in the file .

Then open the TF modular , Look at the coordinate system of the robot

6. This section exercises

practice 1： Try changing the robot's body color to blue , Transparency is 50%(0.1 0.1 1.0 0.5)

practice 2： Try to URDF Add imu_link And use imu_joint Fix it above the center of the car body 2cm,imu The geometry used is box. Length, width and height are 2cm

Result display ：

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Technical communication && Ask for help ：

• WeChat official account and exchange group ： Fish fragrance ROS

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The authors introduce ：

I'm little fish , Senior players in Robotics , Now a one legged robot Algorithm Engineer in Shenzhen
Junior high school learning programming , High school began to contact robots , During the University, playing robot related competitions to achieve monthly income 2W+（ The prize money for the competition ）
Currently outputting Robot Learning Guide 、 Notes to the paper 、 Work experience , Welcome to pay attention to little fish , Exchange technology together , Learning robots