Gazebo robot simulation learning notes

Keywords: Ubuntu

Gazebo robot simulation learning notes

1, Experimental preparation

Refer to the video tutorial: 70 minute quick start Gazebo robot simulation.
Experimental function Pack:

git clone https://gitee.com/bingda-robot/bingda_tutorials

Some third-party feature packs

2, world model building

1) Install the official model library of Gazebo

git clone https://gitee.com/bingda-robot/gazebo_models

After the clone is finished, find / home/.gazebo. There is a model in it. You need to put the downloaded file in it.

Possible problems in this step: sometimes Gazebo cannot pop up the file manager. At this time, minimize it and open it again. But I didn't find this problem when I installed Ubuntu 20.04 and noetic on the physical machine. I guess it may be related to the virtual machine.

2) Self built model

Click Edit - > building editor in the title bar. You can select maps on the left. Click file to save and exit

After exiting, you can see your model in the world. You can add some small objects and save the world

When using, put it into the world folder in the function package, and modify the launch file.

<launch>
  <include file="$(find gazebo_ros)/launch/empty_world.launch">
      <!--   My file name is myroom，So modify the following line -->
      <arg name="world_name" value="$(find bingda_tutorials)/world/myroom"/>
    
      <arg name="paused" value="false"/>
    <arg name="use_sim_time" value="true"/>
    <arg name="gui" value="true"/>
    <arg name="headless" value="false"/>
    <arg name="debug" value="false"/>
  </include>
</launch>

3, Robot model building

Introduction to URDF file

Introduction to ROS official website
Label of URDF , commonly used are robot, link and joint
Example

<?xml version="1.0"?>  


<robot name="mybot">  
  <!-- Start label -->
  
  <link name="base_footprint"/>
  <!-- ROS In fact, it is an "empty" coordinate without inertia, vision, etc
       ROS In, base_link It refers to the coordinates of the robot body, and base_footprint refer to base_link Projection of -->
  
  <joint name="base_joint" type="fixed">  
    <parent link="base_footprint"/>  
    <child link="base_link"/>  
    <origin rpy="0 0 0" xyz="0 0 0"/>  
  </joint>  
  
  <link name="base_link">  
    <!-- Inertial parameters -->
    <inertial>
     <origin xyz="0 0 0" rpy="0 0 0"/>
     <mass value="0.1"/>
     <inertia ixx="0.0001"  ixy="0"  ixz="0" iyy="0.0001" iyz="0" izz="0.001" />
    </inertial>

    <!-- Visual parameters -->
    <visual>  
      <geometry>  
        <box size="0.25 0.16 0.05"/>  
      </geometry>  
      <origin rpy="0 0 0" xyz="0 0 0"/>  
      <material name="blue">  
          <color rgba="0 0 0.8 1"/>  
      </material>  
    </visual>  

    <!-- Collision parameters -->
    <!-- The general setting is the same as the vision, so that the naked eye can see whether there is a collision -->
   <collision>
     <origin xyz="0 0 0" rpy="0 0 0"/>
     <geometry>
       <box size="0.25 0.16 0.05"/>
     </geometry>
   </collision>

  </link>  
 
  <link name="right_wheel_link">  
    <inertial>
     <origin xyz="0 0 0" rpy="0 0 0"/>
     <mass value="0.1"/>
     <inertia ixx="0.0001"  ixy="0"  ixz="0" iyy="0.0001" iyz="0" izz="0.0001" />
    </inertial>

    <visual>  
      <geometry>  
        <cylinder length="0.02" radius="0.025"/>  
      </geometry>  
      <material name="black">  
        <color rgba="0 0 0 1"/>  
      </material>  
    </visual>  

    <collision>
     <origin xyz="0 0 0" rpy="0 0 0"/>
     <geometry>
       <cylinder length="0.02" radius="0.025"/> 
     </geometry>
    </collision>
  </link>  
 
  <joint name="right_wheel_joint" type="continuous">  
    <axis xyz="0 0 -1"/>  
    <parent link="base_link"/>  
    <!-- Body↑And wheels↓connect -->
    <child link="right_wheel_link"/>  
    <origin rpy="1.5707 0 0" xyz=" 0.1 -0.09 -0.03"/>  
  </joint>  
 
  <link name="left_wheel_link">  
    <inertial>
     <origin xyz="0 0 0" rpy="0 0 0"/>
     <mass value="0.1"/>
     <inertia ixx="0.0001"  ixy="0"  ixz="0" iyy="0.0001" iyz="0" izz="0.0001" />
    </inertial>

    <visual>  
      <geometry>  
        <cylinder length="0.02" radius="0.025"/>  
      </geometry>  
      <material name="black">  
        <color rgba="0 0 0 1"/>  
      </material>  
    </visual>  

    <collision>
     <origin xyz="0 0 0" rpy="0 0 0"/>
     <geometry>
       <cylinder length="0.02" radius="0.025"/> 
     </geometry>
    </collision>   
  </link>  
 
  <joint name="left_wheel_joint" type="continuous">  
    <axis xyz="0 0 -1"/>  
    <parent link="base_link"/>  
    <child link="left_wheel_link"/>  
    <origin rpy="1.5707 0 0" xyz="0.1 0.09 -0.03"/>  
  </joint>  
 
  <link name="ball_wheel_link">  
    <inertial>
     <origin xyz="0 0 0" rpy="0 0 0"/>
     <mass value="0.1"/>
     <inertia ixx="0"  ixy="0"  ixz="0" iyy="0" iyz="0" izz="0" />
    </inertial>

    <visual>  
      <geometry>  
        <sphere radius="0.025"/>  
      </geometry>  
      <material name="black">  
        <color rgba="0 0 0 1"/>  
      </material>  
    </visual>  

    <collision>
     <origin xyz="0 0 0" rpy="0 0 0"/>
     <geometry>
       <sphere radius="0.025"/> 
     </geometry>
    </collision>   
  </link>  

  <joint name="ball_wheel_joint" type="fixed">  
    <axis xyz="0 0 1"/>  
    <parent link="base_link"/>  
    <child link="ball_wheel_link"/>  
    <origin rpy="0 0 0" xyz="-0.10 0 -0.03"/>  
  </joint>  

</robot>

You can run check_urdf to check
- First, cd to the directory where urdf is stored
```
check_urdf yoururdf.urdf
```
- You may be prompted that the command cannot be found here. Just install the tool
```
sudo apt install liburdfdom-tools
```
- After successful operation, the link condition should be displayed

It can also be used with the launch file, and the following instructions are used to observe in rviz
```
roslaunch bingda_tutorials display_robot.launch 
```

Similarly, the launch file is also required for startup in gazebo

<launch>

  <include file="$(find bingda_tutorials)/launch/gazebo_world.launch"/>
  <!--Start our world first-->
  
    <node name="spawn_model"  pkg="gazebo_ros"  type="spawn_model" args="-file $(find bingda_tutorials)/urdf/mybot.urdf -urdf -model robot_description" output="screen" />

</launch>

4, Sensor and actuator installation

xacro file introduction

xacro file is a supplement and perfection of urdf file

The main differences between the xacro file of the example and the urdf file are as follows

Install some sensors

  
  <!-- imu sensor -->
  <link name="imu">  
    <visual>  
      <geometry>  
        <box size="0.01 0.01 0.01"/>  
      </geometry>  
      <material name="white">  
          <color rgba="1 1 1 1"/>  
      </material>  
    </visual>  
  </link>  

  <joint name="imu_joint" type="fixed">  
    <parent link="base_link"/>  
    <child link="imu"/>  
    <origin xyz="0.08 0 0.025"/>  
  </joint> 

  <!-- camera -->
  <link name="base_camera_link">  
    <visual>  
      <geometry>  
        <box size="0.02 0.03 0.03"/>  
      </geometry>  
      <material name="white">  
          <color rgba="1 1 1 1"/>  
      </material>  
    </visual>  
  </link>  

  <joint name="camera_joint" type="fixed">  
    <parent link="base_link"/>  
    <child link="base_camera_link"/>  
    <origin xyz="0.1 0 0.025"/>  
  </joint> 
  <!-- laser lidar -->
  <link name="base_laser_link">  
    <visual>  
      <geometry>  
        <cylinder length="0.06" radius="0.04"/>   
      </geometry>  
      <material name="white">  
          <color rgba="1 1 1 1"/>  
      </material>  
    </visual>  
  </link>  
  
  <joint name="laser_joint" type="fixed">  
    <parent link="base_link"/>  
    <child link="base_laser_link"/>  
    <origin xyz="0 0.0 0.06"/>  
  </joint>

Reference xacro files, such as C's h file

  <robot name="mybot" xmlns:xacro="http://ros.org/wiki/xacro">  
  
    <xacro:include filename="$(find bingda_tutorials)/urdf/mybot.gazebo.xacro" />

It is better to separate the model xacro file from the simulation related file, which can improve the reusability of our code

xacro file about gazebo simulation

Tutorial: Using a URDF in Gazebo This link explains the usage and meaning of tags in detail

Tutorial: Using Gazebo plugins with ROS The sensor and radar shall be inserted in the way of plugin

<?xml version="1.0"?>
<robot name="mybot" xmlns:xacro="http://ros.org/wiki/xacro">
  <xacro:arg name="laser_visual" default="false"/>
  <xacro:arg name="camera_visual" default="false"/>
  <xacro:arg name="imu_visual"   default="false"/>

  <gazebo reference="base_link">
    <material>Gazebo/DarkGrey</material>
  </gazebo>

  <gazebo reference="left_wheel_link">
    <mu1>0.5</mu1>
    <mu2>0.5</mu2>
    <kp>500000.0</kp>
    <kd>10.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>1.0</maxVel>
    <fdir1>1 0 0</fdir1>
    <material>Gazebo/DarkGrey</material>
  </gazebo>

  <gazebo reference="right_wheel_link">
    <mu1>0.5</mu1>
    <mu2>0.5</mu2>
    <kp>500000.0</kp>
    <kd>10.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>1.0</maxVel>
    <fdir1>1 0 0</fdir1>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

  <gazebo reference="ball_wheel_link">
    <mu1>0.1</mu1>
    <mu2>0.1</mu2>
    <kp>500000.0</kp>
    <kd>100.0</kd>
    <minDepth>0.001</minDepth>
    <maxVel>1.0</maxVel>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

  <gazebo reference="imu">
    <sensor type="imu" name="imu">
      <always_on>true</always_on>
      <visualize>$(arg imu_visual)</visualize>
    </sensor>
    <material>Gazebo/FlatBlack</material>
  </gazebo>

    <!-- Speed controller -->
  <gazebo>
    <plugin name="mybot_controller" filename="libgazebo_ros_diff_drive.so">
      <commandTopic>cmd_vel</commandTopic>
      <odometryTopic>odom</odometryTopic>
      <odometryFrame>odom</odometryFrame>
      <odometrySource>world</odometrySource>
      <publishOdomTF>true</publishOdomTF>
      <robotBaseFrame>base_footprint</robotBaseFrame>
      <publishWheelTF>false</publishWheelTF>
      <publishTf>true</publishTf>
      <publishWheelJointState>true</publishWheelJointState>
      <legacyMode>false</legacyMode>
      <updateRate>30</updateRate>
      <leftJoint>left_wheel_joint</leftJoint>
      <rightJoint>right_wheel_joint</rightJoint>
      <wheelSeparation>0.180</wheelSeparation>
      <wheelDiameter>0.05</wheelDiameter>
      <wheelAcceleration>10</wheelAcceleration>
      <wheelTorque>100</wheelTorque>
      <rosDebugLevel>na</rosDebugLevel>
    </plugin>
  </gazebo>

  <gazebo>
    <plugin name="imu_plugin" filename="libgazebo_ros_imu.so">
      <alwaysOn>true</alwaysOn>
      <bodyName>imu</bodyName>  
      <frameName>imu</frameName>
      <topicName>imu</topicName>
      <serviceName>imu_service</serviceName>
      <gaussianNoise>0.0</gaussianNoise>
      <updateRate>0</updateRate>
      <imu>
        <noise>
          <type>gaussian</type>
          <rate>
            <mean>0.0</mean>
            <stddev>2e-4</stddev>
            <bias_mean>0.0000075</bias_mean>
            <bias_stddev>0.0000008</bias_stddev>
          </rate>
          <accel>
            <mean>0.0</mean>
            <stddev>1.7e-2</stddev>
            <bias_mean>0.1</bias_mean>
            <bias_stddev>0.001</bias_stddev>
          </accel>
        </noise>
      </imu>
    </plugin>
  </gazebo>

  <gazebo reference="base_laser_link">
    <material>Gazebo/FlatBlack</material>
    <sensor type="ray" name="rplidar_sensor">
      <pose>0 0 0 0 0 0</pose>
      <visualize>$(arg laser_visual)</visualize>
      <update_rate>7</update_rate>
      <ray>
        <scan>
          <horizontal>
            <samples>720</samples>
            <resolution>0.5</resolution>
            <min_angle>0.0</min_angle>
            <max_angle>6.28319</max_angle>
          </horizontal>
        </scan>
        <range>
          <min>0.120</min>
          <max>12.0</max>
          <resolution>0.015</resolution>
        </range>
        <noise>
          <type>gaussian</type>
          <mean>0.0</mean>
          <stddev>0.01</stddev>
        </noise>
      </ray>
      <plugin name="gazebo_ros_rplidar_controller" filename="libgazebo_ros_laser.so">
        <topicName>scan</topicName>
        <frameName>base_laser_link</frameName>
      </plugin>
    </sensor>
  </gazebo>

  
  <gazebo reference="base_camera_link">
    <sensor type="camera" name="csi Camera">
      <always_on>true</always_on>
      <visualize>$(arg camera_visual)</visualize>
      <camera>
          <horizontal_fov>1.085595</horizontal_fov>
          <image>
              <width>640</width>
              <height>480</height>
              <format>R8G8B8</format>
          </image>
          <clip>
              <near>0.03</near>
              <far>100</far>
          </clip>
      </camera>
      <plugin name="camera_controller" filename="libgazebo_ros_camera.so">
        <alwaysOn>true</alwaysOn>
        <updateRate>30.0</updateRate>
        <cameraName>/</cameraName>
        <frameName>base_camera_link</frameName>
        <imageTopicName>image_raw</imageTopicName>
        <cameraInfoTopicName>camera_info</cameraInfoTopicName>
        <hackBaseline>0.07</hackBaseline>
        <distortionK1>0.0</distortionK1>
        <distortionK2>0.0</distortionK2>
        <distortionK3>0.0</distortionK3>
        <distortionT1>0.0</distortionT1>
        <distortionT2>0.0</distortionT2>
      </plugin>
    </sensor>
  </gazebo>

</robot>

Startup file

<launch>
  <arg name="x_pos" default="0.0"/>
  <arg name="y_pos" default="0.0"/>
  <arg name="z_pos" default="0.0"/>
  <param name="/use_sim_time" value="true" />  
  
   <!-- Start the environment first-->
  <include file="$(find bingda_tutorials)/launch/gazebo_world.launch"/>
  
  
   <!--Start the robot description and generate the robot-->
  <param name="robot_description" command="$(find xacro)/xacro --inorder $(find bingda_tutorials)/urdf/mybot.xacro" />
  <node pkg="gazebo_ros" type="spawn_model" name="spawn_urdf" args="-urdf -model mybot.xacro -x $(arg x_pos) -y $(arg y_pos) -z $(arg z_pos) -param robot_description" />
   
   <!--Start a controller-->
  <node name="robot_state_publisher" pkg="robot_state_publisher" type="robot_state_publisher" />

</launch>

After starting the launch file, we can use the following instructions to view the topic
```
rostopic list
rostopic info
```
Finally, start the keyboard control node to control the movement of the trolley

Posted by Residue on Tue, 30 Nov 2021 15:50:29 -0800

Programmer Group

Gazebo robot simulation learning notes

Gazebo robot simulation learning notes

1, Experimental preparation

2, world model building

1) Install the official model library of Gazebo

2) Self built model

3, Robot model building

Introduction to URDF file

4, Sensor and actuator installation

xacro file introduction

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