ROS 2 Wheels Robot

  1. Create package. 
    2. 
catkin_create_pkg robot2wheels urdf sensor_msgs cv_bridge rospy std_msgs rviz controller_manager gazebo_ros joint_state_publisher robot_state_publisher
cd robot2wheels 
mkdir launch urdf
  2. Initialize the world.
    3. 
roscore
roslaunch gazebo_ros empty_world.launch
  3. Tune the model by spawn and reset, calculate the inertia as well, (red:x, green: y, blue: z)
    4. 
roslaunch robot2wheels spawn.launch
rosservice call /gazebo/delete_model "my_robot"
rosrun calculator inertia_calculator.py
  4. The following is the final robot model, (however this is an unbalanced model, it cannot move smoothly)
  5. Run simulation,
    6. 
roslaunch robot2wheels spawn.launch
roslaunch robot2wheels rviz.launch # please add robotmodel and camera
rostopic pub /cmd_vel geometry_msgs/Twist "linear: x: -1.0 y: 0.0 z: 0.0 angular: x: -1.0 y: 0.0 z: 0.0"
robot.urdf

<?xml version="1.0"?>
<robot name="my_robot" xmlns:xacro="http://ros.org/wiki/xacro">
  <xacro:property name="M_PI" value="3.1415926535897931" />

  <link name="link_body">
    <pose>0 0 0.03 0 0 0</pose>
    <inertial>
      <mass value="5"/>
      <origin xyz="0 0 0.03" rpy="0 0 0"/>
      <inertia ixx="0.016833333333" ixy="0" ixz="0"
 	       iyy="0.004333333334" iyz="0" izz="0.020833333333"/>
    </inertial>

    <collision name="collision_body">
      <geometry>
	<box size="0.10 0.20 0.02"/>
      </geometry>
    </collision>

    <visual>
      <origin xyz="0 0 0.03" rpy="0 0 0"/>
      <geometry>
	<box size="0.10 0.20 0.02"/>
      </geometry>
    </visual>

    <collision name="collision_caster">
      <origin xyz="0.025 0 0" rpy="0 0 0"/>
      <geometry>
	<sphere radius="0.01"/>
      </geometry>
      <surface>
	<friction>
	  <ode>
	    <mu>0</mu>
	    <mu2>0</mu2>
	    <slip1>1.0</slip1>
	    <slip2>1.0</slip2>
	  </ode>
	</friction>
      </surface>
    </collision>

    <visual name="visual_caster">
      <origin xyz="0.025 0 0.008" rpy="0 0 0"/>
      <geometry>
	<sphere radius="0.017"/>
      </geometry>
    </visual>


  </link>


  <link name="link_camera">
    
    <inertial>
      <mass value="0.05"/>
      <origin xyz="0 0 0.05" rpy="0 0 0"/>
      <inertia ixx="0.000003333333" ixy="0" ixz="0"
 	       iyy="0.0000033333333" iyz="0" izz="0.00000333333333"/>
    </inertial>

    <collision name="collision_camera">
      <geometry>
	<box size="0.02 0.02 0.02"/>
      </geometry>
    </collision>

    <visual>
      <origin xyz="0 0 0.05" rpy="0 0 0"/>
      <geometry>
	<box size="0.02 0.02 0.02"/>
      </geometry>
    </visual>
  </link>


  <link name="link_laser">
    
    <inertial>
      <mass value="0.05"/>
      <origin xyz="0 0 0.07" rpy="0 0 0"/>
      <inertia ixx="0.000002916666667" ixy="0" ixz="0"
 	       iyy="0.000002916666667" iyz="0" izz="0.0000025"/>
    </inertial>

    <collision name="collision_laser">
      <geometry>
	<cylinder length="0.02" radius="0.01"/>
      </geometry>
    </collision>

    <visual>
      <origin xyz="0 0 0.07" rpy="0 0 0"/>
      <geometry>
	<cylinder length="0.02" radius="0.01"/>
      </geometry>
    </visual>
  </link>


  <link name="link_imu">
    
    <inertial>
      <mass value="0.05"/>
      <origin xyz="0 0 0.05" rpy="0 0 0"/>
      <inertia ixx="0.000003333333" ixy="0" ixz="0"
 	       iyy="0.000003333333" iyz="0" izz="0.00000333333333"/>
    </inertial>

    <collision name="collision_imu">
      <geometry>
	<box size="0.02 0.02 0.02"/>
      </geometry>
    </collision>

    <visual>
      <origin xyz="0 0 0.05" rpy="0 0 0"/>
      <geometry>
	<box size="0.02 0.02 0.02"/>
      </geometry>
    </visual>
  </link>


  <link name="link_left">
    
    <inertial>
      <mass value="1"/>
      <origin xyz="-0.02 0.1 0.02" rpy="0 1.5707 1.5707"/>
      <inertia ixx="0.0002583333334" ixy="0" ixz="0"
 	       iyy="0.0002583333334" iyz="0" izz="0.00045"/>
    </inertial>

    <collision name="collision_left">
      <geometry>
	<cylinder length="0.02" radius="0.03"/>
      </geometry>
    </collision>

    <visual>
      <origin xyz="-0.02 0.1 0.02" rpy="0 1.5707 1.5707"/>
      <geometry>
	<cylinder length="0.02" radius="0.03"/>
      </geometry>
    </visual>
  </link>



  <link name="link_right">
    
    <inertial>
      <mass value="1"/>
      <origin xyz="-0.02 -0.1 0.02" rpy="0 1.5707 1.5707"/>
      <inertia ixx="0.0002583333334" ixy="0" ixz="0"
 	       iyy="0.0002583333334" iyz="0" izz="0.00045"/>
    </inertial>

    <collision name="collision_left">
      <geometry>
	<cylinder length="0.02" radius="0.03"/>
      </geometry>
    </collision>

    <visual>
      <origin xyz="-0.02 -0.1 0.02" rpy="0 1.5707 1.5707"/>
      <geometry>
	<cylinder length="0.02" radius="0.03"/>
      </geometry>
    </visual>
  </link>







  <joint type="fixed" name="body_camera_joint">
    <origin xyz="0.04 0 0.00" rpy="0 0 0"/>
    <child link="link_camera"/>
    <parent link="link_body"/>
    <axis xyz="0 0 0"/>
  </joint>


  <joint type="fixed" name="camera_laser_joint">
    <origin xyz="0.00 0 0.000" rpy="0 0 0"/>
    <child link="link_laser"/>
    <parent link="link_camera"/>
    <axis xyz="0 0 0"/>
  </joint>

  <joint type="fixed" name="body_imu_joint">
    <origin xyz="0 0 0.00" rpy="0 0 0"/>
    <child link="link_imu"/>
    <parent link="link_body"/>
    <axis xyz="0 0 0"/>
  </joint>




  <joint type="continuous" name="body_left_joint">
    <origin xyz="-0.02 0.01 0.00" rpy="0 0 0"/>
    <child link="link_left"/>
    <parent link="link_body"/>
    <axis xyz="0 1 0" rpy="0 0 0"/>
    <limit effort="10000" velocity="1000"/>
    <joint_properties damping="1.0" friction="1.0"/>
  </joint>


  <joint type="continuous" name="body_right_joint">
    <origin xyz="-0.02 -0.01 0.00" rpy="0 0 0"/>
    <child link="link_right"/>
    <parent link="link_body"/>
    <axis xyz="0 1 0" rpy="0 0 0"/>
    <limit effort="10000" velocity="1000"/>
    <joint_properties damping="1.0" friction="1.0"/>
  </joint>

  <gazebo>
    <plugin filename="libgazebo_ros_diff_drive.so" name="differential_drive_controller">
      <legacyMode>false</legacyMode>
      <alwaysOn>true</alwaysOn>
      <updateRate>20</updateRate>
      <leftJoint>body_left_joint</leftJoint>
      <rightJoint>body_right_joint</rightJoint>
      <wheelSeparation>0.2</wheelSeparation>
      <wheelDiameter>0.3</wheelDiameter>
      <torque>0.1</torque>
      <commandTopic>cmd_vel</commandTopic>
      <odometryTopic>odom</odometryTopic>
      <odometryFrame>odom</odometryFrame>
      <bodyBaseFrame>link_body</bodyBaseFrame>
    </plugin>
  </gazebo>


  <gazebo reference="link_camera">
      <sensor type="camera" name="camera_camera_sensor">
        <update_rate>30.0</update_rate>
        <camera>
          <pose>0.035 0 0.078 0 0 0</pose>
          <horizontal_fov>${85 * M_PI/180.0}</horizontal_fov>
          <image>
            <format>R8G8B8</format>
            <width>1020</width>
            <height>1020</height>
          </image>
          <clip>
            <near>0.01</near>
            <far>1000</far>
          </clip>
        </camera>

        <plugin name="camera_camera_controller" filename="libgazebo_ros_camera.so">
          <alwaysOn>true</alwaysOn>
          <updateRate>0.0</updateRate>
          <cameraName>arm_sensor/camera</cameraName>
          <imageTopicName>image_raw</imageTopicName>
          <cameraInfoTopicName>camera_info</cameraInfoTopicName>
          <frameName>link_camera</frameName>
          <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>

References

  1. Adding Physical and Collision Properties to a URDF Model
  2. urdf/XML/joint
  3. Make a Mobile Robot
  4. Exploring ROS using a 2 Wheeled Robot #1: Basics of Robot Modeling using URDF
  5. Tutorial: Using a URDF in Gazebo