Gazebo使用筆記（10） —— gazebo插件與傳感器的添加

0. 插件類型

當前有6種插件類型：

• World
• Model
• Sensor
• System
• Visual
• GUI

可通過URDF文件引用的類型：

• ModelPlugins, 提供對 physics::Model API的訪問，傳送門
• SensorPlugins, 提供對 sensors::Sensor API的訪問，傳送門
• VisualPlugins, 提供對 rendering::Visual API的訪問，傳送門

添加ModelPlugin

用於指示傳遞給gazebo的信息

<robot>
  ... robot description ...
  <gazebo>
    <plugin name="differential_drive_controller" filename="libdiffdrive_plugin.so">
      ... plugin parameters ...
    </plugin>
  </gazebo>
  ... robot description ...
</robot>

添加SensorPlugin

連接到link

<robot>
  ... robot description ...
  <link name="sensor_link">
    ... link description ...
  </link>

  <gazebo reference="sensor_link">
    <sensor type="camera" name="camera1">
      ... sensor parameters ...
      <plugin name="camera_controller" filename="libgazebo_ros_camera.so">
        ... plugin parameters ..
      </plugin>
    </sensor>
  </gazebo>

</robot>

1. 相機

普通相機

<!--joint定義-->
  <joint name="camera_joint" type="fixed">
    <axis xyz="0 1 0" />
    <origin xyz="${camera_link} 0 ${height3 - axel_offset*2}" rpy="0 0 0"/>
    <parent link="link3"/>
    <child link="camera_link"/>
  </joint>

<!--link定義-->
  <!-- Camera -->
  <link name="camera_link">
    <collision>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <geometry>
    <box size="${camera_link} ${camera_link} ${camera_link}"/>
      </geometry>
    </collision>

    <visual>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <geometry>
    <box size="${camera_link} ${camera_link} ${camera_link}"/>
      </geometry>
      <material name="red"/>
    </visual>

    <inertial>
      <mass value="1e-5" />
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
    </inertial>
  </link>

<!--傳感器配置-->
  <!-- camera -->
  <gazebo reference="camera_link">
    <sensor type="camera" name="camera1">
      <!--每秒獲取的圖像次數，但如果物理仿真運行速度快於傳感器生成速度，那麼它可能會滯後於這一目標速度-->
      <update_rate>30.0</update_rate>
      <camera name="head">
        <!--匹配物理相機硬件上製造商提供的規格數據-->
        <horizontal_fov>1.3962634</horizontal_fov>
        <image>
          <width>800</width>
          <height>800</height>
          <format>R8G8B8</format>
        </image>
        <clip>
          <near>0.02</near>
          <far>300</far>
        </clip>
        <noise>
          <type>gaussian</type>
          <!-- Noise is sampled independently per pixel on each frame.
               That pixel's noise value is added to each of its color
               channels, which at that point lie in the range [0,1]. -->
          <mean>0.0</mean>
          <stddev>0.007</stddev>
        </noise>
      </camera>
      <!--gazebo_ros/gazebo_ros_camera.cpp-->
      <plugin name="camera_controller" filename="libgazebo_ros_camera.so">
        <alwaysOn>true</alwaysOn>
        <updateRate>0.0</updateRate>
        <!--類似名稱空間-->
        <cameraName>rrbot/camera1</cameraName>
        <!--圖像topic-->
        <imageTopicName>image_raw</imageTopicName>
		<!--相機信息topic-->        
        <cameraInfoTopicName>camera_info</cameraInfoTopicName>
        <!--
        在本例中，實際使用時，應訂閱以下主題：
        /rrbot/camera1/image_raw
		/rrbot/camera1/camera_info
			-->
			
		<!--圖像在tf樹中發佈的座標系-->   
        <frameName>camera_link</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>

注意：①傳感器的名稱必須是唯一的；②gazebo reference的名稱必須與相應的link名稱相同

多機位相機

同步多個相機的快門，以便它們將圖像一起發佈。通常用於立體攝像機，使用與純Camera插件非常相似的界面。

---

注意：目前僅支持stereo cameras

以Atlas的雙目相機爲例：

  <gazebo reference="left_camera_frame">
    <sensor type="multicamera" name="stereo_camera">
      <update_rate>30.0</update_rate>
      <camera name="left">
        <horizontal_fov>1.3962634</horizontal_fov>
        <image>
          <width>800</width>
          <height>800</height>
          <format>R8G8B8</format>
        </image>
        <clip>
          <near>0.02</near>
          <far>300</far>
        </clip>
        <noise>
          <type>gaussian</type>
          <mean>0.0</mean>
          <stddev>0.007</stddev>
        </noise>
      </camera>
      <camera name="right">
        <pose>0 -0.07 0 0 0 0</pose>
        <horizontal_fov>1.3962634</horizontal_fov>
        <image>
          <width>800</width>
          <height>800</height>
          <format>R8G8B8</format>
        </image>
        <clip>
          <near>0.02</near>
          <far>300</far>
        </clip>
        <noise>
          <type>gaussian</type>
          <mean>0.0</mean>
          <stddev>0.007</stddev>
        </noise>
      </camera>
      <plugin name="stereo_camera_controller" filename="libgazebo_ros_multicamera.so">
        <alwaysOn>true</alwaysOn>
        <updateRate>0.0</updateRate>
        <cameraName>multisense_sl/camera</cameraName>
        <imageTopicName>image_raw</imageTopicName>
        <cameraInfoTopicName>camera_info</cameraInfoTopicName>
        <frameName>left_camera_optical_frame</frameName>
        <!--<rightFrameName>right_camera_optical_frame</rightFrameName>-->
        <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>

深度相機

以Kinect爲例：

<gazebo reference="${link_name}">
  <sensor name="${link_name}_camera" type="depth">
    <update_rate>20</update_rate>
    <camera>
      <horizontal_fov>1.047198</horizontal_fov>
      <image>
        <width>640</width>
        <height>480</height>
        <format>R8G8B8</format>
      </image>
      <clip>
        <near>0.05</near>
        <far>3</far>
      </clip>
    </camera>
    <plugin name="${link_name}_controller" filename="libgazebo_ros_openni_kinect.so">
      <baseline>0.2</baseline>
      <alwaysOn>true</alwaysOn>
      <updateRate>1.0</updateRate>
      <cameraName>${camera_name}_ir</cameraName>
      <imageTopicName>/${camera_name}/color/image_raw</imageTopicName>
      <cameraInfoTopicName>/${camera_name}/color/camera_info</cameraInfoTopicName>
      <depthImageTopicName>/${camera_name}/depth/image_raw</depthImageTopicName>
      <depthImageInfoTopicName>/${camera_name}/depth/camera_info</depthImageInfoTopicName>
      <pointCloudTopicName>/${camera_name}/depth/points</pointCloudTopicName>
      <frameName>${frame_name}</frameName>
      <pointCloudCutoff>0.5</pointCloudCutoff>
      <pointCloudCutoffMax>3.0</pointCloudCutoffMax>
      <distortionK1>0.00000001</distortionK1>
      <distortionK2>0.00000001</distortionK2>
      <distortionK3>0.00000001</distortionK3>
      <distortionT1>0.00000001</distortionT1>
      <distortionT2>0.00000001</distortionT2>
      <CxPrime>0</CxPrime>
      <Cx>0</Cx>
      <Cy>0</Cy>
      <focalLength>0</focalLength>
      <hackBaseline>0</hackBaseline>
    </plugin>
  </sensor>
</gazebo>

關於配置深度相機的更詳細說明參見：傳送門

2. 激光

GPU Laser

如sensor_msgs中所述，通過廣播LaserScan消息來模擬激光測距傳感器，參考https://wiki.ros.org/hokuyo_node

 <joint name="hokuyo_joint" type="fixed">
    <axis xyz="0 1 0" />
    <origin xyz="0 0 ${height3 - axel_offset/2}" rpy="0 0 0"/>
    <parent link="link3"/>
    <child link="hokuyo_link"/>
  </joint>

  <!-- Hokuyo Laser -->
  <link name="hokuyo_link">
    <collision>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <geometry>
    <box size="0.1 0.1 0.1"/>
      </geometry>
    </collision>

    <visual>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <geometry>
        <mesh filename="package://rrbot_description/meshes/hokuyo.dae"/>
      </geometry>
    </visual>

    <inertial>
      <mass value="1e-5" />
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
    </inertial>
  </link>



<!------------------------------------>
 <!-- hokuyo -->
  <gazebo reference="hokuyo_link">
    <sensor type="gpu_ray" name="head_hokuyo_sensor">
      <pose>0 0 0 0 0 0</pose>
      <visualize>false</visualize>
      <update_rate>40</update_rate>
      <ray>
        <scan>
          <horizontal>
            <samples>720</samples>
            <resolution>1</resolution>
            <min_angle>-1.570796</min_angle>
            <max_angle>1.570796</max_angle>
          </horizontal>
        </scan>
        <range>
          <min>0.10</min>
          <max>30.0</max>
          <resolution>0.01</resolution>
        </range>
        <noise>
          <type>gaussian</type>
          <!-- Noise parameters based on published spec for Hokuyo laser
               achieving "+-30mm" accuracy at range < 10m.  A mean of 0.0m and
               stddev of 0.01m will put 99.7% of samples within 0.03m of the true
               reading. -->
          <mean>0.0</mean>
          <stddev>0.01</stddev>
        </noise>
      </ray>
      <plugin name="gazebo_ros_head_hokuyo_controller" filename="libgazebo_ros_gpu_laser.so">
        <topicName>/rrbot/laser/scan</topicName>
        <frameName>hokuyo_link</frameName>
      </plugin>
    </sensor>
  </gazebo>

Laser

 <joint name="hokuyo_joint" type="fixed">
    <axis xyz="0 1 0" />
    <origin xyz="0 0 ${height3 - axel_offset/2}" rpy="0 0 0"/>
    <parent link="link3"/>
    <child link="hokuyo_link"/>
  </joint>

  <!-- Hokuyo Laser -->
  <link name="hokuyo_link">
    <collision>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <geometry>
    <box size="0.1 0.1 0.1"/>
      </geometry>
    </collision>

    <visual>
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <geometry>
        <mesh filename="package://rrbot_description/meshes/hokuyo.dae"/>
      </geometry>
    </visual>

    <inertial>
      <mass value="1e-5" />
      <origin xyz="0 0 0" rpy="0 0 0"/>
      <inertia ixx="1e-6" ixy="0" ixz="0" iyy="1e-6" iyz="0" izz="1e-6" />
    </inertial>
  </link>



<!------------------------------------>
 <!-- hokuyo -->
  <gazebo reference="hokuyo_link">
    <sensor type="ray" name="head_hokuyo_sensor">
      <pose>0 0 0 0 0 0</pose>
      <visualize>false</visualize>
      <update_rate>40</update_rate>
      <ray>
        <scan>
          <horizontal>
            <samples>720</samples>
            <resolution>1</resolution>
            <min_angle>-1.570796</min_angle>
            <max_angle>1.570796</max_angle>
          </horizontal>
        </scan>
        <range>
          <min>0.10</min>
          <max>30.0</max>
          <resolution>0.01</resolution>
        </range>
        <noise>
          <type>gaussian</type>
          <!-- Noise parameters based on published spec for Hokuyo laser
               achieving "+-30mm" accuracy at range < 10m.  A mean of 0.0m and
               stddev of 0.01m will put 99.7% of samples within 0.03m of the true
               reading. -->
          <mean>0.0</mean>
          <stddev>0.01</stddev>
        </noise>
      </ray>
      <plugin name="gazebo_ros_head_hokuyo_controller" filename="libgazebo_ros_laser.so">
        <topicName>/rrbot/laser/scan</topicName>
        <frameName>hokuyo_link</frameName>
      </plugin>
    </sensor>
  </gazebo>

與GPU Laser的區別在於sensor的type和plugin不同！

Block Laser

提供柵格式激光測距儀仿真（例如Velodyne）

3. IMU

IMU (GazeboRosImu)

模擬IMU傳感器，測量是由ROS插件而不是Gazebo計算的

<robot>
:
  <gazebo>
    <plugin name="imu_plugin" filename="libgazebo_ros_imu.so">
      <alwaysOn>true</alwaysOn>
      <bodyName>base_footprint</bodyName>
      <topicName>imu</topicName>
      <serviceName>imu_service</serviceName>
      <gaussianNoise>0.0</gaussianNoise>
      <updateRate>20.0</updateRate>
    </plugin>
  </gazebo>
</robot>

IMU sensor (GazeboRosImuSensor)

模擬一個慣性運動單元傳感器，與IMU（GazeboRosIMU）的主要區別是：

• 從SensorPlugin繼承而不是ModelPlugin
• 測量是由gazebo ImuSensor給出的，而不是由ros插件計算的
• 重力包括在慣性測量中

  <gazebo reference="imu_link">
    <gravity>true</gravity>
    <sensor name="imu_sensor" type="imu">
      <always_on>true</always_on>
      <update_rate>100</update_rate>
      <visualize>true</visualize>
      <topic>__default_topic__</topic>
      <plugin filename="libgazebo_ros_imu_sensor.so" name="imu_plugin">
      	<!--發佈的話題名稱-->
        <topicName>imu</topicName>
        <bodyName>imu_link</bodyName>
      	<!--更新頻率-->
        <updateRateHZ>100.0</updateRateHZ>
      	<!--高斯噪聲-->
        <gaussianNoise>0.0</gaussianNoise>
        <xyzOffset>0 0 0</xyzOffset>
        <rpyOffset>0 0 0</rpyOffset>
        <frameName>imu_link</frameName>
        <initialOrientationAsReference>false</initialOrientationAsReference>
      </plugin>
      <pose>0 0 0 0 0 0</pose>
    </sensor>
  </gazebo>

查看插件libgazebo_ros_imu_sensor.so的位置：

locate libgazebo_ros_imu_sensor.so

訂閱IMU數據：

#!/usr/bin/env python
# 參考自https://zhuanlan.zhihu.com/p/62607472
import rospy
import math
from sensor_msgs.msg import Imu

def imu_data(imu_data):

    # Read the angular velocity of the robot IMU
    w_x = imu_data.angular_velocity.x
    w_y = imu_data.angular_velocity.y
    w_z = imu_data.angular_velocity.z

    # Read the linear acceleration of the robot IMU
    a_x = imu_data.linear_acceleration.x
    a_y = imu_data.linear_acceleration.y
    a_z = imu_data.linear_acceleration.z
    
    # Read the quaternion of the robot IMU
    x = imu_data.orientation.x
    y = imu_data.orientation.y
    z = imu_data.orientation.z
    w = imu_data.orientation.w

    # Convert Quaternions to Euler-Angles
    rpy_angle = [0, 0, 0]
    rpy_angle[0] = math.atan2(2 * (w * x + y * z), 1 - 2 * (x**2 + y**2))
    rpy_angle[1] = math.asin(2 * (w * y - z * x))
    rpy_angle[2] = math.atan2(2 * (w * z + x * y), 1 - 2 * (y**2 + z**2))
    return

if __name__ == '__main__':
    rospy.init_node('imu_data', anonymous=True)
    rospy.Subscriber("/imu", Imu, imu_data)
    rospy.spin()

4. 其他

F3D (Force Feedback Ground Truth)

Description: broadcasts external forces on a body in simulation over WrenchStamped message as described in geometry_msgs.

Force

Description: ROS interface for applying Wrench (geometry_msgs) on a body in simulation.

參考這篇博文：傳送門

Joint Pose Trajectory

Description: listens to a jointtrajectoryaction and plays back the set of joint positions. Sets the set of joints to exact positions without regards to simulated physics and forces.

P3D (3D Position Interface for Ground Truth)

Description: broadcasts the inertial pose of any body in simulation via Odometry message as described in nav_msgs via ROS topic.

保險槓

通過ContactsState message提供反饋

<gazebo>
  <plugin name="${name}_gazebo_ros_bumper_controller" filename="libgazebo_ros_bumper.so">
    <alwaysOn>true</alwaysOn>
    <updateRate>${update_rate}</updateRate>
    <bumperTopicName>${name}_bumper</bumperTopicName>
    <frameName>world</frameName>
  </plugin>
</gazebo>

差速驅動

<gazebo>
  <plugin name="differential_drive_controller" filename="libgazebo_ros_diff_drive.so">

    <!-- Plugin update rate in Hz -->
    <updateRate>${update_rate}</updateRate>

    <!-- Name of left joint, defaults to `left_joint` -->
    <leftJoint>base_link_left_wheel_joint</leftJoint>

    <!-- Name of right joint, defaults to `right_joint` -->
    <rightJoint>base_link_right_wheel_joint</rightJoint>

    <!-- The distance from the center of one wheel to the other, in meters, defaults to 0.34 m -->
    <wheelSeparation>0.5380</wheelSeparation>

    <!-- Diameter of the wheels, in meters, defaults to 0.15 m -->
    <wheelDiameter>0.2410</wheelDiameter>

    <!-- Wheel acceleration, in rad/s^2, defaults to 0.0 rad/s^2 -->
    <wheelAcceleration>1.0</wheelAcceleration>

    <!-- Maximum torque which the wheels can produce, in Nm, defaults to 5 Nm -->
    <wheelTorque>20</wheelTorque>

    <!-- Topic to receive geometry_msgs/Twist message commands, defaults to `cmd_vel` -->
    <commandTopic>cmd_vel</commandTopic>

    <!-- Topic to publish nav_msgs/Odometry messages, defaults to `odom` -->
    <odometryTopic>odom</odometryTopic>

    <!-- Odometry frame, defaults to `odom` -->
    <odometryFrame>odom</odometryFrame>

    <!-- Robot frame to calculate odometry from, defaults to `base_footprint` -->
    <robotBaseFrame>base_footprint</robotBaseFrame>

    <!-- Odometry source, 0 for ENCODER, 1 for WORLD, defaults to WORLD -->
    <odometrySource>1</odometrySource>

    <!-- Set to true to publish transforms for the wheel links, defaults to false -->
    <publishWheelTF>true</publishWheelTF>

    <!-- Set to true to publish transforms for the odometry, defaults to true -->
    <publishOdom>true</publishOdom>

    <!-- Set to true to publish sensor_msgs/JointState on /joint_states for the wheel joints, defaults to false -->
    <publishWheelJointState>true</publishWheelJointState>

    <!-- Set to true to swap right and left wheels, defaults to true -->
    <legacyMode>false</legacyMode>
  </plugin>
</gazebo>

防滑轉向驅動

<gazebo>
  <plugin name="skid_steer_drive_controller" filename="libgazebo_ros_skid_steer_drive.so">
    <updateRate>100.0</updateRate>
    <robotNamespace>/</robotNamespace>
    <leftFrontJoint>front_left_wheel_joint</leftFrontJoint>
    <rightFrontJoint>front_right_wheel_joint</rightFrontJoint>
    <leftRearJoint>back_left_wheel_joint</leftRearJoint>
    <rightRearJoint>back_right_wheel_joint</rightRearJoint>
    <wheelSeparation>0.4</wheelSeparation>
    <wheelDiameter>0.215</wheelDiameter>
    <robotBaseFrame>base_link</robotBaseFrame>
    <torque>20</torque>
    <topicName>cmd_vel</topicName>
    <broadcastTF>false</broadcastTF>
  </plugin>
</gazebo>

視頻插件

<gazebo reference="display_screen_link">
  <visual>
    <plugin name="display_video_controller" filename="libgazebo_ros_video.so">
      <topicName>image</topicName>
      <height>120</height>
      <width>160</width>
    </plugin>
  </visual>
</gazebo>

平面移動插件

該插件允許使用geometry_msgs/Twist消息沿水平面移動任意對象（例如立方體，球體和圓柱體）;該插件通過在每個週期將線性速度（XY）和角速度（Z）操作對象。

<robot name="test_model">

  <!-- root link, on the ground just below the model origin -->
  <link name="base_footprint">
   <visual>
      <origin xyz="0 0 0" rpy="0 0 0" />
      <geometry>
        <box size="0.001 0.001 0.001" />
      </geometry>
    </visual>
  </link>

  <joint name="base_link_joint" type="fixed">
    <origin xyz="0.0 0 1.25" rpy="0 0 0" />
    <parent link="base_footprint"/>
    <child link="base_link" />
  </joint>

  <!-- the model -->
  <link name="base_link">
    <inertial>
      <mass value="50" />
      <origin xyz="0 0 -1.25" />
      <inertia ixx="50.0" ixy="0.0" ixz="0.0"
        iyy="50.0" iyz="0.0"
        izz="50.0" />
    </inertial>
    <visual>
      <geometry>
        <box size="0.5 0.5 1.0" /> <!-- does not need to match collision -->
      </geometry>
    </visual>
    <collision>
      <origin xyz="0 0 -1.0" />
      <geometry>
        <cylinder length="0.5" radius="0.25" />
      </geometry>
    </collision>
  </link>

  <gazebo>
    <plugin name="object_controller" filename="libgazebo_ros_planar_move.so">
      <commandTopic>cmd_vel</commandTopic>
      <odometryTopic>odom</odometryTopic>
      <odometryFrame>odom</odometryFrame>
      <odometryRate>20.0</odometryRate>
      <robotBaseFrame>base_footprint</robotBaseFrame>
    </plugin>
  </gazebo>

</robot>

Node：

• ① 在大型工程中，建議使用單獨的xacro來配置傳感器、控制插件等；

---

參考文獻：

• http://gazebosim.org/tutorials?tut=ros_gzplugins#IMUsensor(GazeboRosImuSensor)
• https://zhuanlan.zhihu.com/p/62607472
• http://gazebosim.org/tutorials?tut=plugins_hello_world&cat=write_plugin