教程 | 阿克曼结构移动机器人的gazebo仿真（五）

2023-05-16

第四章、用xacro优化URDF并配置gazebo仿真插件

1►前言

上节用简易模型写了一个小车的URDF代码，这一节将用xacro对其进行优化，这里我并不打算用宏对参数进行封装，因为我个人觉得这样看起来会比较直观，方便读者阅读。

2►配置主xacro文件

新建racecar.xacro文件，将上一节racebot.urdf中的代码复制过来并进行修改，整体代码如下：

<?xml version="1.0" encoding="utf-8"?>
<robot name="racebot" xmlns:xacro="http://www.ros.org/wiki/xacro">
    <xacro:include filename="$(find racebot_description)/urdf/ackermann/macros.xacro" />  
    <link name="base_footprint">
    </link>
    <link name="base_link">
        <visual>
            <geometry>
                <box size="0.28 0.1 0.03"/>
                <!-- <mesh filename="package://tianracer_description/meshes/base_link.STL" /> -->
            </geometry>
            <!-- <origin xyz="0 0 -0.023" rpy="0 0 0" /> -->
            <origin xyz="0 0 0" rpy="0 0 0" />
            <material name="yellow">
                <color rgba="0.8 0.3 0.1 0.5" />
            </material>
        </visual>
        <collision>
            <geometry>
                <box size="0.28 0.1 0.03" />
            </geometry>
            <origin xyz="0.0 0.0 0.0" rpy="0.0 0.0 0.0" />
        </collision>
    </link>
    <joint name="base_link2base_footprint" type="fixed">
        <parent link="base_footprint" />
        <child link="base_link"/>
        <origin xyz="0 0 0.032" rpy="0 0 0" />
    </joint>
    <link name="base_inertia">
    <inertial>
            <origin xyz="0 0 0" />
            <mass value="4" />
            <inertia ixx="0.0264" ixy="0" ixz="0" iyy="0.0294" iyz="0" izz="0.00364" />
        </inertial>
    </link>    
    <joint name="chassis_inertia_joint" type="fixed">
    <origin xyz="0 0 0" rpy="0 0 0" />
    <parent link="base_link" />
    <child link="base_inertia" />
  </joint>
    <link name="left_steering_hinge">
        <visual>
            <geometry>
                <cylinder radius="0.01" length="0.005" />
                <!-- <sphere radius="0.015" /> -->
            </geometry>
            <origin xyz="0 0 0" rpy="1.57 0 0" />
            <material name="black">
                <color rgba="0.0 0.0 0.0 1.0" />
            </material>
        </visual>
        <collision>
            <geometry>
                <cylinder radius="0.01" length="0.005" />
                <!-- <sphere radius="0.015" /> -->
            </geometry>
            <origin xyz="0.0 0.0 0.0" rpy="1.57 0.0 0.0" />
        </collision>
        <inertial>
            <origin xyz="0 0 0" />
            <mass value="0.5" />
            <inertia ixx="1.35E-05" ixy="0" ixz="0" iyy="1.35E-05" iyz="0" izz="2.5E-05" />
        </inertial>
    </link>
    <joint name="left_steering_hinge_joint" type="revolute">
        <parent link="base_link" />
        <child link="left_steering_hinge" />
        <origin xyz="0.13 0.065 0" />
        <axis xyz="0 0 1" />
        <limit lower="-0.6" upper="0.6" effort="5.0" velocity="1000.0"/>
    </joint>
    <xacro:steering_hinge_transmission name="left_steering_hinge" />
    <link name="left_front_wheel">
        <visual>
            <geometry>
                <cylinder radius="0.033" length="0.02" />
            </geometry>
            <origin xyz="0 0 0" rpy="1.57 0 0" />
            <material name="black">
                <color rgba="0.0 0.0 0.0 1.0" />
            </material>
        </visual>
        <collision>
            <geometry>
                <cylinder radius="0.032" length="0.02" />
            </geometry>
            <origin xyz="0.0 0.0 0.0" rpy="1.57 0.0 0.0" />
        </collision>
        <inertial>
            <origin xyz="0 0 0" />
            <mass value="2.0" />
            <inertia ixx="6.64E-04" ixy="0" ixz="0" iyy="6.64E-04" iyz="0" izz="1.02E-03" />
        </inertial>
    </link>

    <joint name="left_front_wheel_joint" type="continuous">
        <parent link="left_steering_hinge" />
        <child link="left_front_wheel" />
        <origin xyz="0 0.025 0" />
        <axis xyz="0 1 0" />
        <limit effort="10" velocity="1000" />
    </joint>
     <xacro:wheel_transmission name="left_front_wheel" />
<link name="right_steering_hinge">
        <visual>
            <geometry>
                 <cylinder radius="0.01" length="0.005" />
            </geometry>
            <origin xyz="0 0 0" rpy="1.57 0 0" />
            <material name="black">
                <color rgba="0.0 0.0 0.0 1.0" />
            </material>
        </visual>
        <collision>
            <geometry>
                <cylinder radius="0.01" length="0.005" />
            </geometry>
            <origin xyz="0.0 0.0 0.0" rpy="1.57 0.0 0.0" />
        </collision>
        <inertial>
            <origin xyz="0 0 0" />
            <mass value="0.5" />
            <inertia ixx="1.35E-05" ixy="0" ixz="0" iyy="1.35E-05" iyz="0" izz="2.5E-05" />
        </inertial>
    </link>
    <joint name="right_steering_hinge_joint" type="revolute">
        <parent link="base_link" />
        <child link="right_steering_hinge" />
        <origin xyz="0.13 -0.065 0" />
        <axis xyz="0 0 1" />
        <limit lower="-0.6" upper="0.6" effort="5.0" velocity="1000.0"/>
    </joint>
    <xacro:steering_hinge_transmission name="right_steering_hinge" />
     <link name="right_front_wheel">
        <visual>
            <geometry>
                <cylinder radius="0.033" length="0.02" />
            </geometry>
            <origin xyz="0 0 0" rpy="1.57 0 0" />
            <material name="black">
                <color rgba="0.0 0.0 0.0 1.0" />
            </material>
        </visual>
        <collision>
            <geometry>
                <cylinder radius="0.032" length="0.02" />
            </geometry>
            <origin xyz="0.0 0.0 0.0" rpy="1.57 0.0 0.0" />
        </collision>
        <inertial>
            <origin xyz="0 0 0" />
            <mass value="2.0" />
            <inertia ixx="6.64E-04" ixy="0" ixz="0" iyy="6.64E-04" iyz="0" izz="1.02E-03" />
        </inertial>
    </link>
    <joint name="right_front_wheel_joint" type="continuous">
        <parent link="right_steering_hinge" />
        <child link="right_front_wheel" />
        <origin xyz="0 -0.025 0" />
        <axis xyz="0 1 0" />
        <limit effort="10" velocity="1000" />
    </joint>
    <xacro:wheel_transmission name="right_front_wheel" />
    <link name="left_rear_wheel">
        <visual>
            <geometry>
                <cylinder radius="0.032" length="0.02" />
            </geometry>
            <origin xyz="0 0 0" rpy="1.57 0 0" />
            <material name="black">
                <color rgba="0.0 0.0 0.0 1.0" />
            </material>
        </visual>
        <collision>
            <geometry>
                <cylinder radius="0.032" length="0.02" />
            </geometry>
            <origin xyz="0.0 0.0 0.0" rpy="1.57 0.0 0.0" />
        </collision>
        <inertial>
            <origin xyz="0 0 0" />
            <mass value="2.0" />
            <inertia ixx="6.64E-04" ixy="0" ixz="0" iyy="6.64E-04" iyz="0" izz="1.02E-03" />
        </inertial>
    </link>
    <joint name="left_rear_wheel_joint" type="continuous">
        <parent link="base_link" />
        <child link="left_rear_wheel" />
        <origin xyz="-0.13 0.09 0" />
        <axis xyz="0 1 0" />
        <limit effort="10" velocity="1000" />
    </joint>
    <xacro:wheel_transmission name="left_rear_wheel" />
    <link name="right_rear_wheel">
        <visual>
            <geometry>
                <cylinder radius="0.032" length="0.02" />
            </geometry>
            <origin xyz="0 0 0" rpy="1.57 0 0" />
            <material name="black">
                <color rgba="0.0 0.0 0.0 1.0" />
            </material>
        </visual>
        <collision>
            <geometry>
                <cylinder radius="0.032" length="0.02" />
            </geometry>
            <origin xyz="0.0 0.0 0.0" rpy="1.57 0.0 0.0" />
        </collision>
        <inertial>
            <origin xyz="0 0 0" />
            <mass value="2.0" />
            <inertia ixx="6.64E-04" ixy="0" ixz="0" iyy="6.64E-04" iyz="0" izz="1.02E-03" />
        </inertial>
    </link>
    <joint name="right_rear_wheel_joint" type="continuous">
        <parent link="base_link" />
        <child link="right_rear_wheel" />
        <origin xyz="-0.13 -0.09 0" />
        <axis xyz="0 1 0" />
        <limit effort="10" velocity="1000" />
    </joint>
    <xacro:wheel_transmission name="right_rear_wheel" />
    <link name="camera">
        <visual>
            <geometry>
                <box size="0.005 0.03 0.03"/>
            </geometry>
            <origin xyz="0 0 0" rpy="0 0 0" />
            <material name="black">
                <color rgba="0.0 0.0 0.0 1.0" />
            </material>
        </visual>
        <collision>
            <geometry>
                <box size="0.005 0.03 0.03"/>
            </geometry>
            <origin xyz="0.0 0.0 0.0" rpy="0.0 0.0 0.0" />
        </collision>
        <inertial>
            <origin xyz="0 0 0" />
            <mass value="0.05" />
            <inertia ixx="6.64E-04" ixy="0" ixz="0" iyy="6.64E-04" iyz="0" izz="1.02E-03" />
        </inertial>
    </link>
    <joint name="camera_joint" type="fixed">
        <parent link="base_link" />
        <child link="camera" />
        <origin xyz="0.14851 0.0022137 0.0975" />
        <axis xyz="0 0 1" />
    </joint>
    <link name="real_sense">
        <visual>
            <geometry>
                <box size="0.01 0.1 0.02"/>
            </geometry>
            <origin xyz="0 0 0" rpy="0 0 0" />
            <material name="black">
                <color rgba="0.0 0.0 0.0 1.0" />
            </material>
        </visual>
        <collision>
            <geometry>
                <box size="0.01 0.1 0.02"/>
            </geometry>
            <origin xyz="0.0 0.0 0.0" rpy="0.0 0.0 0.0" />
        </collision>
        <inertial>
            <origin xyz="0 0 0" />
            <mass value="0.05" />
            <inertia ixx="6.64E-04" ixy="0" ixz="0" iyy="6.64E-04" iyz="0" izz="1.02E-03" />
        </inertial>
    </link>

    <joint name="realsense_joint" type="fixed">
        <parent link="base_link" />
        <child link="real_sense" />
        <origin xyz="0.19864 0.0038046 0.052021" />
        <axis xyz="0 0 1" />
    </joint>
    <link name="lidar">
        <visual>
            <geometry>
                <cylinder radius="0.03" length="0.06" />
            </geometry>
            <origin xyz="0 0 0" rpy="0 0 0" />
            <material name="black">
                <color rgba="0.0 0.0 0.0 1.0" />
            </material>
        </visual>
        <collision>
            <geometry>
                <cylinder radius="0.03" length="0.06" />
            </geometry>
            <origin xyz="0.0 0.0 0.0" rpy="0.0 0.0 0.0" />
        </collision>
        <inertial>
            <origin xyz="0 0 0" />
            <mass value="0.1" />
            <inertia ixx="6.64E-04" ixy="0" ixz="0" iyy="6.64E-04" iyz="0" izz="1.02E-03" />
        </inertial>
    </link>
    <joint name="lidar_joint" type="fixed">
        <parent link="base_link" />
        <child link="lidar" />
        <origin xyz="0.093603 0 0.12377" />
        <axis xyz="0 0 1" />
    </joint>
    <link name="imu">
        <visual>
            <geometry>
                <box size="0.01 0.01 0.005"/>
            </geometry>
            <origin xyz="0 0 0" rpy="0 0 0" />
            <material name="black">
                <color rgba="0.0 0.0 0.0 1.0" />
            </material>
        </visual>
        <collision>
            <geometry>
                <box size="0.01 0.01 0.005"/>
            </geometry>
            <origin xyz="0.0 0.0 0.0" rpy="0.0 0.0 0.0" />
        </collision>
        <inertial>
            <origin xyz="0 0 0" />
            <mass value="0.05" />
            <inertia ixx="6.64E-04" ixy="0" ixz="0" iyy="6.64E-04" iyz="0" izz="1.02E-03" />
        </inertial>
    </link>
    <joint name="imu_joint" type="fixed">
        <parent link="base_link" />
        <child link="imu" />
        <origin xyz="0 0 0.02" />
        <axis xyz="0 0 1" />
    </joint>
  <xacro:include filename="$(find racebot_description)/urdf/ackermann/racecar.gazebo" />
</robot>

代码起始和末尾添加了两个文件，通过xacro封装引用进来。这两个xacro文件是接下去要配置的传动文件macros.xacro以及gazebo插件racecar.gazebo。

3►添加传动transmission

创建macro.xacro文件，该代码给前后轮以及前轮摆转配置了传动transmission元素，代码如下：

<?xml version="1.0"?>
<robot name="racebot" xmlns:xacro="http://www.ros.org/wiki/xacro">
<!-- transmission macros -->
<xacro:macro name="wheel_transmission" params="name">
  <transmission name="${name}_transmission" type="SimpleTransmission">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="${name}_joint">
      <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
    </joint>
    <actuator name="${name}_motor">
      <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
    </actuator>
  </transmission>
</xacro:macro>
<xacro:macro name="steering_hinge_transmission" params="name">
  <transmission name="${name}_transmission" type="SimpleTransmission">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="${name}_joint">
      <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
    </joint>
    <actuator name="${name}_motor">
      <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
    </actuator>
  </transmission>
</xacro:macro>
</robot>

值得注意的是，引用该文件时，要将路径代码放置到racecar.xacro代码的最上端位置，如上代码所示，否则将无法引用到，并且在需要添加传动的link后面添加宏定义，以左前轮以及左前轮摆转为例：

<xacro:wheel_transmission name="left_front_wheel" />
 .
 .
 .
 <xacro:steering_hinge_transmission name="right_steering_hinge" />

4►配置gazebo插件

要让小车在gazebo中仿真，并且让小车能够进行建图导航，需要给小车的摄像头，激光雷达等link添加传感器插件，下面将进行配置，新建racecar.gazebo文件，开头代码：

<?xml version="1.0"?>
<robot name="racebot" xmlns:xacro="http://www.ros.org/wiki/xacro">
。
。
。
</robot>

配置各个link的颜色：

由于车轮实际上会接触地面，因此会与地面发生物理相互作用，将各个link添加部件材料的附加信息，并且定义各个link的颜色信息。参考gazebo官网：http://gazebosim.org/tutorials/?tut=ros_urdf

<!-- Gazebo references -->
<gazebo reference="base_link">
  <mu1 value="0.0"/>
  <mu2 value="0.0"/>
  <kp  value="10000000.0" />
  <kd  value="1.0" />
  <material>Gazebo/Red</material>
</gazebo>
<gazebo reference="left_rear_wheel">
  <mu1 value="2.0"/>
  <mu2 value="2.0"/>
  <kp  value="10000000.0" />
  <kd  value="1.0" />
  <fdir1 value="1 0 0"/>
  <material>Gazebo/Black</material>
</gazebo>
<gazebo reference="right_rear_wheel">
  <mu1 value="2.0"/>
  <mu2 value="2.0"/>
  <kp  value="10000000.0" />
  <kd  value="1.0" />
  <fdir1 value="1 0 0"/>
  <material>Gazebo/Black</material>
</gazebo>
<gazebo reference="left_front_wheel">
  <mu1 value="2.0"/>
  <mu2 value="2.0"/>
  <kp  value="10000000.0" />
  <kd  value="1.0" />
  <fdir1 value="0 0 1"/>
  <material>Gazebo/Black</material>
</gazebo>
<gazebo reference="right_front_wheel">
  <mu1 value="2.0"/>
  <mu2 value="2.0"/>
  <kp  value="10000000.0" />
  <kd  value="1.0" />
  <fdir1 value="0 0 1"/>
  <material>Gazebo/Black</material>
</gazebo>
<gazebo reference="lidar">
  <material>Gazebo/Black</material>
</gazebo>
<gazebo reference="camera">
  <material>Gazebo/Black</material>
</gazebo>
<gazebo reference="real_sense">
  <material>Gazebo/Grey</material>
</gazebo>

配置ros_control：

由于gazebo并没阿克曼车型的插件，要链接gazebo与ros，我们先添加ros_control插件，它读取所有transmission标记，以及joint_state_publisher插件。

<!-- Gazebo Plugins -->
<gazebo>
  <plugin name="gazebo_ros_control" filename="libgazebo_ros_control.so">
    <robotNamespace>/racebot</robotNamespace>
    <robotParam>robot_description</robotParam>
    <robotSimType>gazebo_ros_control/DefaultRobotHWSim</robotSimType>
    <legacyModeNS>true</legacyModeNS>
  </plugin>
</gazebo>

注意命名空间要设置为/racebot。

配置激光雷达插件：

<!-- hokuyo -->
  <gazebo reference="lidar">
    <material>Gazebo/Grey</material>
    <sensor type="ray" name="hokuyo_sensor">
      <pose>0 0 0.0124 0 0 0</pose>
      <visualize>false</visualize>
      <update_rate>40</update_rate>
      <ray>
        <scan>
          <horizontal>
            <samples>1081</samples>
            <resolution>1</resolution>
            <min_angle>-2.3561944902</min_angle>
            <max_angle>2.3561944902</max_angle>
          </horizontal>
        </scan>
        <range>
          <min>0.1</min>
          <max>10.0</max>
          <resolution>0.01</resolution>
        </range>
        <noise>
          <mean>0.0</mean>
          <stddev>0.01</stddev>
        </noise>
      </ray>
      <plugin name="gazebo_ros_hokuyo_controller" filename="libgazebo_ros_laser.so">
        <topicName>/scan</topicName>
        <frameName>lidar</frameName>
      </plugin>
    </sensor>
  </gazebo>

配置深度相机插件：

由于配置realsense插件过于复杂，因此这里用kinect插件来代替realsense插件。

<gazebo reference="real_sense">
      <sensor type="depth" name="real_sense">
          <always_on>true</always_on>
          <update_rate>20.0</update_rate>
          <camera>
              <horizontal_fov>${60.0*3.14/180.0}</horizontal_fov>
              <image>
                  <format>R8G8B8</format>
                  <width>640</width>
                  <height>480</height>
              </image>
              <clip>
                  <near>0.05</near>
                  <far>8.0</far>
              </clip>
          </camera>
          <plugin name="kinect_real_sense_controller" filename="libgazebo_ros_openni_kinect.so">
              <cameraName>real_sense</cameraName>
              <alwaysOn>true</alwaysOn>
              <updateRate>10</updateRate>
              <imageTopicName>rgb/image_raw</imageTopicName>
              <depthImageTopicName>depth/image_raw</depthImageTopicName>
              <pointCloudTopicName>depth/points</pointCloudTopicName>
              <cameraInfoTopicName>rgb/camera_info</cameraInfoTopicName>
              <depthImageCameraInfoTopicName>depth/camera_info</depthImageCameraInfoTopicName>
              <frameName>real_sense</frameName>
              <baseline>0.1</baseline>
              <distortion_k1>0.0</distortion_k1>
              <distortion_k2>0.0</distortion_k2>
              <distortion_k3>0.0</distortion_k3>
              <distortion_t1>0.0</distortion_t1>
              <distortion_t2>0.0</distortion_t2>
              <pointCloudCutoff>0.4</pointCloudCutoff>
          </plugin>
      </sensor>
  </gazebo>

配置单目相机插件：

<!-- camera -->
<gazebo reference="camera">
  <material>Gazebo/Grey</material>
    <sensor type="camera" name="camera">
      <update_rate>30.0</update_rate>
      <camera name="camera">
        <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="camera_controller" filename="libgazebo_ros_camera.so">
        <alwaysOn>true</alwaysOn>
        <updateRate>0.0</updateRate>
        <cameraName>rrbot/camera1</cameraName>
        <imageTopicName>image_raw</imageTopicName>
        <cameraInfoTopicName>camera_info</cameraInfoTopicName>
        <frameName>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>

配置imu插件：

<gazebo reference="imu">
        <material>Gazebo/Orange</material>
        <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">
                <topicName>imu</topicName>
                <bodyName>imu</bodyName>
                <updateRateHZ>100.0</updateRateHZ>
                <gaussianNoise>0.0</gaussianNoise>
                <xyzOffset>0 0 0</xyzOffset>
                <rpyOffset>0 0 0</rpyOffset>
                <frameName>imu_link</frameName>
            </plugin>
            <pose>0 0 0 0 0 0</pose>
        </sensor>
</gazebo>

5►配置gazebo插件在gazebo中显示并演示传感器效果

创建racebot_gazebo功能包，并创建如下文件夹：

在launch文件夹中创建racebot.launch文件：

<?xml version="1.0"?>
<launch>
      <!-- 设置launch文件的参数 -->
    <arg name="paused" default="false"/>
    <arg name="use_sim_time" default="true"/>
    <arg name="gui" default="true"/>
    <arg name="headless" default="false"/>
    <arg name="debug" default="false"/>
    <!--模型车的起点放置位置-->
    <arg name="x_pos" default="0"/>
    <arg name="y_pos" default="0"/>
    <arg name="z_pos" default="0"/>
    <arg name="R_pos" default="0"/>
    <arg name="P_pos" default="0"/>
    <arg name="Y_pos" default="0"/>
  <!--运行gazebo仿真环境-->
  <include file="$(find gazebo_ros)/launch/empty_world.launch">
          <arg name="debug" value="$(arg debug)" />
          <arg name="gui" value="$(arg gui)" />
          <arg name="paused" value="$(arg paused)"/>
          <arg name="use_sim_time" value="$(arg use_sim_time)"/>
          <arg name="headless" value="$(arg headless)"/>
          <arg name="world_name" value="$(find racebot_gazebo)/worlds/room_mini.world"/>
               <!-- .world文件的地址-->
      </include>
  <!-- 加载机器人模型描述参数 -->
  <param name="robot_description" command="$(find xacro)/xacro --inorder '$(find racebot_description)/urdf/ackermann/racecar.xacro'"/>
        <!-- 在gazebo中加载机器人模型-->
    <node name="urdf_spawner" pkg="gazebo_ros" type="spawn_model" respawn="false" output="screen"
          args="-urdf -model racebot -param robot_description -x $(arg x_pos) -y $(arg y_pos) -z $(arg z_pos) -R $(arg R_pos) -P $(arg P_pos) -Y $(arg Y_pos)"/> 
    <!-- <node name="urdf_spawner" pkg="gazebo_ros" type="spawn_model" respawn="false" output="screen"
          args="-urdf -model tianracer -param robot_description -x $(arg x_pos) -y $(arg y_pos) -z $(arg z_pos)"/>  -->
         
  <!-- ros_control racecar launch file -->
    <!--Launch the simulation joystick control-->
<!-- <node pkg="tf2_ros" type="static_transform_publisher" name="static_transform_publisher" args="0 0 0 -1.57 0 -1.57 /real_sense /real_sense_depth" /> -->
</launch>

在worlds文件夹中，将之前用于mini小车仿真的room_mini.world文件放入，使得racebot载入有room_mini地图的gazebo仿真环境中。

roslaunch racebot_gazebo racebot.launch

可以看到小车已经加载到gazebo环境中，然而此时无法控制小车运动，因为还未配置controllers，但是我们可以读取到传感器参数。

读取imu参数：

rostopic echo /imu

读取雷达数据：

打开rviz

rviz

将fixed_frame改为base_footprint, 点击add-->by topic-->laserScan,此时在rviz中即可显示雷达点云

单目摄像头：

在rviz中add-->by topic-->/rrbot/camera1/image_raw/camera即可添加相机插件，并显示图像：

深度摄像头：

深度摄像头查看深度图像与单目摄像头同理add-->by topic-->realsense/depth/image_raw/camera

只是在添加pointcloud2时会出现问题，add-->by topic-->realsense/depth/points/pointcloud2,会发现彩色点云出现在小车正上方,原因是在kinect中图像数据与点云数据使用了两套坐标系统，且两套坐标系统位姿并不一致。

解决方法有两种：

1.可以在launch文件中加入坐标变换，即可解决这一现象。

<node pkg="tf2_ros" type="static_transform_publisher" name="static_transform_publisher" args="0 0 0 -1.57 0 -1.57 /support /support_depth" />

详细参考奥特学园《kinect信息仿真以及显示》https://sourl.cn/ziwDEU

2.第二种方法是在urdf中加入新的link，即使用点云数据的link，并通过joint做坐标变换来解决。

<link name="realsense_depth"/>
    <joint name="realsense_depth_joint" type="fixed">
            <origin xyz="0 0 0" rpy="-1.5708 0 -1.5708"/>
            <parent link="real_sense"/>
            <child link="realsense_depth"/>
    </joint>

修改插件

<gazebo reference="real_sense">
      <sensor type="depth" name="real_sense">
          <always_on>true</always_on>
          <update_rate>20.0</update_rate>
          <camera>
              <horizontal_fov>${60.0*3.14/180.0}</horizontal_fov>
              <image>
                  <format>R8G8B8</format>
                  <width>640</width>
                  <height>480</height>
              </image>
              <clip>
                  <near>0.05</near>
                  <far>8.0</far>
              </clip>
          </camera>
          <plugin name="kinect_real_sense_controller" filename="libgazebo_ros_openni_kinect.so">
              <cameraName>real_sense</cameraName>
              <alwaysOn>true</alwaysOn>
              <updateRate>10</updateRate>
              <imageTopicName>rgb/image_raw</imageTopicName>
              <depthImageTopicName>depth/image_raw</depthImageTopicName>
              <pointCloudTopicName>depth/points</pointCloudTopicName>
              <cameraInfoTopicName>rgb/camera_info</cameraInfoTopicName>
              <depthImageCameraInfoTopicName>depth/camera_info</depthImageCameraInfoTopicName>
              <frameName>realsense_depth</frameName>
              <baseline>0.1</baseline>
              <distortion_k1>0.0</distortion_k1>
              <distortion_k2>0.0</distortion_k2>
              <distortion_k3>0.0</distortion_k3>
              <distortion_t1>0.0</distortion_t1>
              <distortion_t2>0.0</distortion_t2>
              <pointCloudCutoff>0.4</pointCloudCutoff>
          </plugin>
      </sensor>
  </gazebo>

6►小结

本节内容关于小车传动的添加，以及配置了小车上面的一些插件，下一节内容，通过配置controller让小车动起来。

参考资料：

1.古月老师的《ROS机器人开发实践》

2.奥特学园《6.7.4 kinect信息仿真以及显示》https://sourl.cn/ziwDEU

3.gazebo官网 http://gazebosim.org/tutorials/?tut=ros_urdf

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