# 前言:
你有可能讀過這份筆記:[WSL Ubuntu ROS gazebo 環境實作](https://hackmd.io/qMBSwzaxQiuouKfqZnZ0aQ?view)
以下的操作環境基礎皆承襲上述筆記的狀態

且接下來預設你:
1.會使用linux環境
2.會使用基礎ros
3.會sdf、urdf檔(xml語法)

**#注意以下範例指令與程式碼中的<your_xxx>請替換成你自己命名的名稱!**

# Refferences:
1.[使用ROS開啟Gazebo](https://axxx2934.medium.com/%E4%BD%BF%E7%94%A8ros%E9%96%8B%E5%95%9Fgazebo-92271e0ec410)
2.[ROS 安裝與教學與Gazebo](https://hackmd.io/@afB3H1HCSXqZfB9gz4ZmqA/rJVmRaUmi)
3.[一個營建系學生的韌體之路-自走車篇](https://ithelp.ithome.com.tw/users/20140433/ironman/6692)
4.[ROS系統控制自走車搭配點雲雷達(隧道檢測裝置) ](https://ithelp.ithome.com.tw/m/users/20129807/ironman/3282)

# 1.建立及載入基礎空白世界
1.在workspace中建立gazebo的package
* `cd ~/catkin_ws/src`
* `catkin_create_pkg <your_pkg> std_msgs rospy roscpp gazebo_ros gazebo_plugins`

2.退回workspace層級編譯
* `cd ~/catkin_ws`
* `catkin_make`

3.package內建立`launch`及`worlds`資料夾
* `cd ~/catkin_ws/src/<your_pkg>`
* `mkdir launch`
* `mkdir worlds`

4.在`worlds`資料夾中建立一個`.world`檔
* `cd ~/catkin_ws/src/<your_pkg>/worlds`
* `code <your_world>.world`
<your_world>.world:

<?xml version="1.0" ?>
<sdf version="1.4">
  <world name="default">
  
    <!-- a global light source -->
    <include>
      <uri>model://ground_plane</uri>
    </include>
    
    <!-- a ground plane -->
    <include>
      <uri>model://sun</uri>
    </include>
    
  </world>
</sdf>

5.在`launch`資料夾中建立一個`.launch`檔
* `cd ~/catkin_ws/src/<pkg_name>/launch`
* `code <your_launch>.launch`
<your_launch>.launch:

<launch>
  <!-- We resume the logic in empty_world.launch, changing only the name of the world to be launched -->
  <include file="$(find gazebo_ros)/launch/empty_world.launch">
    <arg name="world_name" value="$(find <your_pkg>)/worlds/<your_world>"/>
    <!-- more default parameters can be changed here -->
  </include>
</launch>

6.回到`catkin_ws`做`catkin_make`與`source devel/setup.bash`
* `cd ~/catkin_ws`
* `catkin_make`
* `source devel/setup.bash`

7.啟動gazebo並載入世界，啟動`.launch`，可見到基礎空白世界
* `roslaunch <your_pkg> <your_launch>.launch`

# 2.建立你的機器人並放入世界(.urdf)
1.package內建立`urdf`資料夾
* `cd ~/catkin_ws/src/<your_pkg>`
* `mkdir urdf`

2.在`urdf`資料夾中建立一個`.urdf`檔
* `cd ~/catkin_ws/src/<your_pkg>/urdf`
* `code <your_urdf>.urdf`
<your_urdf>.urdf:

<?xml version="1.0"?>
<robot name="practice_car">

  <!-- 顏色材質  -->

  <material name="blue">
    <color rgba="0 0 0.5 1"/>
  </material>

  <material name="red">
    <color rgba="0.5 0 0 1"/>
  </material>

  <material name="green">
    <color rgba="0 0.5 0 1"/>
  </material>

  <material name="white">
    <color rgba="1 1 1 1"/>
  </material>

  <!-- 車體  -->

  <link name="base_link"/>

  <link name="chaiss">
    <visual>
        <geometry>
            <box size="0.6 0.4 0.2"/>
        </geometry>
        <origin xyz="0 0 0.1" rpy="0 0 0"/>
        <material name="blue"/>
    </visual>

    <collision>
        <geometry>
            <box size="0.6 0.4 0.2"/>
        </geometry>
        <origin xyz="0 0 0.1" rpy="0 0 0"/>
    </collision>

    <inertial>
        <origin xyz="0 0 0.1" rpy="0 0 0"/>
        <mass value="1.0"/>
        <inertia ixx="0.017" ixy="0" ixz="0"
                 iyy="0.033" iyz="0"
                 izz="0.043" />
    </inertial>
  </link>
  
  <joint name="base_joint" type="fixed">
    <parent link="base_link"/>
    <child link="chaiss"/>
    <origin xyz="0 0 0.1" rpy="0 0 0"/>
  </joint>

  <!-- 右輪  -->

  <link name="right_wheel">
    <visual>
        <geometry>
            <cylinder radius="0.1" length="0.05" />
        </geometry>
        <origin xyz="0 0 0" rpy="1.57 0 0" />
        <material name="white"/>
    </visual>

    <collision>
        <geometry>
            <cylinder radius="0.1" length="0.05" />
        </geometry>
        <origin xyz="0 0 0" rpy="1.57 0 0" />
    </collision>

    <inertial>
        <origin xyz="0 0 0" rpy="1.57 0 0" />
        <mass value="0.5"/>
        <inertia ixx="0.00135" ixy="0" ixz="0"
                 iyy="0.00135" iyz="0"
                 izz="0.0025" />
    </inertial>
  </link>

  <joint name="right_wheel_joint" type="continuous">
    <parent link="chaiss"/>
    <child link="right_wheel"/>
    <origin xyz="-0.15 -0.225 0" rpy="0 0 0"/>
    <axis xyz="0 1 0"/>
  </joint>

  <!-- 左輪  -->

  <link name="left_wheel">
    <visual>
        <geometry>
            <cylinder radius="0.1" length="0.05" />
        </geometry>
        <origin xyz="0 0 0" rpy="1.57 0 0" />
        <material name="white"/>
    </visual>

    <collision>
        <geometry>
            <cylinder radius="0.1" length="0.05" />
        </geometry>
        <origin xyz="0 0 0" rpy="1.57 0 0" />
    </collision>

    <inertial>
        <origin xyz="0 0 0" rpy="1.57 0 0" />
        <mass value="0.5"/>
        <inertia ixx="0.00135" ixy="0" ixz="0"
                 iyy="0.00135" iyz="0"
                 izz="0.0025" />
    </inertial>
  </link>

  <joint name="left_wheel_joint" type="continuous">
    <parent link="chaiss"/>
    <child link="left_wheel"/>
    <origin xyz="-0.15 0.225 0" rpy="0 0 0"/>
    <axis xyz="0 1 0"/>
  </joint>

  <!-- 牛眼輪  -->

  <link name="front_wheel">
    <visual>
        <geometry>
            <sphere radius="0.1" />
        </geometry>
        <material name="red"/>
    </visual>

    <collision>
        <geometry>
            <sphere radius="0.1" />
        </geometry>
    </collision>

    <inertial>
        <mass value="0.5"/>
        <inertia ixx="0.002" ixy="0" ixz="0"
                 iyy="0.002" iyz="0"
                 izz="0.002" />
    </inertial>
  </link>

  <joint name="front_wheel_joint" type="fixed">
    <parent link="chaiss"/>
    <child link="front_wheel"/>
    <origin xyz="0.2 0 0" rpy="0 0 0"/>
  </joint>

</robot>

3.一樣回到`catkin_ws`做`catkin_make`與`source devel/setup.bash`
4.若你的世界已經關閉則再次開啟世界
5.將機器人生成進世界中，可以看到世界中出現你的小車
* ``rosrun gazebo_ros spawn_model -file `rospack find <your_pkg>`/urdf/<your_urdf>.urdf -urdf -x 0 -y 0 -z 1 -model <your_urdf>``

# 3.