rplidar & hector slam without odometry

　　接上一篇：1.rplidar测试

　　方式一：测试使用rplidar A2跑一下手持的hector slam，参考文章：用hector mapping构建地图

　　但是roslaunch exbotxi_bringup 2dsensor.launch 和 roslaunch exbotxi_nav hector_mapping_demo.launch

　　这两个文件都没有搜索到。需要更新exbot_xi开发包。https://github.com/yuanboshe/exbot_xi/tree/hydro/exbotxi_bringup/launch

cd ~/catkin_ws/src/exbot_xi
git pull

　　如果出现 Already up-to-date. 的提示，则更新成功。如果对包有所修改，可能有些情况下无法更新，那么可以使用

　git reset --hard

　　reset一下，然后再使用 git pull 更新。

　　之后编译。

cd ~/catkin_ws/
catkin_make

　　修改rplidar_2d_sensor.launch.xml 文件，/home/exbot/catkin_ws/src/exbot_xi/exbotxi_bringup/launch/includes/rplidar_2d_sensor.launch.xml，修改

<node name="exbot_rplidar" pkg="rplidar_ros" type="rplidarNode" output="screen">

　　完整文件：（奇怪，端口<arg name="laser_port" default="/dev/ttyUSB1" />似乎也应该改啊，改成/dev/ttyUSB0，没改居然也没问题）

<launch>
  <arg name="scan_topic" default="scan" />
  <arg name="laser_frame" default="laser_link" />
  <arg name="laser_port" default="/dev/ttyUSB1" />
  
  <node name="exbot_rplidar" pkg="rplidar_ros" type="rplidarNode" output="screen">
    <param name="com_path" type="string" value="$(arg laser_port)" />
    <param name="com_baudrate" type="int" value="115200" />
    <param name="frame_id" type="string" value="$(arg laser_frame)" />
    <param name="range_min" type="double" value="0.18" />
    <param name="range_max" type="double" value="6.0" />
    <remap from="scan" to="$(arg scan_topic)"/>
  </node>
</launch>

　　修改hector_mapping.launch.xml文件，/home/exbot/catkin_ws/src/exbot_xi/exbotxi_nav/launch/includes/hector_mapping.launch.xml

    <param name="base_frame" value="base_frame" />
    <param name="odom_frame" value="base_frame" />

　　完整文件：

<launch>

  <arg name="scan_topic" default="scan" />

  <node pkg="hector_mapping" type="hector_mapping" name="hector_mapping" output="screen">
    <param name="pub_map_odom_transform" value="true"/>
    <param name="map_frame" value="map" />
    <param name="base_frame" value="base_frame" />
    <param name="odom_frame" value="base_frame" />
    <param name="map_resolution" value="0.05" />
    <param name="map_size" value="1024" />
    <param name="laser_max_dist" value="3.9" />
    <param name="tf_map_scanmatch_transform_frame_name" value="odom_laser" />
    <remap from="scan" to="$(arg scan_topic)"/>
  </node>
</launch>

　　编译之后按照 用hector mapping构建地图 文章中的步骤：

roscore
roslaunch exbotxi_bringup fake_exbotxi.launch
roslaunch exbotxi_bringup 2dsensor.launch
roslaunch exbotxi_nav hector_mapping_demo.launch
roslaunch exbotxi_rviz view_navigation.launch

　　新建5个终端，让rplidar水平移动，会出现建图结果。

---

另外的实现方式：从原始代码编译hector_slam，参考 http://blog.csdn.net/eaibot/article/details/51044718

编译hector_slam过程中出现Cmake Error，好像是找不到Find cmake_modules.cmake什么的。猜想是cmake_modules包没有安装。

解决方法。

exbot@ubuntu:~$ cd ~/catkin_ws/src
exbot@ubuntu:~/catkin_ws/src$ git clone https://github.com/ros/cmake_modules.git
Cloning into 'cmake_modules'...
remote: Counting objects: 344, done.
remote: Total 344 (delta 0), reused 0 (delta 0), pack-reused 344
Receiving objects: 100% (344/344), 61.88 KiB | 34 KiB/s, done.
Resolving deltas: 100% (191/191), done.

exbot@ubuntu:~/catkin_ws/src$ cd ..
> 
exbot@ubuntu:~/catkin_ws$ catkin_make --pkg cmake_modules

　　之后按照参考文献的步骤，可以实现同样的结果。

　　在rplidar_ros/launch/目录下添加hector_mapping_demo.launch文件，内容如下：

<launch>

<node pkg="hector_mapping" type="hector_mapping" name="hector_mapping" output="screen">
<!-- Frame names -->
<param name="pub_map_odom_transform" value="true"/>
<param name="map_frame" value="map" />
<param name="base_frame" value="base_link" />
<param name="odom_frame" value="base_link" />

<!-- Tf use -->
<param name="use_tf_scan_transformation" value="true"/>
<param name="use_tf_pose_start_estimate" value="false"/>

<!-- Map size / start point -->
<param name="map_resolution" value="0.05"/>
<param name="map_size" value="2048"/>
<param name="map_start_x" value="0.5"/>
<param name="map_start_y" value="0.5" />
<param name="laser_z_min_value" value = "-1.0" />
<param name="laser_z_max_value" value = "1.0" />
<param name="map_multi_res_levels" value="2" />

<param name="map_pub_period" value="2" />
<param name="laser_min_dist" value="0.4" />
<param name="laser_max_dist" value="5.5" />
<param name="output_timing" value="false" />
<param name="pub_map_scanmatch_transform" value="true" />
<!--<param name="tf_map_scanmatch_transform_frame_name" value="scanmatcher_frame" />-->

<!-- Map update parameters -->
<param name="update_factor_free" value="0.4"/>
<param name="update_factor_occupied" value="0.7" />    
<param name="map_update_distance_thresh" value="0.2"/>
<param name="map_update_angle_thresh" value="0.06" />

<!-- Advertising config --> 
<param name="advertise_map_service" value="true"/>
<param name="scan_subscriber_queue_size" value="5"/>
<param name="scan_topic" value="scan"/>
</node>

<node pkg="tf" type="static_transform_publisher" name="base_to_laser_broadcaster" args="0 0 0 0 0 0 /base_link /laser 100"/>

  <node pkg="rviz" type="rviz" name="rviz"
    args="-d $(find hector_slam_launch)/rviz_cfg/mapping_demo.rviz"/>

</launch>

　　ros命令 

roslaunch rplidar_ros hector_mapping_demo.launch
roslaunch rplidar_ros rplidar.launch