Cartographer_using_Delta_III_Lidar

A tutorial about running Cartographer toolkit with Delta III Lidar.

1 Install Cartographer

sudo apt install ros-melodic-cartographer
sudo apt install ros-melodic-cartographer-ros
sudo apt install ros-melodic-cartographer-ros-msgs

Then you can find these three packages in /opt/ros/melodic/share . If not, type rospack find packagename in the terminal to find the path.

1.1 Run a demo bag

1.1.1 Install a bag

https://storage.googleapis.com/cartographer-public-data/bags/backpack_2d/cartographer_paper_deutsches_museum.bag

Copy this link to download the demo bag（470MB）named cartographer_paper_deutsches_museum.bag. The default saving path is /home/username/Downloads

1.1.2 Run the bag

roslaunch cartographer_ros demo_backpack_2d.launch bag_filename:=${HOME}/Downloads/cartographer_paper_deutsches_museum.bag

You could see the real-time laser scan data in rviz. Click the "Add" button, add an topic named "/map", the you can see the real-time updated map as follow.

This implies you have installed cartographer successfully.

2 Start the LiDAR

Weblink of Delta_III Lidar produced by 3irobotix:

http://www.3irobotics.com/pro_s.php?id=168

To install the driver and make the Lidar run，please reference delta_III_ros

2.1 Acquire the needed info of Lidar

Start the Lidar

roslaunch delta_lidar view_delta_lidar.launch

You could see the real-time laser scan data in rviz, then type rostopic list to acquire the topic name.

Here, Delta_III publishes a topic named /scan Print the information of /scan

rostopic echo /scan

Find the frame_id: “laser”. This will be used later.

3 Modify Files

3.1 Modify .lua

Find the file named revo_lds.lua in /opt/ros/melodic/share/cartographer_ros/launch , copy it and rename as my_revo_lds.lua Constrained by the Insufficient Permissions, you could complete the tasks as follow: Open a new terminal and cd /opt/ros/melodic/share/cartographer_ros/launch, then:

sudo cp revo_lds.lua my_revo_lds.lua

Modify the file:

sudo gedit my_revo_lds.lua

Open my_revo_lds.lua, implement the following modification:

//Change the original frame "horizontal_laser_link" into our "laser"
tracking_frame = "laser",
published_frame = "laser",

3.2 Modify .launch

Find the file named demo_revo_leds.launch in /opt/ros/melodic/share/cartographer_ros/configuration_files, copy it and rename as my_demo_revo_lds.launch 修改以下内容:

//Since it's not bag simulation, set the following value as false.
<param name="/use_sim_time" value="false" />

//Use our own configuration: change revo_lds.lua into my_revo_lds.lua
<node name="cartographer_node" pkg="cartographer_ros"
      type="cartographer_node" args="
          -configuration_directory $(find cartographer_ros)/configuration_files
          -configuration_basename my_revo_lds.lua"

//Change horizontal_laser_2d into our topic scan
<remap from="scan" to="scan" />

//Delete the following codes.
<node name="playbag" pkg="rosbag" type="play"
      args="--clock $(arg bag_filename)" />

4 Mapping

Firstly start the lidar and assure that there is effictive output laser data topic. Then

roslaunch cartographer_ros my_demo_revo_lds.launch

Start to construct a occupancy grid map..

5 Save the map

Open another terminal and type:

//End the first trajectory, and no further data will be added. rosservice call /finish_trajectory 0

//Generate a pbstream file rosservice call /write_state "{filename: '${HOME}/Downloads/mymap.pbstream'}"

//transform pbstream to pgm and yaml

rosrun cartographer_ros cartographer_pbstream_to_ros_map -map_filestem=/home/kai/Downloads/mymap -pbstream_filename=/home/kai/Downloads/mymap.pbstream -resolution=0.05

The address and file name could be modified according to your preference.

zfc-zfc/Cartographer_ros