big_bot_description

Big bot is a six-wheeled robot used to generate a 3D map simulation of a V-shaped cave structure

1. Prerequisites

teleop_twist_keyboard package; source: http://wiki.ros.org/teleop_twist_keyboardhttp://wiki.ros.org/teleop_twist_keyboard
ouster_example package; source: https://github.com/ouster-lidar/ouster_example
octomap_server package; source: https://github.com/OctoMap/octomap_mapping

2. Installing the Package

git clone the package into your catkin_ws/src (or whatever you named your ros workspace) using the following line in the terminal

git clone https://github.com/AntarCreates/big_bot_description.git
Build the workspace using catkin_make
Source the bash file using source devel/setup.bash

3. Verify Installation

Run the following command to bring up Big bot in gazebo

roslaunch big_bot_description gazebo.launch
This should bring up the robot in the Gazebo interface as depicted below-

And you are pretty much set!

4. Setting-up the Environment

Press the "insert" option in gazebo
If you have everything set up adequately, you should find two objects by the following names under the "models used" folder on the left plane inside gazebo
- Cave Corner 01 Type B
- cave_straight_01
Drag and drop the models to generate your desired shape. I went for a V-shaped one like the image attached below:

5. 3D Map Generation

The procedure can be subdivided into five (5) separate steps

Initialize visualization
Editing the octomap_mapping.launch file
Running the octomap node to start generating 3D map
Running the teleop_twist_keyboard.py node to drive the bot as the map is being generated, and
Saving the generated 3D map

5.1 Initialize visualization

To viaualize the process, we'll use RViz, the default ROS visualizer. Open a new tab in the terminal and run the following line:

roslaunch big_bot_description display.launch

This should bring-up RViz, and you should find various options like robot model, Tf, etc. I recommend to uncheck the robot model box, as doing so keeps the map visualization cleaner.

note: In case you don't have your system set up for removing the irritating need for sourcing it each time a new terminal is opened, you must run source devel/setup.bash every time you open a new tab in the terminal, which you will be doing a lot in the next few steps

5.2 Editing the octomap_mapping.launch file

Find the octomap_server package in your system using rospack find octomap_server . It should give you a path to its file location.
copy the path and open the file location (GUI) using nautilus <your copied path>
Find and open the octomap_mapping.launch file in the launch folder and edit the following lines as below:

<param name="frame_id" type="string" value="odom" />

<remap from="cloud_in" to="/depth/points" />

5.3 Running the Octomap node to start generating 3D map

Now this is quite a critical phase so be a bit more cautious

Start the octomapping process by running the following line in a separate terminal tab ( Don't forget to source the bash!)

roslaunch octomap_server octomap_mapping.launch
In RViz press "Add" then "Add by topic" and press on "MarkerArray" as depicted in the snap below and set the fixed frame to be "odom":

By this time you should see blue cubes forming up along the red lidar rays near the big bot in the RViz window. That means the octomap is running! Good job!

note: The octomap terminal may give you a warning with something like "octree is empty.Nothing to publish". You can ignore that as long as your mapping process is running.

5.4 Running the teleop_twist_keyboard.py node to Drive the bot as the Map is being generated

Now all you have to do is drive the bot through your desired path using keyboard inputs
Run rosrun teleop_twist_keyboard teleop_twist_keyboard.py in a separate terminal tab to drive the robot using keyboard inputs (e.g., "i" for forward, "," for backward, etc.)

If everything works as expected, you should see a similar process as depicted in the following clip:

3D_cave.1.1.mp4

5.5 Saving the generated 3D map

If you made it this far, you are basically done! Congratulations! Now just save the map using the following line in a separate terminal in a desired directory ( don't forget to source the bash):

rosrun octomap_server octomap_saver -f <name of your map>.bt

6. Loading the Map

To load or open the saved map, close the RViz window using Ctrl+c in the corresponding terminal tab and relaunch it using rosrun rviz rviz
Add MarkerArray subscribing to the similar topic as before and set the fixed frame to be "Odom"
Run the following command in the terminal tab

rosrun octomap_server octomap_server_node <name of your map>.bt
This should bring up the map in RViz window that you can rotate as you wish

....AAAnd that's it! Pat yourself on the back! You just made a pretty dope 3D map!

AntarCreates/big_bot_description