udacity-robond-p5

Home Service Robot - Final project of the Udacity Robotics Software Engineer Nanodegree

Set-up

Check out the setup for the Udacity Workspace here.

1. Clone the repository

git clone https://github.com/PenguinLemma/udacity-robond-p5.git $PATH_TO_PARENT_DIR/penguin_lemma_hsr

2. Build all packages involved

cd $PATH_TO_PARENT_DIR/penguin_lemma_hsr
catkin_make

3. Install xterminal The scripts that take care of launching all processes for each of the functional steps in this projects use xterminal as a mean to produce independent new terminals that will run a certain set of commands. To install it, one just needs to run

sudo apt install xterm

Note that to terminate correctly all processes open, it is necessary to do Ctrl+C in each of the xterminal open. Otherwise, even if we close all related windows, processes such as gzserver could still be running under the hood, and that would prevent us from running some other script or using gazebo for some other purpose.

4. Set-up environment In every new terminal, it is necessary to

cd $PATH_TO_PARENT_DIR/penguin_lemma_hsr
source src/scripts/set_environment.$TERMINAL

where $TERMINAL can be bash, sh or zsh.

Paths are not relative to where the terminal is when you source that script, so you could also use the following commands

cd $PATH_TO_PARENT_DIR/penguin_lemma_hsr/src/scripts
source set_environment.$TERMINAL

5. Run a simple test To check that xterminal is installed and can be run, open and setup a terminal as above and then run

chmod +x src/scripts/launch.$TERMINAL
./src/scripts/launch.$TERMINAL

As a result, gazebo and rviz should open and roscore will be up and running.

Mapping

It is as simple as running the command

source src/scripts/test_slam.$TERMINAL

It can also be done as follows:

chmod +x src/scripts/test_slam.$TERMINAL
./src/scripts/test_slam.$TERMINAL

This script will launch:

• Turtlebot inside the world in src/world.
• gmapping demo
• rviz with a configuration that will show navigation
• keyboard_teleop, a node that will allow you to command the turtlebot with your keyboard

In order to map a different world, edit src/scripts/test_slam.$TERMINAL substituting the path to your .world file after world_file:=.

Drive the turtlebot around for a while and when you are happy with the map, before terminating gmapping node, use the following command in a new terminal (setting it up as explained above):

rosrun map_server map_saver -f /path/to/map/name

Do not include any extension, as this command will create both the .pgm file with the map and the .yaml configuration file.

Localization and navigation

Now that we created a map for our world, our robot will be able to localize itself in the map and also navigate to any goal in its reach. In the case of the localization, we are using AMCL (Adaptive Monte Carlo Localization). For navigation, we rely on ROS Navigation stack, which is based on Dijkstra's algorithm. To see it in action:

chmod +x src/scripts/test_navigation.$TERMINAL
./src/scripts/test_navigation.$TERMINAL

In the case we are using another world, we would only need to edit src/scripts/test_navigation.$TERMINAL substituting the path to the target .world file after world_file:= and the location of the configuration for the map we created in the previous section after map_file:=. In this case, we need to explicitely add the extension .yaml to the command.

Now go to the xterminal that is running rviz, select 2D Nav Goal and locate it wherever in the map you want the robot to move.

ROS nodes

Let's now introduce the two nodes that were written for this project: pick_objects and add_markers.

pick_objects

Instead of adding the goals manually, we would like to have a node that does this for us. pick_objects will command our robot to:

• Go to a pick-up location in our map
• Wait for 5 seconds (simulating picking up a virtual object)
• Go to a drop-off location in our map
• Inform us at every stage

Both pick-up and drop-off targets can be customized as parameters in src/pick_objects/launch/pick_objects.launch.

To test this node, we need to run:

chmod +x src/scripts/pick_objects.$TERMINAL
./src/scripts/pick_objects.$TERMINAL

in a properly set up terminal.

add_markers

This node serves us as visual aid to show what the robot is asked to do. The node will publish markers (so that rviz can display them) related to the actions commanded by pick_objects. There are two modes for this node:

1. Robot independent

This mode is basically the testing phase of our node. The behaviour expected is:

• Show marker in pick-up zone for 5 seconds
• Hide marker
• Wait 5 seconds
• Show marker in drop-off zone

To test it, run

chmod +x src/scripts/add_markers.$TERMINAL
./src/scripts/add_markers.$TERMINAL

2. Robot dependent

In this case, the node is tracking the robot and will:

• Show marker in pick-up zone
• Hide marker once robot reaches pick-up zone
• Show marker in drop-off zone once the roboto reaches it

We will test this node in the next and last step, as we will need to integrate it with pick_objects.

Pick-up and drop-off zones for both modes can be set through parameters in src/add_markers/launch/add_markers.launch and src/add_markers/add_markers_tracking_robot.launch respectively.

Home Service Robot

Finally, we integrate all the previous parts to achieve the following:

• Robot can localize itself and navigate through the map
• It goes to the pick up zone, marked with a blue marker visible in rviz
• Once there, the marker disappears and the robot waits for 5 seconds, simulating picking up the virtual object
• The robot goes then to the drop-off zone
• Once there, a blue marker is displayed

Run the following commands to see this process:

chmod +x src/scripts/home_service.$TERMINAL
./src/scripts/home_service.$TERMINAL

License

Original version of the license of this repository can be found here: https://gist.github.com/laramartin/7796d730bba8cf689f628d9b011e91d8