bt_executer

bt_executer is a specialized package designed to run behavior trees based on BehaviorTree.ROS2. It functions through the use of bt_executer_node.cpp, a node that can be initiated using bt_executer.launch.py. This launch process is responsible for importing configurations from config/bt_config_template.yaml and config/skills_config_template.yaml through the cnr_param utility:

• bt_config_template.yaml specifies which skill plugins should be loaded, as well as identifies the package and the name of the .xml file that contains the behavior tree structure.
• skills_config_template.yaml outlines the necessary parameters for each node (leaf) within the tree.

It's important to ensure that the behavior tree's .xml file is located within the trees directory of the package identified by bt_package in bt_config_template.yaml. Furthermore, each leaf node within the tree is equipped with an input port named param_ns, which is used to specify the sub-namespace for its parameters.

Within the skills folder, you will find a collection of predefined skills. These are made available as plugins, adhering to a specific naming convention: skill_name_plugin. This standardized naming convention is crucial for the bt_executer node to locate and load the plugins, thereby enhancing the system's modularity and ease of use.

Use in an external package

If you want to execute a behavior tree in your specific application, you should:

1. Copy config/bt_config_template.yaml and config/skills_config_template.yaml to your_package/config/bt_config.yaml and your_package/config/skills_config.yaml;
2. Copy trees/main_tree.xml (or write it from scratch) to your_package/trees/ folder, and modify the .xml file as needed;
3. Set the list of plugins to load, the name of your_package and of the .xml file inyour_package/config/bt_config.yaml and the skills parameters in your_package/config/skills_config.yaml;
4. Copy launch/bt_executer.launch.py to your_package/launch/ folder and change the line config_folder = PathJoinSubstitution([FindPackageShare("bt_executer"),"config"]) to config_folder = PathJoinSubstitution([FindPackageShare("your_package"),"config"])

Note that the main behavior tree must have <BehaviorTree ID="MainTree">.

Install

Dowload the deps.repo file, which contains all the dependecies of the bt_executer package, and compile:

cd ws/src
wget  --backups=1 https://raw.githubusercontent.com/JRL-CARI-CNR-UNIBS/bt_executer/master/deps.repo
vcs import < deps.repo
cd ..
colcon build --symlink-install 

Examples

Here you can find some examples of how to use the package, based on this cell.