Beetree

A lightweight implementation of Behavior Trees in Python that interfaces with the ROS framework. It is based loosly on the C++ implementation by Alejandro Marzinotto Cos at KTH. His original code can be found at here, and a publication here. A great overview of behavior trees (from the ROS perspective) can be found here.

BEETREE IS STILL UNDER DEVELOPMENT! SOME NODES ARE NOT IMPLEMENTED!

Not all of the nodes found in Marzinotto's implementation are finished. This is a work in progress. If you have any questions, please let me know at [email protected].

Dependencies

Besides ROS (catkin), Beetree depends on the package rqt_dot (https://github.com/jbohren/rqt_dot) for visualization of the behavior trees.

Usage

To run an example that generates dot code for a sample tree, run the command:

rosrun beetree beetree_test.py

This will print out a large chunk of graphviz dot code, as well as a string of text that shows the traversal of a single tick through the tree, based on the structure in the image above:

Executing Root: (root)
Executing Parallel: (para)
Executing Action: (act_detect_object)
  -  Node: act_detect_object returned status: SUCCESS
Executing Sequence: (sec_pick_move_to_bin): current child: cond_found_obj
Executing Condition: (cond_found_obj)
  -  Node: cond_found_obj returned status: SUCCESS
Executing Sequence: (sec_pick_up): current child: act_move_to_obj
Executing Action: (act_move_to_obj)
  -  Node: act_move_to_obj returned status: SUCCESS
Executing Action: (act_grab)
  -  Node: act_grab returned status: SUCCESS
Executing Action: (act_lift)
  -  Node: act_lift returned status: SUCCESS
  -  Node: sec_pick_up returned status: SUCCESS
Executing Action: (act_move)
  -  Node: act_move returned status: SUCCESS
Executing Sequence: (sec_place): current child: act_move_to_bin
Executing Action: (act_move_to_bin)
  -  Node: act_move_to_bin returned status: SUCCESS
Executing Action: (act_release)
  -  Node: act_release returned status: SUCCESS
  -  Node: sec_place returned status: SUCCESS
Executing Action: (act_reset)
  -  Node: act_reset returned status: SUCCESS
  -  Node: sec_pick_move_to_bin returned status: SUCCESS
  -  Node: para returned status: SUCCESS
ROOT: Child returned status: SUCCESS

To run an example that publishes the same tree to rqt_dot (a lightweight graphviz visualizer), run the following command:

roslaunch beetree test_beetree.launch

This will start the example tree and publish dot code to the rqt_dot visualizer. You will need to put the topic name "/beetree/dot" in the DOTCODE TOPIC field in rqt_dot and click the "Subscribe" button to see it.

Currently in the example, unimplemented nodes have been hard coded to return SUCCESS.