Flexible Behavior Trees provides the integration of Behavior Trees (BTs) into the HFSM behavior engine FlexBE. The packages are derived from the ROS2 Navigation2 nav2_behavior_tree package. Flexible Behavior Trees uses the BehaviorTree.CPP (v4.6+) framework for developing and loading BTs as XML files and interfaces with the FlexBE Behavior Engine with state implementations. These HFSM states allow a user to specify the loading and execution of BTs by sending a BT server the XML file names to load and execute. Moreover, these HFSM BT states can be chained together to allow for executing multiple BTs in a series while providing for user supervision and adjustable autonomy to better control contingencies and recovery behaviors.
This system provides specific states to load and execute various BTs from robot navigation to arm manipulation. This system has two main components a BT server and FlexBE state implementations. The FlexBE state implementations send goals to the BT server to load and execute a BT with and without a user defined goal. FlexBE orchestrates the execution of different BTs while the BehaviorTree.CPP framework executes the BTs and passes data between nodes and BTs.
The Flexible Behavior Trees system has been tested using the latest version of ROS2 Iron. You should first follow the ROS2 Install Guide and get that set up before proceeding.
After installing ROS2, git clone this package into a ROS2 workspace and build the packages using
the automated build tool colcon.
Please use the following publication for reference when using Flexible Behavior Trees:
- Joshua M. Zutell, David C. Conner, and Philipp Schillinger, "Flexible Behavior Trees: In search of the mythical HFSMBTH for Collaborative Autonomy in Robotics", March 2022.
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Joshua Zutell, David C. Conner and Philipp Schillinger, "ROS 2-Based Flexible Behavior Engine for Flexible Navigation ,", IEEE SouthEastCon, April 2022.
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Philipp Schillinger, Stefan Kohlbrecher, and Oskar von Stryk, "Human-Robot Collaborative High-Level Control with Application to Rescue Robotics", IEEE International Conference on Robotics and Automation (ICRA), Stockholm, Sweden, May 2016.
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Stefan Kohlbrecher et al. "A Comprehensive Software Framework for Complex Locomotion and Manipulation Tasks Applicable to Different Types of Humanoid Robots." Frontiers in Robotics and AI 3 (2016): 31.
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Alberto Romay et al., “Collaborative autonomy between high-level behaviors and human operators for remote manipulation tasks using different humanoid robots,” Journal of Field Robotics, September 2016.