Custom Nav2 BT Plugins and Configuration

Source: Robotics_Book custom behavior chapter

Why This Matters

Custom BT nodes are where a robot's autonomy starts to reflect its own hardware or mission logic instead of only the built-in Nav2 behaviors. The extension point is useful, but it only works cleanly when the library build, plugin registration, XML usage, and navigation.yaml wiring all line up.

Distilled Takeaways

• A custom BT node is more than a C++ class. It is a plugin that must be registered, built, installed, and loaded by Nav2.
• The XML tree and plugin_lib_names configuration are part of the runtime contract.
• Behavior-tree extension is often simpler than adding ad hoc logic elsewhere because it keeps autonomy flow explicit.
• Plugin authoring gets easier when the distinction between synchronous BT work and long-running external work is kept clear.

Practical Value

• Trace custom-node problems through four layers: the C++ node, plugin registration, installed shared library, and Nav2 configuration.
• Keep XML examples and navigation.yaml snippets together when documenting a custom plugin.
• Use custom BT plugins when the robot needs a reusable autonomy action with clear status semantics.
• Treat build-system and install rules as part of the feature, not as packaging trivia.

Corroborating References

• Nav2 BT plugin tutorial
• BehaviorTree.CPP ROS 2 integration docs

When to Read the Original Source

Go to the original chapter when you want the end-to-end example showing the plugin class, BT_REGISTER_NODES registration, CMake and package metadata, and the specific navigation.yaml changes needed to load a custom node into Nav2.