nav2-architecture-overview

Nav2 architecture connects the planner, controller, and costmaps through lifecycle-managed servers orchestrated by the BT Navigator. The Behavior Tree dictates the control flow, routing goals to the Planner and Controller servers while they read shared costmap data.

The BT Navigator in the Nav2 navigation stack serves as the central orchestrator for system behavior. It executes Behavior Trees to coordinate the Planner and Controller servers, managing the data flow from initial goal reception to final velocity commands.

To trace the data flow from a navigation goal to cmd_vel in Nav2, follow the lifecycle transitions and topic subscriptions across the stack. Goals enter the BT Navigator, which calls the Planner and Controller servers, ultimately publishing velocity commands to the cmd_vel topic.

Changing a planner in Nav2 affects the control flow and safety checks because the BT Navigator dynamically routes execution based on the active server configuration. Different planners interact uniquely with shared costmaps, altering how the Controller server evaluates path safety.

You can visualize lifecycle management and the launch structure for nav2_bringup through a system architecture overview. This illustrates how lifecycle-managed servers transition between states and how component nodes are initialized and configured during the startup sequence.

You need to understand Nav2 component interactions for debugging when a robot fails to reach its goal or exhibits unexpected navigation behavior. Reasoning about the architecture helps isolate issues across the BT Navigator, Planner, Controller, and costmap data flows.