Technical Documentation: Navigation Screen

The Navigation Screen is the most complex component, integrating the MapView widget with ROS 2 Action Servers and navigation stacks.

Architecture

The Navigation module serves as the primary coordination layer between the user interface and the Nav2 (Navigation 2) stack running on the robot.

• File Path: lib/screens/navigation_screen.dart
• ROS Topics:
  • /map: Receives static environment data.
  • /goal_pose: Publishes the destination coordinate.
  • /initialpose: Publishes manual localization corrections.
  • /plan: Subscribes to the Nav2 global path.
  • /local_plan: Subscribes to local trajectory updates.

Interaction Logic

Map Tapping & Coordinate Transformation

The onTap logic converts screen coordinates (Pixels) into Map coordinates (Meters) using the map.info.resolution and map.info.origin.

Initial Pose Tools (Manual Localization)

Manual localization is performed via the /initialpose topic. The UI triggers a set of tools to publish the estimated coordinate and orientation.

Sidebar & System Integration

Map Loading

The Navigation screen integrates with the CustomSidebar to allow real-time map switching. When a map is selected, the UI triggers a ROS-level map load service.

Device Trigger Interactions

Users can initiate direct device commands (triggers) which are passed through to the ROS backend for low-level hardware interaction.

State Management & Pose Persistence

The system tracks the robot's current pose by subscribing to the tf (Transform Tree) map -> base_link transform.

Safety Systems

• Auto-Stop: Listens to the /estop topic; if triggered, the Navigation Screen visually locks and displays a critical warning overlay.