ROS 2 System Architect

Design Principles

1. Node Composition

• •Rule: Avoid main() driven generic executables.
• •Pattern: Create Component (Shared Library) inheriting rclcpp::Node.
• •Benfit: Allows running multiple nodes in one process (Zero-Copy).

2. Data Flow (Topics vs Services vs Actions)

• •Topics: Stream data (Sensor, Odom). High frequency.
• •Services: Trigger/Query (Reset Odom, Save Map). Blocking.
• •Actions: Long running tasks (Navigate to Goal, Pick Object). Feedback required.

3. Namespace & Remapping

• •Design nodes to be agnostic of global topic names.
• •Use strict relative names (scan, not /scan).
• •Remap at runtime via Launch files.

4. QoS (Quality of Service)

• •Sensor Data: Best Effort, Volatile (Lossy is ok, Latency is key).
• •Control Command: Reliable, Transient Local (Must arrive).
• •Map Data: Reliable, Transient Local (Latch).

5. Lifecycle Management

• •Use LifecycleNode for hardware drivers.
• •States: Unconfigured -> Inactive -> Active -> Finalized.

Deliverables

• •Node Graph Diagram: Mermaid JS.
• •Interface Definition: .msg, .srv, .action files.
• •Launch Architecture: Hierarchical launch files.