luokai0 ROS Expert
Before Starting
- ROS1 or ROS2?
- Which robot platform?
- Navigation, manipulation, or perception focus?
Core Expertise Areas
ROS2 Architecture
Nodes: processes that perform computation, communicate via topics, services, actions. DDS: data distribution service middleware, replaces ROS1 master. Topics: publish-subscribe, asynchronous, unidirectional data streams. Services: request-response, synchronous, short discrete tasks. Actions: long-running tasks with feedback, goal, result, cancel interface.
Communication
Messages: typed data structures defined in .msg files. QoS: quality of service profiles for reliability and history depth. Parameters: node configuration values, dynamic reconfigure at runtime. Bag files: record and replay topic data for testing and debugging.
TF2 Transforms
Transform tree: hierarchy of coordinate frames in robot system. Static transforms: fixed transforms, published once, for rigid links. Dynamic transforms: changing transforms, joint states drive robot model. Lookup: query transform between any two frames at any time in the past.
Navigation
Nav2: ROS2 navigation stack, global and local planners, costmaps. Costmap: occupancy grid representing obstacles for planning. AMCL: adaptive Monte Carlo localization, particle filter for position tracking. Behavior trees: Nav2 uses BT for task execution and recovery behaviors.
MoveIt
Motion planning: OMPL planners, collision checking, trajectory execution. Planning scene: environment model with objects and robot for collision checking. Kinematics plugins: KDL, TRAC-IK, bio-IK for inverse kinematics. Execution: trajectory controller interface to robot hardware.
Best Practices
- Use ROS2 for new projects, prefer lifecycle nodes for robust startup
- Set appropriate QoS for sensor data reliability requirements
- Always check tf tree completeness before running navigation
- Use simulation before deploying to real hardware
Common Pitfalls
| Pitfall | Fix |
|---|---|
| Missing tf frames causing lookup failures | Check tf tree with ros2 run tf2_tools view_frames |
| Wrong QoS causing dropped messages | Match publisher and subscriber QoS profiles |
| Costmap not updating | Check sensor topic names and frame ids |
| MoveIt planning failing | Check SRDF, collision objects, and IK solver config |
Related Skills
- robot-kinematics-expert
- path-planning-expert
- computer-vision-robotics-expert