Implements node watchdog ROS2 node that monitors heartbeats from critical
systems and triggers safety fallback when motor driver is lost >2s.
Features:
- Monitor heartbeats from: balance, motor_driver, emergency, docking
- Alert on /saltybot/node_watchdog (JSON) if heartbeat lost >1s
- Safety fallback: zero cmd_vel if motor driver lost >2s
- Republish cmd_vel on /saltybot/cmd_vel_safe with safety checks
- 20Hz monitoring and publishing frequency
- Configurable heartbeat timeout thresholds
Heartbeat Topics:
- /saltybot/balance_heartbeat (std_msgs/UInt32)
- /saltybot/motor_driver_heartbeat (std_msgs/UInt32)
- /saltybot/emergency_heartbeat (std_msgs/UInt32)
- /saltybot/docking_heartbeat (std_msgs/UInt32)
- /cmd_vel (geometry_msgs/Twist)
Published Topics:
- /saltybot/node_watchdog (std_msgs/String) - JSON status
- /saltybot/cmd_vel_safe (geometry_msgs/Twist) - Safety-checked velocity
Package: saltybot_node_watchdog
Entry point: node_watchdog_node
Launch file: node_watchdog.launch.py
Tests: 20+ unit tests covering:
- Heartbeat reception and timeout detection
- Motor driver critical timeout (>2s)
- Safety fallback logic
- cmd_vel zeroing on motor driver loss
- Health status JSON serialization
- Multi-node failure scenarios
Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
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