Troubleshooting Lidar

Under construction 🏗️

A common issue when building a localization system is having lidar drops. This can localization module output estimate to diverge from vehicle pose.

The symptoms:

• Output looks correct when vehicle is driving slowly (20kph) in a straight line
• High-frequency dynamics are not captured, so output diverges when taking a sharp 90deg+ turn or switching lanes at high speeds

The types:

• Consistently Lower frame rate
  • Easier to debug
• Random lidar drops

Potential causes:

• Networking
  • The router is saturated - Lidar messages are heavy bandwidth, a 128 channel lidar TODO LINK EXAMPLE publishes XYZI at GBps
• CPU contention
  • The CPU isn't powerful enough

Identifying it

• Finding offline it on bagfile
  • Use plotjuggler to plot the timestamp and look for ?
    • // show an example of with and without frame-drop
  • Can plotjuggler use custom code to plot for moving average frequency?
  • Use ros2 topic hz
• Finding on vehicle
  • ros2 topic check
  • deploy [[frequency monitors]]
  • deploy [[CPU monitors]]