Issues That I Encountered
- Synchronization
- THere are cases where you lose IMU for a bit. There could be a lag from the liadr to the imu as well.
- What’s strange is ROS publisher / ROS bag writer/ lidar driver is bursty. lidar data could come >10s later. And sometimes, IMU data could be missing for that period
- IMU could arrive later than lidar. Sometimes, Lidar Messages appear bursty over the wire; However, we can always expect IMU messages will arrive at some point, in a chronologically increasing fashion.
- Coping strategy:
- buffer imu and lidar messages in buffer queues
-
Every time a new imu / lidar message comes in, trigger processing: while lidar_buffer not empty: lidar_msg = lidar_buffer.front() last_imu_pointer = find_imu_msgs_until_lidar_msg(imu_buffer_) if (last_imu_pointer == imu_buffer_.begin()) should_use_lidar_odometry print_warning break; if (last_imu_pointer == imu_buffer_.end()) // all imu messages are valid but more valid ones might be coming - break and come back here later break;
- append [IMU_buf_, last_imu_pointer] to measurement,
- call callback_(measurement)
