Sensor output delayed

[olohyun]

Sometimes, the sensor output of IMU, lidar and camera is delayed during the simulation. Not only the 'ros2 topic echo', but also the subscriber of each codes receives the delayed data, and this makes the control of our vehicles unavailable.

Is there any methods to solve the delay? We have paused the simulator until ros2 receive all delayed sensor data, but the sensor are delayed again as soon as we resume the simulator.

While other sensors are delayed, the sensor output of "mbzirc_naive_3d_scanning_radar" (top-left side of the terminal) is not delayed. What is the difference?

[iche033]

It's hard to say where the delay is coming from. mbzirc_naive_3d_scanning_radar is operating at only 1hz while the other, e.g. imu, lidar, camera, are either operating at higher frequency or has a larger data packet to process. So the delay could be due to extra time spent copying / processing large msgs, e.g. in the ign-ros2 bridge, and how high the cpu load of the machine is. Delays could also be different between machines.

On the other hand, if the problem is about synchronizing times from different streams of data (some with delays, some without), one option is to use the ros message_filters package.