ROS SIM Time

This section introduces the method to synchronize MORAI SIM Time with ROS TIME.

Reference page : http://wiki.ros.org/Clock, http://wiki.ros.org/roscpp/Overview/Time

• ROS Time System

  • ROS nodes use ROS Time to maintain a synchronized flow of time when interacting.

  • ROS Time is essential for operation cycles, message synchronization confirmation, and more.

    • The time included in the message's header is used to verify synchronization between messages.

  • The ROS Time default setting uses the operating PC Time.

  • When use_sim_time is enabled and the /clock topic is published, the /clock topic is used as ROS Time instead of the PC Time.

• When integrating ROS Time in MORAI SIM Time Management: Use use_sim_time.

  • If use_sim_time is not enabled, ROS time and MORAI SIM time are not synchronized.

    • (e.g., Sensor Message subscribe node)

      • In MORAI SIM, the defined simulation time is entered in the Sensor Message header.

      • ROS nodes access the current time information by calling ROSTIME.

      • Since ROSTIME and MORAI SIM Time are different, normal operation is impossible.

  • MORAI SIM Time is published on the /clock topic to synchronize ROSTIME with the simulator.

• Considerations for Development

  • When publishing a topic, set the IP/Port → Send it to all IPs using ROS.

    • Publish the /clock topic to all ROS IPs receiving data from the simulator.

  • The timing and frequency of topic publication need to be determined.

    • Automatically publish the /clock topic when Time Management runs.

    • 1ms interval.

• User Guide (ROS)

  • After running roscore, set use_sim_time to true in the ROS parameters.

    • CODE

      rosparam set use_sim_time true

  • Set to publish the /clock topic in MORAI SIM.