Diiferent calculation of velocity in odometry topic caused by timestamp type.

[shanpenghui]

ISSUE TEMPLATE ver. 0.4.0

1. Which TurtleBot3 platform do you use?

   • [ ] Burger
   • [ ] Waffle
   • [√ ] Waffle Pi

2. Which ROS is working with TurtleBot3?

   • [ ] ROS 1 Kinetic Kame
   • [ ] ROS 1 Melodic Morenia
   • [ ] ROS 1 Noetic Ninjemys
   • [ ] ROS 2 Dashing Diademata
   • [ ] ROS 2 Eloquent Elusor
   • [√ ] ROS 2 Foxy Fitzroy
   • [ ] etc (Please specify your ROS Version here)

3. Which SBC(Single Board Computer) is working on TurtleBot3?

   • [ ] Intel Joule 570x
   • [ ] Raspberry Pi 3B+
   • [ √] Raspberry Pi 4
   • [ ] etc (Please specify your SBC here)

4. Which OS you installed on SBC?

   • [ ] Raspbian distributed by ROBOTIS
   • [ ] Ubuntu MATE (16.04/18.04/20.04)
   • [√ ] Ubuntu preinstalled server (18.04/20.04)
   • [ ] etc (Please specify your OS here)

5. Which OS you installed on Remote PC?

   • [ ] Ubuntu 16.04 LTS (Xenial Xerus)
   • [ ] Ubuntu 18.04 LTS (Bionic Beaver)
   • [ √] Ubuntu 20.04 LTS (Focal Fossa)
   • [ ] Windows 10
   • [ ] MAC OS X (Specify version)
   • [ ] etc (Please specify your OS here)

6. Specify the software and firmware version(Can be found from Bringup messages)

   • Software version: [foxy-devel]
   • Firmware version: [foxy-devel]

7. Specify the commands or instructions to reproduce the issue.

   • ros2 launch turtlebot3_bringup robot.launch.py

8. Copy and Paste the error messages on terminal.

   • The output of velocity in odometry is zero.

9. Please describe the issue in detail.

   • HERE I'm doing the job that integrate the odom and imu. But the result seems something get wrong when I fuse the odometry data. So I check the odometry and found that the timestamp format is the reason. The origin code is below in turtlebot3_node/src/odometry.cpp

 static rclcpp::Time last_time = joint_state_msg->header.stamp;
 rclcpp::Duration duration(joint_state_msg->header.stamp.nanosec - last_time.nanoseconds());

And the velocity output is zero. But the output is correct when I change the type from rclcpp::Time to builtin_interfaces::msg::Time.

  static builtin_interfaces::msg::Time last_time = joint_state_msg->header.stamp;
  rclcpp::Duration duration(joint_state_msg->header.stamp.nanosec - last_time.nanosec);

There are two functions used that type: joint_state_callback and joint_state_and_imu_callback.

Please check it if I get something missed or wrong.

Thank you very much.

[ROBOTIS-Ashe]

Hi @shanpenghui . Thank you for your questions.

rclcpp::Time is a function Initializes the time values ​​for seconds and nanoseconds individually. But builtin_interfaces::msg::Time is of type msg. Please refer to the link below for more details.

• rclcpp::Time Class Reference

Also, it is an image of /odom & /joint_states topic when publishing cmd_vel to turtlebot3 burger

• /joint_states

• /odom

Thank you for your reference.