How does your robot know which way is forward? Is it in the x-axis, or y-axis? Positive or negative?

In this video we are going to look at the convention for coordinate frames. This convention is specified in REP 103 – Standard Units of Measure and Coordinate Conventions. In this part 1, we will look at the coordinate frame for linear motion.

RELATED LINKS

▸ REP 103
▸ ROS Development Studio (ROSDS)
▸ Robot Ignite Academy

Step 1. Create a project in ROS Development Studio(ROSDS)

According to the REP03 standard, the positive x means forward, the positive y means left and positive z means up. Although you can check the REP03 standard with your hand, it’s better to see how it works in ROS. The ROSDS helps you follow our tutorial in a fast pace without dealing without setting up an environment locally. If you haven’t had an account yet, you can create a free account here. Let’s launch a AR Drone simulation from Simulations->AR.Drone.

Step 2. Check it with the command

You can publish to the cmd_vel topic to move the drone with the following command.

rostopic pub -1 /cmd_vel [TAB] [TAB]

When you press tab while typing the command, ROS will do auto-compilation for you. You can see that it directly find the message type is called geometry msgs/Twist and there are linear x y z and angular x y x value in this message. To check it, change the value of linear x to some positive value. The drone will move forward like the REP03 standard said. You can also send to the linear y and z to check if it’s true. In the next post. We will talk about the angular part.

Want to learn more?

If you want to learn more about ROS, please check our Robot Ignite Academy.

Edit by: Tony Huang

Feedback

Did you like this video? Do you have questions about what is explained? Whatever the case, please leave a comment on the comments section below, so we can interact and learn from each other.

If you want to learn about other ROS topics, please let us know on the comments area and we will do a video about it.