Discussion - Nav2 Introduction (Making a Mobile Robot Pt 16)

Blog post coming soon

This is the discussion topic for the video and blog post linked above. Please keep all replies relevant to the content, otherwise create a new topic.

Hi
I’m having troubles making the robot turn when i send a goal in rviz, the robot do well going straight but he struggles when he turn, I tried tunning PID parameters and it goes better but not enough, I want to know if is there others parameters

Hey Marcelo, I’m sorry it took so long to reply. I don’t have a perfect answer but my thoughts are below and I hope they help :slight_smile:

My first suggestion would be to make sure you have a good understanding of how your robot responds to command velocities. E.g. if you send reasonable requests for forward and turn with the joystick (or manually publishing messages), can it achieve them ok? If not there are a few things to test and chase down there. Is that what you meant by the PID parameters?

To do that you should have a bit of a vibe for what you expect the robot/motors to be able to achieve.

Assuming the control side of things is ok, it then comes down to Nav2 which I have less experience in.
I’d recommend combing through the nav2_params.yaml (assuming you copied that the same as me) and looking for parameters that aren’t correct for your robot.

Particularly, I’d take a look at the controller_server section, then FollowPath under that, where you should see the following:

      min_vel_x: 0.0
      min_vel_y: 0.0
      max_vel_x: 0.26
      max_vel_y: 0.0
      max_vel_theta: 1.0
      min_speed_xy: 0.0
      max_speed_xy: 0.26
      min_speed_theta: 0.0
      # Add high threshold velocity for turtlebot 3 issue.
      # https://github.com/ROBOTIS-GIT/turtlebot3_simulations/issues/75
      acc_lim_x: 2.5
      acc_lim_y: 0.0
      acc_lim_theta: 3.2
      decel_lim_x: -2.5
      decel_lim_y: 0.0
      decel_lim_theta: -3.2

If those values seem wrong to you, have a go at changing them!

P.S. I also shot you a message through Patreon so please check that out when you get a chance. I find the Patreon message system to be a bit clunky sometimes and it’s easy to miss messages.