Hello all,

I get a strange result when using the ROS2 foxy diffdrivecontroller to publish odometry!

I am using a joystick controller node that publishes to the "diffbotbasecontroller/cmdvelunstamped" topic. Our real robot is rather heavy. So, it takes some initial joystick push for the robot to rotate around itself. Let's say, I have to push the joystick past 10% of its range for the robot to start rotating.

The problem is that when I push the joystick to 9%, while the robot is not rotating yet, the odometry topic is already showing angular rotation. If I keep the joystick at 9%, the odometry keeps increasing the rotation angle, whereas the real robot is not rotating at all! If I let go of the joystick (which goes back to 0 rotation command), the odometry rotation stops increasing.

Interestingly enough, the wheel encoders also DO NOT show any speed or change in wheel rotation angles, when the joystick is at 9%.

Question 1: Why is this happening?

Question 2: Can I force the diffdrivecontroller odometry publisher to ignore the command and just rely on wheel encoders?

Question 3: The diffdrivecontroller has a parameter "open_loop: true" in the YAML config file. I have not found any mention of that in the documentations. What does that do?

Thanks so much for your help in advance!