Robot not able to rotate when following "Driving TurtleBot via ROS2 messages" tutorial

[siddharth.amaranth]

Isaac Sim Version

4.5.0

Operating System

Ubuntu 22.04

Topic Description

Detailed Description

I followed this tutorial Turtlebot3 and it works great. I am able to control Turtlebot3 as expected.

Now, I’m trying to control a new robot(A Forklift) similar to this. So, I followed the same tutorial. Now, I’m able to control the forklift using linear velocity but I’m not able to do the same for angular velocity.

Ex:
In the case of forklift, this command works as expected

 ros2 topic pub /cmd_vel geometry_msgs/Twist '{linear: {x: 5, y: 0.0, z: 0.0}, angular: {x: 0.0, y: 0.0, z: 0.0}}'

while this doesn’t

ros2 topic pub /cmd_vel geometry_msgs/Twist '{linear: {x: 0.0, y: 0.0, z: 0.0}, angular: {x: 0.0, y: 0.0, z: 5}}'

Additional Information

What I’ve Tried

I’ve used the same action graph as the one from the tutorial, just changed a couple of joint names.

Can someone please help me to control the forklift?
For reference, this is the forklift I’m using forklift_c.

[zhengwang]

Hey @siddharth.amaranth! Since forklift_c is a different robot, did you adjust the parameters of Differential Controller node accordingly?
Also what is your maxAngularSpeed in Differential Controller? If it is smaller than 5 (in your case, you send a twist message with angular speed 5), then the robot cannot move.

[siddharth.amaranth]

Yes, I adjusted the parameters of the Differential Controller. This the parameters in my case

When I give a twist message with the angular speed, I can see the back wheels to be moving. So, I thought I should input all the joint_names to the Articulation Controller node but then I got this issue with the shapes

[Warning] [omni.graph.core.plugin] /root/ActionGraph/articulation_controller: [/root/ActionGraph] OmniGraph Warning: shape mismatch: value array of shape (1,2) could not be broadcast to indexing result of shape (1,4)

Due to which now none of the wheels are moving

[zhengwang]

Hi @siddharth.amaranth! I noticed that the dt in your differential_controller is 0. Did you connect Delta Seconds in On Playback Tick to dt?

I followed the tutorial but with forklift_c (with left/right back wheel joints), but I am not able to reproduce your issue.

Here is my action graph

differential controller:

articulation controller:

If you can share your usd, I can take a closer look.

[siddharth.amaranth]

I looked at my usd file again and I noticed that the ground wasn’t even and it has many bumps in it. The wheels were getting stuck in them and that’s why the forklift wasn’t rotating. I changed the position and now it works as expected. I have my action graphs as the same as yours but I’m getting dt as 0. Is it an issue?

Thank you so much for your help!!

[zhengwang]

Great!

Here is the formula for differential controller so it looks like dt doesn’t affect it.

Document: [isaacsim.robot.wheeled_robots] Wheeled Robots — Isaac Sim

[siddharth.amaranth]

That’s great then. Thank you for your help.