# Robot not able to rotate when following "Driving TurtleBot via ROS2 messages" tutorial **URL:** \ **Category:** Isaac Sim\ **Tags:** isaac-sim-v4-5-0\ **Created:** [March 17, 2025, 11:39am UTC](https://forums.developer.nvidia.com/t/robot-not-able-to-rotate-when-following-driving-turtlebot-via-ros2-messages-tutorial/327346 "2025-03-17T11:39:44Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![siddharth.amaranth](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@siddharth.amaranth](https://forums.developer.nvidia.com/u/siddharth.amaranth)\ **Post date:** [March 17, 2025, 11:39am UTC](https://forums.developer.nvidia.com/t/robot-not-able-to-rotate-when-following-driving-turtlebot-via-ros2-messages-tutorial/327346/1 "2025-03-17T11:39:44Z")
### Isaac Sim Version 4.5.0 ### Operating System Ubuntu 22.04 ## Topic Description ### Detailed Description I followed this tutorial [Turtlebot3](https://docs.isaacsim.omniverse.nvidia.com/latest/ros2_tutorials/tutorial_ros2_drive_turtlebot.html) 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 ```auto 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 ```auto 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. ![image](https://global.discourse-cdn.com/nvidia/original/4X/0/c/4/0c4d306d8514690aa0d485b548f221ccc9401f78.png) Can someone please help me to control the forklift? For reference, this is the forklift I’m using [forklift\_c](https://omniverse-content-production.s3-us-west-2.amazonaws.com/Assets/Isaac/4.5/Isaac/Robots/Forklift/forklift_c.usd). ---
**Author:** ![zhengwang](https://sea2.discourse-cdn.com/nvidia/user_avatar/forums.developer.nvidia.com/zhengwang/32/256893_2.png) [@zhengwang](https://forums.developer.nvidia.com/u/zhengwang)\ **Post date:** [March 17, 2025, 9:54pm UTC](https://forums.developer.nvidia.com/t/robot-not-able-to-rotate-when-following-driving-turtlebot-via-ros2-messages-tutorial/327346/3 "2025-03-17T21:54:49Z")
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. ---
**Author:** ![siddharth.amaranth](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@siddharth.amaranth](https://forums.developer.nvidia.com/u/siddharth.amaranth)\ **Post date:** [March 18, 2025, 6:43am UTC](https://forums.developer.nvidia.com/t/robot-not-able-to-rotate-when-following-driving-turtlebot-via-ros2-messages-tutorial/327346/4 "2025-03-18T06:43:54Z")
Yes, I adjusted the parameters of the Differential Controller. This the parameters in my case ![image](https://global.discourse-cdn.com/nvidia/original/4X/2/5/4/254e74249e009248c5d39eb5ab38ad346adb8a98.png) 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 ---
**Author:** ![zhengwang](https://sea2.discourse-cdn.com/nvidia/user_avatar/forums.developer.nvidia.com/zhengwang/32/256893_2.png) [@zhengwang](https://forums.developer.nvidia.com/u/zhengwang)\ **Post date:** [March 19, 2025, 8:55pm UTC](https://forums.developer.nvidia.com/t/robot-not-able-to-rotate-when-following-driving-turtlebot-via-ros2-messages-tutorial/327346/5 "2025-03-19T20:55:26Z")
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 ![image](https://global.discourse-cdn.com/nvidia/original/4X/5/b/2/5b29b0560540af3ca1f31c1853254df901925d8f.png) differential controller: ![image](https://global.discourse-cdn.com/nvidia/original/4X/8/5/d/85dfe3f1c8a0d0522817547413ea667cd88741bd.png) articulation controller: ![image](https://global.discourse-cdn.com/nvidia/original/4X/a/e/f/aef028aad298b68405a11926e1f55e34a29a6f7f.png) If you can share your usd, I can take a closer look. ---
**Author:** ![siddharth.amaranth](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@siddharth.amaranth](https://forums.developer.nvidia.com/u/siddharth.amaranth)\ **Post date:** [March 20, 2025, 8:43am UTC](https://forums.developer.nvidia.com/t/robot-not-able-to-rotate-when-following-driving-turtlebot-via-ros2-messages-tutorial/327346/6 "2025-03-20T08:43:09Z")
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!! ---
**Author:** ![zhengwang](https://sea2.discourse-cdn.com/nvidia/user_avatar/forums.developer.nvidia.com/zhengwang/32/256893_2.png) [@zhengwang](https://forums.developer.nvidia.com/u/zhengwang)\ **Post date:** [March 20, 2025, 5:40pm UTC](https://forums.developer.nvidia.com/t/robot-not-able-to-rotate-when-following-driving-turtlebot-via-ros2-messages-tutorial/327346/7 "2025-03-20T17:40:29Z")
Great! Here is the formula for differential controller so it looks like dt doesn’t affect it. ![image](https://global.discourse-cdn.com/nvidia/original/4X/9/5/4/95460242e84914e31b15de93fa5bf3778a2df013.png) Document: [[isaacsim.robot.wheeled\_robots] Wheeled Robots — Isaac Sim](https://docs.isaacsim.omniverse.nvidia.com/latest/py/source/extensions/isaacsim.robot.wheeled_robots/docs/index.html#isaacsim.robot.wheeled_robots.controllers.DifferentialController) ---
**Author:** ![siddharth.amaranth](https://developer.download.nvidia.com/images/forums/profile-default-devtalk-84.png) [@siddharth.amaranth](https://forums.developer.nvidia.com/u/siddharth.amaranth)\ **Post date:** [March 24, 2025, 6:23am UTC](https://forums.developer.nvidia.com/t/robot-not-able-to-rotate-when-following-driving-turtlebot-via-ros2-messages-tutorial/327346/8 "2025-03-24T06:23:31Z")
That’s great then. Thank you for your help. ---
**Author:** ![system](https://sea2.discourse-cdn.com/nvidia/user_avatar/forums.developer.nvidia.com/system/32/68080_2.png) [@system](https://forums.developer.nvidia.com/u/system)\ **Post date:** [April 7, 2025, 6:24am UTC](https://forums.developer.nvidia.com/t/robot-not-able-to-rotate-when-following-driving-turtlebot-via-ros2-messages-tutorial/327346/9 "2025-04-07T06:24:31Z")
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