# Unit 2 Exercise 2.7.1 - Joints are not responding

**URL:** <https://get-help.theconstruct.ai/t/unit-2-exercise-2-7-1-joints-are-not-responding/23586>\
**Category:** ROS2 Control Framework\
**Created:** [April 7, 2023, 1:06pm UTC](https://get-help.theconstruct.ai/t/unit-2-exercise-2-7-1-joints-are-not-responding/23586 "2023-04-07T13:06:00Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![HusamArdah](https://get-help.theconstruct.ai/letter_avatar_proxy/v4/letter/h/edb3f5/32.png) [@HusamArdah](https://get-help.theconstruct.ai/u/HusamArdah)\
**Post date:** [April 7, 2023, 1:06pm UTC](https://get-help.theconstruct.ai/t/unit-2-exercise-2-7-1-joints-are-not-responding/23586/1 "2023-04-07T13:06:00Z")

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When I launched the my\_robot.launch.py the first time when going through the exercise, I was able to modify joint1 of the robot. However, when I added the modifications to joint2 in the files for exercise 2.7.1 and ran the launch file again, it launched successfully but did not update the joint values. I just get this message on the terminal:

 ![image](https://get-help.robotigniteacademy.com/uploads/default/original/2X/8/8cd95f3c5834ffa191d6ebddf3ccd3e4168e478f.png)

I made sure that the code I copied is similar as in the notebook. Anything I am doing wrong?

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**Author:** ![rzegers](https://get-help.theconstruct.ai/user_avatar/get-help.theconstruct.ai/rzegers/32/7010_2.png) [@rzegers](https://get-help.theconstruct.ai/u/rzegers)\
**Post date:** [April 12, 2023, 10:15am UTC](https://get-help.theconstruct.ai/t/unit-2-exercise-2-7-1-joints-are-not-responding/23586/2 "2023-04-12T10:15:23Z")

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Hello @HusamArdah,

The message that you are seeing is the expected message that you get when commanding a position to the robot arm. I assume that your problem is that the robot is not moving in simulation, is this correct?

Perhaps your robot is already at the indicated position, and therefore this command does not move the robot?  
Experiment with sending various different values and observe the robot’s motion:

For instance:

```auto
ros2 topic pub /forward_position_controller/commands std_msgs/msg/Float64MultiArray "data:
- 1.57
- -1.57" -1

```

and then:

```auto
ros2 topic pub /forward_position_controller/commands std_msgs/msg/Float64MultiArray "data:
- -1.57
- 0.79" -1

```

Do you see the robot move now?

Cheers,

Roberto

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<div class="post-metadata">

**Author:** ![HusamArdah](https://get-help.theconstruct.ai/letter_avatar_proxy/v4/letter/h/edb3f5/32.png) [@HusamArdah](https://get-help.theconstruct.ai/u/HusamArdah)\
**Post date:** [April 17, 2023, 12:30pm UTC](https://get-help.theconstruct.ai/t/unit-2-exercise-2-7-1-joints-are-not-responding/23586/3 "2023-04-17T12:30:36Z")

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Unfortunately the robot did not respond.

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<div class="post-metadata">

**Author:** ![HusamArdah](https://get-help.theconstruct.ai/letter_avatar_proxy/v4/letter/h/edb3f5/32.png) [@HusamArdah](https://get-help.theconstruct.ai/u/HusamArdah)\
**Post date:** [April 17, 2023, 12:35pm UTC](https://get-help.theconstruct.ai/t/unit-2-exercise-2-7-1-joints-are-not-responding/23586/4 "2023-04-17T12:35:08Z")

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I also made sure that my config and launch files were the same as provided. Is there any code file I should provide you?

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**Author:** ![rzegers](https://get-help.theconstruct.ai/user_avatar/get-help.theconstruct.ai/rzegers/32/7010_2.png) [@rzegers](https://get-help.theconstruct.ai/u/rzegers)\
**Post date:** [April 18, 2023, 8:30am UTC](https://get-help.theconstruct.ai/t/unit-2-exercise-2-7-1-joints-are-not-responding/23586/5 "2023-04-18T08:30:29Z")

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Hello @HusamArdah,

yes I would need to look at your code, could you please post here the contents of the `rrbot.xacro` file located here: ` ~/ros2_ws/src/ros2_control_course/unit2/rrbot_unit2/urdf`. Additionally I need to have a look at your **controller\_configuration.yaml** file, located here `~/ros2_ws/src/my_robot_bringup/config`.

Also, from you title I understand that you are doing exercise 2.7.1. , but does everything explained under Section “2.6 Test your ros2\_control pipeline”, work?

Thank you,

Roberto

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**Author:** ![system](https://get-help.theconstruct.ai/uploads/default/original/2X/9/9d3ce8305cc0d0d9b6e07d15767a6f245c526f1b.jpeg) [@system](https://get-help.theconstruct.ai/u/system)\
**Post date:** [April 25, 2023, 8:30am UTC](https://get-help.theconstruct.ai/t/unit-2-exercise-2-7-1-joints-are-not-responding/23586/6 "2023-04-25T08:30:32Z")

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