Gazebo simulation not working

[davizinho5]

Hello,

I'm trying to use the universal packages in Ubuntu 18.04 and ROS-melodic.

I installed the packages from source and downloaded all the dependencies manually.

When I launched the Gazebo simulation, first it complained about not having control parameters in the PIDs. I solved it following the last comment in issue #397 , adding some gains.

I don't see any error in the launch log, only the controller manager and spawner "finishing cleanly" make me make me doubt if this message is correct. You can see it below:

[ros_control_controller_manager-9] process has finished cleanly log file: /home/amper/.ros/log/607db2d0-82e0-11e9-bdb8-f07bcb7ff7ac/ros_control_controller_manager-9*.log Loaded 'arm_controller' Loaded 'joint_state_controller' Started ['arm_controller'] successfully Started ['joint_state_controller'] successfully [joint_state_controller_spawner-7] process has finished cleanly log file: /home/amper/.ros/log/607db2d0-82e0-11e9-bdb8-f07bcb7ff7ac/joint_state_controller_spawner-7*.log [arm_controller_spawner-8] process has finished cleanly log file: /home/amper/.ros/log/607db2d0-82e0-11e9-bdb8-f07bcb7ff7ac/arm_controller_spawner-8*.log

Then, the arm looks weird to me:

Finally, when I try to move it by commanding a trajectory, it looks like it tries to moves but it cannot:

rostopic pub /arm_controller/command trajectory_msgs/JointTrajectory "header:
  seq: 0
  stamp:
    secs: 0
    nsecs: 0
  frame_id: ''
joint_names:
 ['shoulder_pan_joint', 'shoulder_lift_joint', 'elbow_joint', 'wrist_1_joint', 'wrist_2_joint', 'wrist_3_joint']
points:
- positions: [2,0,0,0,0,0]
  velocities: []
  accelerations: []
  effort: []
  time_from_start: {secs: 2, nsecs: 0}" 

Anyone knows why this happens?
Could it be that the gains are not appropiate? How can I know when they are?
If it is because the controllers die, can you imagine why?

Best,

[miguelprada]

Could it be that the gains are not appropiate? How can I know when they are?

It could be, yes. What happens if you revert your fix to the the PID error and try to move the robot?

If it is because the controllers die, can you imagine why?

It's not the controllers that are dying, but the process that takes care of spawning them. That's perfectly normal.

[davizinho5]

Hi, thanks for the answer.

I reverted it and it works. I'm going to point this out in #397 because the answers are quite confusing.
My problem was that yesterday I tried a movement that made the arm collision with the floor, and I understood that a similar problem was happening.

However, following the instructions in here (http://wiki.ros.org/ur_gazebo) for working with a simulated robot in gazebo (with limited joint position) and planning with moveit, I still find problems.

This first launch works fine:
roslaunch ur5_moveit_config ur5_moveit_planning_execution.launch sim:=true

Then, the second launch opens the rviz + moveit interface but the robot is in a very strange pose. Besides, when I try to move the goal arrows, it has a strange bahaviour, like if all the links where placed in the same point.
roslaunch ur5_moveit_config moveit_rviz.launch config:=true

Do you know why this might happen?

[gavanderhoorn]

Then, the second launch opens the rviz + moveit interface but the robot is in a very strange pose.

See #374, specifically: #374 (comment).

---

off-topic: I really wish this would be fixed upstream, as it's getting annoying having to support users with this every time.

[davizinho5]

Solved, thanks a lot.
Sorry for not finding the solution in the issues before asking.

[gavanderhoorn]

My comment was not directed at you. It was more a general comment on the fact that the issue with urdfdom and Melodic/Ubuntu Bionic has been around for almost 2 years now and still hasn't been resolved.

[davizinho5]

No worries, I didn't take it personally.
But I can understand that sometimes the solution should be on the side of the ones that are making the questions.

[ar-i-enterprise]

how did you fixed ? please i need help with this error..

[swagatk]

@davizinho5 - HI, can you please let me know how did you figure out the right PID values for the UR5 simulator? How did you fix the PID error?

I reverted it and it works. I'm going to point this out in #397 because the answers are quite confusing.

Can you please elaborate on this - regarding what values did you use. I added the following content to my 'ur_gazebo/controller/arm_controller_ur5.yaml'

gazebo_ros_control: pid_gains: shoulder_pan_joint: {p: 100.0, i: 0.01, d: 10.0} shoulder_lift_joint: {p: 100.0, i: 0.01, d: 10.0} elbow_joint: {p: 100.0, i: 0.01, d: 10.0} wrist_1_joint: {p: 100.0, i: 0.01, d: 10.0} wrist_2_joint: {p: 100.0, i: 0.01, d: 10.0} wrist_3_joint: {p: 100.0, i: 0.01, d: 10.0}
It does not show me any error but I am not able to move the arm by publishing at the rostopic, exactly as you mentioned in your post. But, I could not understand what did you fix the problem.

I will be grateful for your help.

[davizinho5]

Hi,

I did not use any specific gain.
This is the message that explains what I really had to do, it had nothing to do with the gains:

#427 (comment)

[swagatk]

So basically, you are using moveit to control the robot arm. Thanks. This helps. I was spending a lot of time tuning the gains. Regards, Swagat

…

On Sat, Sep 19, 2020 at 9:17 AM davizinho5 ***@***.***> wrote: Hi, I did not use any specific gain. This is the message that explains what I really had to do, it had nothing to do with the gains: #427 (comment) <#427 (comment)> — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#427 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABHBTD3K4RJ2K2ERF5O5KMDSGRSLDANCNFSM4HRFYWIQ> .