Robotiq gripper joints do not move as expected in Rviz

[planetceres]

Using test_mara_model.launch to launch RViz and the joint state publisher, the joints of the gripper do not move in a coordinated manner as shown in the screenshots below.

How can the Robotiq gripper be properly used in simulation so that all joints move together and do not become detached from one another?

[vmayoral]

Thanks for reporting @planetceres, let us have a look and get back to you.

[vmayoral]

@ahcorde, maybe worth reviewing if this also applies to https://github.com/AcutronicRobotics/MARA in ROS 2?

[ahcorde]

This gripper has a parallel mechanism. URDFs are not friends of this kind of circular link connections. Each finger is a circular link.

I have to use a trick, the URDF only contain 3 joints, but in Gazebo cointains the 4 joints. Because I use the tag gazebo.

In ROS 2.0 for sure is happening the same thing. because URDF are pretty similar. the main differences are the plugins that the robot make use (ROS or ROS 2.0)

It's a problem of the URDF library. Not allowing to create circular link connections.

Maybe I can fix this using the tag mimic

[ahcorde]

I have updated the URDFs. Now it's working. I will updated the rest of the things right away.

[vmayoral]

Thanks @ahcorde, please close it when you're done.

[ahcorde]

ROS 1

ROS 2.0 and rviz2

[planetceres]

Thanks for correcting this so quickly. However, after the update, the xacro XML will not load properly:

XML parsing error: mismatched tag: line 380, column 4
when processing file: /workspace/install_isolated/share/robotiq_140_gripper_description/urdf/robotiq_140.urdf.xacro
included from: /workspace/install_isolated/share/mara_description/urdf/mara_robot_gripper_140.urdf.xacro

Check that:
 - Your XML is well-formed
 - You have the xacro xmlns declaration: xmlns:xacro="http://www.ros.org/wiki/xacro"
Invalid <param> tag: Cannot load command parameter [robot_description]: command [/opt/ros/kinetic/lib/xacro/xacro --inorder /workspace/install_isolated/share/mara_description/urdf/mara_robot_gripper_140.urdf.xacro] returned with code [2]. 

The issue persists on both ROS Melodic and Kinetic.

[ahcorde]

which command are you launching in the terminal?

I will try to reproduce it

[planetceres]

roslaunch mara_description test_mara_model.launch

[ahcorde]

Solved:

you can also try with different grippers:

roslaunch mara_description test_mara_model.launch gripper:=140
roslaunch mara_description test_mara_model.launch gripper:=85
roslaunch mara_description test_mara_model.launch gripper:=hande