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HI @pap-x

In the urdf: https://github.com/lihuang3/ur5_ROS-Gazebo/blob/master/src/ur_description/ur5.urdf.xacro

Wrist3 is connected to EE with a fixed joint

<joint name="${prefix}ee_fixed_joint" type="fixed">
  <parent link="${prefix}wrist_3_link" />
  <child link = "${prefix}ee_link" />
  <origin xyz="0.0 ${wrist_3_length} 0.0" rpy="0.0 0.0 ${pi/2.0}" />
</joint>

Vacuum gripper is connected to EE with a revolute link

<joint name="gripper_joint" type="revolute">
  <axis xyz="1 0 0" />
  <parent link="ee_link" />
  <child link="vacuum_gripper" />
  <origin rpy="0 1.5708 0" xyz="0.01 0.0125 0" />
  <limit effort="50" velocity="50" lower="0" upper="0" />
  <dynamics damping="0.0" friction="10"/>
</joint>

The vacuum grippers are small cylinders attached to EE link. If you want to modify the behaviour, you will need to modify the URDF for Wrist3 to have a revolute joint with EE link.

HI @pap-x

In the urdf: https://github.com/lihuang3/ur5_ROS-Gazebo/blob/master/src/ur_description/ur5.urdf.xacro

Wrist3 is connected to EE with a fixed joint

<joint name="${prefix}ee_fixed_joint" type="fixed">
  <parent link="${prefix}wrist_3_link" />
  <child link = "${prefix}ee_link" />
  <origin xyz="0.0 ${wrist_3_length} 0.0" rpy="0.0 0.0 ${pi/2.0}" />
</joint>

Vacuum gripper is connected to EE with a revolute link

<joint name="gripper_joint" type="revolute">
  <axis xyz="1 0 0" />
  <parent link="ee_link" />
  <child link="vacuum_gripper" />
  <origin rpy="0 1.5708 0" xyz="0.01 0.0125 0" />
  <limit effort="50" velocity="50" lower="0" upper="0" />
  <dynamics damping="0.0" friction="10"/>
</joint>

The vacuum grippers are small cylinders attached to EE link. If you want to modify the behaviour, you will need to modify the URDF for Wrist3 to have a revolute joint with EE link.URDF

HI @pap-x

In the urdf: https://github.com/lihuang3/ur5_ROS-Gazebo/blob/master/src/ur_description/ur5.urdf.xacro

Wrist3 is connected to EE with a fixed joint

<joint name="${prefix}ee_fixed_joint" type="fixed">
  <parent link="${prefix}wrist_3_link" />
  <child link = "${prefix}ee_link" />
  <origin xyz="0.0 ${wrist_3_length} 0.0" rpy="0.0 0.0 ${pi/2.0}" />
</joint>

Vacuum gripper is connected to EE with a revolute link

<joint name="gripper_joint" type="revolute">
  <axis xyz="1 0 0" />
  <parent link="ee_link" />
  <child link="vacuum_gripper" />
  <origin rpy="0 1.5708 0" xyz="0.01 0.0125 0" />
  <limit effort="50" velocity="50" lower="0" upper="0" />
  <dynamics damping="0.0" friction="10"/>
</joint>

The vacuum grippers are small cylinders attached to EE link.

A crude sketch:

EDIT: Disregard this: If you want to modify the behaviour, you will need to modify the URDF

Looking at the plugin one can appreciate how the force for each link in contact:

    ignition::math::Vector3d force = norm_force * diff.Pos().Normalize();
    links[j]->AddForce(force);

The force direction applied by the cylinders vacuum won’t change with the EE rotation.

For more information, please check this thread discussion: https://github.com/ros-simulation/gazebo_ros_pkgs/pull/389#discussion_r61185741

HI @pap-x

In the urdf: https://github.com/lihuang3/ur5_ROS-Gazebo/blob/master/src/ur_description/ur5.urdf.xacro

Wrist3 is connected to EE with a fixed joint

<joint name="${prefix}ee_fixed_joint" type="fixed">
  <parent link="${prefix}wrist_3_link" />
  <child link = "${prefix}ee_link" />
  <origin xyz="0.0 ${wrist_3_length} 0.0" rpy="0.0 0.0 ${pi/2.0}" />
</joint>

Vacuum gripper is connected to EE with a revolute linkjoint

<joint name="gripper_joint" type="revolute">
  <axis xyz="1 0 0" />
  <parent link="ee_link" />
  <child link="vacuum_gripper" />
  <origin rpy="0 1.5708 0" xyz="0.01 0.0125 0" />
  <limit effort="50" velocity="50" lower="0" upper="0" />
  <dynamics damping="0.0" friction="10"/>
</joint>

The vacuum grippers are small cylinders attached to EE link.

A crude sketch:

EDIT: Disregard this: If you want to modify the behaviour, you will need to modify the URDF

Looking at the plugin one can appreciate how the force for each link in contact:

    ignition::math::Vector3d force = norm_force * diff.Pos().Normalize();
    links[j]->AddForce(force);

The force direction applied by the cylinders vacuum won’t change with the EE rotation.

For more information, please check this thread discussion: https://github.com/ros-simulation/gazebo_ros_pkgs/pull/389#discussion_r61185741