differential transmission with ros_canopen, HOW to?

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Hello ROS Community,

I have already tried to ask a similar question here: #q304832, however no answer was received so i am trying to ask again from a different perspective.

I am working on the control of a 5DOF robot, where the last two joints (joint_4 and joint_5) create a differential gear/transmission. I found on the official ros_control git an URDF sample, which seems to describe the differential transmission as:

  <transmission name="differential_trans">
    <type>transmission_interface/DifferentialTransmission</type>
    <joint name="joint_4">
      <role>joint2</role>
      <hardwareInterface>hardware_interface/PositionJointInterface</hardwareInterface>
    </joint>
    <joint name="joint_5">
      <role>joint1</role>
      <hardwareInterface>hardware_interface/PositionJointInterface</hardwareInterface>
    </joint>
    <actuator name="actuator_4">
      <role>actuator1</role>
      <mechanicalReduction>1</mechanicalReduction>
    </actuator>
    <actuator name="actuator_5">
      <role>actuator2</role>
      <mechanicalReduction>-1</mechanicalReduction>
    </actuator>
  </transmission>

I tried to test the above code in my URDF, but still joint_4 drives ONLY the fourth motor and joint_5 drives ONLY the fifth motor, however moving one joint should actuate both motors.

I shall mention, that the motors are controlled through ros_canopen. This means that for every joint (joint_1-joint_5) I assigned a canopen id, i.e., a motor driver in the configuration yaml file, For example:

nodes:
  - name: joint_4
     id: 1
     eds_file: ...
  - name: joint_5
    id: 85
    eds_file: ...

It looks like the motors are directly connected with the joints, however i would like to connect them with the actuator outputs of the DifferentialTransmission. (The joint is the node, and not the actuator.)

Did anyone work with this transmission type? How shall it be set up?

Thanks in advance!