Joint force-torque sensor

[chapulina]

We should port Gazebo-classic's ForceTorqueSensor to Ignition. That sensor attaches to a joint and publishes force/torque data to a topic. The Force/Torque Sensor tutorial provides a lot of context.

[nlamprian]

I thought I'd give this a go, but I need some help configuring the workspace, given that the sdf class for the force-torque sensor is in sdformat11.

I assume I target Edifice. I check out the relevant versions, or main if the branches do not exist yet. Then the sdformat dependencies (in ign-sensors, ign-physics, and ign-gazebo) must be bumped up. At this point I get errors

/home/nlamprian/ignition_master_ws/src/ign-gazebo/src/Conversions.cc:284:52: error: ‘const class sdf::v11::Material’ has no member named ‘FilePath’
  284 |           asFullPath(workflow->MetalnessMap(), _in.FilePath()));

which means sdformat master needs to be updated (d03dba22e).

Am I approaching this correctly? And who deals with it?

[chapulina]

the sdf class for the force-torque sensor is in sdformat11.
I assume I target Edifice.

Yeah that's the eventual correct combination, but as you noticed, we're currently pending the upgrade to SDF11 for the entire stack, tracked here: gazebo-tooling/release-tools#360.

Until then, the quickest solution could be to backport gazebosim/sdformat#393 to sdf10 so that you can work with that until we bump to SDF11. CC @azeey

[chapulina]

we're currently pending the upgrade to SDF11 for the entire stack

The main branch is already depending on SDF 11

[keyan]

Now that gazebosim/sdformat#393 has been merged, what work is remaining to resolve this issue?

[chapulina]

what work is remaining to resolve this issue?

I think it's useful to look at how other sensors are implemented throughout the stack. For example, see the IMU. You should need to:

• Add a ForceTorqueSensor to ign-sensors
• On ign-gazebo:
  • Add a ForceTorqueSensor component
  • Add a force_torque_sensor_system

Also add the necessary code to hook it all up, as well as tests.

[diegoferigo]

Is there any missing physics feature in the DART plugin that blocks the support of F/T sensors?

[chapulina]

Leaving a cross reference to gazebosim/gz-physics#143, which seems to be exposing the necessary data from DART through ign-physics, but hasn't been merged because it's computationally expensive.

[vatanaksoytezer]

@chapulina to my understanding this is currently blocked by gazebosim/gz-physics#143. We want to use F/T sensors in ignition, and willing to contribute to get them ported. Can you give some key points / a roadmap for us to look to get this ported?

[chapulina]

Can you give some key points / a roadmap for us to look to get this ported?

We're currently planning to evaluate the DART implementation on Gazebo-classic, which is faster, but less precise, see discussion in gazebosim/gz-physics#124 and gazebosim/gazebo-classic#1321. If that turns out to be unsatisfactory, we'll keep iterating on gazebosim/gz-physics#143.

[chapulina]

Open PRs related to this:

• Joint Force-Torque Systems Plugin gz-sim#977
• Populate JointTransmittedWrench from physics gz-sim#989
• Add GetJointTransmittedWrench feature gz-physics#283
• [dart] Compute Inverse Dynamics for all skeletons to populate joint forces gz-physics#143
• Populate joint forces through physics gz-sim#952
• Joint Force-Torque Sensor #144
• Added Force Torque Noise functions + Unit tests sdformat#669

[rickstaa]

Judging from the comments above, it seems that the force-torque sensor is not yet available in the ignition. Is this still the case, or has the `force_torque sensor already been released? I saw that it is included in both the v6.0.0 source and binary releases of Oct 2, but I am unable to find the right syntax to use it. I have tried to use the syntaxes to include the plugin:

<plugin filename="libignition-sensors6-force_torque" name="ignition::sensors::ForceTorqueSensor">
</plugin>

<plugin filename="libignition-sensors6-force_torque.so" name="ignition::sensors::ForceTorqueSensor">
</plugin>

<plugin filename="libignition-sensors6-force_torque" name="ignition::sensors::ForceTorqueSensorPrivate">
</plugin>

<plugin filename="libignition-sensors6-force_torque.so" name="ignition::sensors::ForceTorqueSensorPrivate">
</plugin>

With all of them I, however, keep receiving the following error:

[Err] [SystemLoader.cc:66] Failed to load system plugin [ignition-gazebo-force-torque-system] : couldn't find shared library.

I have installed the binary of ignition-fortress according to the documentation.

[vatanaksoytezer]

I have been using FT sensors since 6.0.0 without any problems, with source and binary. Here is what it looks like in robot xacro:

  <gazebo reference="${prefix}_joint">
    <sensor name="force_torque_sensor" type="force_torque">
      <always_on>true</always_on>
      <update_rate>50</update_rate>
      <visualize>true</visualize>
      <topic>${prefix}_joint/force_torque</topic>
      <force_torque>
        <frame>sensor</frame>
        <measure_direction>parent_to_child</measure_direction>
      </force_torque>
    </sensor>
  </gazebo>

and I have the following added in the world (sdf) file:

<!-- FT Plugin -->
<plugin
  filename="ignition-gazebo-forcetorque-system"
  name="ignition::gazebo::systems::ForceTorque">
</plugin>

If these don't work please make sure and verify you are using version number greater than 6 with ign gazebo --version

[rickstaa]

@vatanaksoytezer Thanks for the fast response! It was indeed a naming problem. I suspected the shared library name to be equal to the one shown when running the ldconfig -p | grep libignition-sensors6-force command (i.e. libignition-sensors6-force_torque.so). I think the proposal made in #103 would remove this confusion.

[chapulina]

Oh we can close this!

[vbalaji21]

Does the visualisation work in F/T sensor ? I am trying it and unable to see it