Is actuator/⁠adhesion not supported with mjx? #2615

RajGhugare19 · 2025-05-09T16:40:03Z

RajGhugare19
May 9, 2025

Intro

Hi!

I am a graduate student at Princeton University, I use MuJoCo (MJX) for my research on Reinforcement Learning.

My setup

I am using MuJoCo Version: 3.3.0, Python 3.10.16 and Red Hat Enterprise Linux 9.5 (Plow).

My question

I am trying to implement a suction like gripper with the franka emika panda robot

Minimal model and/or code that explain my question

If you encountered the issue in a complex model, please simplify it as much as possible (while still reproducing the issue).

Model:

The following is a modified version of the panda_nohand.xml from mujoco menagerie with a suction gripper.

XML

<mujoco model="panda">
  <compiler angle="radian" meshdir="assets" autolimits="true"/>

  <default>
    <default class="panda">
      <material specular="0.5" shininess="0.25"/>
      <joint armature="0.1" damping="1" axis="0 0 1" range="-2.8973 2.8973"/>
      <general dyntype="none" biastype="affine" ctrlrange="-2.8973 2.8973" forcerange="-87 87"/>
      <position forcerange="-100 100"/>

      <default class="visual">
        <geom type="mesh" contype="0" conaffinity="0" group="2"/>
      </default>
      <default class="collision">
        <geom group="3" type="mesh" contype="0" conaffinity="0"/>
      </default>
      <default class="active_adhesion">
        <geom rgba=".8 .5 .5 1" margin=".01" gap=".01"/>
      </default>
    </default>
  </default>

  <asset>
    <material class="panda" name="white" rgba="1 1 1 1"/>
    <material class="panda" name="off_white" rgba="0.901961 0.921569 0.929412 1"/>
    <material class="panda" name="black" rgba="0.25 0.25 0.25 1"/>
    <material class="panda" name="green" rgba="0 1 0 1"/>
    <material class="panda" name="light_blue" rgba="0.039216 0.541176 0.780392 1"/>

    <!-- Collision meshes -->
    <mesh name="link0_c" file="link0.stl"/>
    <mesh name="link1_c" file="link1.stl"/>
    <mesh name="link2_c" file="link2.stl"/>
    <mesh name="link3_c" file="link3.stl"/>
    <mesh name="link4_c" file="link4.stl"/>
    <mesh name="link5_c0" file="link5_collision_0.obj"/>
    <mesh name="link5_c1" file="link5_collision_1.obj"/>
    <mesh name="link5_c2" file="link5_collision_2.obj"/>
    <mesh name="link6_c" file="link6.stl"/>
    <mesh name="link7_c" file="link7.stl"/>

    <!-- Visual meshes -->
    <mesh file="link0_0.obj"/>
    <mesh file="link0_1.obj"/>
    <mesh file="link0_2.obj"/>
    <mesh file="link0_3.obj"/>
    <mesh file="link0_4.obj"/>
    <mesh file="link0_5.obj"/>
    <mesh file="link0_7.obj"/>
    <mesh file="link0_8.obj"/>
    <mesh file="link0_9.obj"/>
    <mesh file="link0_10.obj"/>
    <mesh file="link0_11.obj"/>
    <mesh file="link1.obj"/>
    <mesh file="link2.obj"/>
    <mesh file="link3_0.obj"/>
    <mesh file="link3_1.obj"/>
    <mesh file="link3_2.obj"/>
    <mesh file="link3_3.obj"/>
    <mesh file="link4_0.obj"/>
    <mesh file="link4_1.obj"/>
    <mesh file="link4_2.obj"/>
    <mesh file="link4_3.obj"/>
    <mesh file="link5_0.obj"/>
    <mesh file="link5_1.obj"/>
    <mesh file="link5_2.obj"/>
    <mesh file="link6_0.obj"/>
    <mesh file="link6_1.obj"/>
    <mesh file="link6_2.obj"/>
    <mesh file="link6_3.obj"/>
    <mesh file="link6_4.obj"/>
    <mesh file="link6_5.obj"/>
    <mesh file="link6_6.obj"/>
    <mesh file="link6_7.obj"/>
    <mesh file="link6_8.obj"/>
    <mesh file="link6_9.obj"/>
    <mesh file="link6_10.obj"/>
    <mesh file="link6_11.obj"/>
    <mesh file="link6_12.obj"/>
    <mesh file="link6_13.obj"/>
    <mesh file="link6_14.obj"/>
    <mesh file="link6_15.obj"/>
    <mesh file="link6_16.obj"/>
    <mesh file="link7_0.obj"/>
    <mesh file="link7_1.obj"/>
    <mesh file="link7_2.obj"/>
    <mesh file="link7_3.obj"/>
    <mesh file="link7_4.obj"/>
    <mesh file="link7_5.obj"/>
    <mesh file="link7_6.obj"/>
    <mesh file="link7_7.obj"/>
  </asset>

  <worldbody>
    <light name="top" pos="0 0 2" mode="trackcom"/>
    <body name="link0" childclass="panda">
      <inertial mass="0.629769" pos="-0.041018 -0.00014 0.049974"
        fullinertia="0.00315 0.00388 0.004285 8.2904e-7 0.00015 8.2299e-6"/>
      <geom mesh="link0_0" material="off_white" class="visual"/>
      <geom mesh="link0_1" material="black" class="visual"/>
      <geom mesh="link0_2" material="off_white" class="visual"/>
      <geom mesh="link0_3" material="black" class="visual"/>
      <geom mesh="link0_4" material="off_white" class="visual"/>
      <geom mesh="link0_5" material="black" class="visual"/>
      <geom mesh="link0_7" material="white" class="visual"/>
      <geom mesh="link0_8" material="white" class="visual"/>
      <geom mesh="link0_9" material="black" class="visual"/>
      <geom mesh="link0_10" material="off_white" class="visual"/>
      <geom mesh="link0_11" material="white" class="visual"/>
      <geom mesh="link0_c" class="collision"/>
      <body name="link1" pos="0 0 0.333">
        <inertial mass="4.970684" pos="0.003875 0.002081 -0.04762"
          fullinertia="0.70337 0.70661 0.0091170 -0.00013900 0.0067720 0.019169"/>
        <joint name="joint1" damping="40"/>
        <geom material="white" mesh="link1" class="visual"/>
        <geom mesh="link1_c" class="collision"/>
        <body name="link2" quat="1 -1 0 0">
          <inertial mass="0.646926" pos="-0.003141 -0.02872 0.003495"
            fullinertia="0.0079620 2.8110e-2 2.5995e-2 -3.925e-3 1.0254e-2 7.04e-4"/>
          <joint name="joint2" range="-1.7628 1.7628" damping="40"/>
          <geom material="white" mesh="link2" class="visual"/>
          <geom mesh="link2_c" class="collision"/>
          <body name="link3" pos="0 -0.316 0" quat="1 1 0 0">
            <joint name="joint3" damping="40"/>
            <inertial mass="3.228604" pos="2.7518e-2 3.9252e-2 -6.6502e-2"
              fullinertia="3.7242e-2 3.6155e-2 1.083e-2 -4.761e-3 -1.1396e-2 -1.2805e-2"/>
            <geom mesh="link3_0" material="white" class="visual"/>
            <geom mesh="link3_1" material="white" class="visual"/>
            <geom mesh="link3_2" material="white" class="visual"/>
            <geom mesh="link3_3" material="black" class="visual"/>
            <geom mesh="link3_c" class="collision"/>
            <body name="link4" pos="0.0825 0 0" quat="1 1 0 0">
              <inertial mass="3.587895" pos="-5.317e-2 1.04419e-1 2.7454e-2"
                fullinertia="2.5853e-2 1.9552e-2 2.8323e-2 7.796e-3 -1.332e-3 8.641e-3"/>
              <joint name="joint4" range="-3.0718 -0.0698" damping="40"/>
              <geom mesh="link4_0" material="white" class="visual"/>
              <geom mesh="link4_1" material="white" class="visual"/>
              <geom mesh="link4_2" material="black" class="visual"/>
              <geom mesh="link4_3" material="white" class="visual"/>
              <geom mesh="link4_c" class="collision"/>
              <body name="link5" pos="-0.0825 0.384 0" quat="1 -1 0 0">
                <inertial mass="1.225946" pos="-1.1953e-2 4.1065e-2 -3.8437e-2"
                  fullinertia="3.5549e-2 2.9474e-2 8.627e-3 -2.117e-3 -4.037e-3 2.29e-4"/>
                <joint name="joint5" damping="2"/>
                <geom mesh="link5_0" material="black" class="visual"/>
                <geom mesh="link5_1" material="white" class="visual"/>
                <geom mesh="link5_2" material="white" class="visual"/>
                <geom mesh="link5_c0" class="collision"/>
                <geom mesh="link5_c1" class="collision"/>
                <geom mesh="link5_c2" class="collision"/>
                <body name="link6" quat="1 1 0 0">
                  <inertial mass="1.666555" pos="6.0149e-2 -1.4117e-2 -1.0517e-2"
                    fullinertia="1.964e-3 4.354e-3 5.433e-3 1.09e-4 -1.158e-3 3.41e-4"/>
                  <joint name="joint6" range="-0.0175 3.7525" damping="2"/>
                  <geom mesh="link6_0" material="off_white" class="visual"/>
                  <geom mesh="link6_1" material="white" class="visual"/>
                  <geom mesh="link6_2" material="black" class="visual"/>
                  <geom mesh="link6_3" material="white" class="visual"/>
                  <geom mesh="link6_4" material="white" class="visual"/>
                  <geom mesh="link6_5" material="white" class="visual"/>
                  <geom mesh="link6_6" material="white" class="visual"/>
                  <geom mesh="link6_7" material="light_blue" class="visual"/>
                  <geom mesh="link6_8" material="light_blue" class="visual"/>
                  <geom mesh="link6_9" material="black" class="visual"/>
                  <geom mesh="link6_10" material="black" class="visual"/>
                  <geom mesh="link6_11" material="white" class="visual"/>
                  <geom mesh="link6_12" material="green" class="visual"/>
                  <geom mesh="link6_13" material="white" class="visual"/>
                  <geom mesh="link6_14" material="black" class="visual"/>
                  <geom mesh="link6_15" material="black" class="visual"/>
                  <geom mesh="link6_16" material="white" class="visual"/>
                  <geom mesh="link6_c" class="collision"/>
                  <body name="link7" pos="0.088 0 0" quat="1 1 0 0">
                    <inertial mass="7.35522e-01" pos="1.0517e-2 -4.252e-3 6.1597e-2"
                      fullinertia="1.2516e-2 1.0027e-2 4.815e-3 -4.28e-4 -1.196e-3 -7.41e-4"/>
                    <joint name="joint7" damping="2"/>
                    <geom mesh="link7_0" material="white" class="visual"/>
                    <geom mesh="link7_1" material="black" class="visual"/>
                    <geom mesh="link7_2" material="black" class="visual"/>
                    <geom mesh="link7_3" material="black" class="visual"/>
                    <geom mesh="link7_4" material="black" class="visual"/>
                    <geom mesh="link7_5" material="black" class="visual"/>
                    <geom mesh="link7_6" material="black" class="visual"/>
                    <geom mesh="link7_7" material="white" class="visual"/>
                    <geom mesh="link7_c" class="collision"/>
                    <body name="link8" pos="0 0 0.107" childclass="active_adhesion">
                      <site name="gripper" group="3"/>
                      <!-- <joint name="joint8" damping="0.01"/> -->
                      <geom name="suction_pad" type="box" size="0.012 0.012 0.008" pos="0 0 0"
                        contype="0" conaffinity="3"/>
                    </body>
                  </body>
                </body>
              </body>
            </body>
          </body>
        </body>
      </body>
    </body>
  </worldbody>

  <actuator>
    <position class="panda" name="actuator1" joint="joint1" kp="1000" kv="20"
     ctrlrange="-2.8973 2.8973"/>
    <position class="panda" name="actuator2" joint="joint2" kp="1000" kv="20"
     ctrlrange="-1.7628 1.7628"/>
    <position class="panda" name="actuator3" joint="joint3" kp="750" kv="4"
     ctrlrange="-2.8973 2.8973"/>
    <position class="panda" name="actuator4" joint="joint4" kp="750" kv="4"
     ctrlrange="-3.0718 -0.0698"/>
    <position class="panda" name="actuator5" joint="joint5" kp="300" kv="2"
     forcerange="-12 12" ctrlrange="-2.8973 2.8973"/>
    <position class="panda" name="actuator6" joint="joint6" kp="300" kv="2" forcerange="-12 12"
      ctrlrange="-0.0175 3.7525"/>
    <position class="panda" name="actuator7" joint="joint7" kp="300" kv="2" forcerange="-12 12"/>
    <adhesion name="adhesion_actuator" body="link8" ctrlrange="0 1" gain="5"/>
  </actuator>
</mujoco>

Adding the adhesion_actuator definition to this xml

adhesion name="adhesion_actuator" body="link8" ctrlrange="0 1" gain="5"

throws the error.

Code:

import mujoco
import epath
from mujoco import mjx

xml_path = epath.Path('/n/fs/url-rg/build-stuff/envs/franka_emika_panda/mjx_panda_no_hand.xml')
xml = xml_path.read_text()
mj_model = mujoco.MjModel.from_xml_string(xml, assets=get_assets())
mjx.put_model(mj_model)

Error:

Cell In[6], line 1 ----> 1 mjx.put_model(mj_model)

File /n/fs/url-rg/.conda/envs/bs/lib/python3.10/site-packages/mujoco/mjx/_src/io.py:152, in put_model(m, device, _full_compat)
    150   missing = set(enum_field) - set(enum_type)
    151   if missing and not _full_compat:
--> 152     raise NotImplementedError(
    153         f'{[mj_type(m) for m in missing]} not supported'
    154     )
    156 mj_field_names = {
    157     f.name
    158     for f in types.Model.fields()
    159     if f.metadata.get('restricted_to') != 'mjx'
    160 }
    161 fields = {f: getattr(m, f) for f in mj_field_names}

NotImplementedError: [<mjtTrn.mjTRN_BODY: 5>] not supported

Confirmations

I searched the latest documentation thoroughly before posting.
I searched previous Issues and Discussions, I am certain this has not been raised before.

Answered by thowell

May 12, 2025

@yuvaltassa @RajGhugare19
confirming that the MJX unsupported feature list includes Transmission BODY
https://mujoco.readthedocs.io/en/latest/mjx.html#feature-parity

View full answer

yuvaltassa · 2025-05-09T16:49:10Z

yuvaltassa
May 9, 2025
Maintainer

I think the answer is "not yet, and we should add that to the unsupported feature list". @thowell can you confirm?

6 replies

RajGhugare19 May 9, 2025
Author

Thanks a lot for your quick answer!

I see that margin and gap are unimplemented for collisions with mesh Geom. So presumably, supporting an at distance suction is more involved.

Meanwhile, what steps would I need to take to use existing features to implement an active contact suction gripper (which only applies force when gap is 0)?

Really appreciate your help :)

thowell May 12, 2025
Collaborator

@yuvaltassa @RajGhugare19
confirming that the MJX unsupported feature list includes Transmission BODY
https://mujoco.readthedocs.io/en/latest/mjx.html#feature-parity

Answer selected by RajGhugare19

RajGhugare19 May 14, 2025
Author

Thanks!

yuvaltassa May 14, 2025
Maintainer

Regarding which steps to take:

Use MuJoCo C instead of MJX.
There is no step 2, you're done 😁

If you really need GPU then I would wait a bit for mjWarp, progress there is quite fast.

RajGhugare19 May 14, 2025
Author

Thanks for letting me know! Yes, we've been keeping a close eye on mjWarp and its very exciting!

MuJoCo C -- this is what I've been doing now. We have used the rollout functionality as a callback for stepping the simulator and made everything else jittable. This also works very fast and has the added benefit of being much more flexible and accurate, especially with increasing number of objects in the scene.

yuvaltassa May 14, 2025
Maintainer

Ah, great to hear that!
cc @aftersomemath

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Is actuator/⁠adhesion not supported with mjx? #2615

Uh oh!

{{title}}

Uh oh!

Replies: 1 comment 6 replies

Uh oh!

{{title}}

Uh oh!

Uh oh!

{{title}}

Uh oh!

Uh oh!

{{editor}}'s edit

{{editor}}'s edit

Uh oh!

Uh oh!

{{title}}

Uh oh!

Uh oh!

{{title}}

Uh oh!

Uh oh!

{{title}}

Uh oh!

Uh oh!

{{title}}

Uh oh!

Uh oh!

{{title}}

Uh oh!

Select a reply

Uh oh!

Is actuator/⁠adhesion not supported with mjx? #2615

Uh oh!

RajGhugare19 May 9, 2025

Intro

My setup

My question

Minimal model and/or code that explain my question

Confirmations

Replies: 1 comment · 6 replies

Uh oh!

yuvaltassa May 9, 2025 Maintainer

Uh oh!

Uh oh!

RajGhugare19 May 9, 2025 Author

Uh oh!

thowell May 12, 2025 Collaborator

Uh oh!

RajGhugare19 May 14, 2025 Author

Uh oh!

yuvaltassa May 14, 2025 Maintainer

Uh oh!

RajGhugare19 May 14, 2025 Author

Uh oh!

yuvaltassa May 14, 2025 Maintainer

RajGhugare19
May 9, 2025

Replies: 1 comment 6 replies

yuvaltassa
May 9, 2025
Maintainer

RajGhugare19 May 9, 2025
Author

thowell May 12, 2025
Collaborator

RajGhugare19 May 14, 2025
Author

yuvaltassa May 14, 2025
Maintainer

RajGhugare19 May 14, 2025
Author

yuvaltassa May 14, 2025
Maintainer