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google-deepmind / mujoco

Multi-Joint dynamics with Contact. A general purpose physics simulator.
https://mujoco.org
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Flex element gives `range[0] should be smaller than range[1] in joint` #2113

Closed ajoardar007 closed 1 month ago

ajoardar007 commented 1 month ago

Intro

Hi!

I am a graduate student at the University of Waterloo, and I am using MuJoCo for validating my control-scripts before running them on the actual robot.

My setup

Based upon the requirements (by running this cell while displaying all outputs):

  1. MuJoCo Version: 3.2.3,
  2. Python: 3.8.10 64-bit,
  3. absl-py: 2.1.0,
  4. etils: 1.3.0 (cannot get it to upgrade it any further),
  5. numpy: 1.24.4

Environment: Python, Architecture: x86_64, OS: Ubuntu 20.04.6 LTS

What's happening? What did you expect?

Objective: Place flex-material pads on the fingers of the end-effector. Result: 

/bin/python3 /home/.../src/flexible_bodies.py                                                                  ──(Wed,Oct02)─┘
Traceback (most recent call last):
  File "/home/.../src/flexible_bodies.py", line 189, in <module>
    model = mujoco.MjModel.from_xml_string(xml)
ValueError: Error: range[0] should be smaller than range[1] in joint
Element name '', id 154, line 84

Expected:

/bin/python3 /home/.../src/flexible_bodies.py                                                              1 ↵ ──(Wed,Oct02)─┘
"Invalid name ''. Valid names: ['cylinder_0/col', 'cylinder_0/viz', 'ground', 'smt/col/base_link/box_body', 'smt/col/base_link/cylinder_lidar', 'smt/col/whl/LF_cylinder', 'smt/col/whl/LR_cylinder', 'smt/col/whl/RF_cylinder', 'smt/col/whl/RR_cylinder', 'smt/viz/base_link', 'smt/viz/whl/LF', 'smt/viz/whl/LR', 'smt/viz/whl/RF', 'smt/viz/whl/RR']"
Hey!
<IPython.core.display.HTML object>

Observation: Element softbody_1 causes no issues in its implementation (I want it to be attached to its parent-body). However, softbody_2 is causing errors, even-though it has been placed significantly far-away to prevent it from initially colliding with any other body.

Steps for reproduction

  1. Run the code below in python (run it on any cell after running cell-1 in the tutorial-notebook).
  2. You will get: 
    /bin/python3 /home/.../src/flexible_bodies.py                                                                  ──(Wed,Oct02)─┘
Traceback (most recent call last):
File "/home/.../src/flexible_bodies.py", line 189, in <module>
model = mujoco.MjModel.from_xml_string(xml)
ValueError: Error: range[0] should be smaller than range[1] in joint
Element name '', id 154, line 84
  3. Comment out softbody_2 element (flexcomp element starting at line 173 to 181), and run again.
  4. You will get: 
    /bin/python3 /home/.../src/flexible_bodies.py                                                              1 ↵ ──(Wed,Oct02)─┘
"Invalid name ''. Valid names: ['cylinder_0/col', 'cylinder_0/viz', 'ground', 'smt/col/base_link/box_body', 'smt/col/base_link/cylinder_lidar', 'smt/col/whl/LF_cylinder', 'smt/col/whl/LR_cylinder', 'smt/col/whl/RF_cylinder', 'smt/col/whl/RR_cylinder', 'smt/viz/base_link', 'smt/viz/whl/LF', 'smt/viz/whl/LR', 'smt/viz/whl/RF', 'smt/viz/whl/RR']"
Hey!
<IPython.core.display.HTML object>

    (successful compilation)

Minimal model for reproduction

No mesh-files needed. The MJCF is included in the script for compactness.

Code required for reproduction

import mujoco
import mediapy as media

xml = """
<mujoco model="playground_wagon_manipulation(v1.0.0)">
    <!--#########################
        ### Compiler Specific ###
        ######################### -->
    <compiler coordinate="local" angle="radian"/>

    <!-- Options: -->
    <option 
        timestep="1e-3"
        iterations="10"
        tolerance="1e-10"
        impratio="1"
        gravity="0 0 -9.81"
        solver="Newton"
        cone="elliptic" 
    />
    <default>
        <geom margin="0.001" solimp="0.99 0.99 0.01" solref="0.01 1" condim="4" /> 
    </default>
    <!-- Statistic -->
    <!-- https://mujoco.readthedocs.io/en/latest/XMLreference.html#statistic -->
    <!-- Looka at this `center` point using the free-camera, which is located at a distance of 1.5x`extent` distance -->
    <!-- Apparently, the camera cannot zoom to within the extent distance, so keep it small. -->
    <!-- The value of `center` does not move the initial location of the camera view-point.-->
    <statistic center="0 0 0" extent="1"/>
    <!-- Visual -->
    <visual>
        <map fogstart="3" fogend="5" force="0.1" znear="0.001"/>
        <quality shadowsize="1024" offsamples="16"/>
        <scale forcewidth="0.05" contactwidth="0.05" contactheight="0.05" 
               connect="0.05" com="0.1" jointlength="0.1" jointwidth="0.01"
               framelength="0.1" framewidth="0.01"/>
        <!-- <global offwidth="1960" offheight="800"/> -->
    </visual>

    <!--############################
        ### Environment Specific ###
        ############################ -->
    <asset>
        <!-- [ENV] Ground PLane -->
        <texture name="groundplane" type="2d" builtin="checker" rgb1=".25 .26 .25" 
            rgb2=".22 .22 .22" width="100" height="100" mark="edge" markrgb=".3 .3 .3"/>
        <material name="MatGnd" texture="groundplane"  texrepeat="5 5" specular="1" shininess=".001" reflectance="0.00001"/>
    </asset>

    <!--##################
        ### Extension: ###
        ################## -->
    <extension>
        <plugin plugin="mujoco.elasticity.solid"/>
    </extension>

    <!--###############
        ### Config: ###
        ############### -->
    <!-- DEFAULT -->
    <default>
        <!-- The class-name being specified under default maps back to the class-names being specified for a body (childclass/class) , or  -->
        <!-- These names have to be unique; it must not clash with class-names for un-intended bodies/joints/geometries -->
        <default class="summit">
        </default>
        <default class="summit/whl">
            <!-- class-names for joints -->
            <joint axis="1 0 0" damping="0.55"/>
            <!-- Bydefault, hinge-type is the default joint type -->
            <!-- https://mujoco.readthedocs.io/en/stable/XMLreference.html#body-joint -->
        </default>
        <default class="summit/col">
            <!-- class-names for geometry-type -->
            <geom contype="1" conaffinity="1" group="0" rgba="0.5 0.6 0.7 0.3"/>
        </default>
        <default class="summit/body/viz">
            <geom contype="0" conaffinity="0" group="1" rgba="0.6 0.6 0.6 1"/>
        </default>
        <default class="summit/wheel/viz">
            <geom contype="0" conaffinity="0" group="1" rgba="0.3 0.3 0.3 1"/>
        </default>
        <default class="summit/camera/viz">
            <geom contype="0" conaffinity="0" group="1" rgba="0.7 0.7 0.7 1"/>
        </default>

        <default class="wam">
            <joint type="hinge" limited="true" pos="0 0 0" axis="0 0 1"  frictionloss=".1"/>
        </default>
    </default>

    <worldbody>
        <!-- GND -->
        <light directional="true" cutoff="60" exponent="1" diffuse="1 1 1" specular=".1 .1 .1" pos=".1 .2 1.3" dir="-.1 -.2 -1.3"/>
        <geom name="ground" type="plane" pos="0 0 0" size="24 24 1" conaffinity="1" contype="1" material="MatGnd" friction="0.0001 0.001 0.001" group="1"/>

        <body name="smt/base_link" childclass="summit" pos="0 0 0">
            <!-- === BASE LINK === === === === -->
            <!-- mobile body -->
            <inertial                                           pos="0 0 0.37" mass="125" diaginertia="1.391 6.853 6.125" />
            <geom name="smt/viz/base_link"                      class="summit/body/viz" pos="0 0 0.42" size="0.24 0.32 0.16" type="box"/>

            <!-- Front Camera -->
            <body name="smt/front/camera" pos="0 0.362 0.373" quat="0 0 0.707107 0.707107">
                <inertial               pos="0 0 0.015" mass="0.095"/>
                <geom                   class="summit/camera/viz" size="0.06 0.04" type="cylinder"/>
                <camera name="smt/front/camera/intel/rgb" pos="0 0 0" quat="0 0 1 0" fovy="55"/>
            </body>
            <!-- Rear Camera --><!-- quant=w x y z -->
            <body name="smt/rear/camera" pos="0 -0.362 0.373" quat="0.707107 0.707107 0 0"> 
                <inertial               pos="0 0 0.015" mass="0.095"/>
                <geom                   class="summit/camera/viz" size="0.06 0.04" type="cylinder"/>
                <camera name="smt/rear/camera/intel/rgb" pos="0 0 0" quat="0 0 1 0" fovy="55"/>
            </body>
            <flexcomp name="softbody_1" type="grid" count="4 4 4" spacing=".01 .01 .01" pos="0 0.32 1" radius=".0" rgba="0 0 0.7 1" dim="3" mass="1">
                <contact condim="3" solref="0.01 1" solimp=".95 .99 .0001" selfcollide="none"/>
                <edge damping="1"/>
                <plugin plugin="mujoco.elasticity.solid">
                    <config key="poisson" value="0.2"/>
                    <config key="young" value="5e4"/>
                </plugin>
                <!-- Without below line, we get 'rank-deficiet matrix' -->
                <pin id="0 1 2 3 16 17 18 19 32 33 34 35 48 49 50 51"/>
            </flexcomp>
            <!-- Simplified the collision into boxes + arm rest -->
            <geom name="smt/col/base_link/box_body"             class="summit/col" pos="0 0 0.42" size="0.24 0.32 0.16" type="box"/>
            <geom name="smt/col/base_link/cylinder_lidar"       class="summit/col" pos="0.246 0.362 0.313" size="0.06 0.044" type="cylinder"/>

            <!-- world placement -->
            <joint name="smt/world_x" armature="0.0001" axis="0 1 0" damping="1e+11" pos="0 0 0" type="slide"></joint>
            <joint name="smt/world_y" armature="0.0001" axis="-1 0 0" damping="1e+11" pos="0 0 0" type="slide"></joint>
            <joint name="smt/world_z" armature="0.0001" axis="0 0 1" damping="1e+0"  pos="0 0 0" type="slide"></joint>

            <!-- control summit base -->
            <joint name="smt/pose/x"                            type="slide" pos="0 0 0.4" axis="0 1 0"  damping="15"/>
            <joint name="smt/pose/y"                            type="slide" pos="0 0 0.4" axis="-1 0 0"  damping="15"/>
            <joint name="smt/orie/z"                            type="hinge" pos="0 0 0.4" axis="0 0 1"  damping="10"/>

            <!-- === whl LINK === === === === -->
            <!-- Mobile whls -->
            <body name="smt/whl/LF_link" pos="0 0 0">
                <geom name="smt/viz/whl/LF"                    class="summit/wheel/viz" pos="-0.220 0.222 0.128" quat="0.707107 0 0.707106 0" size="0.13 0.05" type="cylinder"/>
                <geom name="smt/col/whl/LF_cylinder"           class="summit/col" pos="-0.220 0.222 0.128" quat="0.707107 0 0.707106 0" size="0.13 0.05" type="cylinder" friction="0.0001 0.001 0.001"/>
                <inertial                                                         pos="-0.220 0.222 0.128" mass="10.0" diaginertia="0.04411 0.02467 0.02467"/>
                <joint name="smt/whl_LF"                       class="summit/whl" pos="-0.264 0.222 0.128"/>
            </body>
            <body name="smt/whl/LR_link" pos="0 0 0">
                <geom name="smt/viz/whl/LR"                    class="summit/wheel/viz" pos="-0.220 -0.223 0.128" quat="0.707107 0 0.707106 0" size="0.13 0.05" type="cylinder"/>
                <geom name="smt/col/whl/LR_cylinder"           class="summit/col" pos="-0.220 -0.223 0.128" quat="0.707107 0 0.707106 0" size="0.13 0.05" type="cylinder" friction="0.0001 0.001 0.001"/>
                <inertial                                                         pos="-0.220 -0.223 0.128" mass="10.0" diaginertia="0.04411 0.02467 0.02467"/>
                <joint name="smt/whl_LR"                       class="summit/whl" pos="-0.264 -0.223 0.128"/>
            </body>
            <body name="smt/whl/RF_link" pos="0 0 0">
                <geom name="smt/viz/whl/RF"                   class="summit/wheel/viz" pos="0.220 0.222 0.128" quat="0.707107 0 0.707106 0" size="0.13 0.05" type="cylinder"/>
                <geom name="smt/col/whl/RF_cylinder"          class="summit/col" pos="0.220 0.222 0.128" quat="0.707107 0 0.707106 0" size="0.13 0.05" type="cylinder" friction="0.0001 0.001 0.001"/>
                <inertial                                                        pos="0.220 0.222 0.128" mass="10.0" diaginertia="0.04411 0.02467 0.02467"/>
                <joint name="smt/whl_RF"                      class="summit/whl" pos="0.264 0.222 0.128"/>
            </body>
            <body name="smt/whl/RR_link" pos="0 0 0">
                <geom name="smt/viz/whl/RR"                   class="summit/wheel/viz" pos="0.220 -0.223 0.128" quat="0.707107 0 0.707106 0" size="0.13 0.05" type="cylinder"/>
                <geom name="smt/col/whl/RR_cylinder"          class="summit/col" pos="0.220 -0.223 0.128" quat="0.707107 0 0.707106 0" size="0.13 0.05" type="cylinder" friction="0.0001 0.001 0.001"/>
                <inertial                                                        pos="0.220 -0.223 0.128" mass="10.0" diaginertia="0.04411 0.02467 0.02467"/>
                <joint name="smt/whl_RR"                      class="summit/whl" pos="0.264 -0.223 0.128"/>
            </body>

            <!-- === WAM 7DOF HAND LINK === === === === -->
            <!-- Place WAM Module Here -->
            <!-- WAM -->
            <body name="wam/base_link" childclass="wam" pos="0 0 0">
                <body name="wam/base" childclass="wam" pos="0 0 0">
                    <inertial   pos="-0.14071720 -0.02017671 0.07995294" mass="9.97059584" fullinertia="0.11760385 0.10916849 0.18294303 0.02557874 0.00161433 0.00640270" /> 
                    <geom name="cylinder_0/col" type="cylinder" size=".1 .1" contype="1" conaffinity="1" group="0" rgba=".8 .2 .2 1"/>
                    <geom name="cylinder_0/viz" type="cylinder" size=".1 .1" contype="0" conaffinity="0" group="1" rgba=".2 .2 .2 1"/>
                    <flexcomp name="softbody_2" type="grid" count="4 4 4" spacing=".01 .01 .01" pos="0 0.3 0.4" radius=".0" rgba="0 0 0.7 1" dim="3" mass="1">
                        <contact condim="3" solref="0.01 1" solimp=".95 .99 .0001" selfcollide="none"/>
                        <edge damping="1"/>
                        <plugin plugin="mujoco.elasticity.solid">
                            <config key="poisson" value="0.2"/>
                            <config key="young" value="5e4"/>
                        </plugin>
                        <pin id="0 1 2 3 16 17 18 19 32 33 34 35 48 49 50 51"/>
                    </flexcomp>
                </body>
            </body>
        </body>
    </worldbody>

</mujoco>
"""
model = mujoco.MjModel.from_xml_string(xml)
data = mujoco.MjData(model)
try:
  model.geom()
except KeyError as e:
  print(e)
# enable joint visualization option:
scene_option = mujoco.MjvOption()
scene_option.flags[mujoco.mjtVisFlag.mjVIS_JOINT] = True

duration = 3.8  # (seconds)
framerate = 60  # (Hz)

# Simulate and display video.
frames = []
mujoco.mj_resetData(model, data)
with mujoco.Renderer(model) as renderer:
  while data.time < duration:
    mujoco.mj_step(model, data)
    if len(frames) < data.time * framerate:
      renderer.update_scene(data, scene_option=scene_option)
      pixels = renderer.render()
      frames.append(pixels)

print("Hey!")
media.show_video(frames, fps=framerate)

Confirmations

quagla commented 1 month ago

The reason is that the bodies in flexcomp inherit the wam defaults. Can you set the hinge joint directly in the body instead of using the default?

ajoardar007 commented 1 month ago

Yup. That seemed to resolve the issue. I guess, even if a joint was not defined for the body (no range), the other attributes that were defined as default were absorbed. Maybe, later down the line, a rule, similar to how joint-behavior is defined for body, could be ported to flexcomp; like how a body with no joint-range does not throw the same error as for flexcomp.