N20 wheel (50 mm) and N20 shaft coupler: USD, MJCF, URDF, glTF

Two accessories for the DC motor module (N20 gear motor), packaged like the others. Masses are solid-PLA placeholders.

.gitattributes

@@ -389,3 +389,6 @@ atech_usb_c/gltf/atech_usb_c.glb filter=lfs diff=lfs merge=lfs -text
 24_atech_power_jack/simready_usd/atech_power_jack.usd filter=lfs diff=lfs merge=lfs -text
 24_atech_power_jack/urdf/meshes/atech_power_jack/black.stl filter=lfs diff=lfs merge=lfs -text
 24_atech_power_jack/urdf/meshes/atech_power_jack/gold.stl filter=lfs diff=lfs merge=lfs -text
+25_atech_wheel_n20_50mm/gltf/atech_wheel_n20_50mm.glb filter=lfs diff=lfs merge=lfs -text
+25_atech_wheel_n20_50mm/mjcf/meshes/atech_wheel_n20_50mm/visual.stl filter=lfs diff=lfs merge=lfs -text
+25_atech_wheel_n20_50mm/urdf/meshes/atech_wheel_n20_50mm/visual.stl filter=lfs diff=lfs merge=lfs -text

25_atech_wheel_n20_50mm/.metadata/com.nvidia.simready.packaging.bom.json

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+      "hash": {
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+      "size": 329284,
+      "hash": {
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+      "hash": {
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+      }
+    },
+    {
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+      "size": 1314,
+      "hash": {
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+      "size": 329284,
+      "hash": {
+        "sha256": "3847f0129ed9876c9173948295dcd737e7ae8be72792972c0c9e43c7649534aa"
+      }
+    }
+  ]
+}

25_atech_wheel_n20_50mm/.metadata/com.nvidia.simready.root_usds.json

@@ -0,0 +1,6 @@
+{
+  "format_version": "1.0",
+  "entries": [
+    "simready_usd/atech_wheel_n20_50mm.usd"
+  ]
+}

25_atech_wheel_n20_50mm/com.nvidia.simready.packaging.json

@@ -0,0 +1,13 @@
+{
+  "format_version": "1.0",
+  "package_id": "atech.atech_wheel_n20_50mm",
+  "license": "CC-BY-4.0",
+  "metadata": [
+    {
+      "name": "com.nvidia.simready.packaging.bom.json",
+      "hash": {
+        "sha256": "df7110c38941c36d5a063dbdd2c25c14dcf8cab8819619de66c2225a4d291e58"
+      }
+    }
+  ]
+}

25_atech_wheel_n20_50mm/gltf/atech_wheel_n20_50mm.glb

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:29891cc118477b3eb12f89091c25b6583dc589f6f14189f730bf58092b7ebb52
+size 507604

25_atech_wheel_n20_50mm/mjcf/atech_wheel_n20_50mm.xml

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+<mujoco model="atech_wheel_n20_50mm">
+  <compiler angle="radian" autolimits="true"/>
+  <option timestep="0.002" gravity="0 0 -9.81"/>
+  <custom>
+    <text name="atech:asset_type" data="accessory"/>
+    <text name="atech:id" data="wheel_n20_50mm"/>
+    <text name="atech:name" data="Wheel 50 mm (N20)"/>
+    <text name="atech:category" data="wheel"/>
+    <text name="atech:placeholders" data="mass_kg,colors,physics_material"/>
+    <text name="atech:visual:source" data="BIG_Wheels.stl (Atech, by email; Autodesk export)"/>
+    <text name="atech:visual:sha256" data="136e7af1c3d7a85ab26779314ffc64919b8e5348c26bb13008a4821cf8a82dc1"/>
+  </custom>
+  <asset>
+    <mesh name="atech_wheel_n20_50mm_visual_mesh" file="meshes/atech_wheel_n20_50mm/visual.stl"/>
+  </asset>
+  <worldbody>
+    <light name="key_light" pos="0 0 1" dir="0 0 -1"/>
+    <geom name="floor" type="plane" size="0.5 0.5 0.01" rgba="0.8 0.8 0.8 1"/>
+    <body name="atech_wheel_n20_50mm" pos="0 0 0.035">
+      <!-- Wheel 50 mm (N20): 50 mm diameter, 20 mm wide; 3 mm D-bore through the hub for the N20 gear motor's shaft. Axle along +y. Mass, colour and friction are placeholders. -->
+      <freejoint name="atech_wheel_n20_50mm_free"/>
+      <inertial pos="1.79991e-08 2.2329e-05 1.80461e-08" quat="0.70669939 -0.70673324 -0.023496071 -0.023495339" mass="0.0422291" diaginertia="8.80134e-06 8.80144e-06 1.48006e-05"/>
+      <geom name="atech_wheel_n20_50mm_visual" type="mesh" mesh="atech_wheel_n20_50mm_visual_mesh" rgba="0.2 0.2 0.22 1" contype="0" conaffinity="0" group="2" mass="0"/>
+      <geom name="atech_wheel_n20_50mm_collider" type="cylinder" size="0.025 0.01" quat="0.70710678 -0.70710678 0 0" friction="0.8 0.005 0.0001" rgba="0.2 0.2 0.22 1" group="3" mass="0"/>
+      <site name="atech_wheel_n20_50mm_axle" pos="0 0 0" zaxis="0 1 0" size="0.002" rgba="1 0.2 0.2 1" group="4"/>
+    </body>
+  </worldbody>
+</mujoco>

25_atech_wheel_n20_50mm/mjcf/meshes/atech_wheel_n20_50mm/visual.stl

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:3847f0129ed9876c9173948295dcd737e7ae8be72792972c0c9e43c7649534aa
+size 329284

25_atech_wheel_n20_50mm/urdf/atech_wheel_n20_50mm.urdf

@@ -0,0 +1,27 @@
+<?xml version="1.0"?>
+<!-- Wheel 50 mm (N20): Atech accessory. 50 mm diameter, 20 mm wide; 3 mm D-bore through the hub for the N20 gear motor's shaft. Visual: BIG_Wheels.stl (Atech, by email; Autodesk export). Axle along +y.
+     Mass, colour and friction are placeholders. Atech (atech.dev), CC BY 4.0: credit Atech -->
+<robot name="atech_wheel_n20_50mm">
+  <material name="atech_wheel_n20_50mm_body"><color rgba="0.2 0.2 0.22 1"/></material>
+  <link name="atech_wheel_n20_50mm">
+    <inertial>
+      <origin xyz="1.79991e-08 2.2329e-05 1.80461e-08" rpy="0 0 0"/>
+      <mass value="0.0422291"/>
+      <inertia ixx="8.80134e-06" ixy="3.33859e-12" ixz="-6.53997e-12" iyy="1.48006e-05" iyz="-2.87257e-10" izz="8.80144e-06"/>
+    </inertial>
+    <visual>
+      <geometry><mesh filename="meshes/atech_wheel_n20_50mm/visual.stl"/></geometry>
+      <material name="atech_wheel_n20_50mm_body"/>
+    </visual>
+    <collision>
+      <origin xyz="0 0 0" rpy="-1.5707963 0 0"/>
+      <geometry><cylinder radius="0.025" length="0.02"/></geometry>
+    </collision>
+  </link>
+  <link name="atech_wheel_n20_50mm_axle"/>
+  <joint name="atech_wheel_n20_50mm_axle_joint" type="fixed">
+    <parent link="atech_wheel_n20_50mm"/>
+    <child link="atech_wheel_n20_50mm_axle"/>
+    <origin xyz="0 0 0" rpy="0 0 0"/>
+  </joint>
+</robot>

25_atech_wheel_n20_50mm/urdf/meshes/atech_wheel_n20_50mm/visual.stl

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+version https://git-lfs.github.com/spec/v1
+oid sha256:3847f0129ed9876c9173948295dcd737e7ae8be72792972c0c9e43c7649534aa
+size 329284

26_atech_n20_coupler/.metadata/com.nvidia.simready.packaging.bom.json

@@ -0,0 +1,82 @@
+{
+  "format_version": "1.0",
+  "items": [
+    {
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+      "hash": {
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+      "hash": {
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+      "size": 3484,
+      "hash": {
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+      }
+    },
+    {
+      "relative_path": "simready_usd/.thumbs/256x256/atech_n20_coupler.usd.png",
+      "size": 19653,
+      "hash": {
+        "sha256": "e63247d495e14ca4077a90a0384383339dedcebb2d5b1516f97ebb7313fb6e90"
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+    },
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+      "hash": {
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+      }
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+      "size": 20390,
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+      "size": 1293,
+      "hash": {
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+      }
+    },
+    {
+      "relative_path": "urdf/meshes/atech_n20_coupler/collision_hull.stl",
+      "size": 3484,
+      "hash": {
+        "sha256": "89860884098e4d88dd5cf758174e54380a97617fff5b24e6171a4ffdb2679352"
+      }
+    },
+    {
+      "relative_path": "urdf/meshes/atech_n20_coupler/visual.stl",
+      "size": 10484,
+      "hash": {
+        "sha256": "43955630cdb03d16acd7c83e9b1938837367bdad57efc33f01c3ac036120d5cd"
+      }
+    }
+  ]
+}

26_atech_n20_coupler/.metadata/com.nvidia.simready.root_usds.json

@@ -0,0 +1,6 @@
+{
+  "format_version": "1.0",
+  "entries": [
+    "simready_usd/atech_n20_coupler.usd"
+  ]
+}

26_atech_n20_coupler/com.nvidia.simready.packaging.json

@@ -0,0 +1,13 @@
+{
+  "format_version": "1.0",
+  "package_id": "atech.atech_n20_coupler",
+  "license": "CC-BY-4.0",
+  "metadata": [
+    {
+      "name": "com.nvidia.simready.packaging.bom.json",
+      "hash": {
+        "sha256": "3ce35a76091f2c2050cc664c42eb15e1cb710af3b9f9053effa19a4a6449e797"
+      }
+    }
+  ]
+}

26_atech_n20_coupler/mjcf/atech_n20_coupler.xml

@@ -0,0 +1,29 @@
+<mujoco model="atech_n20_coupler">
+  <compiler angle="radian" autolimits="true"/>
+  <option timestep="0.002" gravity="0 0 -9.81"/>
+  <custom>
+    <text name="atech:asset_type" data="accessory"/>
+    <text name="atech:id" data="n20_coupler"/>
+    <text name="atech:name" data="N20 shaft coupler"/>
+    <text name="atech:category" data="coupler"/>
+    <text name="atech:placeholders" data="mass_kg,colors,physics_material"/>
+    <text name="atech:visual:source" data="atech-atelier models/stl/n20_wheel.stl (preset n20_wheel)"/>
+    <text name="atech:visual:sha256" data="6c5e05b4f0ce33c53b41da15547babb87b18a007d2da2bcbd254d78302db4eca"/>
+  </custom>
+  <asset>
+    <mesh name="atech_n20_coupler_visual_mesh" file="meshes/atech_n20_coupler/visual.stl"/>
+    <mesh name="atech_n20_coupler_hull" file="meshes/atech_n20_coupler/collision_hull.stl"/>
+  </asset>
+  <worldbody>
+    <light name="key_light" pos="0 0 1" dir="0 0 -1"/>
+    <geom name="floor" type="plane" size="0.5 0.5 0.01" rgba="0.8 0.8 0.8 1"/>
+    <body name="atech_n20_coupler" pos="0 0 0.013">
+      <!-- N20 shaft coupler: 6 mm long, 5.4 x 3.7 mm; D-shaped bore for the N20 gear motor's shaft. Axle along +y. Mass, colour and friction are placeholders. -->
+      <freejoint name="atech_n20_coupler_free"/>
+      <inertial pos="-3.8958e-06 -3.1498e-06 7.63001e-05" quat="0.70470923 -0.00015867956 8.179794e-05 -0.70949621" mass="8.11259e-05" diaginertia="3.52216e-10 3.57434e-10 4.81446e-10"/>
+      <geom name="atech_n20_coupler_visual" type="mesh" mesh="atech_n20_coupler_visual_mesh" rgba="0.62 0.62 0.6 1" contype="0" conaffinity="0" group="2" mass="0"/>
+      <geom name="atech_n20_coupler_collider" type="mesh" mesh="atech_n20_coupler_hull" friction="0.4 0.005 0.0001" rgba="0.62 0.62 0.6 1" group="3" mass="0"/>
+      <site name="atech_n20_coupler_axle" pos="0 0 0" zaxis="0 1 0" size="0.002" rgba="1 0.2 0.2 1" group="4"/>
+    </body>
+  </worldbody>
+</mujoco>

26_atech_n20_coupler/urdf/atech_n20_coupler.urdf

@@ -0,0 +1,27 @@
+<?xml version="1.0"?>
+<!-- N20 shaft coupler: Atech accessory. 6 mm long, 5.4 x 3.7 mm; D-shaped bore for the N20 gear motor's shaft. Visual: atech-atelier models/stl/n20_wheel.stl (preset n20_wheel). Axle along +y.
+     Mass, colour and friction are placeholders. Atech (atech.dev), CC BY 4.0: credit Atech -->
+<robot name="atech_n20_coupler">
+  <material name="atech_n20_coupler_body"><color rgba="0.62 0.62 0.6 1"/></material>
+  <link name="atech_n20_coupler">
+    <inertial>
+      <origin xyz="-3.8958e-06 -3.1498e-06 7.63001e-05" rpy="0 0 0"/>
+      <mass value="8.11259e-05"/>
+      <inertia ixx="3.57433e-10" ixy="-3.53144e-14" ixz="4.22243e-14" iyy="3.52217e-10" iyz="1.3914e-14" izz="4.81446e-10"/>
+    </inertial>
+    <visual>
+      <geometry><mesh filename="meshes/atech_n20_coupler/visual.stl"/></geometry>
+      <material name="atech_n20_coupler_body"/>
+    </visual>
+    <collision>
+      <origin xyz="0 0 0" rpy="0 0 0"/>
+      <geometry><mesh filename="meshes/atech_n20_coupler/collision_hull.stl"/></geometry>
+    </collision>
+  </link>
+  <link name="atech_n20_coupler_axle"/>
+  <joint name="atech_n20_coupler_axle_joint" type="fixed">
+    <parent link="atech_n20_coupler"/>
+    <child link="atech_n20_coupler_axle"/>
+    <origin xyz="0 0 0" rpy="0 0 0"/>
+  </joint>
+</robot>

README.md

@@ -21,7 +21,8 @@ tags:
 3-D simulation assets for the Atech boards and modules on [atech.dev](https://atech.dev):
 every module in the [Atech SDK](https://pypi.org/project/atech/) catalog, the products
 the SDK has no firmware for yet (USB-C, Power Jack, Micro-SD Card, Big Screen, Camera,
-Soil Sensor, Load Cell), and the 8-, 10- and 14-port boards.
+Soil Sensor, Load Cell), the 8-, 10- and 14-port boards, and two parts for the DC motor's
+N20 gear motor: a 50 mm wheel and a shaft coupler.
 
 Every asset comes in four formats: **USD** (Isaac Sim / Omniverse), **MJCF** (MuJoCo),
 **URDF** (ROS / Gazebo) and **glTF** (`.glb`: Unity, three.js, Blender, Unreal, Godot,
@@ -75,7 +76,8 @@ Folders are numbered (`01_atech_board_14port`, `02_atech_board_10port`, ...) onl
 the order the Hub lists them in; the files inside carry the plain asset name.
 Asset names are `atech_<module id>` (e.g. `atech_distance_sensor`) and
 `atech_board_<board id>` (e.g. `atech_board_14port`); the robot-arm module is
-`atech_robot_arm_integrator`, its product name.
+`atech_robot_arm_integrator`, its product name. The N20 parts are `atech_wheel_n20_50mm`
+and `atech_n20_coupler`.
 
 Generated with `atech sim-assets --all --board 8port,10port,14port` (USD, MJCF, URDF, glTF)
 (`pip install "atech[sim]"`) on the SDK's development version, then repackaged one
@@ -150,7 +152,15 @@ box colliders, mass).
   product renders; the PIR is drawn as its
   AM312 sensor. The Robot Arm Integrator (`atech_robot_arm_integrator`, catalog id `robot_arm`) plugs into one port, but its housing is two cells
   long: its `connector` frame is the centre of the -x cell.
-- **Masses and inertias are placeholders.** Atech has not published them.
+- **The N20 wheel and coupler** (`25_`, `26_`) are not modules: no port, no
+  connector, no firmware. Their visuals are Atech's printable models (STL), their origin
+  is the part's centre and the bore runs along +y, as the DC motor's shaft does; an
+  `axle` frame (USD prim, MJCF site, URDF link, glTF node) marks it. The wheel is 50 mm
+  across and 20 mm wide with a 3 mm D-bore; its collider is a cylinder. The coupler is
+  6 mm long; its collider is the convex hull of its mesh. Neither was made by
+  `atech sim-assets`.
+- **Masses and inertias are placeholders.** Atech has not published them. The wheel's
+  and coupler's are their mesh volumes as solid PLA.
 - **Tested:** the `.glb` files pass the Khronos glTF validator and render in three.js
   (r170), as in the image above. They have not been opened in Unity here.
 - With real CAD, NVIDIA's SimReady validator reports VG.007 warnings: the CAD