✨ add rotary cartpole env

assets/rotary_cartpole/rotary_cartpole.urdf

@@ -0,0 +1,105 @@
+<?xml version="1.0" encoding="utf-8"?>
+<robot name="rotary_cartpole">
+
+  <!-- Fixed world frame -->
+  <link name="world"/>
+
+  <!-- Base: motor housing, fixed to world -->
+  <link name="base_link">
+    <inertial>
+      <origin xyz="-0.00011 0.00117 0.06055" rpy="0 0 0"/>
+      <mass value="0.921"/>
+      <inertia ixx="0.002385" iyy="0.002484" izz="0.000559"
+               ixy="0.0" iyz="-0.000149" ixz="6e-06"/>
+    </inertial>
+    <visual>
+      <origin xyz="0 0 0" rpy="0 0 0"/>
+      <geometry>
+        <mesh filename="meshes/base_link.stl" scale="0.001 0.001 0.001"/>
+      </geometry>
+    </visual>
+    <collision>
+      <origin xyz="0 0 0" rpy="0 0 0"/>
+      <geometry>
+        <mesh filename="meshes/base_link.stl" scale="0.001 0.001 0.001"/>
+      </geometry>
+    </collision>
+  </link>
+
+  <joint name="base_joint" type="fixed">
+    <parent link="world"/>
+    <child link="base_link"/>
+  </joint>
+
+  <!-- Arm: horizontal rotating arm driven by motor.
+       Real mass ~10g (Fusion assumed dense material, exported 279g). -->
+  <link name="arm">
+    <inertial>
+      <origin xyz="0.00005 0.0065 0.00563" rpy="0 0 0"/>
+      <mass value="0.150"/>
+      <inertia ixx="4.05e-05" iyy="1.17e-05" izz="3.66e-05"
+               ixy="0.0" iyz="1.08e-07" ixz="0.0"/>
+    </inertial>
+    <visual>
+      <origin xyz="0.006947 -0.00395 -0.14796" rpy="0 0 0"/>
+      <geometry>
+        <mesh filename="meshes/arm_1.stl" scale="0.001 0.001 0.001"/>
+      </geometry>
+    </visual>
+    <collision>
+      <origin xyz="0.006947 -0.00395 -0.14796" rpy="0 0 0"/>
+      <geometry>
+        <mesh filename="meshes/arm_1.stl" scale="0.001 0.001 0.001"/>
+      </geometry>
+    </collision>
+  </link>
+
+  <!-- Motor joint: base → arm, rotates around vertical z-axis -->
+  <joint name="motor_joint" type="revolute">
+    <origin xyz="-0.006947 0.00395 0.14796" rpy="0 0 0"/>
+    <parent link="base_link"/>
+    <child link="arm"/>
+    <axis xyz="0 0 1"/>
+    <limit lower="-1.5708" upper="1.5708" effort="10.0" velocity="200.0"/>
+    <dynamics damping="0.001"/>
+  </joint>
+
+  <!-- Pendulum: swings freely at the end of the arm.
+       Real mass: 5g pendulum + 10g weight at the tip (70mm from bearing) = 15g total.
+       (Fusion assumed dense material, exported 57g for the pendulum alone.) -->
+  <link name="pendulum">
+    <inertial>
+      <!-- Combined CoM: 5g rod (CoM ~35mm) + 10g tip weight at 70mm from pivot.
+           Tip at (0.07, -0.07, 0) → 45° diagonal in +X/-Y.
+           CoM = (5×0.035+10×0.07)/15 = 0.0583 along both +X and -Y.
+           Inertia tensor rotated 45° to match diagonal rod axis. -->
+      <origin xyz="0.0583 -0.0583 0.0" rpy="0 0 0"/>
+      <mass value="0.015"/>
+      <inertia ixx="6.16e-06" iyy="6.16e-06" izz="1.23e-05"
+               ixy="6.10e-06" iyz="0.0" ixz="0.0"/>
+    </inertial>
+    <visual>
+      <origin xyz="0.006895 -0.023224 -0.162953" rpy="0 0 0"/>
+      <geometry>
+        <mesh filename="meshes/pendulum_1.stl" scale="0.001 0.001 0.001"/>
+      </geometry>
+    </visual>
+    <collision>
+      <origin xyz="0.006895 -0.023224 -0.162953" rpy="0 0 0"/>
+      <geometry>
+        <mesh filename="meshes/pendulum_1.stl" scale="0.001 0.001 0.001"/>
+      </geometry>
+    </collision>
+  </link>
+
+  <!-- Pendulum joint: arm → pendulum, bearing axis along Y.
+       Joint origin corrected from mesh analysis (Fusion2URDF was 180mm off). -->
+  <joint name="pendulum_joint" type="continuous">
+    <origin xyz="0.000052 0.019274 0.014993" rpy="0 0 0"/>
+    <parent link="arm"/>
+    <child link="pendulum"/>
+    <axis xyz="0 -1 0"/>
+    <dynamics damping="0.0005"/>
+  </joint>
+
+</robot>