From d221d37deadb3b58a57d9339d480298aa206c8d8 Mon Sep 17 00:00:00 2001
From: Ruixiang Du <ruixiang.du@westonrobot.com>
Date: Wed, 1 Apr 2020 18:51:34 +0800
Subject: [PATCH] saved work

---
 NOTE.md                                       |  12 +
 scout_description/urdf/scout_v2.urdf          | 277 ++++++++++++++++++
 scout_description/urdf/scout_v2.xacro         |  33 ++-
 scout_description/urdf/scout_wheel.gazebo     |  12 +-
 .../urdf/scout_wheel_type1.xacro              |   4 +-
 .../urdf/scout_wheel_type2.xacro              |   4 +-
 .../launch/scout_empty_world.launch           |  28 +-
 scout_gazebo_sim/launch/scout_playpen.launch  |   1 +
 .../worlds/weston_robot_empty.world           |  29 ++
 9 files changed, 344 insertions(+), 56 deletions(-)
 create mode 100644 scout_description/urdf/scout_v2.urdf
 create mode 100644 scout_gazebo_sim/worlds/weston_robot_empty.world

diff --git a/NOTE.md b/NOTE.md
index ed4c858..5ede40f 100644
--- a/NOTE.md
+++ b/NOTE.md
@@ -1,3 +1,15 @@
 ```
 $ rostopic pub -1 /scout_motor_fl_controller/command std_msgs/Float64 "data: 0.5"
+```
+
+Convert xacro to urdf
+
+```
+$ rosrun xacro xacro -o model.urdf model.urdf.xacro
+```
+
+Convert urdf to sdf
+
+```
+$ gz sdf -p scout_v2.urdf > scout_v2.sdf
 ```
\ No newline at end of file
diff --git a/scout_description/urdf/scout_v2.urdf b/scout_description/urdf/scout_v2.urdf
new file mode 100644
index 0000000..6031ca5
--- /dev/null
+++ b/scout_description/urdf/scout_v2.urdf
@@ -0,0 +1,277 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- =================================================================================== -->
+<!-- |    This document was autogenerated by xacro from scout_v2.xacro                 | -->
+<!-- |    EDITING THIS FILE BY HAND IS NOT RECOMMENDED                                 | -->
+<!-- =================================================================================== -->
+<robot name="scout_v2">
+  <!-- Virtual link as root -->
+  <link name="vehicle_reference"/>
+  <joint name="veh_ref_joint" type="fixed">
+    <origin rpy="0 0 0" xyz="0 0 0"/>
+    <parent link="vehicle_reference"/>
+    <child link="base_link"/>
+  </joint>
+  <!-- Base link -->
+  <link name="base_link">
+    <visual>
+      <origin rpy="0 0 0" xyz="0 0 0"/>
+      <geometry>
+        <mesh filename="package://scout_description/meshes/base_link.dae"/>
+      </geometry>
+    </visual>
+    <inertial>
+      <mass value="40"/>
+      <!-- <mass value="50" /> -->
+      <!-- <origin xyz="-0.00065 -0.085 0.062" />
+            <inertia ixx="0.6022" ixy="-0.02364" ixz="-0.1197" iyy="1.7386" iyz="-0.001544" izz="2.0296" /> -->
+      <origin xyz="0.0 0.0 0.0"/>
+      <inertia ixx="2.288641" ixy="0" ixz="0" iyy="5.103976" iyz="0" izz="3.431465"/>
+    </inertial>
+    <collision>
+      <origin rpy="0 0 0" xyz="0 0 0.008"/>
+      <geometry>
+        <box size="0.925 0.38 0.21"/>
+      </geometry>
+    </collision>
+    <collision>
+      <origin rpy="0 0 0" xyz="0 0 0.035"/>
+      <geometry>
+        <box size="0.154166666667 0.627 0.07"/>
+      </geometry>
+    </collision>
+  </link>
+  <!-- Base footprint: base_link projected to the gound plane -->
+  <link name="base_footprint"/>
+  <joint name="base_footprint_joint" type="fixed">
+    <origin rpy="0 0 0" xyz="0 0 -0.23479"/>
+    <parent link="base_link"/>
+    <child link="base_footprint"/>
+  </joint>
+  <link name="front_right_wheel_link">
+    <inertial>
+      <mass value="3"/>
+      <origin xyz="0 0 0"/>
+      <inertia ixx="0.7171" ixy="0" ixz="0" iyy="0.1361" iyz="0" izz="0.7171"/>
+    </inertial>
+    <visual>
+      <origin rpy="0 0 0" xyz="0 0 0"/>
+      <geometry>
+        <mesh filename="package://scout_description/meshes/wheel_type1.dae"/>
+      </geometry>
+    </visual>
+    <collision>
+      <origin rpy="1.570795 0 0" xyz="0 0 0"/>
+      <geometry>
+        <cylinder length="0.11653" radius="0.16459"/>
+      </geometry>
+    </collision>
+  </link>
+  <joint name="front_right_wheel" type="continuous">
+    <parent link="base_link"/>
+    <child link="front_right_wheel_link"/>
+    <origin rpy="3.14 0 0" xyz="0.249 -0.29153 -0.0702"/>
+    <axis rpy="0 0 0" xyz="0 -1 0"/>
+  </joint>
+  <link name="front_left_wheel_link">
+    <inertial>
+      <mass value="3"/>
+      <origin xyz="0 0 0"/>
+      <inertia ixx="0.7171" ixy="0" ixz="0" iyy="0.1361" iyz="0" izz="0.7171"/>
+    </inertial>
+    <visual>
+      <origin rpy="0 0 0" xyz="0 0 0"/>
+      <geometry>
+        <mesh filename="package://scout_description/meshes/wheel_type2.dae"/>
+      </geometry>
+    </visual>
+    <collision>
+      <origin rpy="1.570795 0 0" xyz="0 0 0"/>
+      <geometry>
+        <cylinder length="0.11653" radius="0.16459"/>
+      </geometry>
+    </collision>
+  </link>
+  <joint name="front_left_wheel" type="continuous">
+    <parent link="base_link"/>
+    <child link="front_left_wheel_link"/>
+    <origin rpy="0 0 0" xyz="0.249 0.29153 -0.0702"/>
+    <axis rpy="0 0 0" xyz="0 -1 0"/>
+  </joint>
+  <link name="rear_left_wheel_link">
+    <inertial>
+      <mass value="3"/>
+      <origin xyz="0 0 0"/>
+      <inertia ixx="0.7171" ixy="0" ixz="0" iyy="0.1361" iyz="0" izz="0.7171"/>
+    </inertial>
+    <visual>
+      <origin rpy="0 0 0" xyz="0 0 0"/>
+      <geometry>
+        <mesh filename="package://scout_description/meshes/wheel_type1.dae"/>
+      </geometry>
+    </visual>
+    <collision>
+      <origin rpy="1.570795 0 0" xyz="0 0 0"/>
+      <geometry>
+        <cylinder length="0.11653" radius="0.16459"/>
+      </geometry>
+    </collision>
+  </link>
+  <joint name="rear_left_wheel" type="continuous">
+    <parent link="base_link"/>
+    <child link="rear_left_wheel_link"/>
+    <origin rpy="0 0 0" xyz="-0.249 0.29153 -0.0702"/>
+    <axis rpy="0 0 0" xyz="0 -1 0"/>
+  </joint>
+  <link name="rear_right_wheel_link">
+    <inertial>
+      <mass value="3"/>
+      <origin xyz="0 0 0"/>
+      <inertia ixx="0.7171" ixy="0" ixz="0" iyy="0.1361" iyz="0" izz="0.7171"/>
+    </inertial>
+    <visual>
+      <origin rpy="0 0 0" xyz="0 0 0"/>
+      <geometry>
+        <mesh filename="package://scout_description/meshes/wheel_type2.dae"/>
+      </geometry>
+    </visual>
+    <collision>
+      <origin rpy="1.570795 0 0" xyz="0 0 0"/>
+      <geometry>
+        <cylinder length="0.11653" radius="0.16459"/>
+      </geometry>
+    </collision>
+  </link>
+  <joint name="rear_right_wheel" type="continuous">
+    <parent link="base_link"/>
+    <child link="rear_right_wheel_link"/>
+    <origin rpy="3.14 0 0" xyz="-0.249 -0.29153 -0.0702"/>
+    <axis rpy="0 0 0" xyz="0 -1 0"/>
+  </joint>
+  <!-- For testing, hang the robot up in the air -->
+  <!-- <link name="world" />
+    <joint name="world_to_base_link=" type="fixed">
+        <origin xyz="0 0 0.5" rpy="0 0 0" />
+        <parent link="world"/>
+        <child link="base_link"/>
+    </joint> -->
+  <!-- This file is a placeholder which is included by default from
+       husky.urdf.xacro. If a robot is being customized and requires
+       additional URDF, set the HUSKY_URDF_EXTRAS environment variable
+       to the full path of the file you would like included. -->
+  <!-- Additional definitions for simulation -->
+  <!-- <gazebo reference="base_link">
+        <material>Gazebo/Grey</material>
+    </gazebo> -->
+  <!-- kp spring constant, kd damping constant -->
+  <gazebo reference="front_right_wheel_link">
+    <mu1 value="1.0"/>
+    <mu2 value="1.0"/>
+    <kp value="10000000.0"/>
+    <kd value="1.0"/>
+    <fdir1 value="1 0 0"/>
+    <minDepth value="0.001"/>
+    <maxContacts value="64"/>
+  </gazebo>
+  <transmission name="front_right_wheel_trans" type="SimpleTransmission">
+    <type>transmission_interface/SimpleTransmission</type>
+    <actuator name="front_right_wheel_motor">
+      <mechanicalReduction>1</mechanicalReduction>
+    </actuator>
+    <joint name="front_right_wheel">
+      <hardwareInterface>hardware_interface/VelocityJointInterface</hardwareInterface>
+    </joint>
+  </transmission>
+  <!-- kp spring constant, kd damping constant -->
+  <gazebo reference="front_left_wheel_link">
+    <mu1 value="1.0"/>
+    <mu2 value="1.0"/>
+    <kp value="10000000.0"/>
+    <kd value="1.0"/>
+    <fdir1 value="1 0 0"/>
+    <minDepth value="0.001"/>
+    <maxContacts value="64"/>
+  </gazebo>
+  <transmission name="front_left_wheel_trans" type="SimpleTransmission">
+    <type>transmission_interface/SimpleTransmission</type>
+    <actuator name="front_left_wheel_motor">
+      <mechanicalReduction>1</mechanicalReduction>
+    </actuator>
+    <joint name="front_left_wheel">
+      <hardwareInterface>hardware_interface/VelocityJointInterface</hardwareInterface>
+    </joint>
+  </transmission>
+  <!-- kp spring constant, kd damping constant -->
+  <gazebo reference="rear_left_wheel_link">
+    <mu1 value="1.0"/>
+    <mu2 value="1.0"/>
+    <kp value="10000000.0"/>
+    <kd value="1.0"/>
+    <fdir1 value="1 0 0"/>
+    <minDepth value="0.001"/>
+    <maxContacts value="64"/>
+  </gazebo>
+  <transmission name="rear_left_wheel_trans" type="SimpleTransmission">
+    <type>transmission_interface/SimpleTransmission</type>
+    <actuator name="rear_left_wheel_motor">
+      <mechanicalReduction>1</mechanicalReduction>
+    </actuator>
+    <joint name="rear_left_wheel">
+      <hardwareInterface>hardware_interface/VelocityJointInterface</hardwareInterface>
+    </joint>
+  </transmission>
+  <!-- kp spring constant, kd damping constant -->
+  <gazebo reference="rear_right_wheel_link">
+    <mu1 value="1.0"/>
+    <mu2 value="1.0"/>
+    <kp value="10000000.0"/>
+    <kd value="1.0"/>
+    <fdir1 value="1 0 0"/>
+    <minDepth value="0.001"/>
+    <maxContacts value="64"/>
+  </gazebo>
+  <transmission name="rear_right_wheel_trans" type="SimpleTransmission">
+    <type>transmission_interface/SimpleTransmission</type>
+    <actuator name="rear_right_wheel_motor">
+      <mechanicalReduction>1</mechanicalReduction>
+    </actuator>
+    <joint name="rear_right_wheel">
+      <hardwareInterface>hardware_interface/VelocityJointInterface</hardwareInterface>
+    </joint>
+  </transmission>
+  <!-- Controller configurations -->
+  <gazebo>
+    <plugin filename="libgazebo_ros_control.so" name="gazebo_ros_control">
+      <robotNamespace>/</robotNamespace>
+    </plugin>
+  </gazebo>
+  <!-- <gazebo>
+        <plugin name="skid_steer_drive_controller" filename="libgazebo_ros_skid_steer_drive.so">
+            <updateRate>100.0</updateRate>
+            <robotNamespace></robotNamespace>
+            <leftFrontJoint>front_left_wheel</leftFrontJoint>
+            <rightFrontJoint>front_right_wheel</rightFrontJoint>
+            <leftRearJoint>rear_left_wheel</leftRearJoint>
+            <rightRearJoint>rear_right_wheel</rightRearJoint>
+            <wheelSeparation>4</wheelSeparation>
+            <wheelDiameter>0.32918</wheelDiameter>
+            <robotBaseFrame>base_link</robotBaseFrame>
+            <torque>1000</torque>
+            <commandTopic>cmd_vel</commandTopic>
+            <broadcastTF>true</broadcastTF>
+            <odometryTopic>odom</odometryTopic>
+            <odometryFrame>odom</odometryFrame>
+            <covariance_x>0.000100</covariance_x>
+            <covariance_y>0.000100</covariance_y>
+            <covariance_yaw>0.010000</covariance_yaw>
+        </plugin>
+    </gazebo> -->
+  <!-- <gazebo>
+        <plugin name="object_controller" filename="libgazebo_ros_planar_move.so">
+            <commandTopic>cmd_vel</commandTopic>
+            <odometryTopic>odom</odometryTopic>
+            <odometryFrame>odom</odometryFrame>
+            <odometryRate>20.0</odometryRate>
+            <robotBaseFrame>base_footprint</robotBaseFrame>
+        </plugin>
+    </gazebo> -->
+</robot>
diff --git a/scout_description/urdf/scout_v2.xacro b/scout_description/urdf/scout_v2.xacro
index a6523f3..462bf1a 100644
--- a/scout_description/urdf/scout_v2.xacro
+++ b/scout_description/urdf/scout_v2.xacro
@@ -24,14 +24,30 @@
     <xacro:property name="wheel_length" value="1.1653e-01" />
     <xacro:property name="wheel_radius" value="1.6459e-01" />
 
+    <!-- Virtual link as root -->
+    <link name="vehicle_reference" />
+    <joint name="veh_ref_joint" type="fixed">
+        <origin xyz="0 0 0" rpy="0 0 0" />
+        <parent link="vehicle_reference" />
+        <child link="base_link" />
+    </joint>
+
     <!-- Base link -->
     <link name="base_link">
         <visual>
             <origin xyz="0 0 0" rpy="0 0 0" />
             <geometry>
-                <mesh filename="package://scout_description/meshes/base_link_full.dae" />
+                <mesh filename="package://scout_description/meshes/base_link.dae" />
             </geometry>
         </visual>
+        <inertial>
+            <mass value="40" />
+            <!-- <mass value="50" /> -->
+            <!-- <origin xyz="-0.00065 -0.085 0.062" />
+            <inertia ixx="0.6022" ixy="-0.02364" ixz="-0.1197" iyy="1.7386" iyz="-0.001544" izz="2.0296" /> -->
+            <origin xyz="0.0 0.0 0.0" />
+            <inertia ixx="2.288641" ixy="0" ixz="0" iyy="5.103976" iyz="0" izz="3.431465" />
+        </inertial>
         <collision>
             <origin xyz="0 0 0.008" rpy="0 0 0" />
             <geometry>
@@ -55,21 +71,6 @@
         <child link="base_footprint" />
     </joint>
 
-    <!-- Interial link -->
-    <link name="inertial_link">
-        <inertial>
-            <mass value="46.034" />
-            <origin xyz="-0.00065 -0.085 0.062" />
-            <inertia ixx="0.6022" ixy="-0.02364" ixz="-0.1197" iyy="1.7386" iyz="-0.001544" izz="2.0296" />
-        </inertial>
-    </link>
-
-    <joint name="inertial_joint" type="fixed">
-        <origin xyz="0 0 0" rpy="0 0 0" />
-        <parent link="base_link" />
-        <child link="inertial_link" />
-    </joint>
-
     <!-- Scout wheel macros -->
     <!-- wheel labeled from 0 to 3, conter-clockwise, starting from front right wheel -->
     <!-- motor 1 and 2 (left side) are mechanically installed in a reversed direction -->
diff --git a/scout_description/urdf/scout_wheel.gazebo b/scout_description/urdf/scout_wheel.gazebo
index 7ddce49..c867ce2 100644
--- a/scout_description/urdf/scout_wheel.gazebo
+++ b/scout_description/urdf/scout_wheel.gazebo
@@ -28,23 +28,17 @@ ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSI
 <robot xmlns:xacro="http://ros.org/wiki/xacro" name="scout_wheel">
 
     <xacro:macro name="scout_wheel_transmission" params="wheel_prefix">
+        <!-- kp spring constant, kd damping constant -->
         <gazebo reference="${wheel_prefix}_wheel_link">
             <mu1 value="1.0"/>
-            <mu2 value="0.6"/>
+            <mu2 value="0.9"/>
             <kp value="10000000.0" />
             <kd value="1.0" />
             <fdir1 value="1 0 0"/> 
+            <minDepth value="0.001" />
             <maxContacts value="64"/>
         </gazebo> 
 
-        <!-- <gazebo reference="${wheel_prefix}_wheel_link">
-            <mu1 value="1.0"/>
-            <mu2 value="1.0"/>
-            <kp value="10000000.0" />
-            <kd value="1.0" />
-            <fdir1 value="1 0 0"/> 
-        </gazebo> -->
-
         <transmission name="${wheel_prefix}_wheel_trans" type="SimpleTransmission">
             <type>transmission_interface/SimpleTransmission</type>
             <actuator name="${wheel_prefix}_wheel_motor">
diff --git a/scout_description/urdf/scout_wheel_type1.xacro b/scout_description/urdf/scout_wheel_type1.xacro
index 3b0cb4e..960acf6 100644
--- a/scout_description/urdf/scout_wheel_type1.xacro
+++ b/scout_description/urdf/scout_wheel_type1.xacro
@@ -30,9 +30,9 @@ ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSI
     <xacro:macro name="scout_wheel_type1" params="wheel_prefix *joint_pose">
         <link name="${wheel_prefix}_wheel_link">
             <inertial>
-                <mass value="2.637" />
+                <mass value="3" />
                 <origin xyz="0 0 0" />
-                <inertia ixx="0.02467" ixy="0" ixz="0" iyy="0.04411" iyz="0" izz="0.02467" />
+                <inertia ixx="0.7171" ixy="0" ixz="0" iyy="0.1361" iyz="0" izz="0.7171" />
             </inertial>
             <visual>
                 <origin xyz="0 0 0" rpy="0 0 0" />
diff --git a/scout_description/urdf/scout_wheel_type2.xacro b/scout_description/urdf/scout_wheel_type2.xacro
index d8aa310..2435b5b 100644
--- a/scout_description/urdf/scout_wheel_type2.xacro
+++ b/scout_description/urdf/scout_wheel_type2.xacro
@@ -30,9 +30,9 @@ ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSI
     <xacro:macro name="scout_wheel_type2" params="wheel_prefix *joint_pose">
         <link name="${wheel_prefix}_wheel_link">
             <inertial>
-                <mass value="2.637" />
+                <mass value="3" />
                 <origin xyz="0 0 0" />
-                <inertia ixx="0.02467" ixy="0" ixz="0" iyy="0.04411" iyz="0" izz="0.02467" />
+                <inertia ixx="0.7171" ixy="0" ixz="0" iyy="0.1361" iyz="0" izz="0.7171" />
             </inertial>
             <visual>
                 <origin xyz="0 0 0" rpy="0 0 0" />
diff --git a/scout_gazebo_sim/launch/scout_empty_world.launch b/scout_gazebo_sim/launch/scout_empty_world.launch
index 1467714..64be720 100644
--- a/scout_gazebo_sim/launch/scout_empty_world.launch
+++ b/scout_gazebo_sim/launch/scout_empty_world.launch
@@ -1,36 +1,10 @@
-<?xml version="1.0"?>
-<!--
-Software License Agreement (BSD)
-
-\file      husky_empty_world.launch
-\authors   Paul Bovbel <pbovbel@clearpathrobotics.com, Devon Ash <dash@clearpathrobotics.com>
-\copyright Copyright (c) 2015, Clearpath Robotics, Inc., All rights reserved.
-
-Redistribution and use in source and binary forms, with or without modification, are permitted provided that
-the following conditions are met:
- * Redistributions of source code must retain the above copyright notice, this list of conditions and the
-   following disclaimer.
- * Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the
-   following disclaimer in the documentation and/or other materials provided with the distribution.
- * Neither the name of Clearpath Robotics nor the names of its contributors may be used to endorse or promote
-   products derived from this software without specific prior written permission.
-
-THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WAR-
-RANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
-PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, IN-
-DIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
-OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
-ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
-ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
--->
 <launch>
 
     <arg name="robot_namespace" default="/"/>
-    <arg name="world_name" default="worlds/empty.world"/>
+    <arg name="world_name" default="$(find scout_gazebo_sim)worlds/weston_robot_empty.world"/>
 
     <include file="$(find gazebo_ros)/launch/empty_world.launch">
         <arg name="world_name" value="$(arg world_name)"/>
-        <!-- world_name is wrt GAZEBO_RESOURCE_PATH environment variable -->
         <arg name="paused" value="false"/>
         <arg name="use_sim_time" value="true"/>
         <arg name="gui" value="true"/>
diff --git a/scout_gazebo_sim/launch/scout_playpen.launch b/scout_gazebo_sim/launch/scout_playpen.launch
index 00ede1d..afefa40 100644
--- a/scout_gazebo_sim/launch/scout_playpen.launch
+++ b/scout_gazebo_sim/launch/scout_playpen.launch
@@ -29,6 +29,7 @@ ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSI
     <arg name="world_name" default="$(find scout_gazebo_sim)/worlds/clearpath_playpen.world"/>
 
     <include file="$(find gazebo_ros)/launch/empty_world.launch">
+        <arg name="physics" value="bullet" />
         <arg name="world_name" value="$(arg world_name)"/>
         <arg name="paused" value="false"/>
         <arg name="use_sim_time" value="true"/>
diff --git a/scout_gazebo_sim/worlds/weston_robot_empty.world b/scout_gazebo_sim/worlds/weston_robot_empty.world
new file mode 100644
index 0000000..bb55236
--- /dev/null
+++ b/scout_gazebo_sim/worlds/weston_robot_empty.world
@@ -0,0 +1,29 @@
+<?xml version="1.0" ?>
+<sdf version="1.4">
+  <world name="default">
+    <!-- A global light source -->
+    <include>
+      <uri>model://sun</uri>
+    </include>
+
+    <!-- A ground plane -->
+    <include>
+      <uri>model://ground_plane</uri>
+    </include>
+
+    <!-- Physics -->
+    <!-- <physics type="ode">
+      <ode>
+        <solver>
+          <type>world</type>
+        </solver>
+        <constraints>
+          <contact_max_correcting_vel>0.1</contact_max_correcting_vel>
+          <contact_surface_layer>0.0001</contact_surface_layer>
+        </constraints>
+      </ode>
+      <max_step_size>0.001</max_step_size>
+    </physics>
+    <gravity>0.0 0.0 -9.81</gravity> -->
+  </world>
+</sdf>
\ No newline at end of file