URDF model always slipping/ rotating

edit

Hi guys,

I am using a modified version of turtlebot3 and tried to make a quiet simple model in gazebo but when opening it in gazebo its always slipping and/or rotating a bit.

I first tried to have two caster wheels (which is how it really looks though) but decided to first try it with one.. cause that is hard enough for the beginnging.

I hope somebody can help me with this!

Here is my urdf:

<?xml version="1.0" ?>

<robot name="turtlebot3_waffle_pi" xmlns:xacro="http://ros.org/wiki/xacro"> <xacro:include filename="$(find turtlebot3_description)/urdf/common_properties.xacro"/> <xacro:include filename="$(find turtlebot3_description)/urdf/turtlebot3_waffle_pi.gazebo.xacro"/>

<link name="base_footprint"/>

<joint name="base_joint" type="fixed"> <parent link="base_footprint"/> <child link="base_link"/> <origin xyz="0 0 0" rpy="0 0 0"/> </joint>

<link name="base_link"> <visual> <origin xyz="0 0 0" rpy="0 0 0"/> <geometry> <box size="0.52 0.50 1.20"/> </geometry> <material name="light_black"/> </visual>

<collision>
  <origin xyz="0 0 0" rpy="0 0 0"/>
  <geometry>
    <box size="0.52 0.50 1.20"/>
  </geometry>
</collision>

<inertial>
  <origin xyz="0 0 0" rpy="0 0 0"/>
  <mass value="20.00e+00"/>
  <inertia ixx="3" ixy="0" ixz="0"
           iyy="2.82" iyz="0"
           izz="0.83" />
</inertial>

</link>

<joint name="sonar_bottom_right_joint" type="fixed"> <parent link="base_link"/> <child link="sonar_bottom_right_link"/> <origin xyz="0.26 -0.16 -0.51" rpy="0 0 0"/> </joint>

<link name="sonar_bottom_right_link"> <visual> <origin xyz="0 0 0" rpy="0 0 0"/> <geometry> <box size="0.005 0.05 0.05"/> </geometry> <material name="blue"/> </visual>

<collision>
  <origin xyz="0 0 0" rpy="0 0 0"/>
  <geometry>
    <box size="0.005 0.05 0.05"/>
  </geometry>
</collision>

<inertial>
  <origin xyz="0 0 0" />
  <mass value="1.8498940e-02" />
  <inertia ixx="0.1175580e-05" ixy="-3.2369783e-11" ixz="-4.9381719e-09"
           iyy="0.1192413e-05" iyz="-0.4400107e-11"
           izz="0.0712558e-05" />
  </inertial>

</link>

<joint name="sonar_bottom_left_joint" type="fixed"> <parent link="base_link"/> <child link="sonar_bottom_left_link"/> <origin xyz="0.26 0.16 -0.51" rpy="0 0 0"/> </joint>

<link name="sonar_bottom_left_link"> <visual> <origin xyz="0 0 0" rpy="0 0 0"/> <geometry> <box size="0.005 0.05 0.05"/> </geometry> <material name="blue"/> </visual>

<collision>
  <origin xyz="0 0 0" rpy="0 0 0"/>
  <geometry>
    <box size="0.005 0.05 0.05"/>
  </geometry>
</collision>

<inertial>
  <origin xyz="0 0 0" />
  <mass value="1.8498940e-02" />
  <inertia ixx="0.1175580e-05" ixy="-3.2369783e-11" ixz="-4.9381719e-09"
           iyy="0.1192413e-05" iyz="-0.4400107e-11"
           izz="0.0712558e-05" />
  </inertial>

</link>

<joint name="wheel_left_joint" type="continuous"> <parent link="base_link"/> <child link="wheel_left_link"/> <origin xyz="0.26 0.2215 -0.5835" rpy="-1.57 0 0"/> <axis xyz="0 0 1"/> </joint>

<link name="wheel_left_link"> <visual> <origin xyz="0 0 0" rpy="1.57 0 0"/> <geometry> <mesh filename="package://turtlebot3_description/meshes/wheels/left_tire.stl" scale="0.001 0.001 0.001"/> </geometry> <material name="dark"/> </visual>

<collision>
  <origin xyz="0 0 0" rpy="0 0 0"/>
  <geometry>
    <cylinder length="0.018" radius="0 ...