Hello,

I am trying to set different friction coefficients in the different x-y link direction. For that i am using the , and tags provided especially for that purpose. But for some reason the friction coefficients are applied by GAZEBO in the world frame and not the link frame.

In order to test the issue I placed same box, with different and on the ground plane in two orientation (perpendicular to each other) and applied increasing gravity in x direction.

here is the sdf of the ground plane (i use same friction in both directions) :

<?xml version="1.0" ?>
<sdf version="1.5">
  <model name="ground_plane">
    <static>true</static>
    <link name="link">
      <collision name="collision">
        <geometry>
          <plane>
            <normal>0 0 1</normal>
            <size>100 100</size>
          </plane>
        </geometry>
        <surface>
          <friction>
            <ode>
              <mu>100</mu>
              <mu2>100</mu2>
          <fdir1>1 0 0</fdir1>
            </ode>
          </friction>
        </surface>
      </collision>
      <visual name="visual">
        <cast_shadows>false</cast_shadows>
        <geometry>
          <plane>
            <normal>0 0 1</normal>
            <size>100 100</size>
          </plane>
        </geometry>
        <material>
          <script>
            <uri>file://media/materials/scripts/gazebo.material</uri>
            <name>Gazebo/Grey</name>
          </script>
        </material>
      </visual>
    </link>
  </model>
</sdf>

here is the sdf of a box that i use for tests (i set high friction in x direction, and low friction in y direction) :

<?xml version="1.0"?>
<sdf version="1.4">
  <model name="cube1">
    <static>false</static>
    <link name="link">
       <pose>0 0 0.5 0 0 0</pose>
       <collision name="collision">
        <geometry>
            <box>
              <size>2 1 1</size>
            </box>
        </geometry>
        <surface>
          <friction>
            <ode>
              <mu>0.3</mu>
              <mu2>100</mu2>
          <fdir1>1 0 0</fdir1>
            </ode>
          </friction>
         </surface>
    </collision>

      <inertial>
        <pose>0 0 -0.4 0 -0 0</pose>
        <mass>50</mass>
        <inertia>
          <ixx>1</ixx>
          <ixy>0</ixy>
          <ixz>0</ixz>
          <iyy>1</iyy>
          <iyz>0</iyz>
          <izz>1</izz>
        </inertia>
      </inertial>

      <visual name="visual">
         <geometry>
            <box>
              <size>2 1 1</size>
            </box>
        </geometry>
          <material>
            <script>
              <uri>file://media/materials/scripts/gazebo.material</uri>
              <name>Gazebo/Grey</name>
            </script>
          </material>
      </visual>

    </link>
  </model>
</sdf>

as i increase the gravity in x (world) direction both boxes start to slide simultaneously and with the same speed. if i increase the gravity in y (world) direction the boxes do not move.

what am i doing wrong here ?