friction changes on feet wont take effect

[Soshiant David]

i'm tring to simulate the effect of slippery ground and i go to naoGazebo.xacro and change the
<mu>0</mu>
<mu2>0</mu2>
and it still has friction
im working on
https://github.com/ros-naoqi/nao_moveit_config
i even ried adding
<surface>
        <friction>
          <ode>
            <mu>0</mu>
            <mu2>0</mu2>
          </ode>
        </friction>
      </surface>
to the collision part of the nao_sensors.xacro
but still no changes

[Soshiant David]

i changed the property of ground in its sdf and it got solved
but i think gz5 has problem with urdf cause none of the parameters in naoGazebo.xacro make any changes (i only tried fsr properties like  mu max vel and...)

[John Hsu]

Hi,

Looks like you found a workaround already, but I just want to add here that adding friction blocks to urdf could be a little bit tricky. Here's an example that works for Atlas model:

https://bitbucket.org/osrf/drcsim/src/583228ebd72677c36a393b3260f0c5f0bc7b0f87/atlas_description/urdf/atlas_v5.gazebo?at=default&fileviewer=file-view-default#atlas_v5.gazebo-95

In this example, the legacy way of using an extension block to add friction coefficients to a collision looks like this:

  <gazebo reference="r_foot">
    <mu1>1.5</mu1>
    <mu2>1.5</mu2>
  </gazebo>

Alternatively, since sdf3, recommended approach is to use the sdf block in extension, looks like this (see this comment in code):

  <gazebo reference="r_foot">
    <!-- using sdf block syntax directly in extension -->
    <collision>
      <friction>      
        <ode>      
          <mu>1.5</mu>
          <mu2>1.5</mu2>
        </ode>      
      </friction>      
    </collision>
  </gazebo>

On the physics side, ultimately the effective friction coefficient used by the contact constraint is chosen as the minimum of the two coefficients from surfaces in contact (see this code for example). That should explain why reducing the ground friction coefficient worked for you.

Hope this helps.

John

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