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sdf robot model slippery, slides no friction

asked 2013-01-30 18:53:18 -0600

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Hello I got an issue with a humanoid robot modeled in sdf format. The model itself is fine. However, my problem is the model slips, slides, and can't stay in place as soon as i move a joint (via plugin of window).

The model plug in is not the problem in this case.

I tried inserting the <mu> tags, <surface><contact> <kp> <kd> tags but they don'e work. I suspect I need a separate world plugin but i am not sure about this since the model already has a plugin.

You anyone please advise?

Thank you

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Please post your SDF files, and tell us what version of Gazebo you're using.

nkoenig gravatar imagenkoenig ( 2013-01-30 19:06:28 -0600 )edit

i am using Gazebo I am not comfortable posting the whole sdf file. Can i post an sdf file that has only the lower body, that is with links (visual + collision) and joints?

nordegren gravatar imagenordegren ( 2013-02-03 18:47:40 -0600 )edit

thank you hsu i will saw the mu values and they are way higher than what i have, in fact these values are crazy high. i will post some of the code for the links and joints once i figure how to properly use this website.

nordegren gravatar imagenordegren ( 2013-02-06 18:17:39 -0600 )edit

here is a sample of a link

nordegren gravatar imagenordegren ( 2013-02-07 18:49:58 -0600 )edit

<link name="right_foot"> <pose>.030 -.090 .010 0 0 0</pose> <inertial> <mass>1.5</mass> <inertia> <ixx>1.0</ixx><ixy>0.0</ixy><ixz>0.0</ixz><iyy>1.0</iyy><iyz>0.0</iyz><izz>1.0</izz> </inertia> </inertial> <collision name="collision"> <geometry> <box><size>.300 .120 .020</size></box> <!-- <mesh><uri>model://</uri></mesh> --> </geometry> <surface> <friction> <ode><mu>0.3</mu></ode

nordegren gravatar imagenordegren ( 2013-02-07 18:52:09 -0600 )edit

<link name="right_foot"> <pose>.030 -.090 .010 0 0 0</pose> <inertial> <mass>1.5</mass> <inertia> <ixx>1.0</ixx><ixy>0.0</ixy><ixz>0.0</ixz><iyy>1.0</iyy><iyz>0.0</iyz><izz>1.0</izz> </inertia> </inertial> <collision name="collision"> <geometry> <box><size>.300 .120 .020</size></box> <!-- <mesh><uri>model://</uri></mesh> --> </geometry> <surface> <friction> <ode><mu>0.3</mu></ode

nordegren gravatar imagenordegren ( 2013-02-07 18:52:10 -0600 )edit

<link name="right_foot"> <pose>.030 -.090 .010 0 0 0</pose> <inertial> <mass>1.5</mass> <inertia> <ixx>1.0</ixx><ixy>0.0</ixy><ixz>0.0</ixz><iyy>1.0</iyy><iyz>0.0</iyz><izz>1.0</izz> </inertia> </inertial> <collision name="collision"> <geometry> <box><size>.300 .120 .020</size></box> <!-- <mesh><uri>model://</uri></mesh> --> </geometry> <surface> <friction> <ode><mu>0.3</mu></ode

nordegren gravatar imagenordegren ( 2013-02-07 18:52:11 -0600 )edit

It will be hard to debug your problem without a complete SDF file. We can take this offline so that you don't have to post a complete SDF. Please contact me using nate@osrfoundation.org

nkoenig gravatar imagenkoenig ( 2013-03-07 22:55:20 -0600 )edit

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answered 2013-02-07 21:17:35 -0600

hsu gravatar image

I created a world with two copies of your link, one with 0 friction one with high friction:

<?xml version="1.0" ?>
<sdf version="1.3">
  <world name="default">

    <physics type="ode">
      <gravity>0.1 0 -9.81</gravity>
    </physics>

    <!-- A global light source -->
    <include>
      <uri>model://sun</uri>
    </include>

    <!-- A ground plane -->
    <include>
      <uri>model://ground_plane</uri>
    </include>

    <model name="right_foot">
      <pose>0 1 .005 0 0 0</pose>
      <link name="right_foot">
        <pose>.030 .090 .010 0 0 0</pose>
        <inertial>
          <mass>1.5</mass>
          <inertia>
            <ixx>1.0</ixx><ixy>0.0</ixy><ixz>0.0</ixz><iyy>1.0</iyy><iyz>0.0</iyz><izz>1.0</izz>
          </inertia>
        </inertial>
        <collision name="collision">
          <geometry>
            <box><size>.300 .120 .020</size></box>
          </geometry>
          <surface>
            <friction>
              <ode><mu>100000.0</mu><mu2>100000.0</mu2></ode>
              <ode><mu>0.0</mu><mu2>0.0</mu2></ode>
            </friction>
          </surface>
        </collision>
        <visual name="visual">
          <geometry>
            <box><size>.300 .120 .020</size></box>
          </geometry>
        </visual>
      </link>
    </model>
    <model name="left_foot">
      <pose>0 0 .005 0 0 0</pose>
      <link name="left_foot">
        <pose>.030 .090 .010 0 0 0</pose>
        <inertial>
          <mass>1.5</mass>
          <inertia>
            <ixx>1.0</ixx><ixy>0.0</ixy><ixz>0.0</ixz><iyy>1.0</iyy><iyz>0.0</iyz><izz>1.0</izz>
          </inertia>
        </inertial>
        <collision name="collision">
          <geometry>
            <box><size>.300 .120 .020</size></box>
          </geometry>
          <surface>
            <friction>
              <!--<ode><mu>100000.0</mu><mu2>100000.0</mu2></ode>-->
              <ode><mu>0.0</mu><mu2>0.0</mu2></ode>
            </friction>
          </surface>
        </collision>
        <visual name="visual">
          <geometry>
            <box><size>.300 .120 .020</size></box>
          </geometry>
        </visual>
      </link>
    </model>
  </world>
</sdf>

If you save the above world as test.world, then start gazebo by calling

gazebo test.world

One of the boxes slides while the other stays stationary under a lateral gravity field. So it appears to be working correctly for me.

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answered 2013-02-14 18:56:28 -0600

this post is marked as community wiki

This post is a wiki. Anyone with karma >75 is welcome to improve it.

I have posted a sample code of the controller 2 days ago. I don't know why the code is not posted. I will repost again

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Asked: 2013-01-30 18:53:18 -0600

Seen: 16,089 times

Last updated: Jan 05 '18