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2016-07-28 03:38:43 -0600 commented question Setting contact coefficients

I have updated the link for the file. Is it accessible now? So is the ┬┤Attempt 2┬┤ correct way to define the contact / friction parameters in URDF?

2016-07-26 07:09:41 -0600 received badge  Famous Question (source)
2016-07-26 07:09:33 -0600 commented answer Setting contact coefficients

The arm still passes through the object with high vibrations which sends the robot flying. Also, I just noticed that you mentioned it as SDF snippet. Can't I add this in URDF as `gazebo reference`?

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2016-07-26 02:46:47 -0600 commented answer Setting contact coefficients

Sorry but still the same problem

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2016-07-25 01:13:29 -0600 asked a question Setting contact coefficients

We have designed our own magnetic gripper for a pick and place application. I was successfully able to import this and visualize the inertias in Gazebo.

image description

But when I visualize the contacts, the vector keeps on moving frantically. Even though the movements of the arm itself is very smooth, when it comes in contact with another object, it starts vibrating. https://youtu.be/eP29QGYoQhY

I dug into PR2 gripper because it behaves very realistically when it is in contact with other objects and tried to implement the contact coefficients

Attempt 1 :

<surface>
  <friction>
    <ode>
      <mu>0.01</mu>
      <mu2>0.01</mu2>
      <fdir1>0 0 1</fdir1>
      <slip1>0.0</slip1>
      <slip2>0.0</slip2>
    </ode>
  </friction>
  <contact>
    <ode>
      <min_depth>0.005</min_depth>
      <kp>1e8</kp>
    </ode>
  </contact>
</surface>

Attempt 2 : This is exactly like the PR2 gripper

<gazebo reference="gripper_link">
  <turnGravityOff>true</turnGravityOff>
  <selfCollide>false</selfCollide>
  <mu1 value="${finger_tip_mu}" />
  <mu2 value="${finger_tip_mu}" />
  <kp  value="10000000.0" />
  <kd  value="1.0" />
</gazebo>
<gazebo reference="gripper_joint">
  <stopKd value="${finger_stop_kd}" />
  <stopKp value="${finger_stop_kp}" />
  <fudgeFactor value="${finger_fudge_factor}" />
  <provideFeedback value="true"/>
</gazebo>

This is my entire gripper xacro file :

<?xml version="1.0"?>
<robot xmlns:xacro="http://www.ros.org/wiki/xacro">

  <xacro:macro name="gripper_link" >
  <link name="gripper">    
    <inertial>
      <mass value="0.6" />
      <origin xyz="-0.02 0 0.04" />
      <inertia ixx="0.0003" ixy="0.0"  ixz="0.0"
               iyy="0.0009" iyz="0.0"
               izz="0.0008"/>
    </inertial>
    <visual>
       <origin xyz="-0.02 0 0.04" />
      <geometry>
        <mesh filename="package://ur5_pnp/meshes/gripper.stl" scale="0.01 0.01 0.01"/>
      </geometry>
    </visual>
    <collision>
       <origin xyz="-0.02 0 0.04" />
      <geometry>
        <mesh filename="package://ur5_pnp/meshes/gripper.stl" scale="0.01 0.01 0.01"/>
      </geometry>
       <surface>
      <friction>
        <ode>
          <mu>0.01</mu>
          <mu2>0.01</mu2>
          <fdir1>0 0 1</fdir1>
          <slip1>0.0</slip1>
          <slip2>0.0</slip2>
        </ode>
      </friction>
      <contact>
        <ode>
          <min_depth>5</min_depth>
          <kp>1e8</kp>
        </ode>
      </contact>
    </surface>
    </collision>
  </link>
  <gazebo reference="my_gripper">
    <material>Gazebo/Blue</material>
  </gazebo>

  </xacro:macro>
</robot>

But both the times I get the exact same behaviour. Is it something to do with friction or is it some other issue? This is my gripper's stl file

Edit 1: This gripper has no moving parts which is to simulate a magnetic gripper.

Edit 2: Updated link for STL file

2016-07-11 02:09:28 -0600 received badge  Popular Question (source)
2016-07-06 00:41:17 -0600 commented question Interaction between 2 objects in Gazebo

The problem disappears after I enable `kinematic` property in Gazebo GUI for each link of UR5. Also, I can't do this with <gazebo reference="ur5_arm_wrist_3_link"> <selfcollide>1</selfcollide> <kinematic>1</kinematic> </gazebo> The only property which changes is `selfCollide`. How can I change this through URDF? I haven't found any documentation. I could save the world file with the entire setup. Can I load the world file instead of URDF for UR5 as well?

2016-07-06 00:35:16 -0600 commented question Interaction between 2 objects in Gazebo

I am using the inertia of a cuboid macro. So I am not sure if I can make any changes apart from the mass.

2016-07-05 09:49:02 -0600 asked a question Interaction between 2 objects in Gazebo

I am working on a "pick and do" operation in ROS and simulating the same in Gazebo. I have model of a wrench, which is attached to my own gripper in URDF. The gripper in turn is attached to UR5. This setup has to rotate a knob on a panel. But as soon as the gripper touches the knob, the panel flies off even though the mass of the panel has been defined as 800kg in the sdf file. https://youtu.be/7vpE6pHe0x8

I tried the same setup by replacing my gripper with PR2 gripper (and without the wrench) and I getting decent results. So my guess is, again there seems to be some problem with the inertia of my gripper and the wrench. Would be great if anyone could help me in defining it correctly. Remove the .jpg at the end of the file name. C:\fakepath\gripper.stl.jpg

Gripper urdf : C:\fakepath\gripper.urdf.xacro.jpg

Panel sdf : C:\fakepath\model.sdf.jpg

Here's the video after making the panel model static. https://youtu.be/eP29QGYoQhY