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2016-06-22 07:15:34 -0600 commented answer Object slips out of the gripper after jitters

It still doesn't work! When ever gripper gets a grasp on the object it slips over it while lifting and other times object passes through the gripper

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2016-06-21 14:09:49 -0600 commented answer Object slips out of the gripper after jitters

Thanks for such a detailed answer. But could you elaborate on point 3. For, example what exactly are inner iterations and rms_error

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2016-06-21 09:15:33 -0600 asked a question Object slips out of the gripper after jitters

I am trying to make robot arm grasp a cylinder object but when ever the gets in the grasp and the gripper closes, it starts vibrating and the object appears to slip out of it. I am using a position_controller for gripper and the rest of the arm. The problem I can think of could be with the controller as it tries to reach a position which it cannot due to collision with the object so the pid controller starts shaking it.

Pls answer if you have any insight on this. Thanks

<joint name="${prefix}gripper_joint" type="prismatic"> <parent link="${prefix}wrist_roll"/> <child link="${prefix}gripper_finger1"/> <origin xyz="-0.01331 0.00485 0.137225" rpy="0 0 0"/> <limit lower="-0.08" upper="0.008" effort="20.0" velocity="5.0"/> <axis xyz="1 0 0"/> <dynamics damping="0.7" friction="0.0"/> </joint>

<link name="${prefix}gripper_finger1">
  <visual>
    <origin xyz="0 0 0" rpy="0 0 0" />
    <geometry>
      <!--box size="0.015 0.0229 0.0475"/-->
      <mesh filename="package://cyton_gamma_1500_description/meshes/gripper_finger1.dae"/>
    </geometry>
  </visual>
  <collision name="${prefix}gripper_finger1_collision">
    <origin xyz="0 0 0" rpy="0 0 0" />
    <geometry>
      <box size="0.015 0.0229 0.1"/>
  <mesh filename="package://cyton_gamma_1500_description/meshes/gripper_finger1.dae"/>
    </geometry>
  </collision>
  <inertial>
    <mass value="0.01"/>
    <origin rpy="0 0 0" xyz="0 0 0"/>
    <inertia ixx=".0000027" iyy=".0000027" izz=".0000027"
              ixy="0" ixz="0" iyz="0"/>
  </inertial>
</link>

 <gazebo reference="${prefix}gripper_finger1">
  <kp>1000000.0</kp>
  <kd>1.0</kd>
  <mu1>200.0</mu1>
  <mu2>100.0</mu2>
  <minDepth>0.001</minDepth>
</gazebo>


<transmission name="tran8">
<type>transmission_interface/SimpleTransmission</type>
<joint name="${prefix}gripper_joint">
  <hardwareInterface>EffortJointInterface</hardwareInterface>
</joint>
<actuator name="motor8">
  <hardwareInterface>EffortJointInterface</hardwareInterface>
</actuator>

</transmission>

<joint name="${prefix}gripper_joint2" type="prismatic"> <parent link="${prefix}wrist_roll"/> <child link="${prefix}gripper_finger2"/> <origin xyz="0.0098 0.00485 0.137225" rpy="0 0 0"/> <limit lower="-0.008" upper="0.08" effort="20.0" velocity="5.0"/> <axis xyz="1 0 0"/> <dynamics damping="0.7" friction="0.0"/> </joint>

<link name="${prefix}gripper_finger2">
  <visual>
    <origin xyz="0 0 0" rpy="0 0 0" />
    <geometry>
  <!--box size="0.015 0.0229 0.0475"/-->
      <mesh filename="package://cyton_gamma_1500_description/meshes/gripper_finger2.dae"/>
    </geometry>
  </visual>
  <collision name="${prefix}gripper_finger2_collision">
    <origin xyz="0 0 0" rpy="0 0 0" />
    <geometry>
      <box size="0.015 0.0229 0.1"/><!--0.0475-->
  <!--mesh filename="package://cyton_gamma_1500_description/meshes/gripper_finger2.dae"/-->
    </geometry>
  </collision>
  <inertial>
    <mass value="0.01"/>
    <origin rpy="0 0 0" xyz="0 0 0"/>
    <inertia ixx=".0000027" iyy=".0000027" izz=".0000027"
              ixy="0" ixz="0" iyz="0"/>
  </inertial>
</link>

<gazebo reference="${prefix}gripper_finger2">
  <kp>1000000.0</kp>
  <kd>1.0</kd>
  <mu1>200.0</mu1>
  <mu2>100.0</mu2>
  <minDepth>0.001</minDepth>
</gazebo>



<transmission name="tran9">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="${prefix}gripper_joint2">
      <hardwareInterface>EffortJointInterface</hardwareInterface>
    </joint>
    <actuator name="motor9">
      <hardwareInterface>EffortJointInterface</hardwareInterface>
    </actuator>

This is the updated urdf of the gripper

  <?xml version="1.0"?>
<robot name="mug">
<link name="coke_can">
    <inertial>
      <mass value="0.1 ...
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2016-06-20 12:19:19 -0600 commented question Robot gripper passes through object to be grasped

It works! I feel so stupid. I did not check the visual origins with collision origins and the equally quilty company which generated this urdf charged 12k for the arm.

2016-06-20 12:06:04 -0600 commented question Robot gripper passes through object to be grasped

Bravo they are all scattered and not in right places thank you! I'll try to arrange them properly and see if it works.

2016-06-20 09:08:21 -0600 asked a question Robot gripper passes through object to be grasped

Gazebo version 2.2.3 I am trying to implement a grasping algorithm on my custom robot but it passes through the object instead of grasping it. I've checked all the collision tags in both urdfs (robot's and object's) and they are standard, potential problems that I can think of:-

Collision geometry is not correct: Highly unlikely as the robot is using its meshes as geometry and the object is simple cylinder.

Controllers of joint angles of the robot are not right: I've used standard ros_control position controllers and what I've noticed is that on echoing joint_states topic I can see position and velocity but effort is zero for all messages. I configured controllers referencing from master of robot programming book and even in their example the arm passes through the floor.

Arm breaks when I reset the gazebo world: Might have some correlation

If any of these conditions imply something in the context of gripper passing through the object then please help.

Thanks in advance