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Gazebo mimic joints property

asked 2011-06-13 22:51:53 -0500

mbj gravatar image

updated 2011-06-14 12:45:53 -0500

mmwise gravatar image

Hi.

I'm trying to "link" two joints with the mimic joint property. I readed that this property isn't suported officialy yet but there is in the code of Gazebo and can be used.

I readed here: http://www.ros.org/doc/api/urdf/html/joint_8h_source.html and found some exemples like this:

<joint name="r_gripper_r_finger_joint" type="revolute">
  <axis xyz="0 0 -1"/>
  <origin rpy="0 0 0" xyz="0.07691 -0.01 0"/>
  <limit effort="1000.0" lower="0.0" upper="0.548" velocity="0.5"/>
  <dynamics damping="0.2"/>
  <mimic joint="r_gripper_l_finger_joint" multiplier="1" offset="0"/>
  <parent link="r_gripper_palm_link"/>
  <child link="r_gripper_r_finger_link"/>
</joint>

But when I try to link my joints it has no efect, and when I apply one effort to a "joint_left_wheel" the "joint_right_wheel" (presumably connected) keeps in the position. My code is the next (I also tried with the next parameters joint_name="joint_left_wheel" multiplier="1" offset="0"), does you see any mistake?

<joint name="joint_right_wheel" type="continuous">
  <origin xyz="0.35 0 0.1" rpy="0 0 0" />
  <axis xyz="0 0 0" />
  <mimic joint="joint_left_wheel" multiplier="1" offset="0"/>
  <parent link="chassis"/>
  <child link="right_wheel"/>
</joint>

Thanks!

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answered 2011-06-14 11:42:38 -0500

hsu gravatar image

Unfortunately the tags are simply ignored in simulation at this point. To do this right, a mimic constraint needs to be created in underlying physics engine (i.e. ODE) and propagated through gazebo to realize dynamics of mimicking. Please open a ticket if this is a useful feature to you (note, you'll have to setup an account on code.ros.org first before you can create tickets).

Thanks.

John

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Hi John, thanks for answer again. As you say, I created a ticket in code.ros.org, and I owned to you this ticket accidentally. If you wouldn't to work with this ticket, please change the owner. This is the ticket: https://code.ros.org/trac/ros-pkg/ticket/5005 Thanks!
mbj gravatar imagembj ( 2011-06-14 20:48:52 -0500 )edit
all tickets defaults to me in simulator_gazebo, but I'll gladly accept patches or if anyone wants to pick it up :) Thanks.
hsu gravatar imagehsu ( 2011-06-15 09:29:37 -0500 )edit

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Asked: 2011-06-13 22:51:53 -0500

Seen: 1,313 times

Last updated: Jun 14 '11