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Pose calculation in gazebosim tutorial

asked 2015-09-28 15:09:55 -0500

praks411 gravatar image

updated 2015-09-28 15:25:12 -0500

chapulina gravatar image

Hi,

Is there any tutorial or primer to calculate pose of different component required in sdf file. As an example in gazebo tutorial "Make a mobile robot" how can one calculate pose for box, caster_collision and wheel. http://gazebosim.org/tutorials?tut=buildrobot&cat=buildrobot Any link which describes pose calculation would also be useful.

Thanks and Regards, Pradeep

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answered 2015-09-28 15:48:58 -0500

chapulina gravatar image

updated 2015-09-28 15:57:30 -0500

I don't think there's a tutorial for it yet. Here's my attempt at a basic overview:

Transform

Poses in Gazebo represent a transform between two frames. They are defined by 6 values:

<pose> x y z roll pitch yaw </pose>
  • Translation (x y z) is applied before rotation (roll pitch yaw)

  • Fixed axis is used for the rotation

Reference frames

Currently poses are always defined with respect to a specific frame according to the element it belongs to. This is documented in the SDF specification for that element, see link -> pose for an example. I'll list some of the most used ones here as a quick reference:

  • Model -> World
  • Link -> Model
  • Visual -> Link
  • Collision -> Link
  • Joint -> Child link
  • Inertia (CoM) -> Link

Experimenting

I recommend you experiment with poses using the left panel and see how different poses affect your model.

  1. Turn off gravity so your model stays in place: on the left panel, choose Physics and set all gravity elements to zero.

  2. Insert a box, right click it and view it transparent, then also choose to view link origin. This will show the frame you're manipulating.

  3. On the left panel, choose the box and input different poses to see how it moves with respect tot he world frame. Make sure the simulation is not paused.

Reference

You might want to look at the ignition math Pose class for a deeper insight.

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Hi, Thanks for the nice explanation. I'm still trying to understand but bit slow :)

praks411 gravatar imagepraks411 ( 2015-10-09 07:40:10 -0500 )edit
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Asked: 2015-09-28 15:09:55 -0500

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Last updated: Sep 28 '15