Changing the orientation of a pose goal in rviz (python)

asked 2020-09-01 13:01:10 -0500

Matt Gibbon
13 ●3 ●4 ●5

Coming off the back of the rviz tutorials, I've been trying to control the panda arm using only the pose goal but cannot change it's orientation. Changing the "pose_goal.orientation.w" value seems to do nothing and although I've read that rviz uses quaterion values to define orientation I can't understand how this translates to what I'd write in my code to achieve a specific orientation. My goal is to be able to set an orientation for the arm based on coordinates in Cartesian space and either values for pitch/roll/yaw or a direction vector

Here is the part of my code defining the pose goal

def go_to_pose_goal(self):

move_group = self.move_group

print("Starting planning to go to pose goal.\n")
pose_goal = geometry_msgs.msg.Pose()


pose_goal.orientation.w = 1
pose_goal.orientation.x = 1
pose_goal.orientation.y = 1
pose_goal.orientation.z = 1
pose_goal.position.x = 1
pose_goal.position.y = -0.518
pose_goal.position.z = 0.8

move_group.set_pose_target(pose_goal)

plan = move_group.go(wait=True)
move_group.stop()
move_group.clear_pose_targets()

current_pose = self.move_group.get_current_pose().pose
return all_close(pose_goal, current_pose, 0.01

Comments

Coming off the back of the rviz tutorials

please always link to whatever you are referring to.

We can't know what you consider "the rviz tutorials".

gvdhoorn ( 2020-09-02 03:16:27 -0500 )edit

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answered 2020-09-02 02:14:42 -0500

gvdhoorn
86574 ●283 ●1432 ●1054 http://cor.tudelft.nl/

updated 2020-09-02 02:17:50 -0500

I would recommend to take a look at wiki/tf2/Tutorials/Quaternions in addition to a general introduction to what quaternions are (there are various textbooks (ie: math) and sites which discuss them, such as ), as I believe that's mostly where your confusion comes from.

Changing the "pose_goal.orientation.w" value seems to do nothing and although I've read that rviz uses quaterion values to define orientation I can't understand how this translates to what I'd write in my code to achieve a specific orientation

Changing the w element of a quaternion is not something you typically do manually: it's not the yaw component (there is no yaw component directly in a quaternion).

My goal is to be able to set an orientation for the arm based on coordinates in Cartesian space and either values for pitch/roll/yaw or a direction vector

As mentioned on wiki/tf2/Tutorials/Quaternions: Think in RPY then convert to quaternion, you can do this by using convenience/conversion functions from (for instance) the tf.transformations library:

from tf.transformations import quaternion_from_euler

if __name__ == '__main__':

  # RPY to convert: 90deg, 0, -90deg
  q = quaternion_from_euler(1.5707, 0, -1.5707)

  print "The quaternion representation is %s %s %s %s." % (q[0], q[1], q[2], q[3])

(this code is just a copy-paste from the linked wiki page)

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Comments

See also #q9981 for a very old Q&A about this.

gvdhoorn ( 2020-09-02 02:16:00 -0500 )edit

Note also btw: this has nothing to with RViz.

RViz only visualises external data. It's not a simulation or anything which maintains its own environment.

gvdhoorn ( 2020-09-02 03:15:42 -0500 )edit

Thankyou, this has been very helpful

Matt Gibbon ( 2020-09-10 04:44:19 -0500 )edit

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Changing the orientation of a pose goal in rviz (python)

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