How to interpret robot's quaternion?

asked 2018-07-31 18:58:41 -0500

xjman530
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updated 2018-07-31 18:59:30 -0500

Hello Again! (Using Indigo/Rospy)

Is there a way, using the robot's quaternion (using slam_out_pose orientation), to determine if its going towards, or away, from the center of the global map (the origin, 2D). The origin is, I'm assuming, where the robot initial started up its mapping procedure. This is not the same as determining if the robot is going forwards or backwards. This is probably due to my poor understanding of quaternions, especially in the robot's reference frame in conjunction with the static reference frame of the global map. Thank you in advance.

answered 2018-07-31 19:35:25 -0500

stevemacenski

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I think this issue arises from a lack of context on Quaternions. I would recommend looking into resources to better your knowledge of them before attempting what you're trying to do (this is a good learning experience!). What you likely want to do is convert the quaternion to RPY with TF or another equivalent tool and base your logic for your application based on them to give yourself a physical understanding of what's going on.

After that, I would just make a quaternion of the map frame orientation and compare against the robot's to determine the relative difference to know if "to" or "away" from the origin.

https://en.wikipedia.org/wiki/Quatern...