Quaternion has length close to zero... discarding as navigation goal, why?

asked 2012-02-29 10:05:50 -0500

flag of United Kingdom of Great Britain and Northern Ireland

4402 ●23 ●64 ●67 https://www.linkedin.c...

Hello. I am trying to follow a moving target with my robot through simulation, using stage and rviz. I already managed to send a goal, using actionlib, based on the target position plus an offset. It works most of the time, but I keep getting this error message:

Quaternion has length close to zero... discarding as navigation goal

Why?? What does that mean?

thanks

edit retag flag offensive close merge delete

add a comment

2

answered 2012-02-29 10:29:22 -0500

Eric Perko

8406 ●73 ●90 ●144 http://ericperko.com/

What are the quaternions you are actually sending? Any quaternion sent should be a properly normalized one (length = 1). The default constructed quaternion geometry_msgs/Quaternion is not a valid quaternion, since it is all 0's.

edit flag offensive delete link

Comments

thanks. I was actually sending an empty message alternated with a proper one. That is why I could get the robot to move and still get the error messages.

Procópio ( 2012-03-01 20:00:51 -0500 )edit

add a comment

2

answered 2012-02-29 10:30:51 -0500

Stefan Kohlbrecher

24361 ●173 ●299 ●444 https://www.energy-rob...

It probably means the rotation quaternion of your goal pose is not properly normalized (e.g. the square root of the sum of squared elements is not 1). Rotation quaternions are generally expected to be normalized, as using non-normalized quaternions would lead to bugs that are hard to detect.

You'll have to check the code generating the target pose for answering the "why?" question.

edit flag offensive delete link

Comments

thanks for your input!

Procópio ( 2012-03-01 20:16:52 -0500 )edit

add a comment

Quaternion has length close to zero... discarding as navigation goal, why?

2 Answers

Comments

Comments

Question Tools

Stats

Related questions

Quaternion has length close to zero... discarding as navigation goal, why? edit

2 Answers

Comments

Comments

Question Tools

Stats

Related questions

Quaternion has length close to zero... discarding as navigation goal, why?