Home | Tutorials | Wiki | Issues
Ask Your Question
2

Gravity Disabled on Robot Pinned to World

asked 2012-11-08 10:25:27 -0500

liangfok gravatar image

updated 2012-11-29 15:15:10 -0500

I have a simple robot with four links and four revolute joints. The first joint is pinned to the world. When I run the simulation, the robot is not affected by gravity. I know gravity is enabled because when I drag another object like a box and drop it into the world, it falls down. I suspect that gravity is not affecting my four-link robot because it is pinned to the world. Could this be the case? How can I enable gravity for my robot?

Update: The problem was fixed by specifying collision elements for each link in the robot. This is strange since collisions and dynamics should be decoupled. Should this be considered a bug?

edit retag flag offensive close merge delete

Comments

can you post your robot model? (with and without collision bodies?)

hsu gravatar imagehsu ( 2012-11-12 12:24:06 -0500 )edit

can you change your question's title to reflect the issue? i.e. dynamics disabled if missing collision element? thanks.

hsu gravatar imagehsu ( 2012-11-30 20:43:28 -0500 )edit

2 Answers

Sort by ยป oldest newest most voted
1

answered 2012-11-30 20:42:28 -0500

hsu gravatar image

It appears if a model does not have any collision elements, it behaves statically, ticketed here.

edit flag offensive delete link more

Comments

scpeters gravatar imagescpeters ( 2013-01-11 18:14:25 -0500 )edit

[This issue has been resolved](https://bitbucket.org/osrf/gazebo/issue/274).

scpeters gravatar imagescpeters ( 2013-01-11 18:14:32 -0500 )edit
1

answered 2012-11-09 13:44:57 -0500

nkoenig gravatar image

Creating a joint between a model and the world (aka pinning the model to the world), will enforce a joint constraint between the robot and world. This is usually only used if you want to the robot to remain in on fixed location.

I think you may have pinned the robot, and it looks like gravity is not working because the joint is just holding the robot in place.

edit flag offensive delete link more
Login/Signup to Answer

Question Tools

Stats

Asked: 2012-11-08 10:25:27 -0500

Seen: 515 times

Last updated: Nov 30 '12