"Error [Joint.cc:408] Invalid joint index [2] when trying to apply force" with Gazebo 1.3

asked 2013-01-31 09:03:53 -0600

473 ●15 ●19 ●29

updated 2013-01-31 09:04:14 -0600

When spawning a URDF model using some custom controller plugins I get

Error [Joint.cc:408] Invalid joint index [2] when trying to apply force

spammed to the terminal when I spawn it using Gazebo 1.3 in Groovy (using .debs from the shadow-fixed repo). The controller plugins worked fine with fuerte before. Before I try delving deep into the differences between Gazebo plugin interfaces: Has anyone else encountered this and can provide some hints on where to look first? The model otherwise appears to work (sensor data streaming for example).

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answered 2013-02-05 14:05:31 -0600

hsu
1873 ●14 ●19

In older version of gazebo (1.0.x) that was in fuerte, index was ignored inside of ODEHingeJoint::SetForce):

void ODEHingeJoint::SetForce(int /*index*/, double _torque)
{
  if (this->childLink)
    this->childLink->SetEnabled(true);
  if (this->parentLink)
    this->parentLink->SetEnabled(true);
  dJointAddHingeTorque(this->jointId, _torque);
}

In latest groovy, ODEHigneJoint::SetForce was fixed to use the index correctly, thus exposing the bug you are seeing.

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answered 2013-01-31 09:27:59 -0600

nkoenig
7676 ●8 ●44 ●71 http://gazebosim.org/

I think the error message should read "...when trying to get force". I've fixed the message.

The error means that someone is trying to get the force on a joint with an invalid index. The relevant function call is Joint::GetForce(int), and a valid index is 0 or 1 where 0 is the first axis of the joint and 1 is the second axis.

So, I would look in a plugin that is calling GetForce with a value of 2.

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Ok, did the indexing change between Gazebo versions?

Stefan Kohlbrecher ( 2013-01-31 10:09:55 -0600 )edit

No, but the error message maybe new.

nkoenig ( 2013-01-31 10:17:33 -0600 )edit

Stuff that worked previously doesn't work anymore though, so my guess is the error message and the vehicle not moving have a common cause. Will update later if I find the time to look into it in more detail.

Stefan Kohlbrecher ( 2013-01-31 11:02:22 -0600 )edit

The error message vanished after updating our controller plugins to use 0 as joint index all the time instead of 0,1,2 for the x,y,z axis. Was there a change in the semantics of the index or why did the plugins work with previous versions of Gazebo (e.g. 1.0.2 in fuerte)?

Johannes Meyer ( 2013-02-02 13:52:55 -0600 )edit

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"Error [Joint.cc:408] Invalid joint index [2] when trying to apply force" with Gazebo 1.3

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