[ros-users] Gazebo model falls from sky

Hi everybody,

I made an URDF model of our robot, which works quite well in rviz, and now
I want to use it to create a simulation of our robot in gazebo.
As I could not load the entire robot model I did it one part after another.
The problem is that parts of the robot or sometimes the entire robot fall
from the sky after spawning the model.
I checked the accuracy of every value and possible collisions and tried to
solve the problem with trial-and-error but I could not find a mistake or
solve the problem.

I suppose that there is a problem with the links which have no further
function of its own.
As apparently it is not possible to use those links ( <link name="link1"
/> ) within gazebo I filled the attribute values with zeros:
        <link name="link2">
            <inertial>
                <mass value="0.01" />
                <origin xyz="0 0 0" />
                <inertia ixx="1.0" ixy="0.0" ixz="0.0"
                            iyy="1.0" iyz="0.0" izz="1.0" />
            </inertial>
            <visual>
                <origin xyz="0 0 0" rpy="0 0 0" />
                <geometry>
                    <box size="0 0 0" />
                </geometry>

                <material name="red" />
            </visual>
            <collision>
                <origin xyz="0 0 0" rpy="0 0 0" />
                <geometry>
                    <box size="0 0 0" />
                </geometry>
            </collision>
        </link>

I also did some trial-and-error here but it did not work out, too.
So does anybody have a clue of what to do here?

Thanks,
Ricarda