Gazebo: Q&A Forum - RSS feedhttp://answers.gazebosim.org/questions/Open source question and answer forum for GazeboenCopyright Askbot, 2010-2011.Tue, 19 Oct 2021 15:31:25 -0500A link has invalid inertiahttp://answers.gazebosim.org/question/27489/a-link-has-invalid-inertia/What (and where) are the constraints that are checked when loading a model to decide if a link's inertia matrix is valid or not?
In my specific example, I am trying to model a 50 kg cylinder that is 1.5 m long with a 0.2 m radius. According to this [online moment of inertia calculator](https://amesweb.info/inertia/mass-moment-of-inertia-cylinder.aspx), I come up with Ixx=10, Iyy=10, Izz=1, which loads and runs fine. However, when I slightly change Ixx and Iyy to model a somewhat squashed (elliptical) cylinder, I receive the following error.
`[Err] [Server.cc:183] Error Code 18: Msg: A link named hull has invalid inertia.`
The snipped from my .sdf file is below.
<inertial>
<mass>50.24</mass>
<inertia>
<ixx>12.0</ixx>
<ixy>0</ixy>
<ixz>0</ixz>
<iyy>8.0</iyy>
<iyz>0</iyz>
<izz>1.0</izz>
</inertia>
</inertial>nealtannerTue, 19 Oct 2021 15:31:25 -0500http://answers.gazebosim.org/question/27489/SDF: Specifying 6x6 inertia (mass) matrixhttp://answers.gazebosim.org/question/27461/sdf-specifying-6x6-inertia-mass-matrix/Are there any plans to extend the SDF specification such that one can specify a full 6x6 inertia matrix as the inertial property of a link? Currently, it is only possible to specify the centre of gravity, a scalar mass and a 3x3 rotational inertia matrix. However, for systems such as ships and underwater vehicles, the full inertia matrix is not block diagonal and hence additional parameters are required. The default physics engine DART has support for specifying 6x6 inertia matrices.
The current solution in ignition gazebo with the hydrodynamics plugin is not optimal. This is due to the fact that the added mass forces are calculated at the next timestep by numerically differentiating the velocity. nevernudeThu, 14 Oct 2021 05:21:05 -0500http://answers.gazebosim.org/question/27461/