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Like do we need to add inertia to urdf, like when I just set it 0 it still works but when I set to some value it explodes.

Originally posted by harish556 on ROS Answers with karma: 74 on 2021-05-31

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Inertia is mainly important in simulation. If you are just using a URDF for visualization in RVIZ then it really doesn't matter. If you use a URDF to drive simulation (such as using it in gazebo) then it does matter. inertia tags in a URDF are the 3d tensor moments of inertia. This can be calculated with most mainstream CAD packages for complex geometry. If the geometry is simple you could also calculate it yourself using the formulas from here.

EDIT: Some more info is available on the ros wiki as well

As stated the inertia is a 3d tensor so it should have multiple fields. See example below:

Consider a sphere with mass of 10.5kg, and radius of 0.5 meters.

The tensor for a sphere is:

sphere_tensor

So along the diagonal, the values should be 2/5 * m * r^2 => 2/5 * 10.5 * 0.5^2 = 1.05

The inertial tag for this would look like:

<inertial>
  <origin xyz="0 0 0" rpy="0 0 0"/>
  <mass value="10.5"/>
  <inertia
    ixx="1.05"  ixy="0.00"  ixz="0.00"
    iyx="0.00"  iyy="1.05"  iyz="0.00"
    izx="0.00"  izx="0.00"  izz="1.05"
  />
</inertial>

Hope this helps!

Originally posted by djchopp with karma: 328 on 2021-06-01

This answer was ACCEPTED on the original site

Post score: 2

Original comments

Comment by harish556 on 2021-06-02:
thanks alot

Comment by iamsdevaprasad on 2023-07-22:
Hi could you please share the sources from where you found that inertia will not be used in Rviz. Thank you.