traversaro
commented
6 years ago I imagine three main use cases:
- You know the total robot mass, and you want to compute 3D inertia and center of mass for each link
- You know the mass of each link, and you want to compute 3D inertia and center of mass for each link
- You know the mass and the center of mass of each link, and you want to compute the 3D inertia of each link
In the third case, I do not think there is an easy way to use the center of mass information position to aid the 3D inertia computation, but a nice debug check would be compare the center of mass position computed from shapes + uniform density assumption and the "known" one.
Inertial parameters (mass, center of masses and inertia matrices) of rigid bodies are a fundamental quantity in model-based control and simulation of robots that can be considered as composed by rigid bodies.
These parameters are typically obtained from CAD models of the robot used for designing and manufacturing the robot (see for example http://wiki.icub.org/wiki/Creo_Mechanism_to_URDF) or identified from sensor measurements on the robot.
However in practice a good-enough method to obtain inertial parameters, if the total mass of the robot is known and some meshes of its links are available, is to assume that the robot has constant density and compute the inertial parameters as a consequence of this (more details will arrive).