Computation of the combined, full-body inertia (SRBD)

[oliwiermelon]

Hi,

I am trying to use Pinocchio to calculate the combined, full-body inertia of an articulated body which accounts for the floating base and the end-effectors, in their nominal configuration from a URDF for a Single Rigid Body Dynamics (SRBD) model.

I am aware of the CRBA algorithm which produces the joint-space inertia matrix (n x n). I am looking for a function/approach that:

• that transforms it into the reference frame of the base and combines it with its inertia matrix (3 x 3), or
• returns the full-body inertia matrix (3 x 3).

[jcarpent]

Hi @oliwiermelon,

The best solution would be:

1. call crba(model,data,q)
2. retrieve the total spatial inertia with data.Ycrb[1], which is expressed in the base coordinate system (assuming you are working with a free floating system).
3. data.Ycrb[1].inertia() is the quantity you are looking for.

[oliwiermelon]

Thank you @jcarpent, it is exactly what I needed! Note: data.Ycrb[1].inertia

[jcarpent]

Note: data.Ycrb[1].inertia

In Python ;). In C++, data.Ycrb[1].inertia().