Hi,

I don’t understand how the return values map to the urdf inertia values

The calculator returns “Cylinder Ix,y = 0.0002835,Iz = 0.000324”

How does this relate to "

Shouldn’t the calculator return “Cylider Ixx = 0.xxx ixy = 0.xxx, iyy=0.xxx”

Thanks

Various things:

Shouldn’t the calculator return “Cylider Ixx = 0.xxx ixy = 0.xxx, iyy=0.xxx”

Well that would be that it doesnt have any inertia, therefore no mass.

Cylinders have the X and Y inertias the same and the Z different because of their geometry. This is considering an homogeneus material. Of course in reality this is not exactly like this normally there are some differences in the material density throughout the cylinder ( depending on the manufacturing process ).

Have I answerd your question or if not, please elaborate a bit more on what is your question exactly.

I was just confused because inertia needs ixx, ixy, ixz, iyy, iyz, and izz inputs in the urdf file, but the inertia calculator only returns Ix,y,z and I didn’t know which of the inputs it corresponded to.

However, on the instruction sheet it says “you will assume it will only have values in ixx, iyy, and izz.” So I understand that the return values will be only ixx, iyy and izz from the inertia calculator.

Thanks!

Yeah exactly! So the other parameters normally are only used when the inertia is not uniform and regular. It would only be used if you ahev access to an inertia calcualtor machine of all the elements of the physical robot or you calculate the inertias using mathematical tools to calculate them precisely based on materials they are made of and distribution and so on.

For 90% of the simulations you wont need that level of precission… GAzebo is not that precise to really win something being so precise.

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