Mass matrix options?

[smg940679]

Hello

I am doing some experiments concerning dynamic analysis in Robot.
In “Modal Analysis Parameters” I can choose my mass matrix to be:
- Consistent
- Lumped with rotations
- Lumped without rotations

Can anyone explain the difference between these three options?

If I calculate the eigenfrequency just for a simple supported beam, I don’t get the exact same results for the three options.
It is also possible to find more modes if I choose “Lumped with rotations” instead of “Lumped without rotations”. Why is that?

Thanks in advance:)