FAQ A02 - Powertrain: How to compute equivalent inertias for reducing my model?

Category: Simcenter Amesim

Topic: Applicative solutions

Access Level: End User

Publish Date: November 2013

Question

Powertrain: How to compute equivalent inertias for reducing my model?

Answer

You can reduce the number of state variables by reducing the number of inertias / stiffnesses. Below are two examples that show how to compute equivalent inertias. You can also find these examples from the InertiasReductions.ame demo located in the demo/Libraries/TR directory of Simcenter Amesim.

Example 1: Example 1: Inertias in series

In this case, 2 inertias are connected directly through stiffness. The equivalent inertia is simply the sum of 2 inertias:

where J is the moment of inertia [kgm**2].

Example 2: Example 2: Inertias in series with gears

In this case, 2 inertias are connected with stiffness and a gear ratio. The equivalent inertia is computed using the square value of the gear ratio:

where R is working pitch radius of gear [mm].