FAQ A05 - Powertrain: What is the meaning of arrow and plus sign in submodels of masses and inertia?

Category: Simcenter Amesim

Topic: Applicative solutions

Access Level: End User

Publish Date: November 2013

Question

Powertrain: What is the meaning of the arrow and the plus sign in the submodels of masses and inertia?

Answer

We will explain about the meaning of the arrow and the plus sign in the following example:

In this example, the inertias at both ends of the shaft represent the two wheels. They have a different orientation as well as the two other inertias which represent half shaft inertia.

As the main shaft rotary velocity is 1000 rev/min, the four inertias should have the initial values shown in the previous figure. This is due to the sign convention. Think that all the right ports of inertias should have the same values and all the left ports should also have a same absolute value but with a different sign. Ports 1 and 2 of the differential have a velocity of -1000 rev/min, whereas port 3 (left port) has a velocity of +1000 rev/min.

The simplest way to avoid mistakes with the sign convention is to orient the screen in one direction (arrows from left to right) and all arrows on inertias icons must be in the same direction.