User Interface

ID #1081

I see an option in the User Preferences called Dimension Basis. What is this for?

The Dimension Basis user preference was added in HVE version 8.10 (Dec 2010). Its purpose is to allow the user to assign certain vehicle-fixed dimensions (CG to Front Axle, etc.) according to either the sprung mass CG or the total mass CG. There is a difference in sprung and total mass CG location, and while the difference is rather small for most passenger vehicles, it can be significant for on-highway trucks wherein the unsprung masses (wheels and tires) represent a larger fraction of the total vehicle weight.

When executing a 3-D simulation, the equations of motion require all vehicle-fixed coordinates (e.g., wheel locations, connection locations) to be relative to the sprung mass CG. Therefore, HVE has always displayed and stored these coordinate data relative to the sprung mass CG. When HVE is executing a 2-D simulation, the equations of motion require all vehicle-fixed coordinates to be relative to the total mass CG (technically, the reason is that the unsprung masses are included in the total vehicle mass for a 2-D simulation). Prior to Version 8.10, it was assumed that the difference was small and could be ignored. However, as mentioned above, for heavy trucks the difference could be significant. So we introduced the ability to switch between total mass and sprung mass dimensions. Each dialog in HVE’s Vehicle Editor that displays coordinate data automatically switches from sprung mass basis to total mass basis when that preference is selected. (In Version 9.00, the current setting is displayed in HVE’s status bar at the bottom of the screen.)

Here is the takeaway: You can use either preference in the Vehicle Editor. While executing an event, a 3-D simulation (e.g., SIMON) will always use the sprung mass dimensions (as it should). However, 2-dimensional HVE-compatible programs (e.g., EDSMAC4) are designed to use either the sprung mass or total mass CG location (as determined by the current user preference) in order to maintain compatiblity with earlier versions of HVE. So while executing a 2-D event, you should use the Total Mass preference. The Dimension Basis that was used while executing a 2-D event is displayed in the Program Data output report.

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Last update: 2012-06-29 02:02
Author: EDC
Revision: 1.0

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