Auto Entities

Introduction

The vehicle dynamic tools in MotionView model components commonly used in cars, trucks, and buses - like springs and bushings. All auto entities share the following features:

•	They apply equal but opposite forces on two bodies.

•	The force depends on the displacement and velocity of one body relative to the other.

•	The parameters, for example stiffness, used to compute the force are stored in a property file that is independent of the MotionView MDL file and the MotionSolve input deck.

•	The user must supply a property file for each auto entity employed in a MotionView model. A reference (path and name) to the property file is stored in the MotionView MDL file and in the MotionSolve input deck written by MotionView. Currently, only MotionSolve is supported.

•	Property files are:

-	Text files which may be viewed and edited using any common text editor (textpad, wordpad, vim, emacs, ultraedit, notepad++, etc.).

-	Compatible with Adams/Car; property files from Adams/Car may be reused with the Auto Entities in MotionView.

-	Read by MotionSolve just prior to analysis.

The table below gives an overview of the available auto entities:

Entity

Function

Features

Uses

Bushing
(AutoBush )

Elastically mount suspension arms, links, sub-frames, engines, gearboxes, etc. to vehicle chassis.

•	Exerts force and torque all directions.

•	Non-linear force/torque verses deflection interpolated using Akima’s method from tabular data

•	Linear damping

•	Suspension kinematic and compliance analysis

•	Vehicle Dynamics

Frequency Dependent Bushing
(AutoBushFD )

Elastically mount suspension arms, links, sub-frames, engines, gearboxes, etc. to vehicle chassis.

•	Exerts force and torque in all directions.

•	Stiffness and damping dependent on amplitude and frequency of bushing displacement

•	Non-linear static force/torque verses deflection

•	Ride comfort

•	Durability

Bump-stop

(AutoBumpStop )

Limit suspension bump or jounce travel.

•	Exerts a force along a line to repel two bodies when the distance between the bodies is less the a threshold

•	Non-linear force verses deflection interpolated using Akima’s method from tabular data

•	Linear Damping

•	Vehicle Dynamics

•	Durability

Damper
(AutoDamper )

Dissipate energy stored in springs and damp chassis motions.

•	Exerts a force along a line between two bodies

•	Non-linear force verses velocity interpolated using Akima’s method from tabular data stored in a property file

•	Vehicle Dynamics

•	Ride Comfort

•	Durability

Rebound-stop
(AutoReboundstop )

Limit suspension rebound travel.

•	Exerts a force along a line to attract two bodies with the distance between the bodies exceeds a threshold

•	Non-linear force verses deflection interpolated using Akima’s methods from tabular data

•	Linear Damping

•	Vehicle Dynamics

•	Durability

Spring Air
(AutoAirSpring )

•	Limit force in suspension components

•	Maintain ride height for large variations in load

•	Isolate chassis by absorbing energy from vertical road inputs

•	Exerts a force along a line between two bodies

•	Non-linear force verses deflection at different static inflation pressures

•	Set the initial load and spring height to determine the static inflation pressure

•	Suspension Kinematics and Compliance

•	Vehicle Dynamics

•	Ride Comfort

•	Durability

Spring Coil

(AutoSpring )

•	Limit forces in suspension components

•	Isolate chassis by absorbing energy from vertical road inputs

•	Exerts a force along a line between two bodies

•	Non-linear force verses deflection interpolated using Akima’s methods from tabular data

•	Optionally set the initial load or length of the spring at vehicle input position

•	Suspension Kinematics and Compliance

•	Vehicle Dynamics

•	Ride Comfort

•	Durability

Tire – CTI
(AutoCTITire )

Generate forces for steering, accelerating, and braking. Isolate the vehicle from small road irregularities.

•	COSIN FTIRE (flexible ring) and Pacejka 2000 Magic Formula tire models

•	3D and 2D Road Models including Curved Gridded Road (CRG) and COSIN RGR

•	FTIRE: Ride Comfort & Durability

•	Pacejka 2000: – Vehicle Dynamics

Tire – CD
(AutoCDTire )

Generate forces for steering, accelerating, and braking. Isolate the vehicle from small road irregularities.

•	Supports family of CD-Tire models (flexible ring)

•	2D and 3D Road Models including CRG

•	Vehicle Dynamics

•	Ride Comfort

•	Durability

Tire – TNO
(AutoMFTire )

Generate forces for steering, accelerating, and braking. Isolate the vehicle from small road irregularities.

•

MF-TYRE

•	SWIFT-TYRE (rigid-ring)

•	2D and 3D Road Models, including CRG

•	MF-Tyre: Vehicle Dynamics

•	SWIFT-Tyre: Vehicle Dynamics & Ride Comfort

Accessing Auto Entities in MotionView

Follow the steps below to load the MBD-Vehicle Dynamic Tool preference file and access the auto entities in MotionView:

1.	Start MotionView from the installation folder of Altair HyperWorks.

The MotionView version 14.0 window is displayed.

2.	Click File>Load>Preference File from the MotionView Menu Bar.

auto_entity_file_menu_mv

2.	Select MBD-Vehicle Dynamic Tools from the Preferences dialog.

auto_entity_preferences_dialog_mbd_mv

3.	Click on the Load button to register the auto entities in MotionView.

4.	Auto entities are now accessed through the Project Browser Context Menu Add Auto Entity option. Right-click on Model in the session tree and select Add Auto Entity.

auto_entity_browser_context_menu_mv

The Add Entity dialog is displayed.

airspring_add_entity_dialog_mv