RepresentingGeometry (CAD) information in

dynamic (Modelica) models

MSDLAugust 29th, 2009

By Chahé Adourian

Outline Introduction Intro to Block Diagrams (BD) Intro to CAD Assemblies Comparison BD - CAD Mapping CAD to BD Automating the process Example Conversion Conclusion Future Work

Introduction Map CAD Assembly to Block

Diagrams

Introduction Objectives

Provide simple mapping CAD BD Preserve mechanical/geometric

constraints Simulate mechanical behavior in BD

model; Ex. A CAD Model of Robot converted to

BD for simulation of robot dynamics

Intro - Block Diagrams Blocks + Connections Finite Connection points (1 or 2 per

block) Block Parameters Ex.

Intro - CAD Assembly Part and geometry Assemblies and geometric relations Example Geometric relations Infinite connection points

Intro - CAD Assembly Part and geometry

Intro - CAD Assembly Assembly example with geometric

constraints between the parts

Intro - CAD Assembly Ex #1: Planar Mate Geometric Relation

Before and after application

Intro - CAD Assembly Ex #2: Axial Align Geometric Relation

Before and after application

Intro - CAD Assembly Infinite number of connection points

Ex. Planar Mate

Comparison BD – CAD Block diagram is abstract CAD is geometry information rich

Block diagram provides finite connections

CAD geometry provides infinite connections points

Mapping CAD to BD Mapping CAD Part to BD Block

name

r={0,0,0}

1 ba

Mapping CAD to BD CAD versus BD Geometries

Z

XY

nameZ

FacePoint

LineCylinder

Mapping CAD to BD Mapping the infinite geometric choices

using Mathematical constraints Ex. Mapping Mate Relation to equations

Mapping CAD to BD Equations Stored in BD

Mapping CAD to BD Partial list of BD Assembly Relations

name

Cylinder Tangent to Cylinder

name

Mate or Planar Align (normals opposite or aligned)

ZFree

Free x y z

Offset=0

Mate

Planar Align

Axial AlignFree

Locked = true

name

Rotation Angle = RotationAngle

name

rodLengtha b

name

Cylinder Tangent to Face

name

1a b

Motion Along Line

Automating the Process Convert CAD Assembly to BD assembly

automatically Extract CAD Part Geometry Information Extract CAD Assembly Information Example Conversion

Automating the Process Example CAD Part Geometry

Information

Automating the Process Example CAD Assembly Information

Example Conversion

fixed

r={0

,0,0

}

Axial Align Locked

Free Locked=...

axialRelation3d_1

SE_bearing_par_1

r={0,0,0}

1b a

SE_Fit15mm_Par_1

r={0,0,0}

1 ba

Conclusion CAD Mechanical Assembly information

converted to BD form Equivalents for CAD parts, geometries

and assembly relations created CAD to BD Mapping 1-1 Simple Mapping allows BD user to

influence CAD model

Future Work Complete bi-directional model

synchronization algorithm (BD->CAD, CAD->BD)

Demonstrate BD influence on CAD model development