adm701_mdr2_coursenotes

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MD Adams Basic Full Simulation

ADM701 Course Notes

May 2007

Part Number: MDAM*R2*Z*BFS*Z*SM-AD MDAM*R2*Z*BFS*Z*SM-ADM701-NT1 M701-NT1 Copyright 2007 MSC.Software Corporation

DISCLAIMER

This documentation, as well as the software described in it, is furnished under license and may be used only in accordance with the terms of such license. MSC.Software Corporation reserves the right to make changes in specifications and other information contained in this document without prior notice. The concepts, methods, and examples presented in this text are for illustrative and educational purposes only, and are not intended to be exhaustive or to apply to any particular engineering problem or design. MSC.Software Corporation assumes no liability or responsibility to any person or company for direct or indirect damages resulting from the use of any information contained herein. User Documentation: Copyright © 2007 MSC.Software Corporation. Corporation . Printed in U.S.A. All Rights Reserved. This notice shall be marked on any reproduction of this documentation, in whole or in part. Any reproduction or distribution of this document, in whole or in part, without the prior written consent of MSC.Software Corporation is prohibited. This software may contain certain third-party software that is protected by copyright and licensed from MSC.Software suppliers. Portions of this software are owned by UGS Corp. © Copyright 1997. All Rights Reserved. The MSC.Software corporate logo, Adams, Adams/, MD, MD Adams, MSC, MSC Nastran, and MD Nastran are trademarks or registered trademarks of the MSC.Software Corporation in the United States and/or other countries. FLEXlm is a registered trademark of Macrovision Corporation. Parasolid is a registered trademark of UGS Corp. All other trademarks are the property of their respective owners. owners.

Copyright 2007 MSC.Software Corporation

TABLE OF CONTENTS Section 0.0

Page Introduction A Brief History of Adams …………………………………… ………………………………………………… ………………………… ………………………… …………………………. ……………. 0-5 About MSC.Software ...……………………………… ...……………………………………………… …………………………… …………………………… …………………………… ……………… … 0-7 Content of Course …...……………………………………………………………………………………………. 0-8 Getting Help ………...……………………………………………………………………………………………… 0-10

1.0 1.0

Virt Virtua uall Prot Protot otyp ypin ing g Proc Proces ess s Virtual Prototyping Process ………...…………………………………………………………………………….. 1-3

2.0

Adams Adams/Vi /View ew Interf Interface ace Overvi Overview ew Model Hierarchy …………...………...………………………………………….………………………..……….. 2-4 Renaming Objects ……...………...………………………………….……………………………..…………….. 2-5 Adams/View Interface ……………………………… ……………………………………………… ………………….………… ….………………………. ……………..………… .………………. ……. 2-7 Simple Simulations Simulati ons ………………………………………..…………..…………………………..……….……… 2-8 Saving Your Work …………………………………………..…………..………………………..……...…………2-9

3.0

Adams Adams/P /Pos ostPr tProc ocess essor or Interf Interfac ace e Overv Overview iew PostProcessing Interface Overview ………………………………………………….………………………….. 3-3 Animating ………………………… ………………………………………… …………………………… …………………………… ………………………… ………….………… .………………………. ……………... 3-5 Plotting …………………………………………………………………………………….……………………….. 3-6 Reporting Reportin g ………………………………………………………………………………….……………………….. ………………………………………………………………………………….……………………….. 3-7

4.0 4.0

Part Parts s and and Coor Coordi dina nate te Syst System ems s Coordinate Coordina te Systems ………... ………...………………… …………………..………………………………………….…………………….. ..………………………………………….…………………….. 4-4 Part Coordinate System ………...………………………………………………………….…………………….. 4-6 Coordinate System Marker ………...…………………………………………………………………………….. 4-7 Differences Between Parts and Geometry….………………… Geometry….………………………………… ………………………….…… ………….………………… ……………….. ….. 4-9 Parts, Geometry, and Markers …...……………………………………………………….……….…………….. 4-12 Types of Parts in Adams/View …..………………………………… …..……………………………………………… …………………….……… ……….…………………… ……………… … 4-14 Part Mass and Inertia ………...…………………………………………………………….…………………….. 4-15 Measures ……………………...…………………………………………………………….…………………….. 4-17


TABLE OF CONTENTS (cont.) Section 5.0 5.0

Page Init Initia iall Cond Condit itio ions ns and and Poin Pointt Trac Trace e Part Initial Conditions …………………………………………………………………………………..…………. 5-4 Initial Velocities ………………………………………………………………………………………..…………… ………………………………………………………………………………………..…………… 5-5 Point Trace ..…………………………..……………………………………………………………...……………. 5-6

6.0 6.0

Constra strain intts Constraints Constrai nts …………….…………………………………………………………….…………………………….. …………….…………………………………………………………….…………………………….. 6-3 Use of Markers in Constraints …………………………………………………………………………..……….. 6-6 Degrees of Freedom (DOF) ………………………………………………………………………………..…….. 6-8 Joint Initial Conditions …………….……………………………………………………………..……………….. 6-10 Merging Geometry ……………. ……………. ………………………………………………………………….……………….. 6-11 Angle Measures …………….…………… …………….…………………………… …………………………… ………………………… ………………………… ……………….……………. ….……………... 6-13

7.0 7.0

Rota Rotati tion on and and Fric Fricti tion on Euler Angles …………….…………………………………………………………………………………………..7-4 Precise Positioning: Rotate .…………………………………… .………………………………………………… …………………………… …………………..………… …..……………….. …….. 7-6 Modeling Friction ………….……………………………………………………………………………………….. ………….……………………………………………………………………………………….. 7-7 Measures in LCS …………….………………………………………………………………...………………….. 7-11

8.0

Geomet Geometry ry and Precis Precise e Posit Position ioning ing Building Geometry …………….………………………………………………………………….……………….. 8-4 Construction Geometry Properties……………………………………………………………………………….. 8-6 Solid Geometry …………….………………………………………………………………………..…………….. 8-8 Precise Positioning: Move …….………………………………………………………………………………….. 8-10

9.0 9.0

Join Jointt Moti Motion on and and Func Functi tion ons s Applying Motion …………….…………… …………….…………………………… …………………………… ………………………… ………………………… ……………….…………… ….…………….. .. 9-4 Joint Motion …………….………………………………………………………………………………………….. 9-5 Functions Function s in Adams …….……………………………………………………………..………………………….. …….……………………………………………………………..………………………….. 9-7

10.0 10.0

Joint Joint Primi Primitiv tives es Types of Joint Primitives ……….…………………………………………………………………………...……..10-4 Perpendicular Joint Primitive …….………………… …….………………………………… …………………………… ………………………… …………………………… …………………..10-6 …..10-6 Copyright 2007 MSC.Software Corporation

TABLE OF CONTENTS (cont.) Section 11.0 11.0

Page Point Point Motion Motions s and Syste Systemm-lev level el Design Design Applying Point Motions .……………………………… .……………………………………………… …………………………… ……………………..…… ………..………………… ………………. …. 11-4 System-Level Design …………………………… ………………………………………… …………………………… …………………………… ………………….……... …….……...…………11-6 …………11-6

12.0

Measureme Measurements, nts, Displacem Displacement ent Function Functions, s, and CAD Geometry Geometry Taking Measurements …………….…………………………………………………………………..………….. 12-4 Displacement Functions …………………………………………………………………………..………..…….. 12-6 Importing CAD-Based Geometry ……………………………………………………………………. ……………………………………………………………………. ………….. ………….. 12-8 1 2-8

13.0

Add-on Add-on Constrain Constraints, ts, Couplers, Couplers, and Assemblin Assembling g Models Models Add-On Constraints …………….………… …………….………………………… …………………………… ………………………… ………………………… ………………...………… …...………….. .. 13-4 Couplers Coupler s .………………………………………………………………………………………..…….…..……….. 13-6 Assembling Subsystem Models ………….…………… ………….…………………………… …………………………… ………………………… ………………..………… …..………….. .. 13-8

14.0 14.0

Simu Simula lati tion ons s Assemble Simulation …………….…………… …………….………………………… …………………………… ……………………………… …………………………… ……………….…….. ….…….. 14-4 Simulation Hierarchy ……………………………………………………………………………………..……….. 14-6 Types of Simulations …………….…………… …………….………………………… …………………………… ……………………………… ……………………………. …………….……….. ……….. 14-7 Forces in Adams …………….…………………………………………………………………..…………..…….. …………….…………………………………………………………………..…………..…….. 14-11 Spring Dampers in Adams ……….……………… ……….……………………………… …………………………… ………………………… …………………………… ……………………..14-12 ……..14-12 Magnitude of Spring Dampers ….……………………………………………………………………….……….. 14-14

15.0 15.0

Forc Forces es and and Spli Spline nes s Single-Component Forces: Action-Reaction …………………………………… …………………………………………………… ………………………..…… ………..…….. .. 15-4 Spline Functions …………….………………………………………………………………………….…………..15-6 AKISPL Function …….…………………… …….………………………………… ………………………… …………………………… ………………………….… ………….…………….. …………...…..15-8 .…..15-8

16.0 6.0

Bushin shing gs Bushings ……….…………………………………..………………………………………………………………..16-4

17.0

Impact Impact Functions ………………..…………………………………………………………………………………. ………………..…………………………………………………………………………………. 17-4 Velocity Functions ……………………………………………..………………………………...…………………17-8


TABLE OF CONTENTS (cont.) Section 18.0

Page Step Functions and Simulation Scripts STEP Function …………….…………..……………………………………………………………………….….. 18-4 Scripted Simulations ……………………………….………………………………………………………….….. 18-7 Adams/Solver Commands ……………………………………………………………..………………….…….. 18-9

19.0

Adams/Solver Adams/Solver Overview ……….……………………………………………………………………………..….. 19-4 Files in Adams/Solver ………………………………………………………………………………..……….….. 19-5 Example of Adams/Solver Dataset (. adm) File ………………………………………………………….…….. 19-6 Stand-Alone Adams/Solver …………………….……………………………………………………………….. 19-7 Solver Compatibility ……………………………………………………………………………………………….. 19-8 Example: 2D Pendulum ………………………….……………………………………………………………….. 19-9 Formulation of the Equations of Motion …………………………………………………………………...……..19-12 Phases of Solution …………………………………………………………………..…………………………….. 19-13 Debug/Eprint (Dynamics) …………………………..…………………………………………………………….. 19-20

20.0

Sensors and Design Variables Sensors …………….…………………………………………………………………………………..….……….. 20-4 Design Variables ………..………………………………………………………………………………..……….. 20-6

21.0

Splines and Contraints Splines from Traces …………………………….………………………………………………………..……….. 21-4 Curve Constraints ………………….………………………………………………………………………..…….. 21-5 Automated Contact Forces …….…………………………………………………………………………..…….. 21-7 Flexible Parts – Adams/AutoFlex ….……………………………………………………………………..…….. 21-10

22.0

Multi-Component Forces and Design Studies Multi -Component Forces …..………………………..………………………………………..……….………….. 22-4 Design Studies …….…………………………………..…………………………………………….…………….. 22-8


TABLE OF CONTENTS (cont.) Section 23.0

Page Recommended Practices General Approach to Modeling ……………………………………………………………………………..……. 23-4 Modeling Practices: Parts ……………………………………..…………………………………………..……… 23-5 Modeling Practices: Constraints ………………..………………………………………………………….……. 23-7 Modeling Practices: Compliant Connections …………..…………………………………………………..……23-9 Modeling Practices: Run -time Functions ……………………………………………………………….………. 23-10 Debugging Tips ……………………………………………..…………………………………………...………… 23-14

Appendix A Tables


Introduction

ADM701, Introduction, May 2007 Copyright 2007 MSC.Software Corporation

INTRO-1


INTRO-2

Welcome To Adams Basic Training ●

What’s in this section: ●

A Brief History of Adams

●

About MSC.Software Content of Course

●

Getting Help

●


INTRO-3

Welcome To Adams Basic Training ●

●

Adams Full Simulation Package is a powerful modeling and simulating environment that lets you build, simulate, refine, and ultimately optimize any mechanical system, from automobiles and trains to VCRs and backhoes. The Adams Basic Full Simulation Package training guide teaches you how to build, simulate, and refine a mechanical system using MSC.Software’s Adams Full Simulation Package.


INTRO-4

A Brief History of Adams ●

● ●

●

Adams: Automatic Dynamic Analysis of Mechanical Systems. Technology was implemented about 25 years ago. Mechanical Dynamics Incorporated (MDI) formed by researchers who developed the base Adams code at University of Michigan, Ann Arbor, MI, USA. MDI has been part of MSC.Software Corporation since 2002. Large displacement code.


INTRO-5

A Brief History of Adams (cont.) ● ●

●

●

Systems-based analysis. Original product was Adams/Solver, an application that solves nonlinear numerical equations. You build models in text format and then submit them to Adams/Solver. In the early 90’s, Adams/View was released, which allowed users to build, simulate, and examine results in a single environment. Today, industry-specific products are being produced, such as Adams/Car and Adams/Chassis.


INTRO-6

About MSC.Software ●

Find a list of MSC.Software products at: ●

●

Find a list of Adams products at: ●

●

●

http://www.mscsoftware.com/products/products.cfm http://www.mscsoftware.com/products/mdadams.cfm?Q=396 &Z=455

Find additional training at: ●

http://www.engineering-e.com/training/

●

Or your local support center

Run through verification problems at: ●

http://support.mscsoftware.com/kb/results_kb.cfm?S_ID=1KB9587


INTRO-7

Content of Course ●

After taking this course you will be able to: ●

Build Adams/View models of moderate complexity.

●

Understand Adams product nomenclature and terminology.

●

●

●

●

●

Understand basic modeling principles and extend your proficiency by creating progressively more complex models. Use the crawl-walk-run approach to virtual prototyping. Debug your models for the most common modeling challenges (for example, redundant constraints, zero masses, and so on). Use and be informed about all methods of Adams product support. Use the product documentation optimally.


INTRO-8

Organization of Manual ●

●

This manual is organized into modules that get progressively more complex. Each module focuses on solving an engineering-based problem and covers mechanical system simulation (MSS) concepts that will help you use Adams most optimally. The earlier workshops provide you with more step-by-step procedures and guidance, while the later ones provide you with less. Each module is divided into the following sections: ● ● ● ● ●

Problem statement Concepts Workshop Optional tasks Module review


INTRO-9

Getting Help ●

Online Help ●

To access the online help, do either of the following: ●

●

●

From the Help menu, select Adams/View Help to display the home page for the Adams/View online help. While working in any Adams/View dialog box, press F1 to display online help specific to that dialog box.

Once the online help is displayed, you can browse through the table of contents or the index, or search for any terms.


INTRO-10

Getting Help

Table of contents for selected tab ADM701, Introduction, May 2007 Copyright 2007 MSC.Software Corporation

INTRO-11

Getting Help (cont.) ●

Technical support ●

●

●

To read the Service Level Agreement, go to http://www.mscsoftware.com/support/pdf/MSC_Tech_Support _Guide_2006.pdf

Knowledge base ●

●

To find your support center, go to http://www.mscsoftware.com/support/contacts/index.cfm

Go to http://support.mscsoftware.com/kb

Consulting services ●

http://www.mscsoftware.com/services/esg/


INTRO-12

Getting Help (cont.) ●

MSC Virtual Product Development Community ●

● ●

To join the community of MSC.Software users, go to: http://forums.mscsoftware.com. Select Adams to view the Adams discussions. Select MSC News to view product alerts and company news and events.


INTRO-13

Getting Help (cont.)


INTRO-14

SECTION 1 Virtual Prototyping Process

ADM701, Section 1, May 2007 Copyright 2007 MSC.Software Corporation

S1-1


S1-2

Virtual Prototyping Process DESIGN PROBLEM

Cut time and costs

Build

●

Increase quality

Increase efficiency

Review

Test

Build a model of your design using: ●

Bodies

●

Forces Contacts

●

Joints

●

Motion generators

●


S1-3

IMPROVED PRODUCT

Improve

Virtual Prototyping Process (cont.) DESIGN PROBLEM

Cut time and costs

Build

●

Measures

●

Simulations Animations

●

Plots

●

Validate your model by: ●

Importing test data

●

Superimposing test data


Increase efficiency

Review

Test

Test your design using: ●

●

Increase quality

S1-4

IMPROVED PRODUCT

Improve


Cut time and costs

Build

●

Increase efficiency

Review

Test

Review your model by adding: ●

Friction

●

Forcing functions Flexible parts

●

Control systems

●

●

Increase quality

Iterate your design through variations using: ● ●

Parametrics Design Variables


S1-5

IMPROVED PRODUCT

Improve


Cut time and costs

Build

●

●

Increase quality

Increase efficiency

Review

Test

Improve your design using: ●

DOEs

●

Optimization

Automate your design process using: ●

Custom menus

●

Macros

●

Custom dialog boxes


S1-6

IMPROVED PRODUCT

Improve

SECTION 2 Adams/View Interface Overview


S2-1


S2-2

Adams/View Interface Overview ●

What’s in this module: ●

Model Hierarchy

●

Renaming Objects Adams/View Interface

●

Simple Simulations

●

Saving Your Work

●


S2-3

Model Hierarchy ●

Adams/View Modeling Hierarchy ●

●

Adams/View names objects based on this model hierarchy. For example, Adams/View names geometry as .model_name.part_name.geometry_name . To change the parent for an object, rename the object. Model Simulations

More

Objects Measures

C on str ai nt s

Pa rt s

Forces

Analyses Markers

Construction Points

Results Sets

Components

Geometry

Are not saved in model command files (.cmd)

See Also: Assembling Subsystem Models in Section 13 ADM701, Section 2, May 2007 Copyright 2007 MSC.Software Corporation

S2-4

Renaming Objects ●

Adams/View naming conventions: .mod Simulations

Objects

More

.mod.meas_1

.mod.joint_1

.mod.part_1

.mod.spring_1

.mod.run_1 .mod.part_1.mar_1

.mod.part_1.point_1

.mod.run_1.joint_1

.mod.run_1.joint_1.fx


Are not saved in model command files (.cmd)

S2-5

.mod.part_1.box_1

Renaming Objects (cont.) ●

Renaming objects clarifies model topology as follows:

Renamed

Not renamed ADM701, Section 2, May 2007 Copyright 2007 MSC.Software Corporation

S2-6

Adams/View Interface Adams/View Main Window Main Toolbox

Model name


View triad

Working grid

Menus

Tool Arrow denotes tool stack

Toolbox container

S2-7

Status bar

Simple Simulations ●

Simulation versus animation ●

●

Simulations are solutions to equations of motion describing a mechanical system. Animations display a graphical playback of previously completed simulations.

Simulation tool Animation tool

Simulation time interval

Simulation output

End Time: absolute point in time to stop simulation Duration: relative amount of time to simulate over

Step Size: amount of time between steps Steps: total number of steps in a specified amount of time


S2-8

Saving Your Work ●

Most common formats in which you can save Adams/View models ●

Adams/View database files (.bin) ●

● ●

●

Include the entire modeling session including models, simulation results, plots, and so on. Are typically very large. Are platform independent in Adams, as of version 11.0, but all other versions are platform dependent.

Adams/View command files (.cmd) ●

Include only model elements and their attributes.

●

Are relatively small, editable text files.

●

Are platform independent.


S2-9

Saving Your Work (cont.) Adams/View database files (.bin)

Adams/View command files (.cmd)


S2-10

Saving Your Work (cont.) ●

Other formats in which you can import and export data ●

Adams/Solver input files (.adm)

●

Geometry files (STEP, IGES, DXF, DWG, Wavefront, Stereolithography) Test and spreadsheet data files

●

Simulation results files (.msg, .req, .out, .gra, .res).

●


S2-11

SECTION 3 Adams/PostProcessor Interface Overview


S3-1


S3-2

Postprocessing Interface Overview ●


PostProcessing Interface Overview

●

Animating Plotting

●

Reporting

●

For more information, see the Adams/PostProcessor online help.


S3-3

Postprocessing Interface Overview ●

Adams/PostProcessor has three modes: ●

●

Plotting Report

●

Plot 3D (Available only for Adams/Vibration analyses)

●

●

Animation

Example: ●

The tools in the Main toolbar change if you switch between the modes, as shown on the next few pages.


S3-4

Animating Mode type

Treeview

Main toolbar

Viewport

Property editor

Dashboard

For more information, see the Animate tab in the Adams/PostProcessor online help. ADM701, Section 3, May 2007 Copyright 2007 MSC.Software Corporation

S3-5

Plotting Mode type

Treeview

Main toolbar

Viewport

Property editor Dashboard

For more information, see the Plot tab in the Adams/PostProcessor online help. ADM701, Section 3, May 2007 Copyright 2007 MSC.Software Corporation

S3-6

Reporting Mode type

Treeview

Main toolbar

Viewport

For more information, see the Report tab in the Adams/PostProcessor online help. ADM701, Section 3, May 2007 Copyright 2007 MSC.Software Corporation

S3-7

SECTION 4 Parts and Coordinate Systems


S4-1


S4-2

Parts and Coordinate Systems ●


Coordinate Systems

●

Part Coordinate System Coordinate System Marker

●

Differences Between Parts and Geometry

●

Parts, Geometry, and Markers

●

●

Types of Parts in Adams/View Part Mass and Inertia

●

Measures

●


S4-3

Coordinate Systems ●

Definition of a coordinate system (CS) ●

A coordinate system is essentially a measuring stick to define kinematic and dynamic quantities.


S4-4

Coordinate Systems (cont.) ●

Types of coordinate systems ●

Global coordinate system (GCS): ● ●

●

Rigidly attaches to the ground part. Defines the absolute point (0,0,0) of your model and provides a set of axes that is referenced when creating local coordinate systems.

Local coordinate systems (LCS): ●

Part coordinate systems (PCS)

●

Markers


S4-5

Part Coordinate Systems ●

Definition of part coordinate systems (PCS) ● ● ●

●

They are created automatically for every part. Only one exists per part. Location and orientation is specified by providing its location and orientation with respect to the GCS.

When created, each part’s PCS has the same location and orientation as the GCS.


S4-6

Coordinate System Marker ●

Definition of a marker ● ● ●

It attaches to a part and moves with the part. Several can exist per part. Its location and orientation can be specified by providing its location and orientation with respect to GCS or PCS.


S4-7

Coordinate System Marker (cont.) ●

Definition of a marker (cont.) ●

It is used wherever a unique location needs to be defined. For example: ● ●

●

●

The location of a part’s center of mass. The reference point for defining where graphical entities are anchored.

It is used wherever a unique direction needs to be defined. For example: ●

The axes about which part mass moments of inertia are specified.

●

Directions for constraints.

●

Directions for force application.

By default, in Adams/View, all marker locations and orientations are expressed in GCS.


S4-8

Differences Between Parts and Geometry ●

Parts ●

Define bodies (rigid or flexible) that can move relative to other bodies and have the following properties: ●

Mass

●

Inertia

● ●

Initial location and orientation (PCS) Initial velocities


S4-9

Differences Between Parts and Geometry (cont.) ●

Geometry ●

●

Used to add graphics to enhance the visualization of a part using properties such as: ●

Length

●

Radius

●

Width

Not necessary for most simulations. Note: Simulations that involve contacts do require the part geometry to define when the contact force will turn on or off. We will discuss contact forces in Workshop 20 - Hatchback IV.


S4-10

Differences Between Parts and Geometry (cont.) .model_1.UCA (Part)

.model_1.UCA.cyl_1 (Geometry)

.model_1.UCA.sphere_1 (Geometry)


S4-11

Parts, Geometry, and Markers ●

Dependencies in Adams ●

To understand the relationship between parts, geometry, and markers in Adams/View, it is necessary to understand the dependencies shown below: Model .mod

Part .mod.pend

Geometry

.mod.pend.sph


Marker

.mod.pend.mar_1

Marker

.mod.pend.cm

S4-12

Marker

.mod.pend.mar_2

Geometry

.mod.pend.cyl

Parts, Geometry, and Markers (cont.) pend

mar_2 cyl

cm

sph

mar_1


S4-13

Types of Parts in Adams/View ●

Rigid bodies ● ● ●

●

Flexible bodies ● ● ●

●

Are movable parts. Possess mass and inertia properties. Cannot deform. Are movable parts. Possess mass and inertia properties. Can bend when forces are applied to them.

Ground part ●

●

●

Must exist in every model and is automatically created when a model is created in Adams/View. Defines the GCS and the global origin and, therefore, remains stationary at all times. Acts as the inertial reference frame for calculating velocities and acceleration.


S4-14

Part Mass and Inertia ●

Mass and inertia properties ●

●

● ●

●

●

Adams/View automatically calculates mass and inertial properties only for three-dimensional rigid bodies. Adams/View calculates the total mass and inertia of a part based on the part’s density and the volume of its geometry. You can change these properties manually. Adams/View assigns mass and inertial properties to a marker that represents the part’s center of mass (cm) and principal axis. You can change the position and orientation of the part’s cm marker. The orientation of the cm marker also defines the orientation of inertial properties Ixx, Iyy, Izz.


S4-15

Part Mass and Inertia (cont.) Part 1

Part 1

cm marker cm marker (shifts as new geometry is added to the part)


S4-16

Measures ●

Measures in Adams ●

●

Represent data that you would like to quantify during a simulation such as: ●

Displacement, velocity, or acceleration of a point on a part

●

Forces in a joint

●

Angle between two bodies

●

Other data resulting from a user-defined function

Capture values of measured data at different points in time over the course of the simulation.


S4-17

Measures (Cont.) ●

Definition of object measures ●

Measure pre-defined measurable characteristics of parts, forces, and constraints in a model.


S4-18

SECTION 5 Initial Conditions and Point Trace


S5-1


S5-2

Initial Conditions and Point Trace ●

What’s in this module: ● ● ●

Part Initial Conditions Initial Velocities Point Trace


S5-3

Part Initial Conditions ●

Initial location and orientation ●

●

The design configuration of all the parts (their part coordinate systems) in a model defines their initial locations and orientations. You can fix a part’s location and orientation so it can be used during the assemble simulation procedure (covered later).


S5-4

Initial Velocities ●

Initial velocities ●

In Adams, a part initially moves (at t = 0) as follows:

Adams uses a default of zero

Adams uses the Initial velocity specified

Adams calculates initial velocity; It may or may not be zero

Adams uses initial velocity due to the motions/constraints


S5-5

Point Trace ●

Definition of a point trace ● ●

●

Tracks the location of a marker during an animation. Can be used to visualize the clearance between two bodies during a simulation.

Example of a point trace ●

Trajectory of a ball.


S5-6

SECTION 6 Constraints

ADM701, Section 6, May 2007 Copyright 2007 MSC.Software Corporation

S6-1


S6-2

Constraints ●


Constraints

● ●

Use of Markers in Constraints Degrees of Freedom (DOF)

●

Joint Initial Conditions (ICs)

●

A ball is rolling down an inclined plane (no slip). Which constraints will you use?

●

Angle Measures


S6-3

Constraints ●

Definition of a constraint ●

Restricts relative movement between parts.

●

Represents idealized connections. Removes rotational and/or translational DOF from a system.

●


S6-4

Constraints Example


S6-5

Use of Markers in Constraints ●

Constraint equations in Adams ●

Constraints are represented as algebraic equations in Adams/Solver.

●

These equations describe the relationship between two markers. Joint parameters, referred to as I and J markers, define the location, orientation, and the connecting parts:

●

●

First marker, I, is fixed to the first part.

●

Second marker, J, is fixed to the second part.


S6-6

Use of Markers in Constraints (cont.) ●

Anatomy of a constraint in Adams


S6-7

Degrees Of Freedom (DOF) ●

Constraints and DOF ●

Each DOF in mechanical system simulation (MSS) corresponds to at least one equation of motion.

●

A freely floating rigid body in three-dimensional space is said to have six DOF. A constraint removes one or more DOF from a system, depending on its type.

●


S6-8

Degrees Of Freedom (DOF) (cont.) ●

Determining the number of system DOF ●

Adams/View provides an estimated number of system DOF by using the Gruebler’s Count: System DOF  (number of movable parts  DOF/part) 

 [# Constraints  # DOF(Constr aint)] i  type

●

Adams/View also provides the actual number of system DOF, as it checks to see if: ● ● ●

●

●

Appropriate parts are connected by each constraint. Correct directions are specified for each constraint. Correct type of DOF (translational versus rotational) are removed by each constraint. There are any redundant constraints in the system.

See also: DOF removed by a revolute joint in Appendix A.


S6-9

Joint Initial Conditions (ICs) ●

Characteristics of joint initial conditions ●

You can specify displacement and velocity initial conditions for revolute, translational, and cylindrical joints.

●

Adams/View uses the specified initial conditions of the joint while performing a simulation, regardless of any other forces acting on the joint. If you do not specify joint ICs, Adams/Solver calculates the conditions of the connecting parts while performing a simulation depending on the other forces acting on the joint.

●

● Q u e s t i o n : What

would happen if the joint initial conditions in a system were different from the part initial conditions?


S6-10

Merging Geometry ●

Methods of attaching multiple geometry to a part ●

Using fixed joint to constrain geometric objects.


S6-11

Merging Geometry (cont.) ●

Adding new geometry to an existing part.

●

Note: Adams/Solver handles simulations better if you merge geometry on a rigid part as opposed to constraining multiple parts.

●

Q u e s t i o n : When

you merge geometry, is the overlapping volume

accounted for? ADM701, Section 6, May 2007 Copyright 2007 MSC.Software Corporation

S6-12

Angle Measures ●

Definition of angle measures: They are used to measure the included angle, θ: ●

Between two vectors Defined by three markers

●

Defined throughout a simulation

●


S6-13

Angle Measures (cont.) ●

Notes: ●

The units used for angle measures are in current Adams/View angle units (degrees or radians).

●

The sign convention (+/-) is defined such that the first nonzero value is positive.


S6-14

SECTION 7 Rotation and Friction

ADM701, Section 7, May 2007 Copyright 2007 MSC.Software Corporation

S7-1


S7-2

Rotation and Friction ●


Euler Angles (Rotation Sequence)

● ●

Precise Positioning: Rotate Modeling Friction

●

Measures in LCS


S7-3

Euler Angles (Rotation Sequence) ●

Definition of Euler angles ●

Adams/View uses three angles to perform three rotations about the axes of a coordinate system.

●

These rotations can be space-fixed or body-fixed and are represented as Body [3 1 3], Space [1 2 3], and so on, where:

●

●

1 = x axis

●

2 = y axis

●

3 = z axis

For rotation about these axes, use the right hand rule

Default in Adams is Body [3 1 3].


S7-4

Euler Angles (Rotation Sequence) (cont.) ●

Example of body [3 1 3]: [90 , -90, 180]:

●

Example of space [3 1 3]: [90 , -90, 180]:


S7-5

Precise Positioning: Rotate ●

To rotate objects about an axis in Adams/View, specify: ●

The objects to rotate.

●

The axis about which the objects are rotated. The angle through which the objects are rotated.

●

●

Note: Be careful with the sign of the angle. Adams/View uses the right-hand rule. You can rotate several objects at once about the same axis.


S7-6

Modeling Friction ●

Joint friction can be applied to: ●

● ● ● ●

●

Translational joints (Translational Joint, DOF Removed by, see Appendix A) Revolute joints Cylindrical joints Hooke/Universal joints Spherical joints

Friction forces (Ff ) ● ●

● ●

Are independent of the contact area between two bodies. Act in a direction opposite to that of the relative velocity between the two bodies. Are proportional to the normal force (N) between the two bodies by a constant ( μ). Ff = μN


S7-7

Modeling Friction (cont.) ●

Phases that define friction forces ●

Stiction

●

Transition Dynamic

●


S7-8


Idealized Case ●

●

●

●

Stiction |Vrel | = 0 0 < μ < μs Transition 0 < |V rel| = V1 μd < μ < μs Dynamic V 1 < |Vrel| μ = μd

Adams/Solver case ●

●

●

Stiction

|Vrel | < ΔVs 0 < μ < μs Transition Δ Vs < |Vrel| < 1.5 ΔV s μd < μ < μs Dynamic 1.5 ΔVs < |Vrel | μ = μd


S7-9


Effect of maximum deformation on friction

●

Input forces to friction ●

Always include preload and reaction force.

●

Bending and torsional moment are possible (however, advanced uses of joint friction are beyond the scope of this course).


S7-10

Measures in LCS ●

●

Measures can be represented in: ●

Global coordinate system (GCS) (default)

●

A marker’s local coordinate system (LCS)

Example ●

When a ball falls due to gravity:


S7-11

Measures in LCS (cont.) ●

Acceleration due to gravity in the GCS using symbols xˆ g, ŷg, zˆ g to represent the global x, y, and z components is:

●

Acceleration due to gravity in MAR_1's coordinate system is:


S7-12

SECTION 8 Geometry and Precise Positioning


S8-1


S8-2

Geometry and Precise Positioning ●


Building Geometry

●

Construction Geometry Properties Solid Geometry

●

Precise Positioning: Move

●


S8-3

Building Geometry ●

Properties of geometry ● ● ● ●

●

It must belong to a part and moves with the part. It is used to add graphics to enhance the visualization of a part. It is not necessary for performing simulations. Locations and orientations are defined indirectly by parts using anchor markers.

Note: If you move an anchor marker, all associated geometry moves with it. Conversely, anchor markers move when you move the associated geometry.


S8-4

Building Geometry (cont.) ●

Types of geometry in Adams/View ●

●

Construction geometry ●

Includes objects that have no mass (spline, arc, and so on).

●

Is used to define other geometry.

Solid geometry ●

Includes objects with mass (box, link, and so on).

●

Can be based on construction geometry.

●

Is used to automatically calculate mass properties for the parent part.


S8-5

Construction Geometry Properties ●

Marker geometry has ● ● ●

●

Anchor marker, which is itself Parent: part Orientation and location

Point geometry has ●

No anchor marker Parent: part

●

Location

●


S8-6

Construction Geometry Properties (cont.) ●

Polyline geometry has ● ● ● ● ●

●

Arc geometry has ● ● ●

●

No anchor marker Parent: part One line or multiple lines Open or closed Length, vertex points, and angle Anchor marker Parent: part Start and end angle, radius

Spline geometry has ● ● ●

Anchor marker Parent: part Segment count, open/closed, points


S8-7

Solid Geometry ●

Block geometry has ● ● ●

●

Torus geometry has ● ● ●

●

Anchor marker, which is the corner marker Parent: part Length (x), height (y), depth (z) with respect to corner marker Anchor marker, which is the center marker Parent: part Radius Radius of ring ring (xy (xy plane), radius radius of of circular circular cross cross sectio section n ( to xy plane)

Extrusion geometry has ● ● ●

Anchor marker, which is the reference marker Parent: part Open/closed profile, depth, forward/backwards


S8-8

Solid Geometry (cont.) ●

Cylinder Geometry has ● ● ●

Anchor marker, which is the center marker (placed at first end) Parent: part Length (z), radius


S8-9

Precise Positioning: Move ●

To move objects in Adams/View, specify: ●

The object being moved (or copied).

●

And: ●

●

Either, a point on the object, and the location to which the selected point will be moved. Or, a vector and a distance along the vector.


S8-10

Precise Positioning: Move (cont.)

The moved object maintains its orientation.


S8-11

SECTION 9 Joint Motion and Functions


S9-1


S9-2

Joint Motion and Functions ●


Applying Motion

●

Joint Motion Functions in Adams

●


S9-3

Applying Motion ●

●

Adams/View provides two types of motions ●

Joint motion

●

Point motion

Joint motion ●

There are two types: ●

Translational: applied to translational or cylindrical joints (removes 1 DOF).

●

Rotational: applied to revolute or cylindrical joints (removes 1 DOF).

●

You define the joint to which motion is applied. Adams automatically uses the joint’s I and J markers, bodies, and single DOF.

●

You define function for magnitude.

●

Questions: How does a motion remove DOF? Does this mean that a motion is considered a constraint?

●


S9-4

Joint Motion ●

Marker usage in joint motions ●

The I and J markers (and, therefore, the parts to which they belong) referenced in the joint move with respect to each other as follows:


S9-5

Joint Motion (cont.) ●

The I and J markers overlap when motion

●

During simulation, the z-axes of both markers are aligned.

●

You can define motion magnitude as a: ●

Displacement

●

Velocity Acceleration function of time

●


S9-6

θt

= 0.

Functions in Adams ●

Definition of functions in Adams ●

You use functions to define magnitudes of input vectors used in: ● ●

●

●

●

Functions can depend on time or other system states such as displacement, velocity, and reaction forces. Every function evaluates to a single value at each particular point in time. Motion drivers can only be a function of time: ●

●

Motion drivers Applied forces

M = f(time)

Functions defining motion driver magnitudes can be: ● ● ●

Displacement (time) Velocity (time) Acceleration (time)


S9-7

Functions in Adams (cont.) ●

Note: ●

You can use the Function Builder to create and verify functions in Adams/View. To access the Function Builder, right-click any text box that expects a function.

Display the Function Builder and press F1 to learn about creating functions


S9-8

SECTION 10 Joint Primitives


S10-1


S10-2

Joint Primitives ●


Types of Joint Primitives

●

Perpendicular Joint Primitive


S10-3

Types of Joint Primitives


S10-4

Types of Joint Primitives (cont.)

See also: DOF removed by joint primitives, Appendix A ADM701, Section 10, May 2007 Copyright 2007 MSC.Software Corporation

S10-5

Perpendicular Joint Primitive ●

Example using inline and parallel primitives


S10-6

Perpendicular Joint Primitive (cont.) ●

Example of I and J markers in a perpendicular joint primitive


S10-7

Perpendicular Joint Primitive (cont.) ●

●

●

I marker: ●

Parent part: Bucket

●

Its yz-plane is coplanar to the ground plane.

J marker: ●

Parent part: ground

●

Its z-axis is perpendicular to the z-axis of the I marker.

When constrained, the z-axes of the I and J markers are always perpendicular during simulation.

●

Use the construction method 2 Bod-2 Loc.

●

Q u e s t i o n : Would

the lift mechanism behave any differently if the J marker’s parent part was Base?


S10-8

SECTION 11 Point Motions and System-level Design


S11-1


S11-2

Point Motions and System-level Design ●


Applying Point Motions

●

System-level Design


S11-3

Applying Point Motions ●

Point motions ●

●

There are two types: ●

Single-point motion (removes 1 DOF)

●

General-point motion (removes 1 to 6 DOF)

You define: ●

I and J markers to which motion is applied (via two bodies, location and orientation).

●

Constraint nature of the motion (between 1 and 6 DOF).

●

Functions for magnitudes of motion.


S11-4

Applying Point Motions (cont.)


S11-5

System-level Design ●

The crawl-walk-run approach ● ● ●

Do not build the entire mechanism at once. As you add a new component, make sure that it works correctly. Check your model at regular intervals.


S11-6

System-level Design (cont.) ●

Avoid the need for complex debugging by following the crawlwalk-run approach


S11-7

SECTION 12 Measurements, Displacement Functions and CAD Geometry


S12-1


S12-2

Measurements, Displacement Functions, and CAD Geometry ●


Taking Measurements Displacement Functions Importing CAD-Based Geometry


S12-3

Taking Measurements ●

Point-to-point measures ●

●

Measure kinematic characteristics of one point relative to another point, such as the relative velocity or acceleration. To define them, you specify: ●

Characteristic (displacement, velocity, or acceleration)

●

To-point marker location (I marker)

●

From-point marker location (J marker, default is global origin)

●

●

●

Represent coordinates in marker coordinate system (R marker, default is GCS) Component to return (x, y, z, or magnitude)

Adams/View uses displacement, velocity, or acceleration functions.


S12-4

Taking Measurements (cont.) ●

Function measures ●

● ●

Lets you evaluate arbitrary, user-defined expressions of interest during solution runtime, such as: ●

Flow rate

●

Aerodynamic pressure

●

Stress

You can create them in the Function Builder. Unlike other measures, function measures let you specify plotting attributes.


S12-5

Displacement Functions ●

Displacement functions ●

●

For translational displacement, return scalar portions of vector components (measurements are taken to I, from J, resolved in R’s CS), as shown on the next slide. For rotational displacement, return angles associated with a particular rotation sequence.


S12-6

Displacement Functions (cont.) ●

Example:


S12-7

Importing CAD-based Geometry


S12-8

Importing CAD-based Geometry ●

Supported File Formats ●

● ●

●

●

Stereolithography (*.stl) and render (*.slp) files - Polygonal representation of surfaces. Shell (*.shl) files - Geometry representations. Adams specific. CAD Files – Require Adams/Exchange. You can import and export the following geometry formats: STEP, IGES, DXF, DWG, and Parasolid. Wavefront (*.obj) files - Set of output files that contain a description of the model graphics and motion data. N o t e : Adams/Exchange is MSC’s optional software to Adams/View that lets you import and export geometric data in CAD format.


S12-9

Importing CAD-based Geometry ●

Recommendation for CAD File formats ●

●

●

●

For CAD systems based on the Parasolid kernel, there are many benefits to transferring geometry in Parasolid files. Adams/View creates solid bodies from the Parasolid information that allows for further Boolean operations as well as the selection of geometric features such as the center of a circle. The simpler the representation of the geometric information the better. This is why we often recommend that you use Stereolithography over formats such as IGES and STEP. Other simple formats include render and shell files. Successful transfer of IGES and STEP files from CAD systems to Adams/View depends on both systems. Some CAD systems export information that is easily processed by Adams/View while other CAD systems generate files that are difficult or impossible for Adams/View to import. For comparison of CAD file formats and recommendations for exporting CAD data please refer to the online Help.


S12-10

SECTION 13 Add-on Constraints, Couplers, and Assembling Models


S13-1


S13-2

Add-on Constraints, Couplers, and Assembling Models ●


Add-on Constraints Couplers Assembling Subsystem Models


S13-3

Add-on Constraints ●

●

Add-on (complex) constraints ●

Set up relationships between existing constraints in a system.

●

Connect parts directly and indirectly.

Types of Add-on constraints


S13-4

Add-on Constraints (cont.) ●

Types of Add-on constraints (cont.)


S13-5

Couplers ●

Definition of couplers ● ● ●

●

Couplers connect multiple parts indirectly by coupling 2 joints. Couplers remove 1 DOF. Couplers can be defined: ●

By displacements

●

By scales

●

User defined

Modeling of couplers requires two joints (applicable types are translation, revolute, and cylindrical)


S13-6

Couplers (cont.) ●

Example of a coupler

For help on defining By Displacement and User Defined, press F1.


S13-7

Assembling Subsystem Models ●

When you assemble models ● ● ●

Any number of models can be assembled. Assembling models will create a new model. All assembled models (model1, model2) will continue to exist in the database along with the new model (model3).


S13-8

Assembling Subsystem Models (cont.)


S13-9

Assembling Subsystem Models (cont.) ●

Parts in assembled models ●

●

●

They maintain their global location and orientation, unless otherwise specified. If parts have the same name in different merged models, Adams/View will either: ●

Merge them into one part.

●

Rename the parts.

See also: Model Hierarchy in Section 2


S13-10

SECTION 14 Simulations


S14-1


S14-2

Simulations ●


Assemble Simulation

●

Simulation Hierarchy Types of Simulations

●

Forces in Adams

●

Spring Dampers in Adams

●


S14-3

Assemble Simulation ●

Definition of assemble simulation ●

●

●

Attempts to resolve any conflicts in the initial conditions specified for the entities in the model (for example, broken joints). Also known as an initial conditions simulation.

Initial location and orientation of parts ●

●

You specify the initial position and orientation for a part when you create it. For a part to be held fixed during the assemble simulation, you can specify up to three positions (xg, ŷg, zg) and up to three orientations (psi, theta, phi).


S14-4

Assemble Simulation (cont.)

●

N o t e :

Use initial positions sparingly. If you fix the initial positions of too many parts, the assemble simulation can fail.


S14-5

Simulation Hierarchy Assemble Simulation Assemble

Nonlinear

Linear

Motion Study

Equilibrium Calculation(s)

Default*

Static*

Nonlinear

DOF > 0

DOF = 0 Kinematic*

Eigensolution or State Matrices

Dynamic* Linear

*

●

Automatically p erforms an assemble simulation

N o t e : Often

a linear simulation is used after a static equilibrium or dynamic simulation. While working in any Adams/View dialog box, press F1 to display online help specific to that dialog box.


S14-6

Types of Simulations ●

Static ● ●

●

●

System DOF > 0. All system velocities and accelerations are set to zero. Can fail if the static solution is a long way from the initial condition.

Dynamic ● ●

●

System DOF > 0. Driven by a set of external forces and excitations. Nonlinear differential and algebraic equations (DAEs) are solved.


S14-7

Types of Simulations (cont.) ●

Kinematic ●

System DOF = 0.

●

Driven by constraints (motions). Only constraint (algebraic) equations are being solved.

●

Calculate (measure) reaction forces in constraints.

●


S14-8


Linear ●

●

Adams/Solver can linearize the system of nonlinear equations of motion about a particular operating point. From the linear set of equations, you can ask for an eigensimulation to obtain eigenvalues and eigenvectors for the linearized system to: ●

Visualize the natural frequencies and mode shapes of your system.

●

Compare with test data or results data from FEA.


S14-9


Example of linear simulation ● ● ●

Must linearize about an operating point (often the equilibrium). Extraction of natural frequency. Natural frequency =


S14-10

Forces in Adams ●

Definition of forces ●

●

Do not perfectly connect parts together the way constraints do. Do not absolutely prescribe movement the way motion drivers do.

●

Neither add nor remove DOF from a system.

●

●

Try to make parts move in certain ways.

Characteristics of forces


S14-11

Spring Dampers in Adams ●

Definition of spring dampers ●

They are pre-defined forces.

●

They represent compliance: ●

Between two bodies.

●

Acting over a distance.

●

Along or about one particular direction.


S14-12

Spring Dampers in Adams (cont.) ●

Characteristics of spring dampers

●

See Also: Characteristics of a spring damper, Appendix A


S14-13

Magnitude of Spring Dampers ●

Magnitude based on stiffness and damping coefficients ●

Linear spring-damping relationship can be written as:

ForceSPDP = -k(q – q0) – cq + F 0 where: q - Distance between the two locations that define the spring damper q - Relative speed of the locations along the line-of-sight between them k - Spring stiffness coefficient (always > 0) c - Viscous damping coefficient (always > 0) F0 - Reference force of the spring (preload) q0 - Reference length (at preload, always > 0) t - Time


S14-14

Magnitude of Spring Dampers (cont.) ●

In Adams/Solver, the user-defined equation is: -k * (DM(I, J) – q0) – c * VR(I, J) + F 0

●

Spring-damper forces become ill-defined if endpoints become coincident because of undefined direction.


S14-15

SECTION 15 Forces and Splines


S15-1


S15-2

Forces and Splines ●


Single-Component Forces: Action-Reaction Spline Functions AKISPL Function


S15-3

Single-Component Forces: Action-Reaction ●

Characteristics of action-reaction single-component forces (Sforces)


S15-4

Single-Component Forces: Action-Reaction (cont.)

See Also: Characteristics of an action-reaction S-force, Appendix A N o t e : Adams

applies action and reaction forces to the I and J markers that it automatically creates. ADM701, Section 15, May 2007 Copyright 2007 MSC.Software Corporation

S15-5

Spline Functions ●

Test data that can be incorporated into a simulation includes ●

●

●

Empirical data from suppliers or standard tables for: ●

Nonlinear compliances (force versus velocity).

●

Curves for torque versus motor speed (torque versus angular velocity).

Data taken from physical prototype simulations for: ●

Accelerometer data (acceleration versus time).

●

Tire lateral force as a function of normal force and slip angle.

To incorporate data into a simulation ●

First, create a spline from either: ●

Data points entered manually into the Spline Editor.

●

Imported test data from a file.


S15-6

Spline Functions (cont.)

●

Then, reference the spline through a spline function used in a motion or force. Several interpolation methods are available (using the function type): ●

Cubic-fitting method (CUBSPL)

●

Akima-fitting method (AKISPL)

●

B-spline method (CURVE)


S15-7

Akispl Function ●

Syntax for AKISPL function AKISPL (x, z, spline, iord) ● ●

●

●

x - Independent variable specifying the value along the x-axis. z - Optionally, a second independent variable specifying the value along the z-axis of the surface being interpolated. spline - Spline used to map the one-to-one correspondence of the dependent variables (y) against independent variable values (x or z). iord - An integer variable that specifies the order of the interpolated point (usually 0, but can be 1 or 2).


S15-8

Akispl Function (cont.) ●

Example of an AKISPL function AKISPL (DM(I, J), 0, spline_1, 0)

●

N o t e :

You can create the CUBSPL and CURVE functions exactly as you create the AKISPL function.


S15-9

SECTION 16 Bushings


S16-1


S16-2

Bushings ●


Bushings


S16-3

Bushings ●

Definition of a bushing ●

Pre-defined force

●

Represents compliance: ●

Between two bodies

●

Along or about three vectors


S16-4

Bushings (continued) ●

Characteristics of a bushing

●

See Also: Forces Tables (Incomplete), Appendix A


S16-5

SECTION 17 Impact


S17-1


S17-2

Impact ●


Impact Functions

●

Velocity Functions


S17-3

Impact Functions ●

Impact functions in Adams ●

●

●

Used with user-defined force elements to model contacts, impacts, collisions, and so on. Mimic nonlinear spring and damping forces that turn on and off depending on the distance between two objects. Just like a compression-only spring damper, Adams turns the force on when the distance between two objects, q, becomes less than the user-specified reference distance, q 0:


S17-4

Impact Functions (cont.) ●

Applications of one-sided impact functions (IMPACT)

●

Applications of two-sided impact functions (BISTOP)


S17-5


Syntax for IMPACT function ●

IMPACT(q, q, q 0, k, e, cmax, d) where : q - Actual distance between the two objects (defined with a displacement function) q - Time rate of change of the variable q q0 - Trigger distance used to determine when the contact force turns on and off; it should be specified as a real, constant value k - Stiffness coefficient e - Stiffness force exponent c - Damping coefficient d - Damping ramp-up distance


S17-6


In Adams, the one-sided impact force is calculated as


S17-7

Velocity Functions ●

Definition of velocity and acceleration functions ●

●

●

Returns scalar portions of velocity or acceleration vector components (translational or rotational).

Syntax for velocity functions ●

VM(I,[J], [L])

●

VR(I,[J], [L])

●

VX, VY, VZ(I,[J],[R], [L])

Notes: ●

● ●

Velocity function, VR, is used to define velocity along the line of sight, which is commonly used in spring dampers. If the markers are separating: VR > 0. If the markers are approaching: VR < 0.


S17-8

SECTION 18 Step Functions and Simulation Scripts


S18-1


S18-2

Step Functions and Simulation Scripts ●


STEP Function Scripted Simulations Adams/Solver Commands


S18-3

Step Function ●

Definition of a STEP function ●

●

●

●

In Adams, the STEP function approximates an ideal mathematical step function (but without the discontinuities). Avoid discontinuous functions because they lead to solution convergence difficulties. The STEP function steps quantities, such as motions or forces, up and down, or on and off.

A STEP function is used when a value needs to be changed from one constant to another. N o t e :


S18-4

Step Function (cont.) ●

Syntax for STEP function ●

●

STEP (q, q 1, f 1 , q2, f 2 )

where: q - Independent variable q1 - Initial value for q f 1 - Initial value for f q2 - Final value for q f 2 - Final value for f N o t e :

q1 < q2


S18-5

Step Function Example ●

Example


S18-6

Scripted Simulations ●

●

In Adams/View there are two ways to run a simulation ●

Scripted

●

Interactive

Simulation scripts ● ●

● ●

●

Let you program the simulation before submitting the simulation. Let you quickly repeat a simulation with the same set of parameters. Let you perform more sophisticated simulations. Are required for design studies, design of experiments, and optimization simulations. Simulation scripts are children of a model, and are, therefore, saved in a command file.


S18-7

Scripted Simulations (cont.) ●

Types of scripted simulations in Adams/View ● ● ●

Simple run Adams/View commands Adams/Solver commands


S18-8

Adams/Solver Commands ●

Scripted simulations based on Adams/Solver commands ●

Adams/Solver commands let you perform sophisticated simulations, such as: ● ●

●

Changing model parameters during a simulation. Using different output step sizes over different simulation intervals (versus specifying only one duration and output step size). Using different solution parameters (such as convergence tolerance) over different intervals.


S18-9

Adams/Solver Commands (cont.) ●

Example of a simulation script that changes model topology while you work on your model: simulate/dynamic, end=3.0, steps=30 deactivate/joint, id=3 simulate/dynamic, duration=2.0, steps=200


S18-10

SECTION 19 Adams/Solver


S19-1


S19-2

Adams/Solver ●


Adams/Solver Overview

● ●

Files in Adams/Solver Example of an Adams/Solver Dataset (.adm) File

●

Stand-Alone Adams/Solver

●

Example: 2D Pendulum

● ●

Formulation of the Equations of Motion Phases of Solution

●

Debug/Eprint (dynamics)


S19-3

Adams/Solver Overview Adams/View Integrated Adams/Solver

Import

Export

Analysis files . out .gra .req .res

Dataset . adm

Output

Input Input

Adams/Solver

OR

Input Output Message file . msg ADM701, Section 19, May 2007 Copyright 2007 MSC.Software Corporation

S19-4

Interactive Solver commands

Adams Command file .acf

Files in Adams/Solver ●

Adams/Solver dataset files (.adm) ●

Statements define an element of a model such as a part, constraint, force, and so on.

●

Functions are numeric expressions that define the magnitude of an element such as a force or motion. For more information, see the Adams/Solver online help.

●

Adams/Solver command files (.acf) ●

Commands define an action that needs to be taken during a simulation.

●

See also: Adams/Solver Commands in Section 18


S19-5

Example of an Adams/Solver Dataset (.adm) File


S19-6

Stand-Alone Adams/Solver ●

Simulations in stand-alone Adams/Solver ●

●

●

●

Interactive: ●

Not scripted: enter commands one by one.

●

Scripted: use an Adams/Solver command file (.acf).

Batch - Run multiple jobs in the background using an Adams/Solver command file (.acf). Note: Adams/Solver command files must start with the name of the model to be analyzed and must end with a STOP command.

You can run simulations externally in Adams/Solver from within Adams/View


S19-7

Solver Compatibility ●

With Adams, the new Adams/Solver (C++) version has added significant functionality. With these additions, Adams/Solver (C++) now supports some entities that are not supported for Adams/Solver (FORTRAN). For this reason, a solvercompatibility check has been added. When using Adams/View, this check is called as each object is created.

●

The check is also called for: ●

Each object as it is created when a .cmd file is imported

●

The entire model when an .adm file is imported

●

The entire model before simulation


S19-8

Example: 2D Pendulum ●

Adams Implementation: Euler-Lagrange Equations

●

Description ●

A link of mass M, moments of inertia I, and length 2L is attached to ground using a revolute joint at the global origin O. The joint is oriented in such a way that motion is only allowed in the X-Y plane of the global coordinate system.

●

The coordinates of the center of mass of the link, with respect to the global origin, are represented by the states (x,y).

●

A coordinate system (Op-Xp-Yp) is attached at the center of mass of the link, such that Xp is along the length of the link. The angle between Xp and Xg is denoted by θ.


S19-9

Example: 2D Pendulum (cont.)


S19-10

Example: 2D Pendulum (cont.) ●

Force balance equations

●

Momentum equations (only in θ)

●

Kinematic differential equations

●

Constraint equations


S19-11

Formulation of The Equations Of Motion ●

Nonlinear system - Nine differential and algebraic equations (DAE’s) Equations of Motion Unknown Force balances

Momenta

Kinematics


S19-12

Phases of Solution ●

Task ●

Solve the differential and algebraic equation:

●

Two major components: Predictor and Corrector

●

Phase 1: ●

●

Phase 2: ●

●

Correct the prediction

Phase 3: ●

●

Predict an initial solution

Evaluate quality of solution (accept solution)

Phase 4: ●

Prepare for next step


S19-13

Phases of Solution (cont.) ●

Task ●

●


Phase 1: ●

Predict an initial solution ● ●

●

●

Phase 2: ●

●


Phase 3: ●

●

Predict an initial value using an explicit method. The predictor is simply looking at past values to guess the solution at the next time. The governing equations for G are not satisfied. This is simply a good starting point for the next phase.


Phase 4: ●



S19-14


Task ●

●

Phase 1: ●

●

Solve the differential and algebraic equation: Predict an initial solution

Phase 2: ●


●

Evaluate G. If G is near zero, corrector is finished. Go to phase 3. ●

Use the Newton-Raphson method to correct the prediction.

●

Solve for ∆y. Update y.

●

Repeat iteration until || ∆ y|| < corrector error tolerance


S19-15


Example:

As a first guess, set q=2

●

●

Phase 3: ●

●

The exact answer is q = 1.0 Evaluate quality of solution (accept solution)

Phase 4: ●



S19-16


Task ●

●

Phase 1: ●

●


Phase 2: ●

●



Phase 3: ● ●

Evaluate quality of solution (accept solution) Estimate local truncation error ●

if estimated < ( εL)

●

Yes – Accept solution. Go to phase 4

●

No – Reject solution and repeat phase 1 and 2 with new step size


S19-17


Global Error ( εG) ●

●

Local Truncation Error ( εL) ●

●

The difference between the current solution and the true solution The error introduced in a single step

Phase 4: ●



S19-18


Task ●

●

Phase 1: ●

●


Phase 3: ●

●


Phase 2: ●

●



Phase 4: ● ● ● ●

Prepare for the next step Update higher order derivatives used in prediction for the next step Determine step size and order for next step Go back to phase 1, and start a new step


S19-19

DEBUG/EPRINT (Dynamics) ●

Each GSTIFF integrator step consists of two phases: ●

Phase 1: a forward step in time (the predictor for dynamics) 1. The step number - A running count of the number of steps taken and can

be used as a measure of how hard Adams/Solver is working. 2. The order of the predictor for dynamics - Corresponds to the order of the

polynomial Adams/Solver uses to predict the solution at the end of the integration step. 3. The value of time at the beginning of the step. 4. The size of the step.


S19-20

DEBUG/EPRINT (Dynamics) (CONT.) ●

Phase 2: the solution of the equations of motion (the corrector for dynamics). 5. The cumulative number of iterations - A running count of the iterations

needed to solve the equations of motion and can be used as a measure of how many computations Adams/Solver is performing. 6. The iteration number - One at the beginning of each step and increments

by one until Adams/Solver converges to a solution or exceeds the maximum allowable number of iterations. 7. Absolute value of largest equation residual error - This number is an

indicator of how far Adams/Solver is from a solution. This number should decrease after every iteration in healthy simulations. 8. Dataset element associated with #7 - The equation that has the largest

equation residual error for the above dataset element. 9. Equation associated with #8.


S19-21

DEBUG/EPRINT (Dynamics) (cont.) 10. Absolute value of the largest change in a variable - The final iteration

should not need to change variables very much. This number is an indicator of how far Adams/Solver needs to change variables to approach a solution. Ideally, this number should decrease after every iteration. 11. Dataset element associated with #10. 12. Variable with the largest change for #11. 13. Jacobian updates - If Adams/Solver has updated the Jacobian, YES

appears under the new Jacobian header.


S19-22

DEBUG/EPRINT (Dynamics) (cont.) 3. Time at beginning of step 1. Running count of successful steps

4. 6.

7.

8.

9.

2. Order of predicting polynomial

5.

10.

11.

12.

13. Corrector information


S19-23

SECTION 20 Sensors and Design Variables


S20-1


S20-2

Sensors and Design Variables ●


Sensors

●

Design Variables


S20-3

Sensors ●

Sensors ●

●

Monitor any quantity of interest in a model during a simulation, and take a specified action when the quantity reaches or exceeds a critical value. Take one of the following actions: ● ●

●

Completely stop the simulation. If used with a script, sensors halt the current simulation and continue with the next command in the script. Can be used to evaluate certain expressions when the required condition is met. You can access this value using the Adams/Solver function, SENVAL. See the following Knowledge Base Articles: ●

●

Using SENVAL to count full rotations of a spinning part: http://support.mscsoftware.com/kb/results_kb.cfm?S_ID=1-KB10703 Finding min/max of a state using a SENSOR: http://support.mscsoftware.com/kb/results_kb.cfm?S_ID=1-KB12377


S20-4

Sensors (Continued) ●

●

A sensor basically represents an ●

If quantity

●

Then

If/Then

statement:

= value (+/- tolerance)

take a specified action

Example of using sensors with scripts ●

●

Monitor the reaction force in a constraint and deactivate the constraint when the force exceeds a specified value. Monitor the distance between two objects and reduce the solution step size just before contact, to avoid convergence problems.


S20-5

Design Variables ●

Design variables ● ●

●

Define independent parameters that can be tied to objects. Organize the critical parameters of the design into a concise list of values that can be easily reviewed and modified.

Example ●

You can create a design variable called cylinder_length to control the lengths of all three cylinders as shown in the next slide:


S20-6

Design Variables (Continued)

N o t e :

You can also use parametric analyses to automatically run a series of simulations that vary your design variables, which you will do in Workshop 22. ADM701, Section 20, May 2007 Copyright 2007 MSC.Software Corporation

S20-7

SECTION 21 Splines and Constraints


S21-1


S21-2

Splines and Constraints ●


Splines from Traces

●

Curve Constraints Automated Contact Forces

●

Flexible Parts - Adams/Flex

●


S21-3

Splines from Traces ●

Definition of spline from a trace ●

● ●

●

A point trace tracks a location of a marker or circle over time with respect to another part. Adams/View can create a two- or three-dimensional spline from a trace. Creating a spline from a trace is used to back-calculate (reverse engineer) the shape of an existing part based on its motion (cam synthesis).

Notes: ●

●

When you trace an object and create a spline from it, the point or circle should move in a smooth, even path. If the path is closed, you should simulate for one cycle only.


S21-4

Curve Constraints ●

●

Types of curve constraints in Adams ●

Point-on-curve

●

Curve-on-curve

Curve-on-curve constraints ●

● ●

●

Used where a curved edge on one part always follows a curved edge on a different part. Remove two DOF. Modeling of curve-on-curve constraints requires: ●

Two parts

●

Two curves that will always remain in contact

Typical applications include general cam-to-cam systems.


S21-5

Curve Constraints (cont.)

N o t e :

Curve-on-curve constraints do not allow lift off.

See Also:

DOF removed by curve constraints in Appendix A


S21-6

Automated Contact Forces ●

Contact forces ●

●

●

Special forces acting on parts that are activated when part geometries come in contact with each other. Have values that are determined by a set of contact parameters identical to those in the IMPACT function. Multiple contact forces can be combined to create more complex contacts.


S21-7

Automated Contact Forces (cont.) ●

Contact pairs in Adams


S21-8

Automated Contact Forces (cont.) ●

Things to note while creating automated contact forces ●

Point-to-curve

●

Curve-to-curve Sphere-to-plane

●

Curve-to-plane

●

Point-to-plane

●


The xy planes of the two reference markers must be parallel. The z-axis of the reference marker of the plane (the plane’s normal vector) must point away from the plane and at the circle or sphere.

S21-9

Flexible Parts – Adams/Flex ●

Better loading predictions for durability analyses ● ●

●

The flexible component is the focus of your attention. Basically asking the question: "What is the system doing to my flexible component?"

Improved system performance ●

●

The model fidelity is the focus of your attention. Component flexibility is just another parameter of the system design. Basically asking the question: "What is the flexible component doing to my system?"


S21-10

Flexible Parts – Adams/Flex (cont.) ● ●

●

Allows you to create flexible bodies in the Adams environment Allows for easy substitutions of flexible bodies for rigid bodies in your Adams models Can perform quick modifications on the flexible bodies to perform multiple iterations of the flexible body model

To run through a workshop, see the Adams/Flex Examples. For more information, see the Adams/Flex online help.


S21-11

SECTION 22 Multi-Component Forces and Design Studies


S22-1


S22-2

Multi-Component Forces and Design Studies ●


Multi-Component Forces

●

Design Studies


S22-3

Multi-Component Forces ●

Types of multi-component forces ● ● ●

●

Vector force (three translational components) Vector torque (three rotational components) General force vector (three translational, three rotational components)

Characteristics of vector force


S22-4

Multi-Component Forces (cont.) ●

Notes: ●

●

The floating J marker always maintains the same location as the I marker. The characteristics of other multi-component forces conceptually work the same way.


S22-5


Example of a force vector ●

A vector force representing a contact between a ball and a cantilever:


S22-6


●

●

●

Because the J marker belongs to part B, the force acts on part B when the bodies collide. Because the J marker moves with the I marker, part B knows where to apply the reaction force. N o t e : In

the example, the J and R markers must belong to the same part. However, the R marker can belong to any part. See Also: Characteristics of a multi-component force, in Appendix A


S22-7

Design Studies ●

Trial and error method (manual iterations) Model Parts Joints Forces

Simulate

View results

Is the design optimal?

Loop is repeated several times

Manually change the variable


No

S22-8

Yes

Completed

Design Studies (cont.) ●

Design study method (automated iterations) Design Variable (V) Objective (O)

Model Parts Joints Forces

Model gets updated

Results automatically generated

Simulate

Variable changes automatically

No

Is this the final iteration? (i=n)

Yes The loop goes through specified number of iterations (i=1,…n)


S22-9

Tabular Plot O versus V report (for each iteration)


Definition of a design study ● ● ●

●

Varies a single design variable (V) across a range of values. Runs a simulation at each value. Reports the performance measure for each simulation.

From the results generated, you can determine: ● ●

The best value for V among the values simulated. The approximate design sensitivity of V (rate of change of performance measure with respect to V).


S22-10


Sensitivity, S, at iteration, I

●

Looking at Trial 4 (i = 4):

●

S4 is the approximate slope at Trial 4 (tip_y_loc=10.6) in the plot.


S22-11

Design Studies (cont.)


S22-12

SECTION 23 Recommended Practices


S23-1


S23-2

Recommended Practices ●


General Approach to Modeling

●

Modeling Practices: Parts Modeling Practices: Constraints

●

Modeling Practices: Compliant Connections

●

Modeling Practices: Run-time Functions

●

Debugging Tips

●


S23-3

General Approach To Modeling ●

Crawl-walk-run ●

Try to understand the mechanism from a physical standpoint.

●

Use building blocks of concepts that have worked in the past. Add enhancements to the model while testing periodically.

●

Build kinematic models before building dynamic models.

●

Use motions to check models before applying forces.

●

● ●

Use motions which start with zero velocity. Verify enhancements to a complex model on a simpler model first.


S23-4

Modeling Practices: Parts ●

Geometry associativity errors ●

●

Mass properties ●

● ● ●

●

●

Geometry may be added to the wrong part. Using imported CAD-created geometry (IGES, STL, and so on) can yield inaccurate mass properties. Ensure inertia matrix is realistic. Use aggregate mass for a quick check of system mass and inertia. Use the Table Editor to do a quick check and potentially fix individual part masses and inertia. Small part mass and inertia lead to unrealistically high frequencies.

Initial velocities ●

Check to see that part initial velocities are consistent (look in the .out file).


S23-5

Modeling Practices: Parts (cont.) ●

Dummy parts ● ●

●

Whenever possible, avoid using them. If absolutely needed, constrain all six DOF and assign a mass of 0.0 (not 1e-20).

Design configuration ●

Build a model close to assembled position.

●

Build a model close to a stable equilibrium position, if possible.


S23-6

Modeling Practices: Constraints ●

Fixed joints ●

●

●

●

●

●

Not needed, since two or more parts can be combined or merged into a single part. An extra part with a fixed joint adds unnecessary equations to your system. When locking a part to ground, enormous torque may develop due to large moment arms. If absolutely needed, then add fixed joints at the center-of-mass (cm) location of lightest part. If locking a part to ground, consider assigning a very large mass/inertia to it so it can behave like ground.

Note: Whenever possible, avoid using fixed joints.


S23-7

Modeling Practices: Constraints (cont.) ●

Universal joints ●

●

Motion ●

●

When a universal joint is at 90º, you get a singular matrix. Motion elements should only be functions of time.

Note: Avoid redundant constraints.


S23-8

Modeling Practices: Compliant Connections ●

Spring dampers ● ● ●

●

Ensure that the marker endpoints (DM(I,J)) are never superimposed. Watch out for springs with very stiff spring constants. Watch out for springs with no damping.

Bushings ●

Watch out for bushings with large rotations.


S23-9

Modeling Practices: Run-time Functions ●

Function Builder ● ● ●

●

Velocity ●

●

Assists in building functions. Assists in function verification. Has function plot capability. Make sure velocities are correct in force expressions. For example, in the damping function: -c*VX(i, j, j, _), the fourth term is missing.

Splines ● ● ● ● ●

Approximate forces with smooth, continuous splines. Extend the range of spline data beyond the range of need. Cubic splines (CUBSPL) work better on motions than Akima. Akima splines (AKISPL) work better on forces than Cubic. The Akima interpolation method is faster and can be defined as a surface, but its derivatives are generally discontinuous.


S23-10

Modeling Practices: Run-time Functions (cont.) ●

IMPACTs/BISTOPs ● ●

●

Do not use 1.0 for exponent on IMPACT or BISTOP functions. Models with IMPACTs/BISTOPs should have slight penetration in design position when doing statics.

Measures ● ● ●

Set up measures of your run-time functions. Set up measures of components of your run-time functions. Ensure that your function will not try to divide by zero.


S23-11


Contacts ● ●

●

Do not use 1.0 for exponent on IMPACT or BISTOP functions. Models with contacts should have slight penetration in design position when doing statics.

Tires ●

●

Models with tires should have slight penetration in model position when doing statics. If only rear tires penetrate, the static position could be a “handstand.”


S23-12


Units ●

●

● ●

●

●

Use consistent units throughout the model (time, mass, stiffness, damping, and so on). Choose units (mass, force, time, and so on) that do not require using very large or very small numbers. Be wary when your model contains numbers like 1e+23 or 1e-20. Use appropriate units—when modeling large models such as an aircraft landing on a runway, length units of millimeters may not be appropriate. Conversely, when modeling small models such as a power window switch (made up of small moving parts), using length units of meters may not be appropriate. Use reasonable time units—high frequencies may be better modeled with time units of milliseconds rather than seconds.

Gravity ● ●

Check magnitude and direction. Check for multiple gravity elements.


S23-13

Debugging Tips ●

Model verify ●

●

Lists Gruebler's count and actual DOF count. Lists redundant constraints.

●

Reports misaligned forces/force elements, joints, and so on.

●

Helps identify and eliminate causes for input warning (don't ignore).

●

●

Lists number of moving parts, number of each type of constraint.

Model topology ●

Text or graphical model topology.

●

Table Editor provides spreadsheet-like overview of model content.


S23-14

Debugging Tips ●

Icon Feedback ●

●

Table Editor ●

●

Broken icon in design configuration probably means incorrectly defined joint or force. Convenient way to inspect and modify models (particularly large ones).

Interactive Simulation ●

By default is turned on.


S23-15

Debugging Tips (cont.) ●

Model display update ●

●

As Adams/Solver performs the simulation, you have the option to get immediate graphical feedback of the simulation at every: ●

Output step

●

Integration step

●

Iteration

Icons visible during simulation ●

This may help you monitor behavior of model components.


S23-16


Subroutines ● ●

●

Check for their existence. While debugging a model, eliminate user subroutines so that they are not the source of the error.

Gravity ●

Turning gravity off can accentuate modeling errors and make debugging easier.


S23-17


Statics ●

When applicable, perform an initial static simulation first.

●

If static solution fails: ●

●

Turn on Model display update = at every iteration to provide additional insight. Identify and eliminate the undesired static configuration—there could be more than one static configuration and Adams/Solver could be finding the undesired one.

●

Check to see if there are any floating parts.

●

Check the signs of applied forces.

●

Experiment with Alimit/Tlimit/Maxit/Stability.

● ●

Check if impacts are initially in contact; if not, they should be. Running an initial dynamic simulation can help you determine why the model is not finding static equilibrium.


S23-18


Dynamics ●

If integrator fails to start-up: ● ● ● ● ● ●

●

Check sign and magnitude of forces. Look at accelerations to understand what is happening. Perform initial static analysis first. Try a quasi-static simulation. Try changing integrator parameter - HINIT. Try a different integrator.

If integrator fails in the middle of a simulation: ● ● ● ●

● ● ●

Look at animation and plots until failure, to understand simulation. Decrease integrator parameter - HMAX. Do not let the integrator step over important events. Short duration events, such as an impulse can be captured by setting the maximum time step, HMAX, to a value less than the impulse width. Use HMAX so Adams/Solver acts as a fixed-step integrator Decrease error. Try a different integrator.


S23-19


●

If integrator takes very small steps: ●

Look for sudden changes in force and motion input.

●

Rescale model to get more uniform numbers.

Velocities at time=0 ●

Check initial velocities using the .out file.


S23-20

APPENDIX A Tables

ADM701, Appendix A, May 2007 Copyright 2007 MSC.Software Corporation

Appendix A-1


Appendix A-2

Tables ●

What’s in this appendix: ●

Constraints Tables (Incomplete)

●

Forces Tables (Incomplete) Constraints Tables (Completed)

●

Forces Tables (Completed)

●


Appendix A-3

Constraint Tables (Incomplete)


Appendix A-4

Constraint Tables (Incomplete)


Appendix A-5

Force Tables (Incomplete)


Appendix A-6

Force Tables (Incomplete)


Appendix A-7

Constraint Tables (Completed)


Appendix A-8

Constraint Tables (Completed)


Appendix A-9

Forces Tables (Completed)


Appendix A-10

adm701_mdr2_coursenotes

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