Professor Mike BlundellPhd, MSc, BSc (Hons), FIMechE, CEng

Lecture 3 – Use of CAE and ADAMS

Bergamo UniveristyItalyJune 12th-13th 2012

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Product Development Process for Manufacturers

DesignDesign ValidateValidate AssemblyAssembly ServiceServiceConceptConcept

Improvements with MBS

IMPROVEMENT

With MBS

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MBS

Integrated CAE Technologies

FEA CFD ?

Controls

Testing

CAD

Hydraulics

Multibody Systems Analysis (MBS)

Virtual Prototyping (MBS) may be summarised as:

• The Analysis and Simulation of Mechanical Systems

• Systems can consist of rigid and flexible bodies

• Bodies are assembled using rigid joints or flexible connections

• System elements such as springs and bushes can be nonlinear

• The mechanism can move through large displacement motion

• Automatic formation and solution of equations of motion

• Animated and plotted presentation of results

• Commercial Software available – ADAMS, SIMPACK, DADS, …

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Typical Constraint Elements - Joints

Planar

Revolute Spherical Cylindrical Translational

Fixed Universal Rack & Pinion

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Joint Library

Cylindrical Joint Spherical Joint

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Joint Library

Planar Joint Revolute Joint

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Joint Library

Translational Joint Universal Joint

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Main Types of Analysis

• KINEMATIC - Movement controlled by joint selection and motion inputs.Movements not effected by external forces or mass properties.Systems have zero rigid body Degrees of Freedom. 

• STATIC - Determine static equilibrium position and reaction forces. Velocities and accelerations are set to zero. Often needed before dynamic analysis (ie. full vehicle models). Can be run QUASI-STATIC in time domain. 

• DYNAMIC - Complete nonlinear transient multi-degree of freedom systems using numerical integration to solve the equations of motion. Users can select the integrator for solution and control the accuracy of the solution process. 

Graphical User Interface

Model Parameterisation

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Occupant Protection Studies

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MADYMO Simulation of Pedestrian Impact

Pedestrian Human Body Model positioned:

- Walking posture

- Knee extended

- balanced in an upright position

No pedestrian initial velocity

Vehicle initial velocity 39 km/h

Bumper level 390 mm

Bumper lead distance 200 mm

Hood edge level 720 mm

Adaptable Car Structures (ACS)

Active-reversible bumper and bonnet concept (Pneumatic Muscle)

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Typical Design Study

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Characteristic Curves of Automotive Suspension

• Toe, Caster, Camber curves are essential properties of a suspension

• Curves represent change in angular orientation of wheel under different loading conditions

• Curves must be continually evaluated as design changes

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Simulation of Vertical Motion

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Typical Problem Statement

• Packaging problems with current design• Tie-rod spindle connection point must be moved• Would like to move tie rod:

– 10 mm outboard– 14 mm aft– 15 mm up

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A Past Approach

• Run two analyses: nominal and design change (considered)

• Compare the results

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Typical Report (old approach)

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Modern Methods

• Setup Design of Experiments Analysis (DOE)

– Define design space

– Define trial runs

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Application of DOE

• Utilize parametric modeling tool

– Analyse set of trials picked by DOE theory

• Use DOE theory and the response surface method

– Fitted results give continuous information throughout design space

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Start with Design Space

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Add DOE Design Points

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Assign Trial Numbers

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Analyze Model at Each Trial

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Calculate Objective at Each Trial

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Map Trial Objectives back to Design Space

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Create Response Surface

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Response Surface Method

• Provides continuous knowledge within design space!• Can be extended (hard to visualize)

– More than 2 factors– More complex objective types

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Contact Examples

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Forced Contact Step Output

• Animate using defined output steps• Or animate additional contact frames• Displays contacts between output steps

50 STEPS 152 STEPS

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ADAMS/Flex

FE Modes

ADAMS Simulation

Stress Distribution

• Integrating System-Level Motion Simulation and Component-Level FEA

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Flexible Satellite with Automatic Controls

• Stabilizing the satellite’s orientation during deployment of flexible solar panels

Customization

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Digital Functional Vehicle

Full Vehicle

Chassis Engine Driveline Body

Suspension

Steering

Brakes

Tires

Valvetrain

Cranktrain

Chain/Belt

Acc. Drives

Transmission

Clutch

Differential

Axles/CV

Body-in-white

Frame

Seating

Restraints

Road

Driver

Test Rigs

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Total Vehicle Modelling

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Tutorial 4 - ADAMS Demonstration Session

• Using ADAMS/Solver Files (Solver)

• Building Models interactively in ADAMS/VIEW

• Using an ADAMS/Command Files (AVIEW)

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Double Wishbone Example

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• Prepare a System Schematic

• Calculate the model Degrees of Freedom

• Plan the ADAMS/Solver Input File