Design and analysis of a flexure based 3 dof micro positioner
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MSc presentation · R.H.S. Bruinen. Supervisor · Prof . ir . R. H. Munnig Schmidt Daily supervisor · P . Estevez Castillo MSc. Design and analysis of a flexure based 3-DOF micro positioner. Content. Introduction Conceptual design Stiffness analysis Results and conclusions.

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Design and analysis of a flexure based 3-DOF micro positioner

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MSc presentation · R.H.S. Bruinen

Supervisor · Prof. ir. R. H. Munnig Schmidt

Daily supervisor · P. Estevez Castillo MSc

Design and analysis ofa flexure based 3-DOF micro positioner


Content

  • Introduction

  • Conceptual design

  • Stiffnessanalysis

  • Results and conclusions


Introduction


Introduction / Application

Sources: apple.com, shavers.co.uk, delfly.nl


Introduction / Haptic teleoperation

Gripper

User

Command

Haptic interface

Micropositioner robot

Force & vision

feedback

Sources: micropositioners.net, mekabot.com


Introduction / My project

Specifications

  • Workspace 20x20x20mm

  • MIM (minimum incremental motion) 0,2µm

  • Naturalfrequency > 100Hz

  • Actuator forces < 1N

  • Velocity 0.1 m/s

  • Acceleration 1.5 m/s2

Allow3D translations, constrainrotations

Micropositioner robot

Source: micropositioners.net


Conceptual design


Conceptual design / Serialor parallel

Low moving mass

High stiffness

Small workspace

Serial

Parallel

Sources: xyz-stage.com, pi.com


Conceptual design / Parallel mechanisms

Adept Quattro

Tripteron

Sources: robot.gmc.ulaval.ca, motionsystemdesign.com


Conceptual design / Bearingsorflexures

No dry friction

Short range

Bearings

Flexures

Sources: rchellevoet.nl, flexpivots.com


Conceptual design / Architecture

Mechanism

Legs

Joints

Beams

1 DOF

2 DOF

3 DOF

Sources: kxcad.net,hephaist.co.jp


Conceptual design / Architecture

Design optionsfromliterature

e.g. Jin and Zhao “New kinematic structures for 2-, 3-, 4-, and 5-DOF parallel manipulator designs”

Examples:

1 DOF joints

High stiffness

Selected:

Modified Delta

Cartesianmechanism

U* design

Source: Jin and Zhao “New kinematic structures…”, Gosselin “Compact dynamic models…”


Conceptual design / Geometry

  • Main design variables

  • Upper leg angle

  • Lower leg angle

  • Line of actuation

90°

90°

in line with upper leg


Conceptual design / Joints

  • Flexure requirements

  • Low pivot stiffness  Large workspace

  • High off-axis stiffness  High resonances & precision

Intersecting cross

Notch

3-leaf


Stiffnessanalysis


Stiffness analysis / Introduction

Stiffness

  • Dimensioning

  • Mechanism size

  • Joint length, width and thickness

  • Mechanism performance

  • Workspace

  • MIM

  • Resonances

F

Stick-slip

Case 1: Actuation force

Case 2: Interaction force


Stiffness analysis / Introduction

Stiffness

  • Dimensioning

  • Mechanism size

  • Joint length, width and thickness

  • Mechanism performance

  • Workspace

  • Resonances

  • MIM

Existing literature

Howell and Midha “A Method for the Design of Compliant Mechanisms With Small-Length Flexural Pivots”

- 1 DOF joint

- No parallel mechanisms

Pham and Chen “Stiffness modeling of flexure parallel mechanism”

- Theoretical approach


Stiffness analysis / Introduction

Stiffness

  • Dimensioning

  • Mechanism size

  • Joint length, width and thickness

  • Mechanism performance

  • Workspace

  • Resonances

  • MIM

Stiffness analysis

Joints

Legs

Mechanism


Stiffness analysis / Joints

Leaf

Joint

Bending:

Stiffness around pivot axis

Stiffness around off-axis

Compression:


Stiffness analysis / Legs

Example: Translation, X direction

θ= M·Cp

= F·ll·Cp

Cp = joint compliance around pivot axis

Δx = θ·ll

= Fx·ll2·Cp

Case 1: Actuation force

Case 2: Interaction force


Stiffnessanalysis / Mechanism

Case 1: Actuation force

Case 2: Interaction force


Stiffnessanalysis / Mechanismtransformation

Transform to horizontal-verticalcoordinate system

withEulerrotations


Stiffnessanalysis / Dimensioning

Stiffness

  • Mechanism size 16cm

  • Joint length 8mm, width 10mm and thickness 0.15mm

  • Dimensioning

  • Mechanism size

  • Joint length, width and thickness

  • Mechanism performance

  • Workspace

  • Resonances

  • Stick-slip

18x18x18 mm3

240 Hz

75 nm

20x20x20 mm3

100 Hz

200 nm

-

++

++

Stiffness analysis

Joints

Legs

Mechanism


Results and conclusions


Results

  • Designed a flexurebased 3 DOF micropositioner

  • Developedstiffnessanalysismethodforflexure parallel mechanisms

  • ‘Second International Symposium onCompliantMechanisms’

    • Submitted a paper

    • Created3D print

    • Presentation and demonstration


Conclusions

  • The stiffnessanalysis

    • Addition to existingliterature

    • Tool for the design of flexure parallel mechanisms

    • More insightinto the mechanism

  • The final design

    • High precision performance with a largeworkspace

    • Use in industryor research


Design and analysis ofa flexure based 3-DOF micro positioner


Mechanismspecifications


Conceptual design / Actuators and sensors

  • Selected actuator: Lorentz motor

  • No friction, no backlash

  • No added stiffness in system

  • Selected sensor: optical encoder

  • Sufficient range and resolution

  • Affordable


Stiffness analysis / Legs

Example: Translation, X direction

M=Fx·ll

θ=M·Cp

Δx2 = θ1·ll

Δx3 = Fx·ll2·Cp

CxI = ll2·Cp

Case I


Stiffnessanalysis / Mechanism performance

Workspace

Stick-slip

Resonances


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