Modeling & Simulation of a Spring-Assisted Robot Arm
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Modeling & Simulation of a Spring-Assisted Robot Arm. ME 6105 Fall 2012 – 12/06/2012 Lewis Lo, Benjamin Daniels, Matthew Rosen, Merlin Morlock. abb.com. Introduction & Domain. 4 axis robot based on the ABB IRB660 palletizing & materials handling  up to 250 kg load

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Modeling & Simulation of a Spring-Assisted Robot Arm

ME 6105 Fall 2012 – 12/06/2012

Lewis Lo, Benjamin Daniels, Matthew Rosen, Merlin Morlock

abb.com


Introduction & Domain

  • 4 axis robot based on the ABB IRB660

  • palletizing & materials handling  up to 250 kg load

  • Torsional spring at lower arm

  •  Goal: design a motor with spring at lower arm joint to maximize utility

  • performance attributes: 1. Energy consumption

  • 2. End-effector position error

ME6105 - Spring Assisted Robot Arm


Motor Parameters Design

  • Back calculating Torque (~20kN) to find k and R, motor paramters

  • Use of gear box (~182/1)to increase Torque

  • Thanks for help from Prof. Paredis in Motor Cost estimation

ME6105 - Spring Assisted Robot Arm


SwitchingMass

  • Halfwaythroughtrajectorythepayloadmassisdecreased

  • from 60 kg to 1kg  simulates picking & placing

ME6105 - Spring Assisted Robot Arm


Controller Design 1/2 - Inverse Dynamics

  • Advantage

    • inverse dynamicsautomaticallycalculatesneededvoltageforgiven angle

    •  PID controllershaveminorworkto do tocompensateuncertaintiesanddisturbances

ME6105 - Spring Assisted Robot Arm


Controller Design 1/2 - Inverse Dynamics

  • But howtorealize Inverse Dynamics?

    • change all inputstooutputs

ME6105 - Spring Assisted Robot Arm


Controller Design 1/2 - Inverse Dynamics

  • But howtorealize Inverse Dynamics?

    • change all inputstooutputs

comicforum.de


Controller Design 1/2 - Inverse Dynamics

  • But howtorealize Inverse Dynamics? Let Dymola do thework!

    • copy model

    • change all inputstooutputsandviceversa

    • e.gsensorstoactuatorsandviceversa

    • makeresistance negative

    • makedamping negative

  • Disadvantageof Dymola Trick

    • problemsoccuredwith multiple inputsandoutputswhenthereisdamping & resistance

Physically

Not meaningful

But doesthejob

ME6105 - Spring Assisted Robot Arm


Example

INVERSION ofmotor & mechanics

ME6105 - Spring Assisted Robot Arm


Controller Design 2/2 – PID controllerused in project

  • Advantage

    • SISO control design  easy

  • Disadvantages

    • PID controllers pull all theweight

    •  Trick: make controller extremely stiff: P=40 000 !!

ME6105 - Spring Assisted Robot Arm


Overall Model Structure

  • Trajectories, PID Controllers, DC Motors & Mechanics

  • Error & Energy measurement performance attributes


Animation for Fixed Path

ME6105 - Spring Assisted Robot Arm


Whatisthe Spring goodfor?

  • parabolicfunctionforenergyconsumption morethan 50% energysavingspossible

Energyconsumption

Spring stiffness

Max Motor speed

ME6105 - Spring Assisted Robot Arm


Detailed Demand Spreadsheet

ME6105 - Spring Assisted Robot Arm


Detailed Demand Spreadsheet

  • Modify Profit in `ProfitUtility´ spreadsheet

    • Fordiscountfactors

    • Discount Limits

Realizewithifstatement

  • Modify thisanddragtorightand down

ME6105 - Spring Assisted Robot Arm


Detailed Demand Spreadsheet

  • Modify Utility in `ProfitUtility´ spreadsheet

    • introduce time preference discountprofitandplug in intoutilityfunction

  • But don‘tforgettochangethecalculationofexpecteddemandsincecostdepends on demandnow = `loop´

  • Modify thisanddragtorightand down

change

In ProfitUtility usingPre-predictor

In TEAM_USE

ME6105 - Spring Assisted Robot Arm


Motor Cost & Loop

  • Motor Costas design variable

  • ´Loop´ in spreadsheetcanbeseen ininfluencediagram

ME6105 - Spring Assisted Robot Arm


Design Space Exploration & Optimization

  • Changed of modification cost at zero spring size to exponential function to ensure smooth design surface

  • Optimization results not too close to design space bounds.

ME6105 - Spring Assisted Robot Arm


Design Problem Results

Profit

ME6105 - Spring Assisted Robot Arm


BomfunkMC‘s - Freestyler


ME6105 - Spring Assisted Robot Arm


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