Tools for Robotic Microassembly

worrisomebelgianAI and Robotics

Nov 2, 2013 (3 years and 9 months ago)

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Institute of Robotics and Intelligent Systems
Diploma Thesis
Tools for Robotic Microassembly
Vincent Hess
Adviser: Berk Yesin
Institute of Robotics and Intelligent Systems
Contents
•Introduction
•Problem Specification
•Literature Research
•Concept
•Design
•Conclusion and Outlook
•Discussion
Institute of Robotics and Intelligent Systems
Introduction
Microassemblyat IRIS:
MicroassemblystationMicrorobot
Institute of Robotics and Intelligent Systems
Introduction
Assemblyapplication:dummymicrorobotparts
Dimensions(largestpart): 950 ×400 ×50µm
Fabrication: Electroplating
Material: Nickel
→meso-/microscale
Institute of Robotics and Intelligent Systems
Problem Specification
Goals of the Diploma Thesis
•Review the state of the art in microassembly
processes and tools and develop new concept
•Design and build prototypes
•Interface the tools with the rest of the system
Institute of Robotics and Intelligent Systems
LiteratureResearch
MicroassemblyProcesses
Many papers about microgrippersand
parallel microassemblytechniques, few
about serial microassemblyprocesses.
•Serial assembly Processes: visually
guided pick-translate-insert operations
•Mostly parts are inserted into feature on
wafer
•No reports on assembly of autonomous
device
[1] N. Dechev, Department of Mechanical
Engineering, University of Toronto
Institute of Robotics and Intelligent Systems
Literature Research
Microgripping: 4 main cagtegoriesof microgrippers
Mechanical
microgripperswith
integrated
actuation (MEMS):
Mechanical
microgripperswith
external actuation:
Non-mechanical
microgrippers:
Passive
microgrippers:
[1]
[4] CSEM SA, Switzerland
[2] W. H. Lee, Center for
Automation Technologies,
Rensselaer Polytechnic
Institute
[3] G. Yang, Department of
Mechanical Engineering,
University of Minnesota
Institute of Robotics and Intelligent Systems
Literature Research
Microgripping
•Sticking effects: adhesion forces dominate gravity
–Methods for reducing sticking effects
–Assembly strategies for making sticking effects
irrelevant
•Forces transmitted from meso-to micro-scale:
possible damage of microparts/-tools
–Force sensing and feedback
–Compliance
–Large assembly tolerances
[5] D. O. Popa, Center for Automation
Technologies, Rensselaer
Polytechnic Institute
Institute of Robotics and Intelligent Systems
Concept
General Ideas and Keywords
•Multi-purpose
•Flexibility
•Modularity
•Space-saving
•High reliability
•Simple operations
→one tool system for all operations of the assembly process, no
tool changes desired
[6] Victorinox, Switzerland
Institute of Robotics and Intelligent Systems
Concept
Assembly Strategy:Never let go of the part.
•Hand it over from one position constrained situation to the other
→sticking effects are irrelevant because higher forces dominate
at all times
•Parts need to be secured before being released by the
microgripper
–Gluing
–Self-locking parts
[1]
Institute of Robotics and Intelligent Systems
Concept
Microtools
•Part serving platform: provide parts storage area and
assembly worspace
•Microgripper: pick parts from part serving platform
•Glue injection tool: inject glue into part gaps
Assembly Process
1.Inject glue into space into which part will be inserted
2.Pick part
3.Translate part into desired position
4.Insert part into predefined location and adjust position
5.Shine assembly with UV light to cure glue
6.Open gripper and release part
Institute of Robotics and Intelligent Systems
Design
Animation of the Assembly
Process
Institute of Robotics and Intelligent Systems
Concept
Institute of Robotics and Intelligent Systems
Design
Microgripper
•Working principle:
•Microgripperis designed to fit inside dome
•Gripper tip is always in remote center of motion
•Retraction mechanism: retract gripper tip from field of
view to make room for glue injection tool
•Tweezers can easily be exchanged
Institute of Robotics and Intelligent Systems
Design
Animation of the Gripper
Working Principle
Institute of Robotics and Intelligent Systems
Design
Tweezer
•Micro wire EDM machined spring steel
•Tip thickness: 0.1mm
•Optimized for minimal stress and maximal
gripping force with FE-analysis
Institute of Robotics and Intelligent Systems
Design
MicrogripperTechnical Specifications
Length55mm (dome radius 60mm)
Retraction
displacement
5mm
Max. tip opening0.8mm
Max. gripping force70mN
Position Resolution of
the clamping tube
1300 encoder ticks per mm
Actuator8mm, 0.15mNm DC motor, 1024:1
gear reduction, 8 impulses/revolution
encoder
Institute of Robotics and Intelligent Systems
Design
Three Proposed Setups
Simple SetupPart Array SetupSelf-locking Setup •Parts loosely on platform
•Hole for insertion of first assembly part
•Parts glued with UV curing adhesive
•Arrays of parts tethered to base
•First assembly part tethered to base
•Parts glued with UV curing adhesive
•Parts have self-locking mechanism
•No more glue injection tool needed
Institute of Robotics and Intelligent Systems
Conclusionsand Outlook
Conclusions
•New concepts and ideas for microassemblyprocesses,
microtoolsand micropartshave been developed
•Prototype of microgripperis being built
Subsequent Work
•Take microgripperinto operation
•Build prototype of part serving platform and glue injection tool
•Carry out first assembly operations
Institute of Robotics and Intelligent Systems
Conclusion and Outlook
Outlook
•Microtools: integrate additional functions
–Microgripper: force sensing
–Part serving platform: vacuum pipette for holding parts
–Glue injection tool: include several tools in turret mechanism
•Assembly Process:
–Design tethered part arrays and methods for breaking parts
away
–Design self-locking parts
Institute of Robotics and Intelligent Systems
Discussion
Thank you for your attention.
Please feel free to ask questions.
Institute of Robotics and Intelligent Systems
Literature Research
Methods for Reducing Sticking Effects
•Assembly while immersed in a fluid, which eliminates electrostatic and surface tension
forces.
•Minimize contact electrification by using materials with small contact potential difference for
the gripper and object.
•Use conductive materials which don't easily firm highly insulating native oxides.
•Gripper surfaces should be rough to minimize contact area.
•The high contact pressure from can derWaalsand electrostatic forces can cause local
deformation at the contact site. This deformation can increase the contact area and
increase the net adhesive force. Hard materials are preferable to rubber or plastic.
•A dry atmosphere can help to reduce surface tension effects. Surface tension can be used
to help parts adhere better to the target location than to the gripper.
[7] R. S. Fearing, “Survey of Sticking Effects for MicropartsHandling”, Proceedings of the IEEE/RJS
International Conference on Intelligent Robots and Systems, 1995
Institute of Robotics and Intelligent Systems
Design
Relation Between Clamping Tube Displacement and Tip
Displacement