Reconfiguration Mechanism Design Mark Yim Associate Professor and Gabel Family Associate Professor Dept. of Mechanical Engineering and Applied Mechanics, University of Pennsylvania

There are two fundamental electro- mechanical components to self- reconfiguring robot systems –An attaching/detaching mechanism –Some form of motion between reconfigurations. Focus on hardware, however, choices in hardware effect software design and vice versa.

Costs of micro-scale device ( pessimistic view) Module: 1mm x 1mm x 1mm MEMS (silicon) Silicon cost ~ $1/sq inch –2003 Revenue $5.7billion / 4.78 billion sq inch silicon –$200 / 12” diam, $30 /8“ diam wafers –100um-2000um thick (choose 1mm) Assume processing costs ~$9/sq inch Modules cost 1.6¢ Synthesize human shape Mark weighs 65 Kg -> 65,000 cm 3 –Assume density of water (1kg = 1000 cm 3 ) 65,000,000 modules –1000 modules per cm 3 Cost: $1,007,

Costs of micro-scale device ( optimistic view) In mature systems, cost goes by the pound. –E.g. Xerox machines –Optimization in space/volume The process cost can be reduced. Ultimately to near the cost of silicon (factor of 10 savings) Fill factor of modules does not need to be 100% (factor of 10 savings) Find a smaller person to synthesize (factor of 2 savings) Cost $5,037

Outline Review of Motion mechanisms –Chain style reconfiguration –Lattice style reconfiguration Review of Latching mechanisms Discussion

Three Classes of Existing Self-Reconfigurable Robots Chain Lattice Mobile

Telecube G1 Lattice Self-Reconfiguration

Proteo (never built) Proteo Rhombic Face (Edge length = 5 cm)

I-Cube, Cem CMU Metamorphic, Hopkins

Dartmouth Molecule: Kotay & Rus Crystal: Vona & Rus

Satoshi Murata (lattice) Fracta 3D fracta

Molecube, cornell ATRON, Ostergaard, et. U. S. Denmark

Riken, Vertical Inoue, Pnumatic

Stochastic/Graph Grammars No main actuation (external) –Klavins –Lipson Latching –Magnets –Pressure differential in oil

Chain Self-Reconfiguration PolyBot Generation 2 (G2), and 3 (G3)

Polypod UPenn superbot

Conro, ISI Mtran, Murata et al

Nilsson, Dragon

Lattice vs Chain 1 DOF motion docking Local self-collision detection Higher stiffness dock No singularities, –No mechanical advantage Discrete motions –GeneralManipulation difficult –Unstructured environments difficult 6 DOF motion docking Global self-collision detection Lower stiffness dock Singularities –Complicates control Arbitrary motions Lattice is easier for self-reconfiguration Chain is easier for locomotion/manipulation

Main drives: Geared DC motors (most popular) Magnetic Pneumatic None Not shown yet: Combustive: easier if modules are large Thermal (nuclear?): perhaps in space Mechanochemical: does this exist? Electrostatic: ok if small? High voltages Molecular motors: if very tiny

Latching mechanisms Magnetic – issue: strength Mechanical – issue: actuator (size (strength/speed)) Pneumatic – issue: valves, supply Hydraulic – issue: valves, supply Not shown yet: Electrostatic: ok if small? High voltages Dry Adhesive: attach/detach motion?

Stolen from: Esbed Ostergaard Thesis U. Southern Denmark

Questions What are the important parameters for the motion part? What are the tradeoffs? –DOF? –Shape? –#of attachments –Workspace? What are the important parameters for attaching/detaching mechanisms?

ItemTradeoffMetric DOFComplexity vs capability, cost # of DOF, MTBF (per task)

What on earth are we going to do with these robots? NASA program –It’s going to be more robust to send specialized machine per task –Multifunction cost savings vs capability –Space station repair –Mars exploration –Moon station (selfreplication) Construction –Locomotion with manipulation –E.g. mine sensor support w/shoring –Building construction –Architecture Exploration –Search and rescue –Undersea mining –Planetary mining Shape only –Structures –Telepario –Shady robots –Programmable antennae Research contribution for itself On microscale –Self assembling chips (self-walking chips?) –Mechanical RSA (tiles form shapes to open locks) –Mechanical FPGA

Shape vs function –3 people do shape only Fundamental assumptions(?) Self –Organizing –Reconfiguring –Repairing –Funding Communities to relate to? –Complexity systems community –Nanoscience community (foundations of nanoscience) Availability of low cost reliable hardware helps to enable robotics research –Common platform, (e.g. mote like) Sources of funding? –DARPA, NSF, Europe, (Brad has money) –Japan Aist/TiTech last