A Platform for Local Interactions between Robots in Large Formations Ross Mead Jerry B. Weinberg...

A Platform for Local A Platform for Local Interactions between Robots Interactions between Robots

in Large Formationsin Large Formations

Ross MeadRoss Mead

Jerry B. WeinbergJerry B. Weinberg

Jeffrey R. CroxellJeffrey R. Croxell

A Platform for Local Interactions between

Robots in Large Formations

ProblemProblem

swarmswarm formationformation



BackgroundBackground

Fredslund & Mataric 2002Fredslund & Mataric 2002

Balch & Arkin 1998Balch & Arkin 1998Reynolds 1987Reynolds 1987

Farritor & Goddard 2004Farritor & Goddard 2004



Formation ControlFormation Control

Utilize Utilize reactivereactive robot control strategies robot control strategies closely couple sensor input to actionsclosely couple sensor input to actions

Treat the formation as a Treat the formation as a cellular automatoncellular automaton lattice of computational units (lattice of computational units (cellscells)) each cell is in one of a given set of stateseach cell is in one of a given set of states

governed by a set of rulesgoverned by a set of rules



A desired formation, A desired formation, FF, is defined as a , is defined as a geometric description…geometric description… i.e., mathematical functioni.e., mathematical function FF ← y = ax ← y = ax22, where , where aa is some constant is some constant


F ← y = ax2



A robot is chosen as the A robot is chosen as the seedseed, or starting , or starting point, of the formation.point, of the formation.


F ← y = ax2

seed




The desired location on the formation is determined by The desired location on the formation is determined by calculating a relationship vector from calculating a relationship vector from c,c,…… where where cc is the formation-relative position ( is the formation-relative position (xxii, , yyii) of the robot,) of the robot,

… … and the intersection of the function and the intersection of the function FF and a circle and a circle centered at centered at cc with radius with radius rr, where , where rr is the distance to is the distance to maintain between neighbors in the formation.maintain between neighbors in the formation.

c ← (xi, yi)r2 ← (x-cx)2 + (y-cy)2

F ← y = ax2

r r

seed



Relationships and states are communicated locally to Relationships and states are communicated locally to robots in the seed’s neighborhood, which propagates robots in the seed’s neighborhood, which propagates changes in each robot’s neighborhood in succession.changes in each robot’s neighborhood in succession.

Using sensor readings, robots attempt to acquire and Using sensor readings, robots attempt to acquire and maintain the calculated relationship with their neighbors.maintain the calculated relationship with their neighbors.


c ← (xi, yi)r2 ← (x-cx)2 + (y-cy)2

F ← y = ax2

r r

seed



c ← (xi, yi)r2 ← (x-cx)2 + (y-cy)2

Despite only local communication, the calculated Despite only local communication, the calculated relationships between neighbors results in the relationships between neighbors results in the overall organization of the desired global overall organization of the desired global structure.structure.


F ← y = ax2

seed



Thus, it follows that a movement command sent Thus, it follows that a movement command sent to a single robot would cause a chain reaction in to a single robot would cause a chain reaction in neighboring robots, which then change states neighboring robots, which then change states accordingly, resulting in a global transformation.accordingly, resulting in a global transformation.


seed




Likewise, to change a formation, a seed Likewise, to change a formation, a seed robot is simply given the new geometric robot is simply given the new geometric description, and the process is repeated.description, and the process is repeated.

F ← y = 0

seed



Robot PlatformRobot Platform

Each robot features:Each robot features: a a Scooterbot IIScooterbot II base base

differential steering systemdifferential steering system an an XBC v2XBC v2 microcontroller microcontroller

executes formation control algorithmexecutes formation control algorithm a color-coding system and color cameraa color-coding system and color camera

visual identification and tracking of neighborsvisual identification and tracking of neighbors an an XBeeXBee radio communication module radio communication module

sharing information within a robot’s neighborhoodsharing information within a robot’s neighborhood




Scooterbot IIScooterbot II base base precision cut double-decker baseprecision cut double-decker base

rigid expanded PVCrigid expanded PVC strong, but very lightstrong, but very light

2" risers for additional decks2" risers for additional decks differential steering systemdifferential steering system http://www.budgetrobotics.com/http://www.budgetrobotics.com/




XBC v2XBC v2 microcontroller microcontroller executes formation algorithmexecutes formation algorithm back-EMF PID motor controlback-EMF PID motor control fast chargingfast charging

~1 hour to fully charge~1 hour to fully charge http://www.botball.org/http://www.botball.org/




Color-coding systemColor-coding system visual identification and visual identification and

tracking of neighborstracking of neighbors

Color cameraColor camera multi-color, multi-blob multi-color, multi-blob

simultaneous color trackingsimultaneous color tracking

Starty

Stopy

IDy

Starty - IDy

IDy - Stopy

Starty

Stopy

Starty - Stopy

RobotID = IDmax * (Starty - IDy) / (Starty - Stopy)




XBeeXBee radio communication module radio communication module sharing state information within a robot’s neighborhoodsharing state information within a robot’s neighborhood ZigBee/IEEE 802.15.4ZigBee/IEEE 802.15.4 specification specification up to 65,535 nodes on a networkup to 65,535 nodes on a network support for multiple network topologiessupport for multiple network topologies low duty cycle low duty cycle long battery life long battery life collision avoidancecollision avoidance retries and acknowledgementsretries and acknowledgements link quality indicationlink quality indication 128-bit AES encryption128-bit AES encryption http://www.maxstream.net/http://www.maxstream.net/



ReferencesReferences

Balch, T. & Arkin R. 1998. “Behavior-Balch, T. & Arkin R. 1998. “Behavior-based Formation Control for Multi-based Formation Control for Multi-robot Teams” IEEE Transactions on robot Teams” IEEE Transactions on Robotics and Automation, 14(6), pp. Robotics and Automation, 14(6), pp. 926-939.926-939.

Bekey G., Bekey, I., Criswell D., Bekey G., Bekey, I., Criswell D., Friedman G., Greenwood D., Miller D., Friedman G., Greenwood D., Miller D., & Will P. 2000. “Final Report of the & Will P. 2000. “Final Report of the NSF-NASA Workshop on Autonomous NSF-NASA Workshop on Autonomous Construction and Manufacturing for Construction and Manufacturing for Space Electrical Power Systems”, 4-7 Space Electrical Power Systems”, 4-7 April, Arlington, Virginia.April, Arlington, Virginia.

Farritor, S.M., & Goddard, S. 2004. Farritor, S.M., & Goddard, S. 2004. “Intelligent Highway Safety Markers”, “Intelligent Highway Safety Markers”, IEEE Intelligent Systems, 19(6), pp. 8-IEEE Intelligent Systems, 19(6), pp. 8-11.11.

Fredslund J., & Mataric, M.J. 2002. Fredslund J., & Mataric, M.J. 2002. “Robots in Formation Using Local “Robots in Formation Using Local Information”, The 7th International Information”, The 7th International Conference on Intelligent Autonomous Conference on Intelligent Autonomous Systems, Marina del Rey, California.Systems, Marina del Rey, California.

Reynolds, C.W. 1987. “Flocks, Herds, Reynolds, C.W. 1987. “Flocks, Herds, and Schools: A Distributed Behavioral and Schools: A Distributed Behavioral Model, in Computer Graphics”, 21(4) Model, in Computer Graphics”, 21(4) SIGGRAPH ’87 Conference SIGGRAPH ’87 Conference Proceedings, pages 25-34.Proceedings, pages 25-34.

Tejada S., Cristina A., Goodwyne P., Tejada S., Cristina A., Goodwyne P., Normand E., O’Hara R., & Tarapore, Normand E., O’Hara R., & Tarapore, S. 2003. “Virtual Synergy: A Human-S. 2003. “Virtual Synergy: A Human-Robot Interface for Urban Search and Robot Interface for Urban Search and Rescue”. In the Proceedings of the Rescue”. In the Proceedings of the AAAI 2003 Robot Competition, AAAI 2003 Robot Competition, Acapulco, Mexico.Acapulco, Mexico.

Questions?Questions?

For more information,For more information,

visit the visit the exhibitionexhibition or orhttp://roboti.cs.siue.edu/projects/formations/http://roboti.cs.siue.edu/projects/formations/

A Platform for Local Interactions between Robots in Large Formations Ross Mead Jerry B. Weinberg...

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