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
A Platform for Local Interactions between
Robots in Large Formations
BackgroundBackground
Fredslund & Mataric 2002Fredslund & Mataric 2002
Balch & Arkin 1998Balch & Arkin 1998Reynolds 1987Reynolds 1987
Farritor & Goddard 2004Farritor & Goddard 2004
A Platform for Local Interactions between
Robots in Large Formations
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 Platform for Local Interactions between
Robots in Large Formations
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
Formation ControlFormation Control
F ← y = ax2
A Platform for Local Interactions between
Robots in Large Formations
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.
Formation ControlFormation Control
F ← y = ax2
seed
A Platform for Local Interactions between
Robots in Large Formations
Formation ControlFormation Control
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
A Platform for Local Interactions between
Robots in Large Formations
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.
Formation ControlFormation Control
c ← (xi, yi)r2 ← (x-cx)2 + (y-cy)2
F ← y = ax2
r r
seed
A Platform for Local Interactions between
Robots in Large Formations
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.
Formation ControlFormation Control
F ← y = ax2
seed
A Platform for Local Interactions between
Robots in Large Formations
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.
Formation ControlFormation Control
seed
A Platform for Local Interactions between
Robots in Large Formations
Formation ControlFormation Control
A Platform for Local Interactions between
Robots in Large Formations
Formation ControlFormation Control
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
A Platform for Local Interactions between
Robots in Large Formations
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
A Platform for Local Interactions between
Robots in Large Formations
Robot PlatformRobot Platform
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/
A Platform for Local Interactions between
Robots in Large Formations
Robot PlatformRobot Platform
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/
A Platform for Local Interactions between
Robots in Large Formations
Robot PlatformRobot Platform
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)
A Platform for Local Interactions between
Robots in Large Formations
Robot PlatformRobot Platform
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/
A Platform for Local Interactions between
Robots in Large Formations
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/