1. Developing a Low-Cost Robot Colony
General Dynamics Robotic Systems
April 19, 2007
Felix Duvallet
Colony Project, Robotics Club

2. Robotics Club at Carnegie Mellon
Building robots for fun since 1984
Mostly undergraduates (over 100 members)
Several ongoing projects
Colony
Battlebots
RobOrchestra …
Operates out of University Center basement
Lab space
Machine Shop

3. Colony Project Robotics Club Project, started in 2003
About 16 undergraduates
Various years
Different majors (mostly Engineering/CS)
Four weekly meetings
Sources of Funding:
Small Undergraduate Research Grant
Ford Undergraduate Research Grant
Leverage existing research projects (Choset)

4. Motivation (Why Colonies)
Colonies are everywhere in nature
Robustness to robot failure
Many tasks require cooperation
Coverage may necessitate multiple agents
Inherently interesting research problems
Robots are awesome
More robots are more awesome

5. Goals Low-cost robots (~$350)
Homogeneous, distributed architecture (no super-node)
Develop applications that are robust to non-idealities:
Noisy sensor data
Limited computation
Communication delays
Use the Colony as a research platform
Emergent behavior
Path planning
Cooperation
Control
SLAM …

6. Where Colony is now Past: Present: Future:
Substantial work has gone into developing the Colony hardware (robot, sensors)
Infrastructure has been developed (wireless communication, localization)
Present:
Currently developing behaviors
Autonomous recharging and self-sustainability
Future:
Extended duration, large-scale cooperation

7. Outline Past Work Behaviors Sustainability Future Work Robots Sensors
Infrastructure
Behaviors
Sustainability
Future Work

8. Robots

9. Colony Robot BOM Dragonfly Board ORBs Motors Range-Finders
Bearing and Orientation Module (BOM) – robot localization.
ORBs
Motors
Microcontroller
Range-Finders
Tri-color LED x 2
Diff-drive robot.
Obstacle avoidance

10. Colony Robot BOM Dragonfly Board ORBs Motors Range-Finders USB
Program robot User I/O
Dragonfly Board
ORBs
Motors
Range-Finders
Enables robot recharging
USB
Charging Contacts

11. Microcontroller ATMega 128 Programmed in C 8MHz max
128Kbytes program memory
Programmed in C
arv-libc, avr-gcc
open-source, multi-platform tools

12. Sensors

13. Sensors Standard off-the-shelf sensors Custom Sensor
Sharp IR Rangefinder
Bump Sensors
Photoresistors
Pyroelectric sensor (heat) Previously used
Custom Sensor
Bearing and Orientation Module (BOM)

14. Bearing and Orientation Module
IR emitter/detector ring
Emitter mode
All emitters are powered simultaneously (beacon)
Detector mode
Detectors can be polled individually for analog intensity readings

15. Bearing and Orientation Module
IR emissions from one robot are highly visible to all robots within line of sight
All BOMs are coplanar across the colony
Most excited detector is pointing in the direction of the emitting robot

16. Infrastructure Wireless Communication, Localization

17. Communication Network
ZigBee wireless protocol
XBee module (MaxStream)
30m indoor / 100m outdoor range
Network features
Ad-hoc
Distributed
Fault-tolerant
Issues to consider
Packet collisions
No threading on robot
Very low bandwidth

18. Fully-Connected Network
Network Topology
Problem: Packet collisions
Token-Ring Network
Fully-Connected Network

19. Network Topology
Solution: Robots take turns, yet communicate with all other robots
Leverage wireless network and BOM to perform communication and localization simultaneously

20. Wireless Network Integrate BOM and Wireless
Robots beacon BOM when sending a wireless packet
When receiving a packet, poll BOM for direction of sender robot
Propagate connectivity matrix
“Token” path
“Token” path
Wireless Data

21. Connectivity/Bearing Matrix
You share your data 1
Robot 0
Robot 1
Robot 2 . 6 X 5 8 4 2
you
And you receive these rows

22. Topological Localization
Advantages
Simple
Fast
No processing (use sensor data directly)
Metric maps can be extracted:
“Relative Localization in Colony Robots,” in Proceedings of the National Conference on Undergraduate Research, 2005

23. Robot Behaviors

24. Behaviors Individual Robot Light-seeking Feeding/Hunger Roaming
Use sensor data to control actions
Simple local interactions can yield complex global actions
Emergent behavior
Individual and multiple robot behaviors:
Individual Robot
Light-seeking
Feeding/Hunger
Roaming
Obstacle Avoidance
Homing
Multiple Robots
Lemmings
Robots follow a leader in a chain
Hunter/Prey (Tag)
One prey, many hunters
Robots can switch roles

25. Roaming/Obstacle Avoidance
Robots uses Sharp IR rangefinder to avoid obstacles
Behavior can be reproduced on many robots

26. Marching band
Each robot programmed with own music sequence and dance moves
Wireless used for synchronization between robots

27. Lemmings (multi-robot)
Simple follow the leader
Uses both the BOM and wireless network (localization)

28. Simulation Player/Stage Simulate larger number of robots
Eases behavior development
Additions to simulate the BOM

29. Lemmings (simulation)

30. Hunter/Prey (simulation)

31. Formation Control (simulator)

32. Cooperative Maze Solving
Given a maze and a goal, robots cooperate to seek the goal
Start

33. Cooperative Maze Solving
Given a maze and a goal, robots cooperate to seek the goal
Cooperation

34. Cooperative Maze Solving
Given a maze and a goal, robots cooperate to seek the goal
Goal

35. Cooperative Maze Solving
Warning: Early Colony videos ahead

36. Cooperative Maze Solving

37. Cooperative Maze Solving (night vision)

38. Autonomous Recharging

39. Towards Self-Sustainability
Goal is to develop a self-sustainable robot colony
Operate unassisted for long periods of time
Requirements
Autonomous recharging
Task allocation

40. Charging Station … One controller oversees up to 8 bays
Power …
Bay
Bay
Bay
One controller oversees up to 8 bays
Power supply powers bays and charges robots
Wireless communication to talk to colony

41. Charging Bay Pair

42. Charging Bay Pair

43. Charging Station Controller Bays
Salvaged robot controller with XBee module
Acts as robot manager
Bay allocation
Scheduling
Bays
12V supply
Linear BOM
Homing beacon

44. Robot charging Charge board Homing sensor
Charges batteries
Communicates with robot over I2C
Homing sensor
Leverage wireless and BOM localization

45. IR Beacon Homing
Beacon
Max pulse width n 3n 2n
Left
Center
Right

46. Docking with Bay – Procedure
Request charge bay, wait for accept
Locate bay, get to homing range
Home to docking bay
Dock
Wireless
BOM/Wireless
Homing Sensor
Robot

47. Docking Video

48. Button press instead of battery threshold in the interest of time
Incorporating a Task
Roaming
Button press instead of battery threshold in the interest of time

49. Future Work More complex tasks Extended duration
Larger scale cooperation problems
Robustness

50. Colony Members Felix Duvallet Christopher Mar Austin Buchan
Brian Coltin
Brad Neuman
Justin Scheiner
Siyuan Feng
Duncan Alexander
Cornell Wright
Eugene Marinelli
Suresh Nidhiry
Andrew Yeager
Greg Tress
James Kong
Kevin Woo
Ben Berkowitz
Jason Knichel
Aaron Johnson
Prof. George Kantor

51. www.robotcolony.org felixd@cmu.edu