BSAC Research Review Individual Project

1
CotsBots An Off-the-Shelf Platform for
Distributed Robotics
Sarah Bergbreiter and Dr. Kris Pister Berkeley
Sensor and Actuator Center October 29, 2003
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History of CotsBots
1mm
1mm
Add Legs
Smart Dust (Warneke, et al. Sensors2002)
Microrobots (Hollar, Flynn, Pister. MEMS2002)
Add Robot Body
COTS Dust (Hill, et al. ACM OS Review 2000)
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Goals for CotsBots

• Open-source hardware and software platform for
  distributed robotics
• Small, cheap, off-the-shelf, and modular robots

• Emphasize application design software for large
  (gt 50) robot networks
• Reduce startup costs to demonstrate distributed
  multi-robot algorithms

4
Similar Robot Platforms
Size

• Khepera II expensive
• Robomote (USC) custom design
• Millibots (CMU) custom design
• Soccer Robots custom design
• Pioneer large and expensive

TARGET SPACE
Pioneer
Cost
Khepera
Millibots
Soccer Robots
Robomote
Microrobots
Off-the-shelf-1
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CotsBots Hardware
MotorBoard
Mica Mote

• Atmel ATmega128
• 4 Mhz 8-bit CPU
• 4KB RAM
• 128KB Program Memory
• RFM TR1000 radio
• 50 kb/s ASK
• Focused hardware acceleration
• Network programming

• Atmel ATmega8L
• 1-8MHz CPU
• 8KB Program Memory
• 1KB RAM
• 2 Discrete H-Bridge Circuits
• Speed and Direction Control of Motors
• up to 4A, 30V load
• 51-pin bus

Kyosho Mini-Z RC Car Platform (or others)
Sensor boards available including ADXL202e,
magnetometer, light, temp, sound, etc.
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CotsBots Hardware Stats
Size
6cm
13cm
6cm
Cost

• Power 1 hour on 4 AAA batteries
• Speed Over 120 cm/sec
• Turning Radius /- 30o
• 80 robots built thus far

Approximately 10 robots assembled per hour from
purchased components
Off-the-shelf-1
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CotsBots Software

• Use open-source NesC language and code provided
  by TinyOS group (available on SourceForge)
• TinyOS is an event-driven operating system useful
  for behavioral and FSM-type applications
• Try to abstract as much as possible from the
  application writer (developer should focus on
  algorithms)
• Remain flexible by keeping component-based design

8
CotsBots Software

• Use open-source NesC language and code provided
  by TinyOS group (available on SourceForge)
• TinyOS is an event-driven operating system useful
  for behavioral and FSM-type applications
• Try to abstract as much as possible from the
  application writer (developer should focus on
  algorithms)
• Remain flexible by keeping component-based design

9
CotsBots Software

• Use open-source NesC language and code provided
  by TinyOS group (available on SourceForge)
• TinyOS is an event-driven operating system useful
  for behavioral and FSM-type applications
• Try to abstract as much as possible from the
  application writer (developer should focus on
  algorithms)
• Remain flexible by keeping component-based design

Robot Application
Mica Software
Timer
Robot
Radio
Motor Packet
Motor Software
Tank
Motor Packet
Motor1
Motor2
MotorBoard Software
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Building an Application Beep Diffusion

• Simple algorithm to spread robots apart
• Adjusting microphone gain adjusts distance robots
  move apart

Send Msg/Beep
Time Slot Manager
My Slot
Heard Msg
Listen
Done Driving
Heard Beep
Done Driving
Obstacle
Drive
Hit Obstacle
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Building an Application Beep Diffusion

• Build the component graph
• Write some components (blue boxes are free!)
• Add a sensorboard with sensors required (4kHz
  buzzer, mic, 2-axis accelerometer)

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Building an Application Beep Diffusion

• Implementation
• 5 robots in 10ft x 10ft area
• 3.5 second slot time
• Difficulties with buzzer/tone detector hardware
  lead to inconsistent beep radius

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Conclusions

• Reduced the startup costs (time and money) for
  designing distributed robot applications
• A small, inexpensive, off-the-shelf, and modular
  hardware platform has been built for distributed
  robot applications
• TinyOS provides an open-source software platform
  which promotes abstraction, code re-use, and
  flexibility
• Simplified application development for simple
  distributed algorithms

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Acknowledgements

• Doug Gage and DARPA/SDR, DARPA/NEST for funding
• Dr. David Culler and the TinyOS group
• Mica motes distributed by
• http//www.xbow.com
• TinyOS and CotsBots code available at
• http//www.sourceforge.net/projects/tinyos