L
L
Bot
CJ Chung
Associate Professor of Computer Science
Founder & Director of Robofest
L2Bot

L2Bot
Software development has been focusing on non-mobile computers

Now laptops, notebooks are everywhere
L2Bot

The idea
L2Bot

There are four key advantages to using
L2Bot robots for K ~ PhD education
• robotics is multi-disciplinary,
• robots make abstract concepts concrete,
• robotics is hands-on, and
• students usually have higher motivation through robotics

L2Bot
• Low-cost Laptop roBot
• Born in Intelligent Systems and Robotics Lab at LTU
• Two motors and a webcam with a laptop as a single brain
(No micro-controllers). Free sensors from the laptop!
• Affordable (about $200 ~ $240 w/o labor)
• Flexible/Adaptable – Modifications are easy
• Expandable – Lego Mindstorms, NXTs or Handy Boards for motors and sensors
• Programming Language Independent
• Safe – Not too fast!
L2Bot

L2Bot History
• The first one: 2002
• C++
L2Bot

2003
L2Bot

2004
L2Bot

Garmin
GPS
L2Bot
Block Diagram for Extended L2Bot (2004)
Main Control
Module (PC)
USB Hub
Lego IR
Tower
Microcontroller
(68HC11-Based
Handy Board)
Various
Sensors &
Servo Motors
Manual Stop
Switch
Fuse (1 Amp)
Battery
12V 7 amp Hr.
Motor Driver
Board
Left
Motor
Right
Motor
Web
Camera 2
Wireless
Joystick
ER1 Arm
Lego RCX

2005
L2Bot

2006
L2Bot

2007
L2Bot

L2Bot Line Following Demo Video
L2Bot

Features of L2Bot 2007 edition
• Serial Port (cf. old: Parallel Port)
• Lighter
• Simpler
• Lower cost
• 100% Java
L2Bot

2008
L2Bot

Battery
12V 7 amp hr.
Fuse (1 Amp)
Manual Stop
Switch
Main Control
Module (PC)
USB Hub
Motor Driver
Left
Motor
Board
Right
Motor
(Web)
Camera
RF receiver
Lego
NXT
Lego Sensors
& Motors
Joy
Stick
L2Bot

Six essential components of robots
L2Bot
• Brain
• Body
• Sensors
• Actuators
• Power source
• Communication mechanism

Brains (Processors)
• Your laptop, notebook
• Multiple NXTs
L2Bot

LEGO NXT
L2Bot
Processor: 32 bit ARM Atmel AT91SAM256, 50 Mhz
Memory: 64K Static RAM, 256K Flash
20

Robot Body
• Designed and built from off-the-shelf components from:
– Home Depot or Lowes
– Jameco (online robotics store)
– Digi-Key (online electronics store)
L2Bot

Body: Drive Train and Gearing
• Front-wheel drive
• 3-inch pivoting wheels - rotate freely on the axis in both directions
• One 3” Swivel Caster Wheel
L2Bot

Actuators: Motors
Torque @ Max. Efficiency (g-cm)
Current @ Max. Efficiency (mA)
Gear Case Size (Diameter x Length) (inch)
Gear Ratio
Motor Size (Diameter x Length) (inch)
Shaft Size (Diameter x Length) (inch)
Rated Voltage (VDC)
Terminal Type
Speed @ Max. Efficiency (RPM)
3200
82
1.5 x 0.7
100:1
1.3 x 1.0
0.2 x 0.5
12
Solder
60
L2Bot

Actuators: Motor Control
• LoCoMoCo: An H-bridge - electronic circuit which enables DC electric motors to be run forwards or backwards
• Motor commands to robot sent through laptop RS-
232 Serial port interface
L2Bot

Actuators: Lego NXT Servo Motors
L2Bot
• Each motor has an embedded rotation sensor
• 360 counts per rotation
• The counter can be incremented or decremented

Sensors
• Web cam(s)
• Laptop Microphone – Sound sensor
• USB Mouse for proximity
• Available LEGO NXT sensors
– Default sensors by Lego.com, Legoeducation.com:
– 3 rd party sensors:
• mindsensors.com
• hitechnic.com
L2Bot

chung
NXT Sensors
• Light
• Touch
• Ultrasonic (Distance measurement)
• Sound (microphone)
• Rotation – embedded in the motors
• Timer – Internal sensor
• Received Bluetooth messages
• NXT buttons
27
L2Bot

Available NXT 3 party sensors
• EOPD (Electro Optical Proximity Detector )
• Compass Sensor
• Acceleration / Tilt Sensor
• IRSeeker (135 degree view)
• Gyro
• Vision Subsystem
• Pneumatic Pressure Sensor
• Many more!
L2Bot

Power Source
• One 12V 7 Amp Hour battery for motors and motor drive board
• Can last for an hour
• Manual stop switches for battery power
• Laptop has its own rechargeable batteries which also provides power for the webcam
• NXT has its own (rechargeable) batteries – 9V
L2Bot

Communication Mechanism
• L2Bot can be connected to the network through the wireless card on the laptop
• NXTS provides Blue Tooth communication mechanism
• Microsoft Speech synthesis and recognition
Engine is possible
L2Bot

L2Bot Java Software Architecture
Devices
OS
JVM DLLs with JNI
Java APIs (JMF, javax.comm, etc)
Applications
L2Bot
(*) VB, C#, MSRS, and MSRS VPL version will be available in the near future

Performance Specifications
Length
Width
14 in (35 cm)
16 in (41 cm)
Height 9.25 in (25 cm)
Weight without laptop 10.5 lbs (4.8 Kg)
Weight distribution*
(left/right/rear)
Motor RPM
3lb / 3lb / 4lb
(1.37Kg/1.37Kg/2Kg)
60
Motor voltage
Max speed
Battery Life
12 Volts
.875 ft/sec (25.9 cm/sec)
More than 2 Hour
L2Bot
(*) To be updated

How to Use Your L2Bot
• Charge your 12V battery
– Do not charge more than 14 hours…
– Use voltage meter to check, if fully charged
• Connect battery terminals
• Connect your laptop with the serial cable
• Run your program
• Turn on the switch
• It is highly recommended to unconnected battery terminals after using it
L2Bot

Tools needed to assemble your Robot
• A screw driver (power drill)
• Wrenches: 3/8”, ½”, and 9/16” (or one adjustable one)
• 3/32 size L-wrench:
L2Bot

L2Bot website
• www.robofest.net/l2bot
• Software installation of for L2Bot
• Sample programs
• Videos
• Online books
L2Bot

L2Bot line following video clip
L2Bot http://www.robofest.net/l2bot

Collegiate Competitions with L2Bot
• Fall Mini UC
• Robofest Mini UC
L2Bot

Start
2007 Challenge
End
L2Bot

2007 Mini Urban Challenge Video
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2008 Challenge
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Fall 2007 Mini Urban Challenge
L2Bot

Fall 2008 Challenge
3 ft
DEAD
END
L2Bot

Start
2010 Challenge
L2Bot

Advanced Projects Based on the learning from L2Bot
• IGVC (Intelligent Ground Vehicle Competition)
• RoboCup
• DARPA
• TARDEC project
L2Bot

Summary & Conclusion
• Robotics reinvigorates curriculum
• Robotics excites students
• Robotics encourages teamwork
• L2Bot has been a good tool for classes due to the following reasons:
– Affordable, simple, light, extendable, and safe
– Work at home
L2Bot