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Introduction to LEGO NXT robotics and Robot Sumo – Sept 20, 2008
Douglas G. CzinderIEEE SEM R&A Chairpersonchair@semrobotics.org
Professor Keith Bozinkbozin@greaybox.com
CJ Chung, Ph.D.Associate Professor and Director of Robofestchung@LTU.edu
Lawrence Technological University
This program is possible thanks to:
a grant from The Chrysler Foundation
the Southeastern Michigan Chapter of the IEEE Robotics & Automation Society
Workshop Schedule – Sept 20, 2008
9:30 – 10:00 Continental Breakfast (provided) 10:00 – 10:20 Intro to Lego NXT & Robofest 10:20 – 11:00 Basic NXTG programming 11:00 - 11:15 Break 11:15 - 12:30 Programming with Sensors
12:30 - 1:30 Lunch (provided)
1:30 - 2:15 Programming with Sensors (cont’d) 2:15 – 2:30 Break 2:30 – 3:00 Basic Sumo Program 3:00 – 3:30 Improved Sumo Program 3:30 – 4:00 Mini Competition
Introduction to Robotics
What is a true robot? autonomous robot with an on board computer Mechanical, electrical, and computational
components Six fundamental components of a robot
A brain or brains – computer Body: physical chasses that holds other pieces Actuators: motors, hydraulic pistons, pneumatics Sensors Power sources Communication mechanism
What is Robofest?
100% Autonomous Affordable Challenging: Unknown problem No direct adult help allowed during the
competition Qualifiers and a World Championship Various categories including Robot Sumo Two divisions:
5th – 9th grade: Jr. Division 9th – 12th grade: Sr. Division
RoboSumo
Push the other robot out of the Sumo ring
Specifications
Junior Division Senior Division
Sumo ring diameter 77 cm (30 inches) 122 cm (48 in)
Maximum robot mass
1kg (2.2 lbs) 2 kg (4.4 lbs)
Maximum robot width and length
23 cm (9 inches)30 cm (11.75
inches)
Maximum robot height
no limit 30 cm (11.75
inches)
Robot type Any;Lego Mindstorms or NXT
recommended. any
Why Sumo?
The most popular robot competition in the world
Integrator in Science Education – Math, Logic, Computers, Mechanics, and Physics
Good for rookie teams Fun Motivator
Unknown Problem in Robofest Sumo
How to start is unknown Need sensor(s) Teams must bring a computer to program
the unknown parts
Introduction to Lego NXT
Brain – RCX micro computer Body: Lego Technic pieces Actuators: up to 3 motors Sensors: Light, Touch, Ultrasonic, Sound, etc. Power source: 9V (six AA batteries or
rechargeable battery pack) Communication mechanism: USB or Blue
Tooth
Introduction to “SB2 (Sumo Bot 2)”
Left motor: A Right motor: C Touch: 1 Light: 3 Ultra Sonic
(distance): 4
Introduction to NXTG Programming
Please go through Getting Started and Software Overview after this class
First NXT program: Go forward for 2 sec. and stop
Let’s name the program first
Click on Go >> button You’ll see a
programming palette (canvas)
First NXT program using SB1: Go forward for 2 sec. and stop (2/3)
Click on Move button Drag and drop the move block to
the canvas
First NXT program using SB2: Go forward for 2 sec. and stop (3/3)
Change parameters for the Move Port Direction Steering Power Duration Next Action
Block
Configuration Panel
How to run your first program (1/2)
How to run your 1st program (2/2)
If “Found New Hardware” pops up, just follow the instruction
Click on “Download” button Recommended to un-plug the
cable from the Bot Press the orange button 4 times
(Turn on, My files, Software files, Run your program entitled go2stop)
How to rerun the program
Check the program name on the LCD Press the orange button just once again
How to stop the program
Gray button
First NXT Program: Go forward for 2 sec. and stop (Review)
Do not forget:
Save your programs Meaningful file (program) names Use comments
2nd Program: ForwardBack
1. Go Forward 2 rotations2. Wait 3 seconds, then 3. Backward 1 rotation
Go Forward 2 rotations, Wait 3 seconds then Backward 1 rotation – ForwardBack
Making Turns(Instructor Slide)
Turn left
Spin left
Face left
Left wheel Right wheel
Left wheel Right wheel
Left wheel Right wheel
stop
stop
Objective Challenge the students to think about how a turn is made Two ways to turn using one motor (demonstrate by turning with
your leg) Demonstrate advantage of turning by spinning
Making Turns
Turn left
Spin left
Face left
Left wheel Right wheel
Left wheel Right wheel
Left wheel Right wheel
stop
stop
Forward 2 rotations, Turn Left 90 Degrees, and Forward 2 rotations
Turn90Left – Using a Motor Block!
Forward 2 rotations, Turn Left 90 Degrees, and Forward 2 rotations – Turn90Left
How do we make to turn 90 degrees?
Timer? Trial errors Let’s do the math!!!
Width of the robot: 14 cm Diameter of the wheel: 5.5 cm Perimeter of the wheel: 5.5 cm x pi = 17.27
Travel distance needed: (14 x 2 x pi) / 4 = 21.98 cm
Number of rotations needed?
21.98 / 17.27 = 1.272714 cm
Programming with Sensors
Programming with Touch Sensor Light Sensor Ultrasonic Sensor
Repeat Basic Sumo Program
Start-Touch
Wait until the touch sensor is pressed; Then start the robot to go forward Stop after a second
Start-Light
Locate the robot in the middle of the ring Wait until the light sensor detects very
bright (lantern) light Then start the robot to go forward Stop after a second
Start-Light
Stop-Touch
Go straight until the bumper is hit then stop
Stop-Edge
Go straight until the white edge of the ring
Then stop
Loop
To repeat a sequence of code Until
Elapsed time Number of repetitions Sensor condition is met Logic becomes true Forever
Say “Yes” – 10 times
Make the robot move around in the ring – Basic Sumo (Sumo0)
Repeat the following forever: Go forward until the edge Backward slightly Spin right
Sumo0
First Sumo Competition
Some matches Ask students to list ideas to improve the
Sumo robot
Improved Sumo Program
Improved Sumo program Unknown Problem Mini Competition Tips and Ideas to improve your Robot!
Program for the Mini Competition
Press “Shift” to connect parallel sequence beams
Ideas to improve your SumoBot
Improve (debug) your program! Applying Theories learned in Physical
Science Mass, Newton’s laws Friction Gearing Wheel size Power level
Detecting the opponent (can be done later) Touch sensor US sensor(s)
Ideas to increase weight of your Robot
What is the max weight of each division? Add more Lego technic pieces, if you
have some at home Add Coins, Used Batteries, or others –
make a holder using cardboards
Put your team name on the robot. An idea: make a team flag
Ideas to increase friction of your Robot
Use rubber bands Add more wheels later for Worlds
Gearing Ideas
Use gear train to increase gear ratio Considering resources, this is not allowed
for the school qualifier The winner from the school qualifier may
consider this idea later
Changing Wheels?
Using bigger wheels Considering resources, this is not allowed
for the school qualifier The winner from the school qualifier may
consider this idea later
Make sure the Power!
Default power level is 75% Fully charge your battery!!! How to check the voltage level?
See the icon on the LCD
Changing the shape of the Robot
Make it sturdy Front part may need some changes (After
the school qualifier)
Height of the robot matters?
Consider the “center of gravity”
Ideas using 2 Touch Sensors
A touch sensor –front leftAnother touch sensor – front right
If left sensor is pressed – turn left and push hard
If right sensor is pressed – turn right and push hard
If both left and right sensors are pressed, push straight hard
What is next? - Meet with your teacher at least twice before the school qualifier
Improve your programs Add stuff for the max possible weight for
your robot Review what you have learned for the
unknown problem. If you do not solve the unknown problem, you lose automatically
Signed Media Release form must be ready before the qualifying competition date at your school
Online Resources
www.ortop.org/NXT_Tutorial: a great tutorial on how to program in NXTG
nxtasy.org: with more information than you could ever want about LEGO robots and programming; a great place to ask questions
End of Today’s Workshop
Contact us with any questions:
Douglas G. Czinder IEEE SEM R&A Chairperson chair@semrobotics.org
Professor Keith Bozin kbozin@greaybox.com
CJ Chung, Ph.D. Associate Professor and Director of Robofest chung@LTU.edu
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