NXTG Workshop for
Bottle RoboSumo
Lawrence Technological University
Rules
1. Game Objective and Synopsis
First robot to intentionally push the bottle
off the table OR
Be the last robot remaining on the table
6. Game Match Rules
If the robot moves during the first 3
seconds, the robot automatically loses the
game
Robot Configuration for this workshop
Left Motor B
Left Light Sensor 2
Ultrasonic Sensor 4
NXT Brick
Right Motor C
Right Light Sensor 3
Remember the connections!
Left Motor connects to B
Right Motor connects to C
Left Light sensor connects to port no. 2
Right Light sensor connects to port no. 3
Sonar sensor connects to port no. 4
Move “Forever”
Will the robot move
forever?
Download and test this
program
Downloading Programs
Make sure your
robot is plugged
in, and turned
on, then click the
down arrow.
Running a Program
Press the orange button to run your program
and go down a menu level
Press the dark gray button to stop your
program and go up a menu level
Use the arrows to view choices in this menu
level
Move “Forever”
Did it go forever?
Why not?
This Does Work
Put the Move block in
an infinite loop.
Moving Backwards
Column 1
20
0
Row 1
Row 2
Row 3
Row 4
Column 2
Column 3
Spin
Light Sensors
Light Sensor Readings
Connect the robot with the USB cord
Place light sensor 3 over the edge of the
table
A number between 0-100 is displayed here
Now place it over the table
Enter the average of those numbers here
Finding the Edge
Finding the Edge
Use your mouse to draw a green data wire
Put a Move block outside the loop in the
Stop direction
Try out the program!
Problems
If your robot stops too soon or too late, try
adjusting your light sensor value
We only are looking at one light sensor – what if
the other one goes off the table first?
Finding with Both Sensors
Finding with Both Sensors
Finding with Both Sensors
Simple Sumo without detecting
objects (sumo1.rbt)
Ultrasonic Sensor
Measures the distance to the closest object
Uses sonar waves like a bat
Can be used to see if an object is within a
certain range of the robot
Finding the Bottle
Sumo2.rbt – Simple Sumo with
object detection
Wait for a second
3 second wait is
required when the
game starts
Test sumo2
For the qualifying round, each robot will be
placed on a table with two bottles. Practice!
Did your robot find both bottles? Did it spin
around forever? We can avoid it spinning
forever by using a Timer block
For the tournament, there will be two robots and
one bottle on the table at a time. Practice!
Try improving your program so you can win
sumo!
Timer
Whenever you use a timer, it’s
always a good idea to reset it first
Wait to play a sound using the
timer
Physics of sumo
• Your robot will be more effective at pushing
other robots off the table if you use
•
•
•
•
•
Mass
Velocity
Force
Torque
Power
Mass
• m=mass, v=velocity, p=(linear) momentum
• p=m*v
• F=force, a=acceleration
• F=m*a
• If we increase the mass, we increase the
momentum and force
• Where to add mass? Consider the center of
gravity (should be low and inside wheel
base)
Velocity
• m=mass, v=velocity, p=(linear) momentum
• p=m*v
• If we increase the velocity, we increase the
momentum
• The larger the momentum, the more Force is
required to change the acceleration
• How do we increase the velocity of the
robot? (With the motor)
Force
•
•
•
•
T=torque, r=wheel radius
Torque=Force*radius
Force=Torque/radius
How do we increase the Force?
• Increase the torque
• Decrease the radius (smaller wheels)
Torque and Power
• P=Power, T=Torque, w=angular velocity
• P=T*w
• T=P/w
• How do we increase the torque?
• Increase the power (Motor power)
• Decrease the angular velocity
• Make sure batteries are fully charged!
• We can increase the torque by “gearing
down”
Build a better robot (later)
• Sturdy construction
• At least 2 attachment points for each part so
robot stays together
• Compact design
• Triple pegs on multiple beams
• Wheel base
• Wide base for slow turns
• Narrow base for fast turns
• Which is best for stability of robot?
Robot design (2)
• Wheels
•
•
•
•
How many with tires? 2 or more?
Tires- rubber or plastic? (for traction?)
Size – large or small?
Placement of wheels – front or back?
Robot design (3)
• Sensors
• Placement of light sensors (height above
table? How far in front or to side of wheels?)
• Placement of sonar sensor (low or high?)
• Use additional sensor(s)?
•
•
Touch sensor(s) to detect if an opponent is
pushing your robot?
Touch sensor(s) to detect if you are pushing an
opponent or the bottle?
Strategy
•
•
•
•
Try to lift an opponent off the table?
Try to hide from an opponent (cloaking)?
Bounce off an opponent if attacked?
Add a motor to power a mechanical device to
attack your opponent (try to flip your
opponent over)?
• The best strategy is to find the bottle first!