“Toy Story” Revisited:
Robotic Lazer Tag
Phoenix Moorman
CSCI 390 - Senior Seminar & Project
April 26, 2002
Inspiration to Implementation
• Many children fantasize that their toys
become animated and play while they
are not looking
• The advent of robotic kits, Legos have
become the first toys to exhibit
“behaviors” and play games
in front of children’s (and
adult’s) eyes
Robotic Lazer Tag
• Lazer Tag is played between 2 or more players
• The game is played within an enclosed arena.
• Each player is equipped with a 'lazer' gun and a
receiver which is strapped upon the player's body
in plain sight
• The goal of the game is to "tag" the other player
by firing the 'lazer' gun at an opposing player's
receiver. The first player to "tag" the other a predefined number of times is the winner.
Code of Conduct
• Lazer Tag is a non-contact sport. Any accidental contact requires
immediate warnings to both players to be more careful, with further
physical contact subject to immediate censure.
• Sensors Must be Visible. Preventing a Lazer Tag beam from tagging
a sensor is dishonorable.
• Equipment Failure Means Disqualification.
• Sensors Must be Attached.
• Sensors Must be Activated.
• Refreshments are Available.
• Lazer Tag Is a Game. Players must always remember that Lazer Tag
is only a game. It is designed so everyone can have fun. If a player
gets angry, exhausted, or bitter, he should stop playing until he cools
off. Not having fun is
against
code.
(thisTag
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- Worlds
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Wonder
Lazer
Code
of Conduct
Guide
programmer)
The Idea
• Robots are beginning to play a crucial role
in industrial and scientific endeavors
• Developing strategies by which robots
fulfill a task is of optimal importance
• How do we try out different strategies?
• Theoretical Model vs. Real Implementation
Robots
The Handyboard
• Motorola 6811 microprocessor
• 32K RAM memory chip
• 4 Motor Output Ports
• 8 Analog / 8 Digital Input Ports
• 1 Infrared Output Port
• 1 Infrared Input Sensor
Robots
Theoretical Modeling with Robocode
• Robocode was designed to teach beginning
programmers JAVA
• Provides a Lazer Tag-like environment using
bullets instead of infrared transmissions
• Provides a nice API for interfacing with the
theoretical robots
Robots
Theoretical Modeling with Robocode
• Allows for variable-sized arena (used 400 x 400)
• Allows easy access to a lot of useful information about
the robots
• Provides a number of robot strategies to work
with/against
• Allows for object-oriented programming (classes, etc)
• Allows user to utilize the full power of the CPU of
user’s computer with a small penalty of slowdown
• Allows user to utilize full memory of user’s computer
Robots
Simple vs. Complex Strategies
• Simple Strategies
• Rely on patternistic behaviors to find,
tag, and/or avoid the other robot
• Utilize basic sensory data
Robots
Complex Strategies
• Complex Strategies
• Rely on algorithms that make use of a
number of available factors to find, tag,
and/or avoid the other robot
• A Sampler of Factors:
• Velocity (of self or other robot)
• Direction / Bearing
• Size / Topology of Environment
• Number of hits (received or given)
Robots
Simple Strategies: A Case Study
• My implementation: John Dunbar
• Goes in a straight line until it finds a corner,
then backs up and turns
• Sweeps lazer gun/radar back and forth to find
other robot
Robots
Simple Strategies: A Case Study
• Scans over a large area to find opponent
• Hard to pin down and hit repeatedly
• Does comparably well against a variety of
strategies
Robots
Complex Strategies: A Case Study
• My implementation: Tracker/Sun Tzu
• The idea: attempt to discover the other robot’s
strategy
“Thus, what is of supreme importance in war is to attack the
enemy's strategy.” - Sun Tzu, “The Art of War”
Robots
Complex Strategies: A Case Study
Robots
Complex Strategies: A Case Study
Robots
Complex Strategies: A Case Study
Robots
Implementation in Reality
• Hardware issues:
• John Dunbar’s turret can’t turn a full 360
degrees (cord issues)
• 32K RAM doesn’t allow for large programs
• Greater complexity of program, greater the
slowdown (greater time slowdown for
Tracker)
Robots
Implementation in Reality
• Programming issues:
• Interactive C doesn’t support classes (the
global variable solution)
• Interactive C doesn’t allow for reading and
writing to files (the persistent global variable
solution)
Robots
Implementation in Reality
• Programming issues:
• Interactive C’s API isn’t as nice as
Robocode’s! So how does Tracker:
• create grid spaces?
• keep track of its grid space?
• figure out the other robot’s position?
Robots
Implementation in Reality
• The Relativity Solution:
• Pre-define a starting position
• Use velocity (the time to cross grid spaces)
and direction to keep track of Tracker’s grid
spaces
• Use light sources/sensors to define distance
between the robots (ambient light - threshold)
Robots
Implementation in Reality
Robots
Some Conclusions
• Theoretical models are good tools for
developing robotic strategies when several things
are considered:
• The computational power of the model vs. the robot
• While nice features of the model may increase the
ease of use and decrease development time, they must
be easily implementable in the real world
• Murphy’s Law must be incorporated into real-world
adaptations of theoretical designs