Page 180 - LEGO MINDSTORMS - Robotics Invention System-2 Projects

Robot 5 • The Three-in-One Bot

The Three-in-One Bot was built as a simpler yet versatile alternative to the
Roverbot that’s found in the RIS 2.0 Constructopedia. It is a small robot base
that can be configured for a variety of functions. It makes a good beginner’s
model because it uses few parts and can be built within half an hour. In this
implementation, it is equipped with a light sensor for line following, for which
it is eminently suitable. However, it has the potential to be developed further
into a fully functional robot that can be used in competitive challenges such as
the FIRST LEGO League (FLL) contests.
The Three-in-One Bot is powered by two of the LEGO geared motors in a dif-
ferential drive arrangement. The motors are placed in front, creating a sort of
front-wheel drive, for better traction and ease of turning. A gear reduction of 3:2
(or 1.5:1) is used to give the robot a balance between speed and reliability when
used as a line follower. The robot also features a trailing caster wheel, which
gives it great maneuverability, which is an important factor for line following.
The Three-in-One Bot with the light sensor (building instructions for the
light sensor variation are available on the Syngress Solutions Web site at
www.syngress.com/solutions) will work with most line-following programs. It is
customary to have the robot follow the edge of a line (usually the left edge)
while it moves forward.
The Three-in-One robot base can be easily customized—we encourage you to
try the following changes, observing the effect on the robot’s performance:

Motor placement Move the motors back relative to the driving
wheels.

Gear ratio Try different combinations of gears.
Wheels Try different types of wheels.

Trailing wheel Replace the trailing caster with other wheel arrange-
ments, such as a sliding pulley wheel.

Sensors Attach bumpers that activate touch sensors, to turn the robot
into an obstacle avoidance vehicle.

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