Programming instructions

Glossary • 125
APPENDIX B - GLOSSARY
Inventor’s Guide
276-2178-E-0610
Gear Ratio – Motion Subsystem
The mechanical advantage, or “force multiplier”
generated by a group of 2 or more gears turning
together. For simple non-compound gear trains,
this can be calculated as the number of teeth on the
driven gear divided by the number of teeth on the
driving gear.
Gear Train – Motion Subsystem
In general, a group of gears that turn together to
transmit motion from one point to another on the
robot, often providing mechanical advantage along
the way.
Gripper
An attachment designed to pick up or hold an
object, often by “gripping” it with claw-like
appendages.
Gusset – Structure Subsystem
A piece used to strengthen an angled joint.
H
HIGH (Digital value) – Sensor Subsystem
One of two possible values in a digital system (the
other is LOW). The voltage used to indicate HIGH
usually corresponds to the maximum voltage of the
system.
Hub – Motion Subsystem
With wheels, the hub is the center portion of the
wheel that joins to the axle.
I
Idler Gear – Motion Subsystem
A gear in a gear train that is neither the driven
nor the driving gear, and does not share an axle
with another gear in the train (i.e. does not form
a compound gear). Each idler gear in the train
reverses the direction of spin once, but never affects
the gear ratio.
Glossary
Four Wheel Drive – Control Subsystem
A four-wheel drive robot typically has four wheels,
all of which are powered independently. This usage
is analogous, but not identical, to the meaning of the
term with respect to automobiles.
Frequency-Modulated Signals –
Control Subsystem
Frequency-Modulated (FM) signals are used in the
VEX system to encode data in radio transmissions.
Radio waves are a form of electromagnetic wave
with a very high frequency. The frequencies used
by the VEX system all have a carrier frequency
near 75MHz, which is part of the VHF (Very High
Frequency) band of the electromagnetic spectrum.
This carrier wave is then modulated by the signal
wave to produce a third wave, which is transmitted
through the air and received by the RF Receiver
Module on the robot.
Friction – Motion Subsystem
The force between two touching surfaces moving at
different speeds that acts to slow their movement
relative to each other. In robotics, this usually has
one of three contexts: friction between wheels and
ground that results in rolling wheels slowing down,
friction between wheels and ground that allows
wheels to “push off” and start moving to begin with
(rather than spinning in place), and friction between
any two components rubbing together in the robot
that result in loss of energy.
G
Gear – Motion Subsystem
Essentially, gears are spinning discs with teeth that
prevent them from slipping past each other. Gears
are frequently used to transfer rotational motion
from one piece to another, and to provide mechanical
advantage while doing so. The number of teeth on a
gear (assuming the same spacing between teeth on
both gears, so their teeth mesh properly) is directly
proportional to the gear disc’s circumference, thus
the number of teeth can easily be used to calculate
the gear ratios of gear trains.
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