Page 139 - Concise Encyclopedia of Robotics

Generator
An example of a gateway is an intersection between two streets. At a
typical intersection where two straight roads cross each other at a right
angle, a robotized vehicle can do any of four things:
• Continue straight ahead
• Turn left
• Turn right
•Backtrack
When a mobile robot is programmed to travel from one point to
another, gateways must frequently be dealt with. If the machine has a
complete computer map of its work environment, and if the environment is
not too complicated,every gateway possibility can reside in the controller’s
memory or storage medium. If the work environment is complex, or if it
changes with time, the decisions must be based on programming rather
than brute-force data storage.
See also COMPUTER MAP, RELATIONAL GRAPH, and TOPOLOGICAL PATH PLANNING.
GENERATOR
The term generator can refer to either of two devices. A signal generator is
a source of alternating-current (AC) signal current, voltage, or power in
an electronic circuit. An oscillator is a common example. An electric gener-
ator is a device that produces AC electricity from mechanical energy.
Signal generator
A signal generator is used for the purpose of testing audio-frequency
(AF) or radio-frequency (RF) communications, detection, monitoring,
security, navigation, and entertainment equipment. This includes various
types of robotic sensing systems.
In its simplest form, a signal generator consists of a simple electronic
oscillator that produces a sine wave of a certain amplitude in microvolts
( V) or millivolts (mV), and a certain frequency in hertz (Hz), kilohertz
(kHz), megahertz (MHz), or gigahertz (GHz). Some AF signal generators
can produce several different types of waveforms, such as those shown in
Fig. 1. The more sophisticated signal generators for RF testing have ampli-
tude modulators and/or frequency modulators.
A function generator is a signal generator that can produce specialized
waveforms selected by the user.All electrical waveforms can be expressed as
mathematical functions of time. For example, the instantaneous amplitude
of a sine wave can be expressed in the form f(t) = a sin bt, where a is a
constant that determines the peak amplitude and b is a constant that deter-
mines the frequency. Square waves, sawtooth waves, and all other periodic

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