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24 CHAPTER TWO
One of the purposes of this book is to point out fields of endeavor that might lead
you to a life-long career choice. If, for some odd reason, you’re hooked on herring, go
to Iceland (http://siglo.is/herring/en/silver.shtml)!
Central Control Systems

Let’s take a look at centralized control systems. Certainly, an understanding of a single
control system is vital for an understanding of a distributed control system. I’m going
to leave it as an exercise to extrapolate these teachings to any work done on a distrib-
uted control system.
Most control systems are built around the same basic control structures. We’ll look
at a few different structures, but the point is their behavior can be described by the same
math. We can discover for ourselves the sorts of characteristics that these control sys-
tems have by observing a readily available control system. The control system I’ve cho-
sen to demonstrate is, right now, at the tip of your finger. We are shortly going to do
some experiments while you are reading.

Open-Loop Control

Most robot control systems have some sort of input signal and output signal. In between,
the control system responds to the input signal and changes the output signal accord-
ingly. The following is a simple diagram showing an open-loop control system (see
Figure 2-2).
The input signal is generally a low-level control signal. Two examples of an input sig-
nal might be the signal from the power button on a TV remote or the linear voltage from
a rotating dimmer switch. Generally, in a control system, the actuator amplifies and
transforms the input signal. When a person presses the power button on the TV remote,
the remote generates an infrared signal that the TV interprets to close a relay and give

Input Signal Output Signal

Actuator

FIGURE 2-2 An open-loop control system