Page 370 - Sensors and Control Systems in Manufacturing

CHAPTER 7

Industrial Sensors

and Control

7.1 Introduction
Current manufacturing strategy defines manufacturing systems in
terms of sensors, actuators, effectors, controllers, and control loops.
Sensors provide a means for gathering information on manufacturing
operations and processes being performed. In many instances, sensors
are used to transform a physical stimulus into an electrical signal that
may be analyzed by the manufacturing system and used for making
decisions about the operations being conducted. Actuators convert an
electrical signal into a mechanical motion. An actuator acts on the prod-
uct and equipment through an effector. Effectors serve as the “hand”
that achieves the desired mechanical action. Controllers are computers
of some type that receive information from sensors and from internal
programming, and use this information to operate the manufacturing
equipment (to the extent available, depending on the degree of auto-
mation and control). Controllers provide electronic commands that
convert an electrical signal into a mechanical action. Sensors, actuators,
effectors, and controllers are linked to a control loop.
In limited-capability control loops, little information is gathered,
little decision making can take place, and limited action results. In
other settings, “smart” manufacturing equipment with a wide range
of sensor types can apply numerous actuators and effectors to achieve
a wide range of automated actions.
The purpose of sensors is to inspect work in progress, to monitor
the work-in-progress interface with the manufacturing equipment,
and to allow self-monitoring of manufacturing by the manufacturing
system’s own computer. The purpose of the actuator and effector is to
transform the work in progress according to the defined processes of
the manufacturing system. The function of the controller is to allow
for varying degrees of manual, semiautomated, or fully automated con-
trol over the processes. In a fully automated case, such as in computer-
integrated manufacturing, the controller is completely adaptive and
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