Page 371 - Sensors and Control Systems in Manufacturing

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Se v e n
Cha p te r

functions in a closed-loop manner to produce automatic system oper-
ation. In other cases, human activity is involved in the control loop.
In order to understand the ways in which the physical properties
of a manufacturing system affect the functional parameters associated
with the manufacturing system, and in order to determine the types
of physical manufacturing system properties that are necessary to
implement the various desired functional parameters, it is important
to understand the technologies available for manufacturing systems
that use automation and integration to varying degrees.
The least automated equipment makes use of detailed operator
control over all equipment functions. Further, each action performed
by the equipment is individually directed by the operator. Manual
equipment thus makes the maximum use of human capability and
adaptability. Visual observations can be enhanced by the use of micro-
scopes and cameras, and the actions undertaken can be enhanced by
the use of simple effectors. The linkages between the sensory infor-
mation (from microscopes or through cameras) and the resulting
actions are obtained by placing the operator in the loop.
This type of system is clearly limited by the types of sensors used
and their relationship to the human operator, the types of the effec-
tors that can be used in conjunction with the human operator, and the
capabilities of the operator. The manufacturing equipment that is
designed for a manual strategy must be matched to human capabili-
ties. The human–manufacturing equipment interface is extremely
important in many manufacturing applications. Unfortunately, equip-
ment design is often not optimized as a sensor-operator-actuator/
effector control loop.
A manufacturing system may be semiautomated, with some por-
tion of the control loop replaced by a computer. This approach will serve
the new demands on manufacturing system design requirements. Spe-
cifically, sensors now must provide continuous input data for both the
operator and computer. The appropriate types of data must be provided
in a timely manner to each of these control loops. Semiautomated man-
ufacturing systems must have the capability for a limited degree of self-
monitoring and control associated with the computer portion of the
decision making loop. An obvious difficulty in designing such equip-
ment is to manage the computer- and operator-controlled activities in
an optimum manner. The computer must be able to recognize when it
needs operator support, and the operator must be able to recognize
which functions may appropriately be left to computer control. A con-
tinuing machine-operator interaction is part of normal operations.
Another manufacturing concept involves fully automated manu-
facturing systems. The processing within the manufacturing system
itself is fully computer-controlled. Closed-loop operations must exist
between sensors and actuators/effectors in the manufacturing system.
The manufacturing system must be able to monitor its own perfor-
mance and decision making for all required operations. For effective