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CHAPTER 16
GENERAL-PURPOSE CONTROL DEVICES
James H. Christensen
Holobloc, Inc.
Cleveland Heights, Ohio
Robert J. Kretschmann
Rockwell Automation
Mayfield Heights, Ohio
Sujeet Chand
Rockwell Automation
Milwaukee, Wisconsin
Kazuhiko Yokoyama
Yaskawa Electric Corporation
Tokyo, Japan
1 CHARACTERISTICS OF
GENERAL-PURPOSE CONTROL
DEVICES
678
1.1 Hierarchical Control
678
1.2 Programmability
680
1.3 Device Architecture
681
1.4 Sequential Control
682
1.5 Path Control
686
2 PROGRAMMABLE
CONTROLLERS (PLCs)
687
2.1 Principles of Operation
687
2.2
Interfaces
688
2.3 Programming
690
2.4 Programmable Controller
Standard, IEC 61131
691
3 NUMERICAL CONTROLLERS
696
3.1
Introduction and Applications
696
3.2 Principles of Operation
698
3.3 Point-to-Point and Contouring
Numerical Controllers
701
3.4 NC Programming
702
3.5 Numerical Controllers and
CAD/CAM
709
4 ROBOT CONTROLLERS
711
4.1 Composition of a Robot System
711
4.2 Control Program
712
REFERENCES
716
BIBLIOGRAPHY
716
1 CHARACTERISTICS OF GENERAL-PURPOSE CONTROL DEVICES
1.1 Hierarchical Control
As shown in Fig. 1, general-purpose control devices (GPCDs) occupy a place in the hier-
archy of factory automation above the closed-loop control systems described in Chapters
12–15. The responsibility of the GPCD is the coordinated control of one or more machines
or processes. Thus, a GPCD may operate at the ‘‘station’’ level, where it controls part or all
of a single machine or process, or at the ‘‘cell’’ level, where it coordinates the operation of
multiple stations.
In fulfilling its responsibilities, the GPCD must be capable of performing the following
functions, as shown in Fig. 2:
Mechanical Engineers’ Handbook: Instrumentation, Systems, Controls, and MEMS, Volume 2, Third Edition.
Edited by Myer Kutz
Copyright
2006 by John Wiley & Sons, Inc.
1 Characteristics of General-Purpose Control Devices
679
Figure 1 Plant control hierarchy using GPCDs, general-purpose computers (GPCs), and closed-loop
controllers (CLCs).
Figure 2 Communication and control paths of a GPCD.
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