Page 687 - Mechanical Engineers' Handbook (Volume 2)

Mechanical Engineers’ Handbook: Instrumentation, Systems, Controls, and MEMS, Volume 2, Third Edition.
Edited by Myer Kutz

Copyright  2006 by John Wiley & Sons, Inc.

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 3 NUMERICAL CONTROLLERS 696
GENERAL-PURPOSE CONTROL 3.1 Introduction and Applications 696
DEVICES 678 3.2 Principles of Operation 698
1.1 Hierarchical Control 678 3.3 Point-to-Point and Contouring
1.2 Programmability 680 Numerical Controllers 701
1.3 Device Architecture 681 3.4 NC Programming 702
1.4 Sequential Control 682 3.5 Numerical Controllers and
1.5 Path Control 686 CAD/CAM 709
2 PROGRAMMABLE 4 ROBOT CONTROLLERS 711
CONTROLLERS (PLCs) 687 4.1 Composition of a Robot System 711
2.1 Principles of Operation 687 4.2 Control Program 712
2.2 Interfaces 688
2.3 Programming 690 REFERENCES 716
2.4 Programmable Controller
Standard, IEC 61131 691 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:
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