ANNUAL REVIEW
THEODORE J. WILLIAMS
Computers and Process Control Coverage of literature for the period April 1967 to March 1968
hile computer control in general continued to its healthy rate of growth during the past year, and even began to show “signs of maturity” (16C) as an application science, the spotlight during this period has been taken by the application of the digital computer as a monitor, controller, and interpreter for laboratory and on-line analytical instruments, uses first mentioned in last year’s review (55P). Equally important here has been the sudden appearance of a whole family of small but at the same time powerful digital computers advertised as being in the “less than $10,000 class.” These machines have indeed been the key to the sudden increase in use of the “computer-controlled” analytical methods just mentioned, because the combined low cost and high versatility of these small computers permits them to be dedicated completely to such tasks as the operation of a group of chromatographs or of a single mass spectrometer (7F, 4OF, 54F). Next in importance is the fact that another year’s time has allowed many of the manufacturers to eliminate most of the problems from the on-line operating programs for their computer control lines. I n addition, another year of experience has allowed both manufacturer and user to learn more concerning solution or prevention of former problems and vexations of a computer-control installation. Thus, this year’s systems have had a much better delivery performance, have undergone far less difficulty in on-line commissioning, and have had smoother startu p periods. While problems in this area are not yet completely cured, it does appear that we are now in good shape for future installations as long as the present generation of machines continues to be used. Hopefully, an ever-increasing use of F O R T R A N and other compilers for the preparation of user-written programs and the establishment of sets of standard input/output, control, monitoring, and data transmission routines for their machines by each of the vendors will lead to a
Wincrease
76
INDUSTRIAL A N D ENGINEERING CHEMISTRY
transition from today’s machines to the new generation (when it arrives) that is much smoother than has been the history of this field in the immediate past. Another welcome sign is the current effort on the part of user and manufacturer groups alike to look into the possibility of a “standard language,” or at least an industry-wide standard set of routines, for process computer control. Outstanding in this regard has been the effort of the Specialist Group of the British Computer Society which last fall produced a document entitled, “A Language for Real-Time Systems” (8B) which outlines just such a potential standard language. Unfortunately, this proposed standard is based on ALGOL. While ALGOL is popular in Europe, it is very much out of favor in America; thus, the British proposal will probably never be acceptable to the Standards groups in the United States. However, it is the intent rather than the actual format of the standard which is important here. It should be a relatively straightforward task to define an extended FORTRAN which would include all of the advantages of the finished ALGOL programming system with few, if any, of its attendent application problems. The current activity in this area would indicate that this will come to pass in this country within the next few years. Certainly, the present level of computer-control applications, along with the field’s extremely rapid growth and the prevailing shortages of qualified personnel, will require its completion soon. Another area of importance for the combined areas of computers and process control is the current rapidly increasing interest in hybrid computers. AS a combination of one of the current generation of process control computers with one or more consoles of the latest generation of highly automated, analog machines, the current group of available hybrid systems promises to limit severely if not eliminate the chief difficulty of application
which these systems have shown in the past-the tremendous effort required to program two entirely different types of machines to work together in an efficient manner. Making use of much of the knowledge which has been gained from process control and other on-line data systems, programs have already been developed by several of the suppliers of the new hybrid systems to accomplish this latter task. Additionally, research is also under way in many locations to eliminate the sole remaining impediment to widespread use of these devices-the timeconsuming task of wiring the analog patch board. The constantly falling prices of large-scale integrated circuits show promise of making practical the development of a n inexpensive yet large-scale cross-bar switch which could completely automate this final task under the control of the digital computer.
and Computer Systems As in the past, the most popular topic in the field of large-scale computers and their applications has been the subject of remote-access computing or time-shared systems (Tables I and 11) with their attendant problems of multiaccess, multiprogramming, and multiprocessing. T h e first of these terms refers to the ability of several different persons or devices to obtain use of the computer system a t the same or within a closely spaced period of time. T h e second concerns the ability of the computer system to be able to handle several different programs operating alternately during a short period of time, none necessarily finishing its task before relinquishing control of the computer to the next program in the series. Multiprocessing is the ability of several different computer main frames to take a n efficient place in a coniputer system while operating a t the same time. I n the light of these definitions, process control computer systems are already multiaccess and multiprogramming systems through their use of process interrupts to monitor the process and carry out “control by exception” practices. I n addition, when used in a multiple computer or hierarchy fashion they become part of a multiprocessor system as well. Thus, the remote-access computing field has gained much from the experiences of the process control field and more recently the reverse has also occurred. Of interest to the follower of the digital computer field, its history, and its tremendous growth and development over the past three decades, will be the articles by Stibitz (98A), concerning the relay-operated computers deComputers
AUTHOR Theodore J . Williams is Professor of Engineering and Director of the Purdue Laboratory for Applied Industrial Control, Purdue University, Lafayette, Ind. The author acknowledges the help of Phyllis Haldeman and Esther Cegala who have been responsible for the location of a set of articles and for numbering, several times, those which appear in this review. These same ladies have also done an excellent job in preparing the resulting manuscr+t for publication.
TABLE I .
ANALOG AND DIGITAL COMPUTERS
Subject
References
Advances in computers Arithmetic units Automatic check-out systems Automatic fault diagnosis and repair Cathode ray tube display systems and other graphic techniques Computer system design-general Computer system structure Description of typical systems and new computers Digital differential analyzers Digital plotting Error reduction Historical discussions
IA, U6A 75A, 28A, 700A 80A 73A, 7 7 A , 4 7 A 76A, 7 9 A , 3 0 A , 5 Z A , 8 7 A , 9 4 A , 702A 78A, &A, 6 8 A , 96A, 7 70A 6A 47A
66A 6 3 A , 8 5 A , 707A 3 5 A , 43A 3A, 7A,U9A, 74A, 76A, 77A, 79A, 98A, 709A 27A, 33A, 5 3 A , 64A 39A 7 7 A , 8UA 5 A , 74A, 36A, 56A-58A, 6 7 A , 6 9 A , 7 5 A , 9 0 A , 704A
Large-scale integrated circuits Machine translation Magnetic tape units Memories-general Memory hierarchies Memories-use topics Multiprocessor systems-general Multiprocessor systems-special topics On-line and real time computing systems Operation of computer installations Performance evaluations Recording techniques Redundancy in computer systems Reliability-general Simulation techniques Systems communications Textbooks Time-shared operations
4A 26A,ZQA,5UA,87A 72A,37A,6ZA,93A,99A ZA, 37A, 38A, 8 8 A , 8 9 A , Q5A, 706A 55A 27A 5 7 A , 6 7 A , 703A 20A 8A 44A 97A 77A, 7 3 A , 707A 9 A 2UA 25A 3ZA 34A U2A 4 5 A , &0A, &A, 7bA, 7 i A , 862, 702A 70A 22A 23A UOA 5 9 A 6 0 A 7 8 A , 8?A, 8 i A , 9 7 2 , 9.22,IOiA, 1 i l A
TABLE II. COMPUTER PROGRAMMING Subject
References
Aerospace systems Automata Commercial data processing Computational linguistics Computer assisted instruction and learning systems Computer control system programming Decision tables File management systems Flow charts FORTRAN topics Interactive systems Linear algebra Mathematical topics in programming Memory system considerations Microprogramming Mnemonics Multiprogramming P E R T systems P/L I Program debugging Programming-general Real time system programming Simulation languages System generators Time sharing Textbooks Tutorial articles Virtual memory and paging
VOL. 6 1
26B, 37B, 7 7 8 33B 79 B 25B 5ZB, 5 8 B 72B, ZZB, 23B, 37B, 434 66B, 6 9 B 57B 49B 38B 58, ZOB, 3 9 B - 4 7 4 5 7 B UB 9B 7B 17B 48B 29B 7 8 , 138, UUB, 5 9 B ZBB, 5 5 B 28, 6 3 8 , 6 7 B , 6 8 B , 7 0 B 72B lUB, 50B, 5UB, 56B, 6ZB, 6 5 B SB, 75B, 53B 3 5 B , 4.28, 4773, 6 4 B 6B 16B, 7 7 8 , 27B 3 8 , 24B, 30B, 3 4 B , 36B, 4 5 B , 60B 67B IOB, 2 7 8 , 3 2 8 , 4 6 B 78B
NO. 1
JANUARY 1969
77
TABLE 111.
COMPUTER CONTROL AND RELATED TOPICS Subject
References
Batch reactors Chemical industry applications-general Computer control-general Computers for process control Control centers and operator consoles Direct digital control (DDC) Fossil and nuclear steam plants Gas and oil pipelines and terminals Hardware topics other than computers Justification of computer control Mechanical and manufacturing systems control Multiprocessors Oil field control Paper industry applications Petroleum industry applications Production and inventory control Ship and marine applications Simulation of computer control Steel industry applications ' Textbooks Theory and programming topics Traffic control
TABLE IV.
lC, 15C, 27C 29c, 3 9 c 12C, 16C, 26C, 35C, 49C, 57C 21c 8C 2C, 7C, 73C, 20C, 22C, 30C, 38C, 44C, 45C; 48C 5c, 34c 18C, 33C, 41C 6C, lOC, 17C 40C 31C, 37C, 43C, 46C, 50C 25c, 42c
3c
4c 23c, 4 7 c 28C 1IC 32c
QC, 36C 14C 19c 24c
Computer and Other Plant Control Topics
COMPUTER USES OTHER THAN CONTROL OR SIMULATION ~
Subject
References
Algebraic equation solution Analog computer applications D a t a processing Differential equation solutions Distillation, absorption, and extraction column design Communication system design Electronic system design Fast Fourier transform Instrument reading corrections Ma thematical methods-general Matrix problem solution Pattern recognition Physical property data analyses Piping network design Plant design-general Production and inventory scheduling Spectral analysis Uses of time sharing
360, 380, 390 190, 2 1 0 , 290, 3 7 0 , 40D 70,480 7 70, 1 4 0 , 2 5 0 , 2 6 0 , 3 3 0 , 5 2 0 , 5 8 0 2 0 , 7 2 0 , 150-770, 4 4 0 220, 270 8 0 , 2 8 0 , 570 9 0 , rsn, 530 310, 3 2 0 700, 2 0 0 , 2 3 0 , 4 5 0 , 4 7 0 , 5 6 0 4 0 , 4 1 0 , 430
6D 240, 610 10, 130,500 300, 3 4 0 , 4 6 0 , 5 7 0 , 5 9 0 30,350,550,600 50 420, 4 9 0 , 5 4 0
TABLE V. ANALOG-DIGITAL CONVERSION, PLANT DATA HANDLING, TELEMETRY, AND RELATED TOPICS Subject
References
Analog-to-digital conversion Communications systcms applications Data collection-general Data communications Data link operation and control Data processing considerations Data transmission Input/output equipment considerations Process monitoring
4E, 8E l E , 20E 6 E , 72E, 16E, 19E, 23E, 24E 14E, 18E, 22E 9E: 13E, 75E 3 E , 5 E , 7 E , lOE, 17E 2E, 27E 17E
~
78
veloped at the Bell Laboratories, and by Wilkes (709A), concerning the personalities and events of the early years of the field. The Bell Laboratories machines were developed in the late 1930's, over five years before the advent of the famous Mark I and its companions developed by Harvard University and IBM. They have, however, never received the publicity and credit they deserved. The tenth anniversary issue of Datamatzon in September 1967 has also been the means for the presentation of several interesting articles reviewing the developments of the past decade ( 3 4 7 7 4 7 9 A ) . Another major topic of interest in this field is the continued major development of cathode ray tube displays and their attendant techniques and applications (76A, 19A, 30A, 87A, 944, 102A). This area of computer application continues to uphold its promise of being the major method of interaction between people and computer systems in the near future. Its capability for the transitory presentation of great masses of computer-generated and computer-stored data in all types of formats, combined with the light pen and other equally effective methods of direct interrogation by the computer operator, holds our sole major promise of an adequate future method for such use. Otherwise, we face an avalanche of paper with its associated problems of filing and later retrieval.
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
I n the computer control field, direct digital control continues to hold the spotlight of popularity, especially when one considers the number of articles which have appeared concerning this topic as related to others in the field. Of particular importance to the reader here are the successes attained recently in the control of groups of batch reactors as exemplified by the synthetic rubber and the plastics polymerization industries (7C, 27C). Other processes discussed have been steel mill soaking pits (73C) and ammonia plants (22C). Technical topics in this area have included valve actuator adaptation (22C), self-tuning for modes other than proportional only (ZOC), and hand tuning (45C), required backup systems (3OC), and sampling and quantization (44C). I n the computer-control field in general the rate of appearance of applications articles has been gratifying. These have appeared concerning nearly all the industry areas usually considered provinces of computer control. Especially important among these have been those dealing with the discrete parts manufacturing industries as contrasted with the continuous process industries, and especially the fluid-type industries such as petroleum and most chemicals. T o be noted among these articles are those of Schermer (37C), Stuehler and Watkins (43C), and Wendt (502). Many articles of quality continue to appear concerning the ever-present problems of signal conditioning ( 5 7 F ) , noise prevention and grounding techniques (37F, 47F, 7 5 F ) , multiplexing ( 4 5 F ) , analog to digital conversion ( 4 E ) , and input-output equipment (27E). Especially important among these is the article of Von Loesecke
TABLE VI. INSTRUMENTATION TECHNIQUES (GENERAL) INCLUDING COMPUTER-BASED INSTRUMENTATION SYSTEMS Subject
References
Air pollution analysis Analog memories Analytical techniques-general Automated analytical techniques-general Belt-scale weighing and solids flow control Calibration accuracies Control valve sizing and design Digital sensors and transducers Directories and handbooks Fluid amplifiers and controls Fluid flow measurement and control techniques Hydraulic systems Instrumentation and control systems, examples Instrumentation-general Length measurements Level measurement and control Measurement techniques-general Moisture measurement Multiplexing techniques Noise prevention and grounding techniques Nuclear measurements Oscilloscopes Pneumatic systems Pressure measurement and control techniques Programmers Redundancy effects Sequential operations Servomechanisms Signal conditioning Stepping motor application techniques Temperature and heat flux measurement techniques
20F, 59F 5% 43F, 50F, 65F, 74F, 77F i F , 24F, 40F, 53F, 54F 14F, 15F, 31F, 48F, 51F 35F 2F, 66F, 71F lOF, 11F 8F, SF, i 8 F 6F, 42F 13F, lSF, 49F 23F, 33F, 55F 18F, 26F, 36F 17F, 52F, 58F, 68F-?’OF 27F, 73F 16F, 32F, 44F IF, 30F 29F, 63F 45F 37F, 47F, i5F 60F 41F 25F, 28F, i2F 64F 46F 67F 22F 4F, 12F 3F 57F 21F, 34F, 38F, 39F, 56F, 61F, 62F, 76F
TABLE VII. PROCESS LOOP COMPONENTS AND I NST RU M ENTAT I ON HARDWARE Subject
References 22G 2G, 9G, 1% 32G 3G 16G, 33G l G , 5G, 25G, 34G IOG, 14G 73G, lSG, 23G, 28G 7G 71C,35G 27G 12G 4G, 15G 27G 8C 6G, 18G, 20G, 24G, 26G, 29G, 30G 31G
Carbon balance measurement Control valves Differential pressure sensors Digital transducers Electric actuators Flow measuring devices Fluidic devices-general Fluidic sensors Heat flux measuring devices Pressure measuring devices Pumps Recorders Refractometers Stepping motors Temperature measurement devices Textbooks
TABLE VI I I. PROCESS DYNAM ICs AND PROCESS M A T HEM A T I CA L MODEL ING
(75F)on noise pickup and its prevention in process signal lines. We have previously mentioned in this review that the much increased popularity of computer-operated chemical analytical devices, as evidenced by the advent of the numbers of new models of inexpensive but capable machines, was the most popular instrumentation topic this year. Nearly every other area of instrumentation as related to the process plant received its share of attention (Table VI) with most articles either being reviews or oriented toward applications, rather than describing new devices or techniques for use. Process Modeling and Control and Automatic ContrCl Theory
On-line modeling and process dynamics identification techniques continue to be popular topics for investigation, publication, and use in the process dynamics field. Some important topics in this area which have appeared during the past year include errors in frequency response determination from step inputs (7H),frequency response from transient response in general (24H), the human operator’s response as part of a dynamic system (75H, 77H), and a review of dynamic testing methods in general (7ZH). Other important topics in this area have been statistical identification methods (3H, 22H) and state space modeling techniques (28H). In the area of process modeling itself the new texts by Franks ( 7 H ) and Shearer et al. (23H) are to be especially recommended.
Subject
References
Chemical reactor dynamics Dynamics of distillation systems Dynamics of the operator Dynamics testing methods Evaporator dynamics Frequency response from transient response Heat transfer in continuous casting Identification methods Pneumatic system dynamics Process dynamics-general Solids separation Textbooks Transient response-general Turbogenerator dynamic response
8H, 13H ZH, 18H, 25H, 27H 15H, 1i H 12H 26H IH, 24H 16H 3 H , 6H, IOH, 21H, 22H, ZSH, 29H 4H, QH 5H, 1SH 20H 7H, 23H 14H 1lH
TABLE IX.
PROCESS SIMULATION INCLUDING HYBRID COMPUTATION
Analog computation-general Analytical instrument simulations Biomedical applications Blending systems Character recognition simulation Chemical reactor simulation Control system evaluations Digital simulation-general Distillation and related process sirnulation Economic systems Educational uses Error analysis Heat exchange simulation Hybrid computation-general Hybrid computer applications-general Hydraulic system simulation Oil field reserves Probability distributions Simulation-general Simulation of manufacturing and job shop operations Simulation for operator training Steel rolling mill simulation Textbooks
VOL. 6 1
NO. 1
31, 91, 221, 251, 321, 331, 361, 591 371 211, 341 401 101 71, 751, 241,351, 371, 511,631 271, 291, 541 131, 141, 181, 601 SI3 501 381, 531 lgI, 481 621 161, 171, 461 61, 431-451, 521, 571,641 231, 671 21
551 41 81, 121,261, 281,301, 561, 581 11,471 1 11, 421, 491 201 391, 411
JANUARY 1 9 6 9
79
TABLE X.
PROCESS CONTROL THEORY-BASIC Subject
References 4J 9 J , 29J, 3 7 J , 525, 53J
Boolean equation applications Sampled data systems and sample and hold devices Dead time, its treatment and effect Digital compensation Distillation column control Distributed systems Identification methods Laplace transform Man-machine interaction Noninteracting control Nonlinear systems Process control theory-general Relay control systems Root locus methods Sequential-mode control Special controllers and control actions Stability Textbooks, basic Textbooks, intermediate and special topic Tuning of controllers
13J, 17J, ZIJ 36J 7J 54J 41J 25 47.7 55J 2 4 J , 4 0 J , 4 4 J , 50J IbJ, 233, 26J, 35J, 43J, 4QJ 10J 6 J , 4 2 J , 46J, 51J 3J 14J,15J, 3 0 J , 45J I I J , 315 8J, 18.3, 25J, 3 8 J , 48J 55, l Q J ,20J, 22J, 28J, 3 4 J , 39J IJ, 12J, 27J, 3 2 J , 335
TABLE X I . CONTROL SYSTEM THEORY-ADVANCED CONCEPTS APPLICABLE TO PROCESS CONTROL Subject
References
Adaptive control systems Advanced control systems, symposia and reports of advances Advanced control theory-general Boolean functions Cascaded control systems Distributed parameter systems Extrema1 systems with noise Feedforward control Human operator representation Linear filtering Multivariable control systems Noninteracting control systems Nonlinear systems On-off control systems Predictive control Sampled data systems Self-organizing control Stability Textbooks Wiener filters
TABLE X I I .
4K, 22K, 35K, 41K 23K, 25K, 26K, 31K 12K, 39K 5K, 42K 30K 37K 14K 29K 40K 2K 15K, 16K, 27K 28K 7K, 21K, 24K, 43K 32K 9K IOK, I l K , lQK, 20K, 36K, 38K I K , 78K, 34K 33K 6 K , 8K, 13K, 17K
3K
OPTIMIZATION THEORY AND TECH N IQU ES
Subject
References
Chemical process optimization Design optimization Discrete or sampled data systems Distributed parameter systems Dynamic programming Mathematical programming Maximum principle Nonlinear systems Optimal control-general Optimization-general Optimization of power systems Stochastic systems Textbooks
IOL, 21L,24L,27L, 29L,33L 37L, 39L,41L I I L , 16L, 36L 3L, 20L 4L, 17L, 30L, 40L 23L 5L 13L, 19L 6 L , 8 L , 75L,32L,34L, 38L lZL, 14L, 18L, 35L 7L IL, 9L ZL,ZZL,25L,26L,28L,3IL,42L
As usual, the topics of chemical reactor dynamics ( 8 H ) , distillation columns ( Z j H ) , and pneumatic systems (4H, 9H) have proved popular. I t was also gratifying to see the discussion of evaporators (26H) and solids separation (ZOH), along with the study of heat transfer in the continuous casting process (16H). The field of automatic control has been characterized in the past few years by a condition of gradual and steady, if unspectacular, development in the theory areas. This is in contrast to the period from the mid-1950’s to the early 1960’s when new developments seemed to occur at every turn. There has also been a steady increase in the applications content of the so-called theory articles. This has been fostered, of course, by the major publicity which has been given to the so-called
