Some Questions of Hardware Structure of the Integrated Systems Control

(1)

SOME QUESTIONS ON HARDWARE STRUCTURE OF THE INTEGRATED SYSTEMS CONTROL

German Surguchev

June 1975 WP-75-7l

Working Papers are not intended for distribution outside of IIASA, and are solely for discussion and information purposes. The views expressed are those of the author, and do not necessarily reflect those of IIASA.

(2)

The hardware structure of the integrated systems control (ISC) is defined by many factors, for example, the structure of the controlled systems, the functions of ISC, the computer systems already existing, the economic situation and so on.

I would like to discuss some of these problems taking the steel industry as an example.

(3)

Generalization

The hardware structure of an integrated systems control (ISC) must support the functions which are carried out by the ISC.

This idea seems to be very simple at first sight though i t has many aspects and difficulties. It is quite possiblr to formu- late several general objectives for the ISC hardware. They are the following:

- to implement all functions which make up the ISC;

- to be constructed in a hierarchical structure;

- ~o en3ure effective data input, output, processing and storage;

- to take into consideration the possibilities of development and improvement.

Hardware problems will be discussed with these remarks in mind.

The first question to be discussed is what kind of general hardware structure should be used? In this case we must consider two different alternatives:

- use of one or more large-capacity computers to solve the tasks for all the control levels; and

- use of a number of mini- or medium-sized computers at individual levels.

We consider an "ideal" hardware structure in terms of these alternatives and certainly we accept the terms "ideal" rather conditionally.

As an "ideal" hardware structure we imply a kind of structure which makes up the ISC function in each level. In this case each level of the ISC must be supported by specialized hardware systems and must use one or more computers per functional level. The number and size of the computers, peripherals and all technical means correspond to the function to be fulfilled at that level.

An example of an "ideal" hardware structure is given in Fig.1 Such an approach using one or more computers for each functional level helps keep lines of responsibility clear.

A number of steel works are now moving in the direction of minimizing the hardware hierarchy by combining two or more functional levels into one. Some works replace the existing multi-computer four-level hierarchies by a two-level approach.

(4)

MANAGEMENT LEVEL

2

Work 1 Main computer

1 - - - 1 2

I - - - i l

Medium size computer 5 ~""----'---'L-...J

Medium size computer

4 2l---rM::e~d:-i

^u-m--'

size computer

61----....

PRODUCTION CONTROL LEVEL

41--~

lliJ

PROCESS CONTROL LEVEL

l2J--...r~--r--l5

Mini computer

[II -

Switching sys tern

[2] -

Terminals

[] - Cards - and paperreader

rn -

Specialized manual

[3J -

Input devices indicating panels

ffi] - Sensors

Fig. 1 "Ideal" hardware structure

(5)

4 LEVEL CONFIGURATION MEDIUM SIZE SYSTEMS ---~~- 2 L~VFL CONFIGURATION LARGE AND SMALL SYSTEMS DATA BASE 320/158

lC:> y 320/158 360/40

350/40 360/40

w

36~/40 I

~

'\ l

I

I , I I 360/40 360/40 " DC

=

DATA COMMUNICATION :l S/7 ~ CENTRALIZED SYSTEM DISTRIBUTED SYSTEM

Fig.2ChangeintheISChardwareconfiguration.

(6)

Figure 2 shows this change in configuration from several medium -sized systems to two large and a number of small, remore com- puters The configuration is called a distributed system.

By implementing a modular structure of hardware, this problem lessens. Modular structure has several advantages, some of which are the follpwing:

- system flexibility (changing the functional structure, evaluation possibilities);

- higher reliability;

- higher economical efficiency .

.Iardware redundancy can be a disadvantage of a modular

struc~'

turo, but this redundancy is compensated by the benefits to be received. Special features of hardware structure for each control level are discussed below.

Process Control Level Hardware

The control tasks of separate technological units or process- es determine the hardware structure in the process control level. The hardware in this level is working on-line, and the reliability demands of the systems are very high.

The following special hardware features are characteristics for this particular level:

- implementation of a number of mini computers connected with the next production control level;

- implementation of specialized sensors, specialized manual input devices, indicating panels,and so on; and - difficult conditions for the hardware in this level

(high temperature, dust, dirt, and so on).

The implementation of miniccomputers gives us the opportuni- ty to organize an independent control for each technological unit. Mini -computer systems-have a number of other

benefits~

some of which are the following;

- flexible systems structure, which presents the possibi- lity of modifying, replacing or deleting a part of the system without upsetting the rest of the system;

graceful degradation-failure in one or more components does not cause the entire system to fail; and

- high systems' reliability due to the parallel working

of redundant units and subsystems, and so on.

(7)

- 5 -

The cost of these systems is quite low due to the simplified hardware, software and the multiple use of standard components

(many different subsystems can use identical hardware to per- form varied functions). The hardware in the process control level, as in the other levels, has one special feature: almost all steel companies started designing an ISC with computers working on one level. These computers were installed individually without considering the future development of a fully integrated control system. However,' the hardware in the

process control level, as in other levels as well, influences the hardware structure of the integrated systems as a whole.

It is quite likely that one of the biggest problems in the hardware structure is the linking of the process-control

computers, which have been developed as separate, independent systems, with computers in other levels. In this case by

developing the system the same type of the computer or special communication units can be used. The implementation of the hardware modular structure gives more possibilities to link the computer in other levels.

Production Control Levels Hardware

The hardware structure in the production control level is also determined by the reqiired functions. The production control level systems work in.ireal time. The tasks to be solved in this level include material flows, stock control, compilation of reports, and so on. These tasks demand medium- sized computer storage and an expensive peripheral system.

It is significant that, at this level, not only standard computer peripheral systems are being implemented, but also sensors, specialized manual input devices and indicating panels. These specialized peripherals are a particularly important part of hardware here. At this level computer storage capacity can be limited since the complete data bank can be located in the main computer storage.

Higher Levels of the Hardware

Large computers are generally needed for solving the tasks of the higher hierarchical levels (management information

tasks, planning/scheduling, order processing, and so on).

The hardware of all the integrated systems control we have already studied has a structure similar to these higher levels. Such big modern computers as an IBM-370, AEG-60-50 and others have been installed

(8)

l\ gCl1CL-ul p:cobJ.mn of h<'irawaro of -::'he pl:odi.l.ct.ion cO'll'1:~ol level is ~o secu~c an efficient man-machine dialogue fo~ decision- making. Special features of the hardware can be characterized as follo\-ls:

app~ication of the la~s~-sized com~utcrs;

- aj:l.LU_ca·i:.im'. ui st'..nacu.-d Fel.-ipheral devices <ter'minals^I di:Jplay's, and ;:;;0 on) •

'1'he V;::>}~3 b:;:i.ng "wl\yecJ. tu f'.hi;;; level C:.\!l iy, c·:mnec'::e:d \-,ith the

c'F;c.:;.aL).v·~ pJ..,Jnn2.wj-':.;chc:rlu.linCj p}:-obl~·;;:tl:;. In t.his case losses i:':Oitl ~;Y;3·(.cms l;il:reLi.f,bilt·cy can be e.tui·~:-~ ~ligh. One of the

£ViH:cion;; of tho.: 111i.ciu ('c·n;i.·u·~l-::r is a SUP?·:...'J:!.sory Lolc over the lowe;;]~ .!..~\f:Jl:::: O£ UW lw.:;,::clidal.c, throll'}h \lhich the reI iabili ty vi ~hc :.~y:.:;tcm is incL'cased.

Mud(~:(n s\:o~l COlt1,C';-U,j.cs ha'vc ~F:;09:':-2.pb::'..cc::U.y S2.pai::--t.ed loca'cions, '1)1I..i ~iH.u..vidurlJ. \'1'Lk3 (>'.:'1 be lor':iXi':',~d Inmdreds o'Z. J'il()Iilct~rs

dl.)i;lJ.:'·C. EC:H.:h \,'e:·:J"J h' ^J ^{. : .}'C~; m·;. (/OlnVUl:e::~ ~cj,·!·:=.';:,:·;::L iu1 f i 11 t.hc hi'jh L':Vl~J. L.:'..sk~-;. .~11.' c!\;;V'CIUPlfC:'lt or' ccmpu:i::cr I1ci.:\cJo:,'ks b~·i.:",een

~.H.~...)i:1"::'at:~ 11i'),l'-:~0'ii'; r:'-A'·l7"i·.':':"J :1.3 ^a'il i,rnp -;: ,-.^,11\~:~" 3~<. in this case.

j\ 11iS:'l ca,paciLy rWbc:Lk :;.~:.I(li-i:,:: t,he "i.:J:"()l1sfurrl1r~'-j.:m.of geogra-

ohi~ally separaLcd campu(.~r3 ;nto Cile lcgi~al co~puter cellter.

A VCl.y illlP0:Ll:.:Ul\: ques cion concern;::, Lhe 03;:'.m2tcs of sl::Oi-aS!'e volnlll0 needed fo:c dl1 ISC in tl·c stc~l ii~du;:;t,ry. 'l'he storage volwne depends on:

- ~he Htru~ture of stE:3l ~roduction enterprises;

'i::ne task3 ·~o be solved D:rthe ISC for the {unctional ,J'cructure of the ISC;

the ']cllcral p:codticti vitj and i'l. number

or

types and sizcs oi proJucts;

- the hardware 3~ructure of the I~C.

3.3i:Lna;:'C3 of. 3UC.l1 i t.Cl'113 ht:v;:: 1)·.~e'1 made :~"l T~'i9n:=-c 3. 'these

~e3ul~3 ar~ £0£ 2 s'l:eel plail~ which he3 ca0acity about 500000

'i:ca3 _3'j:e~l/yea;:. I t is clear ':chat. this characteristic is not

CilOU3h for ~n ~=cura~c determina~ionai the 3~or~ge volume.

'.I.'he ^1110::.:13 ilt1poitan'j: i.:i1d:i~ation, whicn Pig'lre J gives us is

l:hd& ~he laLgcs~ quan~ity of d~ta is gcner~ted at the roll-

ing mill.s.

The 3\:ii;'ug(~ volumG and si~~ o:'~ other harc]wa:.:-e decc:c.sinc the reliability of ^i-l sy,3cem. The '.1ucJrante:c of the :..:cliai.l::'lit:y of such a system becomes an important, corn}?licatec.l problem if vIe expand the fun.ction of the ISC anJ increase the hardvlare

(9)

Dataquantityinbytesx10 oN~0\(Xl

....

o

....

N OxygenSteelworks~ Bessemersteelworks~

---1>

Hotwidestriplines~~ Hotshearingandslittingnay~~ ---t> ...,J \-

'\¥S z

.C:

'> ~

~

~ tl> ~

I>

- ----

---~

Openhearthsteelworks Ingot/slabmills Sectionmill l' Scarf1ngbays Picklingbath Tandemmill Skinpassstand LineAnnealingplant Finishingstand Fig.3Dataobtainedduring productionstages.

Fishingstand____...l....

I I I I ~ M I \b!

l::

I I \ I I I ~.

". '< o t-t, L--IIII!

g-

M' ~

(10)

capacity. High hardware reliability is limitf~d by the cost of a system.

There are at least tvlO vluyS of increusing the reliabili.ty of the systems: I) increasing of the reliabiiity of each element of the hardware system, and 2) in the organization of a system's reservation.

The first is a general problem of computer industry and a real way of improving the reliability of designed ISC is reservation.

There are two possibilities of reservations:

- element reservation (parallel switching of hardware elements); and

- time reservation (foreseeing the redundant hardware capacity).

The question of reliabiLity/cost is rather important. Although the low levels of hardware \'lOrking on-line must have high reliability, the losses from mistakes made in the high levels, due to low reliability there, can be larger and the consequen- ces mOL'e widespread than in lower levels. No examples of the quantitative estima~es of reliability/cost problems in hardware in the steel industry can be given. And only quantitative

remarks can be made.

Classification of Hardware for the ISC

We divide all the hardware elements implemented by the ISC in to five parts Ongure 4);

- information acquisition;

- data transmission;

- data processing and data storage;

- information output and display; and - local dispatching control systems.

Because the problems of standard computer hardware are well- known, there is no need to discuss there. Solutions are being continuously sough~ by the industry.

We intend to discuss the problems and difficulties which the steel industry has. One of the problems in the steel industry concerns sensors.

Sensors are of great significance for process and production

(11)

- 9 -

bO

.,.-i U)C

.eElo OJ

-P-PcU U)

0.:»^{U) U)}

~

^Selectors

.,.-i 'Or-!

0

~'

r-!H

I

cU-Po c Television

o 0

H 0

~

Indicating panels oc'O^C :»

.,.-i cU cU -P r-!

cU 0. Stand computer paripherals

I

El-PU)

H ;j.,.-i (output)

o 0.'0

~-P

C ~

H 0

Servomotors (executive devices)

bO

~ ^C

v:

.,.-i

Specialized computers

OJ U)

-P U) OJ

U) OJbO

:» o cU

U) o H

H⁰ Universal digital computer

'0 o.-P

OJ U) system

-P cU

cU -P'O

H'-'" cU ^C

bOO ~cU

OJCf.l Analog and hybrid computers

-PHc ...

',.-i 4-ior-l

o H-P MUltiplexors and concen-

U) cco c trators

~

⁰

cUo .,.-i

OJ U)

S cU U)

-P .,.-i Modems, sharing adapters

r-l cUS

cu₀ ~U)c and interfaces

.,.-i _cu

I

c H

.e0 -P Private telephone lines

8OJ

'< Standard computer peripherals

V

^(input²

c co ⁰

',.-i .,.-i-P-P Remote terminals

~'

cU.,.-i S U)H·,.-i

o ;j Specialized manual input

~O'c ⁰ devi,ces

HcU

Sensors

r-!o -PH

oC o

~o U)c cu SOJ

bO

.

.,.-i

Ii<

(12)

control levels. It is not possible in steel industry, for example, to obtain continuous information about the composit- ion of the elemenets in metal and slag, information about the temperature, rolling speed, thickness of slabs, position of the cranes and so on.

There are several methods for measuring thepe variables, but the main problem is to receive continuous and reliable in- formation in the steel plants under hard working conditions and to input this information to computer systems. It is

known that sensors do not work particularly reliably in steel industry. The unavailability of sensors for measurement of basic parameters, or/and the unreliability of those available are primary problems encountered when putting control systems into operation.

Specialized manual input devices are employed in process and production control levels. These devices are designed by separate companies in conformity with their problems and special features. Implementation of these devices

is

a con- sequence of the lack of methods for and devices of measure- ment for a number of variables.

Data transmission hardware as a

~ule

is standard. The deve- lopment of the integrated computer network for large compa- nies possessing several plants is a problem as well. It is possible for them to develop their own special communication means or to use private telephone lines.

Data processing devices are also standard. The most import- ant problem is the choice of storage size as mentioned above.

Information output and display devices have several special features. In addition to standard computer peripherals, the specialized indicating panels are servomotors (operating devices) and are included in this

gronp~

The indicating

panels have a different function and, therefore, a different structure as well. They can be installed in each control level, but are more frequently installed in process or pro- duction control level.

E!spatching control systems are becessary to mention, since they can either be connected with the ISC or can work as a separate part of the system. As a general rule, these sys- tems are developed on 'the basis of standard elements.

Conclusion

This study of the eXisting ISC systems permits several con- clusions:

(1) There is only one possible method of solving high level

(13)

- II -

ta;;ks and t.hat is to employ a large computer with a large

stor~0e capacity.

(2) :E'm: the lmlcs't lcv\::ls i t is more economic to i.mplement systems based 0:Ll mini computers.

(3) There a~c several oppo~t~nities to organize the hardware in middle (production control) levels on the basis of large, metlium. or mini computers'.

(4) The modula:.: hardvlal.'e stl'ucture increases the flexibility, reliClbility and ecollomic efficiency of the systems.

(5) The elc~cnts nud the time resc~vations give us the chance to inc~uasc systems reliability, and this is connected to system cost.

(6)~Thcre aLe some difficulties in developing the ISC hard-

ware, for example:

(a) there are not enough input devices, sensors, to allow recording of all the information needed for an ISC;

(b) links between the lowcl.: and higher levels of hardware are being developed individually without considering the development of a fully integrated system;

(c) i t is difficult to calculate or to estimate the economic efficiency of the ISC.

REPERENCES

1

Kirschgaesser, il.A. aad Gilhert, C. "Data Processing in the Steel Indudt~y: The State of the Art and Trends in Computer Applications." Third International Symposium on the Iron and Steel Industry. Brasilia, Brasil, October 14-21 1973.

2 h'illiams, Th. "System3 Engineering of Hierarchy Computer Control Systems for Large Steel f-1anufacturing Complexes. ^II Purdue University, West Lafayette, Indiana, 1974.

3 Wissel, H. liThe Development and Practice of Applying

r~chanical Data Processing Techniques to Technical Prob- lems in a Steel Works. ^II "Steel and Iron," 89, 1969, No.6,

pp.290-304. - -

4 Belostotsky, A., Chukhma:i1, V. "Investigation and Organi- zation of Droduction while Compiling £'\utomated Control Systems." Metallurgy, Moscow, 1971.

5 Kopelovich, A. , Kno'lC:K, 1'-1., Belostotsky A., Rajevich, S.

"Automated Control System for a Steelmaking Plant."

Metallurgy, Moscow, 1973.