Computers ind. En~n~ Vol.15, Nos 1-4, pp.231-235, 1988

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NETWORKING INTEGRATED MANUFACTURING

THE INDUSTRIAL ENGINEERING ROLE IN CIM NETWORKING

Thomas L. Landers, Ph.D., P.E. University of Arkansas

Donald A. Stanley General Dynamics

Walter A. Whitt Intel

THE IE ROLE

The traditional role of the industrial engineer has been integration of re- sources (such as people, materials, facilities and equipment) for efficient production of goods and services. Industrial engineers (IEs) have histor- ically asserted leadership as the inte- grators in manufacturing, where there has emerged a trend toward computer automation of processes and management information. Computer Integrated Manu- facturing (CIM) is a term used to iden- tify this trend. CIM requires the lin- kage of work centers into an integrated system, through network communications, thus posing both technical and manage- rial challenges for the industrial engineer in manufacturing.

The Department of Industrial Engineer- ing at the University of Arkansas (UofA) is taking broad and specific initiatives to prepare graduating IEs for effective leadership in the CIM environment. The program strategy is based on two principles:

i. The IE is ultimately responsible for continual improvement in manufacturing competitiveness.

2. The IE must maintain technical competence in both traditional and state-of-the-art methods.

To assert leadership in the CIM envi- ronment, the IE must possess technical expertise in process automation and network communications. Hands-on familiarity with the technology enables the IE to evaluate the capabilities, benefits and limitations of the tech- nology and strengthens the IE's leader- ship role among the many specialists involved in CIM. Above all, the IE must assure that the economic goals of the business are met, through the most efficient combination of traditional and technologically advanced resources.

CIM LABORATORY CONCEPT

The Department of Industrial Engineer- ing at the UofA has, for several years, been developing laboratories (labs) and curriculum in automated production.

Dr. C. Ray Asfahl, author of Robots and Manufacturing Automation [I], has led in this effort and has been instrumen- tal in equipping the laboratories with industrial-scale equipment, such as a CNC milling machine, a heavy-duty hydraulic robot and light-duty articu- lating and axis-limit robots.

In 1985 and 1986, two major events occurred to further develop the CIM lab environment. The AT&T Foundation awarded a substantial grant for the acquisition and integration of addi- tional industrial-scale manufacturing and materials handling equipment. Additionally, the IE Department relo- cated into the new Bell Engineering Center on the campus of the University of Arkansas, Fayetteville. Through the further assistance of other companies and the efforts of faculty and graduate students, the CIM lab development is progressing successfully.

Fig. 1 is a plan view of the Automated Production labs, consisting of a Manu- facturing Center and a Materials Hand- ling Center. The lab concept addresses two main objectives:

i. Student projects in introductory programming and use of automated process and handling equipment.

2. Student projects in advanced computer-integration of auto- mated production systems.

Early in conceptual design of the CIM labs, the decision was made to use full-scale industrial equipment, rather than bench-top miniatures. This approach was consistent with the belief that industrial engineers are both motivated and prepared to seek careers in manufacturing, if they are exper- ienced with manufacturing equipment. Also, the opinions of industry practi- tioners (including campus recruiters, members of the department's industrial advisory board and industrialists in the state of Arkansas) weighed heavily in favor of industrial-scale equipment, as providing more relevant experience. Fortunately, the new facilities in the Bell Engineering Center provided space to pursue this approach.

231

232 Proceedings of the lOth Annual Conference on Computers & Industrial Engineering

. . . . . . . . . ,

\

. . . .

Fig. i. CIM laboratory layout.

As of February 1988, the following equipment has been installed (refer to Fig. i):

MANUFACTURING CENTER i. CNC machining center 2. Pneumatic articulating robot 3. Pneumatic axis-limit robot 4. Coordinate measuring machine 5. vision system

MATERIALS HANDLING CENTER 6. Storage carousel 7. Robotic extractor 8. Automatic guided vehicle (AGV) 9. Conveyor system

I0. Bar code scanner and printer.

Both labs are equipped with AT&T 6300+ microcomputers serving as hosts for process control and integrated communi- cations. Fig. 2 illustrates the planned scheme of network communica- tions for the Materials Handling Cen- ter. Within a workcell, the primary modes of communication are parallel digital input/output (DIG I/O) and serial communications. Labs are being linked together with other labs, stu- dent microcomputer centers and faculty offices v~a terminal servers (CS/I) over an IEEE 802.3 CSMA/CD (carrier sense, multiple access with collision detection) local area network.

During the conceptual design phase, serial communication was chosen as the best mode for interfacing. Hardware and software are widely available, at reasonable costs, to provide the needed ~unctions and meaningful, achievable project experiences for undergraduate students. Code-activated switches (SW) provide experience in integration of a microcomputer with multiple peripheral devices, including programmable logic controllers (PLC) in an automatic mode.

Graduate students are gaining valuable experience in CIM research and develop- ment. They have been involved in the overall design, equipment specifica- tion, selection, installation, program- ming and hardware / software debugging. The students have developed software in C [2] and compiled BASIC [3] for serial communications, real-time control, graphics process animation and inven- tory data management. One particularly challenging project involved hardware and software integration of the auto- matic guided vehicle with a host PC, via a serial infrared (IR) data link.

The CIM labs provide an excellent opportunity for students to gain first- hand knowledge of the complexities and problems in network communications. The interfacing requires software development, but also hardware inter- facing, including construction of cables with proper pin-outs. Most importantly for IEs, the students gain an appreciation for economic and sched- ule aspects of implementation and the profound importance of standardization.

SERIAL COMMUNICATIONS

The following discussion is intended to share insights from first-hand experi- ence and to define some issues which should be addressed for further stan- dardization of serial communications in manufacturing. The findings in the UofA CIM lab development parallel some of the same issues which must be addressed in any serial interfacing. Industrial engineers can gain valuable understand- ing of the hardware and software issues in serial communications by interfacing microcomputers with such peripherals as printers, plotters and other business machines. However, experience in interfacing industrial-scale manufac-

Landers et al. : CIM networking 233

MATERIALS HANDLING CENTER

I CAROUSE'-I I XTRAC/°R I

~YoR I JNER J

Fig. 2. CIM laboratory communications.

turing equipment provides the best preparation for IEs entering into manu- facturing.

RS-232-C

The Electronics Industry Association (EIA) developed RS-232-C as a recom- mended standard "applicable to the interconnection of data terminal equip- ment (DTE) and data communication equipment (DCE) employing serial binary data interchange [4]." RS-232-C defines control and signal levels, con- nectors and control encoding [5]. The 25-pin D-shell connector has incor- rectly become synonymous with RS-232-C. Ironically, the standard makes no ref- erence to the 25-pin D-shell connector; yet the connectors are among the few features of serial communication which have become reasonably standard in industrial practice. Even this consis- tency in the industry is eroding, as manufacturers begin to substitute 9-pin D-shell connectors in new applications. EIA has issued another standard, RS-449, which is intended to replace RS-232-C, and which references 37-posi- tion and 9-position interfaces [6].

The distinction between DTE and DCE is a source of much confusion in industry. Data communications equipment includes modems (modulators-demodulators) and common carrier facilities such as phone lines and switches. Data terminal equipment includes computers, terminals and other peripherals [7]. The CIM lab at the University of Arkansas contains equipment implementing all or part (optionally) of the functions defined in RS-232-C.

LAN

IEEE 802. 3

HOST

I IF - -

I J HOST I I MA CHINING L CENTER

[ I I

I I I I I I

I

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Hardware Issues

Serial links are increasingly used for simple, low-cost local area networks (LANs). Industry applications include interconnection of a few microcomputers in an office and integration of mul- tiple AS/R (automatic storage and re- trieval) carousels under control of one microcomputer. Fig. 2 illustrates a similar concept implemented in the UofA CIM labs. These applications involve data transmission over relatively short distances (e.g., less than 50 feet) at a nominal rate of 9600 bits per second [7,8]. Modem access to common carrier phone lines is not required.

When devices are connected by cable without modems, the cable is referred to as a null modem [8]. For varied reasons (including cost, speed, sim- plicity and/or convenience), several of the functions required in modem commu- nications can be omitted in a null modem cable. Since applications need not comply fully to a standard, the equipment manufacturers and their cus- tomers have tended to implement serial interfacing according to their specific perceived needs, without full consider- ation for other possible interconnec- tions.

The absolute minimum configuration for a null modem cable includes data trans- mit (TD), data receive (RD) and signal (reference) ground (SG). A DTE connec- tor uses pin 2 to transmit data and pin 3 to receive data, while a DCE uses pin 2 to receive and pin 3 to transmit. Fig. 3 illustrates the basic options. Part (a) of Fig. 3 defines the pin con-

234 Proceedings of the 10th Annual Conference on Computers & Industrial Engineering

- - - - - 3 RD MODEM SO ? - - - - 7 SG

DTE DCE (a.) m~,t ~e,

TImMmAL I ~ 2 ~2 s D>'<c~ s ~ ~m,,mA,. SG ? - - ? SG

DTZ DT~ (b.) ~ cable

Fig. 3. Simple null modems.

nections for two devices: DTE (such as a terminal) and DCE (such as a modem). This connection is referred to as a "straight cable." Part (bJ of Fig. 3 illustrates the "crossed cable," for connecting DTE to DTE or DCE to DCE. It is essential to know whether a spe- cific piece of equipment is configured as DTE or as DCE, for purposes of serial communications. Unfortunately, this point is not always well docu- mented by the equipment manufacturer.

Microcomputers are generally configured as DTE, while modems are likely to require connection as DCE. However, there is little consistency in the industry, for configuring other periph- eral devices (even printer interfaces vary widely). In the CIM lab, the car- ousel controller was delivered by the manufacturer, configured as DTE, there- fore requiring a crossed-cable connec- tion to a host microcomputer. On the other hand, the extractor controller was configured by its supplier as DCE, necessitating the use of a straight- cable connection to the host microcom- puter.

Standardization would be improved if all such industrial devices were con- sistently configured. For example, if all peripherals were configured as DCE, straight cabling could be used, with the associated benefits of simplicity and lower cost.

Software Issues

The software issues in serial communi- cation include the following:

I. Message format and 2. Programming languages.

The ultimate objective of serial commu- nications in CIM is to transmit the information required for manufacturing functions. Under the typical serial protocol, messages are transmitted one character at a time, in ASCII (American Standard Code for Information Inter- change) characters.

System developers may define a charac- ter to represent information (e.g., the character "R" might be defined as a status indicator, meaning "ready"). The extractor controller in the UofA CIM lab implemented this approach. The byte "1010010" is the ASCII code for the "R" character. An alternative approach is to define each bit of the character R as representing status information. In each bit position, a "i" indicates one state (such as ERROR), while a "0" indicates the oppo- site state (NO ERROR). The carousel controller represented information in this way.

Note that the second alternative per- mits much more information to be commu- nicated in one character of a message string. Consequently, messages can be of shorter length, which is desirable in a real-time control system where speed and reliability are critical. For example, the carousel and extractor are roughly comparable in complexity. However, the carousel controller returns an ll-character status string, whereas the extractor controller returns a 36-character status string.

In the UofA CIM labs, C and BASIC com- pilers have been used for programming. Although BASIC is criticized for its technical limitations, there have been major advances in the utility of this language for industrial automation. The strengths and weaknesses of BASIC were outlined in a paper presented by UofA researchers at the 1987 Spring Annual Conference of IIE [9].

Compiled BASIC continues to grow in popularity for applications in indus- trial automation, due to the availabil- ity of BASIC programmers, at reasonably low cost. Recent BASIC compilers pro- vide more modular, structured program- ming facilities and more extensive sup- port for event trapping [3]. The executive-level software for the auto- matic guided vehicle was developed, by the AGV manufacturer, in compiled BASIC. A UofA graduate student, famil- iar with BASIC, modified the source code for handling infrared data commu- nications with the host microcomputer.

Additionally, the BASIC command and function sets include good facilities for management of serial ports. One disadvantage is the limited number of addressable serial ports. One recent BASIC compiler limits the number of serial ports to two [3]. Compiled BASIC communications software has been developed in the CIM labs, to integrate the carousel and extractor with a com- mon host microcomputer [I0].

The C language is becoming popular for real-time control applications on microcomputers, and is generally pre- ferred, by professional programmers, over BASIC. However, C is relatively difficult to learn, compared to BASIC, and the cost of software development is

Landers et al. : CIM networking 235

accordingly higher. C software devel- oped in the UofA CIM lab has utilized a powerful C compiler [2] and toolbox communications routines (supporting up to two communications ports) [ii]. This work will be reported in a paper to be presented at the 1988 Spring IIE Conference.

CONCLUSIONS

This paper has described the strategy and accomplishments for a program to prepare industrial engineering students for the IE role in CIM networking. The CIM laboratories in the IE department at the University of Arkansas are cen- tral to the strategy, in that the hard- ware and software resources provide knowledge and experiences that estab- lish a firm foundation of technical competence. This technical preparation strengthens the IE's leadership role, and thereby facilitates accomplishment of the primary industrial engineering objective: continual improvement in manufacturing competitiveness.

In CIM implementation, there are numer- ous technical details which the IE may delegate to hardware and software spe- cialists. The IE must have the techni- cal expertise to effectively delegate and coordinate tasks and to garner the respect of the specialists involved in the CIM implementation project.

The industrial engineer also has an important role in assuring that CIM, including network communications, advances the productivity and competi- tiveness of the manufacturing organiza- tion. This role requires knowledge of the traditional and technologically advanced alternatives. The IE must apply risk assessment, economic analy- sis and project management to assure that the CIM implementation minimizes disruption of operations and results in productivity improvements justifying the costs.

Industry standardization tends to ref- ine and mature technology, reduce risks and promote efficiency. Therefore, the IE should be active in the movement toward standardization of network com- munications, including the ISO/OSI (International Standards Organization / Open Systems Interconnection) reference model. However, there are many oppor- tunities for standardization in the basic aspects of serial communications. The standardization needs include:

i. Cable configurations and pin assignments,

2. Electrical signal levels, 3. Protocols, 4. Handshaking, 5. Message formats, and 6. Programming.

Future research, development and instruction in the UofA CIM labs and the industrial engineering curriculum will stress these objectives.

[i]

[2]

[3]

[4]

[5]

[6]

[7]

[8]

[9]

[io]

[11]

REFERENCES

Asfahl, C. Ray. Robots and Manu- facturing Automation, Wiley, 1985.

Lattice C Compiler for MS-DOS, Lattice, Incorporated, 1986.

Microsoft QuickBASIC, Microsoft Corporation, 1987.

EIA Standard RS-232-C, Electron- ics Industry Association.

Kennedy, Ray A. "Using the RS-232-C as an Instrument Interface," Hand- shake (Fall 1987), pp. 21-27.

EIA Standard RS-449, Electronics Industry Association.

Seyer, Martin D. RS-232 Made Easy, Prentice-Hall, 1984.

Friend, George F. et. al. Under- standing Data Communications, Texas Instruments and Howard W. Sams, 1984.

Langston, Marcus C., et. al. "Microcomputer Control and Anima- tion of Materials Handling Sys- tems," 1987 International Indus- trial Engineering Conference Pro- ceedings, pp. 278-284.

Stanley, Donald A. "Analysis of Automated Extraction for a Storage Retrieval Carousel," Master's The- sis, Department of Industrial Engineering, University of Arkan- sas, 1987.

Essential Communications Library, Essential Software, Inc., 1986.

BIOGRAPHIES

Dr. Thomas L. Landers, Assistant Pro- fessor of Industrial Engineering, Uni- versity of Arkansas, Fayetteville. Dr. Landers is involved in teaching and research in automated material handling and the reliability of CIM systems. He has over ten years of experience in reliability engineering, manufacturing management and consulting. He is a registered engineer in Arkansas and Texas, Senior Member of IIE and CPIM in APICS.

Donald A. Stanley, Manufacturing Engi- neer, General Dynamics, Camden, AR. Mr. Stanley is involved in process automation in the aerospace industry, and is currently working on automated inspection of solder joints in elec- tronics assembly. He received B.S. and M.S. degrees in IE from the UofA.

Walter A. Whitt, Industrial Engineer, Intel Corporation, Albuquerque, NM. Mr. Whitt is an IE involved in process automation, particularly automated material handling, in electronics fabrication. He received B.S. and M.S. degrees in IE from the UofA.