Advanced Human Integrated Assembly System

Paavo Voho Technical Research Centre of Finland, Manufacturing Technology

P . 0 . b ~ 1702, FIN-02044 VTT, Finland

Jyrki J. J. Kasvi . Helsinki University of Technology, Laboratory of Industrial Psychology

Otakaari 4A (Ko234), FIN-02150 ESP, Finland

Abstract: The concept of flexible production has been around for several years now. But why are there 80 few really flexible production systems around? The prob- lem is that flexibility haa usually beem seen either as a technical or M a human fadors h e . It is neither, but both. This paper discussee nome queetiona related to reducing the time, risk and complexity of flexible production line design and cutting produd lead time to market by providing on-the-job information support on the shop floor.

1. INTRODUCTION

Dynamic product and production development requires more and more resources being dedicated to greater adaptability of production systems and organizations. Traditional production organizations have to be revised as the world grows smaller and the global marketplace opens its borders. Success means that you have to mas- ter several factors simuItaneously. Customers are not only interested in price anymore. There must be confi- dence in your quality, delivery times and flexibility in volumes and mixtures.

Success rewards companies that are able to readily react to changes in their market environment. To build this ability, the companies must simplify their struc- tures and take the people working on the shop floor into consideration. They are the ones that chum out the money and the last ones to have modern information tools to facilitate their work (fig. 1).

Factories have to become open systems, consisting of self orienting work groups, groups that are able to iden- tify and reach their goals, design and control their works autonomously. In such an organization, people in pro- duction become both suppliers and customers.

There is a need for an advanced concept which inte- grates an up-to-date assembly system and on-the-job information support into an open, adaptable total sys- tem - the FPS System.

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Figure 1. In many organizations it is the people in production who get

their computer systems last.

2. FLEXIBILITY THROUGH MODULARITY

The concept of a flexible production system (the FPS Assembly System Concept) has been developed for the assembly of lightweight products. The aim is to combine flexible material handling with modular work stations that can be manual or automatic or something in be- tween. The resulting hybrid production system is based on the needs of production instead of technical inertia.

The concept is based on standard work station mod- ules that can be combined in different ways to construct the desired production system. An intelligent conveyor system may be used to connect these stations, making it easy to modify or design totally new production lines.

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Figure 2. The FPS System consists of modular elements.

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Figure 3. The structure of the FPS Assembly System.

The concept of a pallet with memory supports both flexible material flow and decentralized control as the product information is embedded into the pallet. It is easy to modify a production line when each of the work t tation modules is completely self-contained. The con- vt ying system, control electronics, software, sensors, acti.iators, pallet positioning mechanisms, all are inte- gratml into modules that can, be readily changed. This modrilarity allows the user to automate the assembly systexii in stages, one work station at a time, without halting the production.

The FPS Assembly System equipment consists of components with clearly defined connections (Fig. 2 and 3). Them components include:

Function modules. Every module performs inde- pendent operations (work station, conveyor, etc.). The user modifies the line by changing or adding these modules. Basic modules. These mechanical basic solutions include for example conveyor crossings and stoppers. Different basic modules and their variants allow us to construct different operation modules, based on the special requirements of the user. Structure modules. These are single components (frame profiles, etc.) of the material handling system, used as the basis for the mechanics.

The FPS - Assembly System uses pallets for product transport. Each function module has an independent decentralized control unit, and they communicate by storing information into the pallet (intelligent pallet). The data can be presented, for example, as a visual binary code, or even with simple mechanical devices or magnetic escort memories. ,This way we may include both automated and manual work stations to the line (Fig. 4). Operatora can read the visual code and accom- plish their tasks. In addition, the information includes

destination data for conveyors and data on individual products and work sequences.

The possible automation of the assembly system will take place through hybrid lines, where both automatic and manual work stations coexist. Manual stations are still preferred when dexterity and multiple senses of a human operator best serve the application. The change to automation can be done later, if deemed necessary.

Figum4.Anossemblylinewith both manualandautomakdworkstations.

In he line here is a double-level two belt conveyor.

The components of an automated work station are modular. The main parts of an automated FPS work station include (F’ig. 5):

A buffer stock for components to be assembled a material feeder for the buffer stock a robot or a manipulator with grippers a connection unit for the pallet circulation conveyor (stopping and positioning of the pallet).

Figure 5. The use of escort memory in he FPS information System.

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There are two kinds of buffer stocks: buffer stocks of components to be assembled and buffers of products. By buffering the products it is possible to reach the handling time flexibility required in the work stations. With non- synchronous transfer utilizing buffers, every station operates independently and a station can be stopped for brief intervals without holding the rest of the system.

3. REQUIREMENTS FOR THE FPS - INFORMATION SYSTEM

The new kind of information flow integration ensures mall batch sizes and fast product changes. The ZTS - Information System acts as a link to other information systems of the factory and supports the FPS - M&le Control system.

The information system must support simultaneous planning; product design, purchasing and production. These actions must have a common information base for products, components etc. Designers need tools to simulate the effects of alternatives (production costs, throughtput time, quality, start-up phase etc.). In addi- tion, the information system must support scheduling of orders for production plans. It must not hinder inde- pendent control of production, though. That would have diverse effects on delivery accuracy, quality, stocks, etc.

The information system must support rapid intro- duction of new products. This means fast component and materials inventorying and automatic generation of new programs for loading, robots, production lines, etc.; rapid routing of new products in production and tools to deliver on-the-job training.

In addition to training, production staff need real time information support, delivered directly into their work stations, to be able to cope with these rapid changes in production. This requires some kind of a database including product and task information and tools to browse this database easily and efficiently.

4. FLEXIBLE PRODUCTION REQUIRES FLEXIBLE SUPPORT ,

Even the most flexible production system is for naught if the people using it are inflexible. Requirements for professional expertise increase with the complexity of the products and the delegation of managerial tasks to the shop floor. Thus the employees need to be flexible, multi-skilled and encourag4 to 'think'.

Figure 6. HOTS system inferads with the rest of the information system.

Brave new production requires brave new tools to provide information support for the shop-floor and to enhance communication between parties involved with production. Even the best training may prove inade- quate when production reacts constantly to market pres- sures. Instead of printed, i.e. remote and outdated, work instructions we need real time information support that is delivered directly into individual work stations (Kasvi 1993).

To study the possibilities and limits of interactive task support on the shop floor, we have built a prototype FPS compatible information upp port system that pro- vides information required for autonomous and flexible production without extanmve training costa. At the mo- ment this HOTS System' is in pilot test stage and the prototype is in use in the Helsinki ABB Industry plant producing DC converters.

This HOTS system has been designed to help the shop floor staff to accommodate to rapid changes in production and to utilize the principles of continuous improvement: It allows people to update its information contents as tasks and working methods evolve through innovation and experience.

In addition to support, the system is utilizable as a training tool. This means embedding effective didactic principles into the system to ensure deep and profound learning. Traditionally, computer based training sys- tems have often proven inflexible and their didactic structures outdated (Kasvi 1991).

Finally, the system may be used as a quality manage- ment tool. Instead of laborious printed quality standard files, the relevant information is stored in the HOTS system where i t is easily updated to recent develop- ments. Certifying these numerous changea in a satisfac-

1 ) The background of ihis acronym is a bit complicated. HOTS stands for a HIPS- On-fhe-job Support System, when, HIPS means a Human lntegmfsd Producfion System for Assembly, a related realization of the FPS concept.

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tory manner may become a problem and requires some thought to ensure the fluency of the required certifica- tion procedures.

The prototype HOTS system has been audited for work instruction delivery use in the IS09001 certificate issued for the Helsinki ABB Industry DC converter production unit in May 1994.

The task has to be analyzed and this analysis turned into a libretto for the hyperdocument (fig. 8). This may prove a much more challenging task than using the software. In addition, the still video pictures have to be taken and imported before the authoring starts. These pictures can be updated later, but there should be some still video footage present when the authoring starts.

4.1 The new concept of authoring We need good training and support software, i.e., we

need good authoring software to make good training and support software. But what is good authoring software made of? First, it has to be so easy to use that anybody can develop good training and support software with it (fig. '7). Second, it should be so efficient that it takes the same time to author computer based material as to prepare paper based material. Finally, the software has to be up to date with advances in didactic and user interface psychology.

Figure 7. A modern authoring system can be opemted by a subpd task

specialist without special knowledge about computers.

The author using the HOTS system to.create infor- mation support hyperdocumente inputs information in two stages. First, he lists the topics to be included: Subtasks, stages of these subtasks, tools, parts and ma- terials, quality factors and a general description of the product. On the basis of these lists the system creates page templates with names and related still video pic- tures. Finally, the author completes each template with text, digitized speech and additional pictures.

It has to be noted, though, that there are several things to be done before running the HOTS software.

Figure 8. Using the HOTS software is only the last stage of authoring.

The reader using the HOTS software to access ready made hypermedia documents can also edit certain parts of them. There may be details he wants clarified, errors he wants to correct and new ideas waiting to be added. Thus, authoring these training and support documents is a continuous process, enabling us to keep them up to date without delays.

4.2 Usability is paramount The author users of the HOTS system can be sup-

posed to have some experience in computer use, but the reader users are completely another matter. For exam- ple, our first test user instinctively held the mouse upside down in her hand. It was her first time face to screen with a computer.

As computerized information tools are implemented on the shop-floor, the usability of these tools becomes paramount. Computers are traditionally associated with white+ollar tasks but now the application domain is expanding to blue-collar work too. These new end users have usually no previous experience in computers but a great potential for resistance, if their initial experiences are negative.

Our studies with HOTS have shown that even the most inexperienced computer user may be able to use the system if the user interface has been honed with care. For this purpose we have excluded all but one mouse button and all double-clicks. In addition, all reader functions are available from the control buttons. Using a menu is much too complex an operation requir- ing experience and sensomotoric finesse.

Usability is an issue both when it comes to accessing and maintaining the information content of the infor- mation support system. As the most relevant informa- tion concerning the actual production is created on the

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shop floor, it should be fed into the system there too. In addition to using the system to support their work, the employees maintain its information contents too.

Figure 9. Testing the usability of h e HOTS system in Helsinki ABB plant.

Note the computer workstation present on the work station module. This

usability testing has been conducted by combining video tapes and log

file analpis. (See also NKol8 Gomoll 1990.)

5. HIPS - ON-THE-JOB SUPPORT SYSTEM

5.1 Small is beautiful To be economically and practically sound, an infor-

mation support system has to be based on readily avail- able standard hardware and software. Task specific training systems are no longer viable as the information tools have to be integrated with existingcomputer based production control systems already present on the shop floor. "his usually means technology often considered outdated by software developers.

The HOTS system is based on standard PGcompat- ible hardware. The hardware environment consists of a 386-compatible computer with a 256 color VGA display unit (640x480 pixels), a sound card to digitize and play- back speech and means to input still video pictures. We have used Canon ION still video cameras. The user interface conforms to Windows standard layout. In ad- dition to. Windows, the system requires ToolBook 1.61 or later to work. When HOTS is used For reading hyper- documents, the runtime version on ToolBook is enough, but for authoring it does not suffice.

Still video pictures and digitized speech require a relatively large amount of disk space - five to fifteen megabytes of unstacked hard disk space for each hyper- document2. Therefore it is practical to have the com- puter workstations in each FPS work station module to be connected into a local area network. This way picture and sound files can be stored and maintained in a single file server. CD-ROM technology will be a boon, though.

6 9 Hypermedia and mental models The principles of hypertext allow us to create data

structures that mimic the mental models that we want to transfer to our readers. By adding various medias, text for information, still video pictures for demonstrations and digitized speech to stress key points, the concept of hypertext expands into hypermedia

The use of hypermedia as a medium has caused some problems, too. The original navigation buttons of HOTS were derived from the mftware designer's mental model of an assembly task. This was considerably different from the mental models of the the shop floor employees, though. When encountered, the problem was resolved by analyzing the end users' mental model and recon- figuring the navigation buttons to reflect it.

Getting lost in information is a major problem with hypermedia (Nielsen 1991). An educational hyperdocu- ment has to enable readers to find their way around and to locate the information they need. In caw of HOTS this is realized with a color coded route through the hyper- documents and their hierarchical treelike structure in- stead of the traditional net structure. Further work on the subject is still required, though, as our usability tests have shown that it is possible to skip large segments of the HOTS hyperdocuments without the reader even noticing it.

2) Further data compression methods am available for both bitmaps and sound files, but they have not yet been applied for HOTS. If o need o r b s to enhance thedisploy resolution, it may become nscesxrrykapplyforexamplefm~l compressionforh bitmapfilesto keepihe hyperdocurnenis manageable.

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The conflict of control over hypermedia between trainee and software can be problematic. It can endanger learning results. An inexperienced trainee does not nec- essarily know his way around a document that allows free movement h m subject to another. Removing this control is not the answer, because computer controlled training software is less motivating than trainee control- led software (Steinberg 1989). Instead, HOTS guides trainees with color coded navigation buttons (fig. 10).

Another problem has arisen from the fluctuating nature of modern production. It has been clear from the beginning that the information content of the informa- tion support system has to be easily updateable. It was surprising, though, to notice that major revisions can be made on a weekly basis to the whole product line. These disturbing results were obtained from a case study con- ducted on a production site still under development. But it is under these conditions when the most desperate need for training and support arises.

REFERENCES

Kaavi, J.J.J. (1991) Tietokoneavusteinen tyonopetus. Espoo: TKK Offset. (In Finnish) Kssvi, J.J.J. (1993) Tietokoneavueteinen tyonopetus- jiirjeatelmii. Masters' Thesis, Helsinki University of Technology, h l a n d . (In Finnish) Nicol, A & Gomoll, K, (1990) User Observation. Guidelines for Apple Developers. Apple Human Inter- face Notes #1, January 1990. NielseJn, J. (1991) Hypertext and Hypermedia. Aca- demic Press. San Diego. Steinberg, E. (1989) Cognition and h e r Control - A Literature Review, 1977-1988. Journal of Computer- Eked Instruction 16,4,117- 121.

AcLnowl-t.: The authors would like to thank the staff of the ABB Industry Helsinki plant for their support. The devulopment of HOTS system

has been funded by Technology Development Centre, Finland.

Figure 10. A sompk screen of a hyperdocument created with HOTS. The still video pictures and texts are instantly available, but speech has to be

activated by pressing a button. This may change in later versions.

6. CONCLUSIONS

Flexible production is not just an 'is" that can be applied without revising the whole sosiotechnical pro- duction system. New tools are required to reap the benefits of new production philosophies. We have taken step to specify and realize some of these tools, like the cloncept of a modular work station, an intelligent pallet and an on-the-job information support system. But there is still a lot of work do be done before we know, whether they are enough or not.

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