Chapter 36
Computer-Based Laboratory for Developing Practical Automated Feedback Control Systems for Batch Polymerizations G. M . Schwab
Downloaded by UNIV OF MINNESOTA on May 12, 2018 | https://pubs.acs.org Publication Date: August 29, 1989 | doi: 10.1021/bk-1989-0404.ch036
Automotive Research Laboratory, The Sherwin-Williams Company, Chicago, IL 60628
In any technical organization, those individuals most knowledgeable about a particular process are seldom those best suited by experience to applying conventional automation tools to that process. In an attempt to allow chemists and engineers expert in the manufacture of coatings polymers to themselves quickly and easily develop automation methods for batch processes without becoming expert programmers, we have designed and built a laboratoryproviding powerful, flexible hardware and software tools for monitoring and controlling a broad range of process experiments. This paper describes how we established criteria for selecting hardware and software, how different kinds of commercial control packages met our criteria, and initial applications of the package selected to routine lab batch preparation, process chemistry experiments, and evaluation of on-line sensors for closed-loop polymer reactor control. Traditionally, most process automation systems have resulted from collaborations among three different groups of people within industrial organizations: 1. Process experts who understand well the chemical engineering details of the process to be automated. 2. Production experts who can best suggest how to actually implement a new process within a manufacturing environment. 3. Computer/control system experts who know how to implement an actual control scheme after a functional specification has been developed i n cooperation with process and production experts. The first two kinds of experts can be considered control system "specifiers"; the third can be considered system "implementers". Many problems with automated control system designs arise from ineffective communication between specifiers and implementers. "Computer people" especially can have great d i f f i c u l t y understanding exactly what those individuals who have spent years learning specific process technologies (and their jargons) really want or need. Process and production experts often do not understand exactly how computer control systems work or what they can and cannot effectively do. For a control project to be assured of success, great emphasis must be placed on a r r i v i n g at a mutually agreed upon optimal (within available resources) specification; once such a specification 0097-6156/89/0404-0469$06.00/0 ο 1989 American Chemical Society
Provder; Computer Applications in Applied Polymer Science II ACS Symposium Series; American Chemical Society: Washington, DC, 1989.
Downloaded by UNIV OF MINNESOTA on May 12, 2018 | https://pubs.acs.org Publication Date: August 29, 1989 | doi: 10.1021/bk-1989-0404.ch036
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COMPUTER APPLICATIONS IN APPLIED POLYMER SCIENCE II
exists, its implementation in hardware and software is usually straightforward. In almost all cases, the individuals with the best process understanding are not those with the most knowledge of automation technology. The quality of the completed system is, therefore, singularly dependent upon the quality of communication between implementers and specifiers. This communication would cease to be a problem i f specifiers could also be implementers. With most automation technology available in the past, this would require chemical engineers and production managers becoming expert programmers, or expert programmers learning a great deal about processes and production management. The primary goal of the work described here is to provide a means whereby specifiers can become implementers; that is, to provide automation systems tools (for the specific case of batch polymerizations) allowing process and production experts to design, implement, maintain, and enhance their own "state-of- the-art" control systems. Our secondary goal is to identify a single set of automation tools applicable directly to lab, pilot plant, and production scales. Such tools w i l l allow us to invent, test, and refine methods in the lab and then very rapidly scale these methods up for production, without needing to consider different control hardware and software. Furthermore, by creating an environment in which everyone - whether engaged in basic or applied research and development or in production - speaks the same automation "language", we can greatly increase productive technology transfer w i t h i n our organization. Our approach to acquiring the tools we require is a simple one and consists of the following steps: 1. Analysis of present and anticipated automation needs. 2. Establishment of needs-based criteria for evaluating candidate hardware, software, and process instruments. 3. Identification and evaluation of candidate hardware, software, and instruments. 4. Purchase, installation, and testing of most-promising candidate software and devices. 5. Development of improved laboratory control methods based on successfully tested software and devices. 6. Rapid transfer of laboratory-developed technology to pilot plant and production. This sequence of steps, shown schematically in Figure 1, can be repeated many times in the course of an automation effort, as new needs arise from emerging product and process technologies and from experimental results. While our specific example is based upon control of batch polymerizations, the procedure we outline could, we feel, be applied equally well to selecting automation tools for many other kinds of processes, particularly those not truly well understood at the outset. This paper briefly describes our progress, to date, along the path we have proposed. NEEDS ANALYSIS Our i n i t i a l intent was not to address specific problems at specific plants, but to draw a broad outline for a laboratory useful in addressing as wide a range of problems as possible. We therefore approached everyone we could identify with expertise or significant interest in polymer batch processing within our company. We toured plants and laboratories to determine where our proposed work could have the greatest cost-effective impact; we then developed detailed criteria for control systems tools intended to address
Provder; Computer Applications in Applied Polymer Science II ACS Symposium Series; American Chemical Society: Washington, DC, 1989.
Automated Feedback Control Systems
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