Practical Process Control Research Articles

A Decentralized Control System for a Distillation Column

The present paper deale with the completely decentralized control of quality-parameters of a distillation column as a part of a distillation system in oil-industry by local twovariable PI-controllers. Here the reduced cost of small microprocessorcontrollers provides the technological force for developing a suitable approsch for designing such local PI-controllers with on-line-tuning properties for setpointcontrol of the multivariable plant under study. From the point of view of process control practice the plant is treated as partly unknown. At first using only structural model knowledge a structural decomposition into a 3-channel system is accomplished. The 3 local PI-controllers are tuned on-line in a sequential manner by a straight forward method using stesdy-state gains obtained from simple experiments applied to the plant. Some selected results sre summarized. The method seems to be an attractive alternative of more sophisticated multivariable control of distillation columns and similar complex plants.

Process Control on Way To Becoming Process Management

Process control technology is undergoing change. In this article, the second in a three-part series to conclude next month, C&EN examines how process control in practice is changing conceptually to...

A theoretical basis for the representation of on-line computer systems to naive users

Computer science has now recognized that in holistic systems design the designer must include not just the terminal, but also the user within the boundaries of the system. Users, particularly if they are computer naive, require a conceptual model of the computer system so that they can form a clear idea of what the system is doing and what it can do. This model is communicated to the user by the representation of the system which appears at his terminal. Existing techniques for the design of terminal dialogues do not include methods for representing conceptual models, so that new techniques are needed. If these are to be reliable they must be based in theory rather than just the intuitions of individual designers. This article examines current theory and practice in psychology, computer sicence and process control, and seeks a consensus for the design of representations suitable for describing the operations of on-line computer systems via their terminal interfaces.

IMPLEMENTATION OF STATISTICAL PROCESS CONTROL (SPC) FOR MANUFACTURING PERFORMANCE IMPROVEMENT

This paper intends to combine the Hourly Data System (HDS) and Statistical Process Control (SPC) practices to improve manufacturing performances in manufacturing companies. The focus of this work is to find out the frequencies and time duration of machine breakdowns as well as the major causes of breakdowns affecting productivity. Total quality management (TQM) was introduced to improve continually the products or services to increase the customer satisfaction level. SPC is an important tool of TQM. Again HDS is the real time view of production floor of any manufacturing industry. In usual practice, SPC is used as quality control tool. However in this research SPC is used to increase total output identifying major loss times from various machine breakdowns using HDS. Successful implementation of the recommendations of this paper can significantly improve the manufacturing performance of a manufacturing environment. Keywords: Total Quality management (TQM), Statistical Process Control (SPC), Hourly Data System (HDS) doi: 10.3329/jme.v40i1.3466 Journal of Mechanical Engineering, Vol. ME40, No. 1, June 2009 15-21

Control-System Behavior Expressed as a Deviation Ratio

Abstract In order to bridge the gap between process-control practice and modern control theory, an attempt is made to reduce this theory to its bare essentials. A simple picture is drawn of what control does and how it does it, use being made of the familiar concepts of resonance and damping. Thus a theoretical background is provided for commonsense judgments on control quality and controller settings. The picture given is applicable to both feedback and feedforward control.