Fuzzy control and its application to a pH process

In the chemical industry, the control of pH is a well-known problem that presents difficulties due to the large variations in its process dynamics and the static nonlinearity between pH and concentration. pH control requires the application of advanced control techniques such as linear or nonlinear adaptive control methods. Unfortunately, adaptive controllers rely on a mathematical model of the process being controlled, the parameters being determined or modified in real time. Because of its characteristics, the pH control process is extremely difficult to model accurately. Fuzzy logic, which is derived from Zadeh's theory of fuzzy sets and algorithms, provides an effective means of capturing the approximate, inexact nature of the physical world. It can be used to convert a linguistic control strategy based on expert knowledge, into an automatic control strategy to control a system in the absence of an exact mathematical model. The work described in this thesis sets out to investigate the suitability of fuzzy techniques for the control of pH within a continuous flow titration process. Initially, a simple fuzzy development system was designed and used to produce an experimental fuzzy control program. A detailed study was then performed on the relationship between fuzzy decision table scaling factors and the control constants of a digital PI controller. Equation derived from this study were then confirmed experimentally using an analogue simulation of a first order plant. As a result of this work a novel method of tuning a fuzzy controller by adjusting its scaling factors, was derived. This technique was then used for the remainder of the work described in this thesis. The findings of the simulation studies were confirmed by an extensive series of experiments using a pH process pilot plant. The performance of the tunable fuzzy controller was compared with that of a conventional PI controller in response to step change in the set-point, at a number of pH levels. The results showed not only that the fuzzy controller could be easily adjusted to provided a wide range of operating characteristics, but also that the fuzzy controller was much better at controlling the highly non-linear pH process, than a conventional digital PI controller. The fuzzy controller achieved a shorter settling time, produced less over-shoot, and was less affected by contamination than the digital PI controller. One of the most important characteristics of the tunable fuzzy controller is its ability to implement a wide variety of control mechanisms simply by modifying one or two control variables. Thus the controller can be made to behave in a manner similar to that of a conventional PI controller, or with different parameter values, can imitate other forms of controller. One such mode of operation uses sliding mode control, with the fuzzy decision table main diagonal being used as the variable structure system (VSS) switching line. A theoretical explanation of this behavior, and its boundary conditions, are given within the text. While the work described within this thesis has concentrated on the use of fuzzy techniques in the control of continuous flow pH plants, the flexibility of the fuzzy control strategy described here, make it of interest in other areas. It is likely to be particularly useful in situations where high degrees of non-linearity make more conventional control methods ineffective

A methodology for the selection of a paradigm of reasoning under uncertainty in expert system development

The aim of this thesis is to develop a methodology for the selection of a paradigm of reasoning under uncertainty for the expert system developer. This is important since practical information on how to select a paradigm of reasoning under uncertainty is not generally available. The thesis explores the role of uncertainty in an expert system and considers the process of reasoning under uncertainty. The possible sources of uncertainty are investigated and prove to be crucial to some aspects of the methodology. A variety of Uncertainty Management Techniques (UMTs) are considered, including numeric, symbolic and hybrid methods. Considerably more information is found in the literature on numeric methods, than the latter two. Methods that have been proposed for comparing UMTs are studied and comparisons reported in the literature are summarised. Again this concentrates on numeric methods, since there is more literature available. The requirements of a methodology for the selection of a UMT are considered. A manual approach to the selection process is developed. The possibility of extending the boundaries of knowledge stored in the expert system by including meta-data to describe the handling of uncertainty in an expert system is then considered. This is followed by suggestions taken from the literature for automating the process of selection. Finally consideration is given to whether the objectives of the research have been met and recommendations are made for the next stage in researching a methodology for the selection of a paradigm of reasoning under uncertainty in expert system development

Time and Chemical Change: The Development of Temporal Concepts in Chemistry with Special Reference to the Work of Augustus Vernon Harcourt.

The concept of time is an important one in the History of Philosophy and of Science. But ideas concerning time and its related phenomenon, that of change, are inherently complex. The study of chemistry involves an understanding of the process of change, a time—dependent function. In fact, the development of temporal ideas in chemistry evolved very late in its theory, around 1850, when Ludwig Wilhelmy first carried out measurements of chemical rate and Alexander Williamson, in the same year, published his ideas on the dynamics of chemistry. In chemistry, the concept of time is to be found most clearly established in the discipline of reaction kinetics. In its development, this has been bound to the idea of the course of chemical change, as a phenomenon quite distinct from the study of the products of chemical reaction, or chemical composition, on which many of the early chemists were so deeply engrossed. The establishment of time into chemical theory was due largely to the ideas and work of Guldberg and Waage in Norway, and Harcourt and Esson at Oxford. Harcourt recognised at a very early stage in his studies that what chemists had always neglected was the close observation of the actual course of chemical change, of the time factor involved in these changes. The foundations of these ideas were laid at the very beginning Harcourt's long career at Oxford, but he was to spend the subsequent fifty years perfecting his techniques. Perhaps because of the late development of their time awareness, some philosophers of science have come to believe n that chemists desired, somehow, to 'eliminate time' from chemical theory. The present work is an attempt to trace the evolution of temporal ideas in chemistry and the eventual recognition of the course of chemical change as a dynamic phenomenon. It also discusses the role of philosophy in the development of chemical theories, a development which is bound, like all events, to the element of time

National Aeronautics and Space Administration (NASA)/American Society for Engineering Education (ASEE) Summer Faculty Fellowship Program: 1996

The objectives of the program, which began nationally in 1964 and at JSC in 1965 are to (1) further the professional knowledge qualified engineering and science faculty members, (2) stimulate an exchange of ideas between participants and NASA, (3) and refresh the research and teaching activities of participants' institutions, and (4) contribute to the research objectives of NASA centers. Each faculty fellow spent at least 10 weeks at JSC engaged in a research project in collaboration with a NASA JSC colleague

Interaction of aerodynamic noise with laminar boundary layers in supersonic wind tunnels

The interaction between incoming aerodynamic noise and the supersonic laminar boundary layer is studied. The noise field is modeled as a Mach wave radiation field consisting of discrete waves emanating from coherent turbulent entities moving downstream within the supersonic turbulent boundary layer. The individual disturbances are likened to miniature sonic booms and the laminar boundary layer is staffed by the waves as the sources move downstream. The mean, autocorrelation, and power spectral density of the field are expressed in terms of the wave shapes and their average arrival rates. Some consideration is given to the possible appreciable thickness of the weak shock fronts. The emphasis in the interaction analysis is on the behavior of the shocklets in the noise field. The shocklets are shown to be focused by the laminar boundary layer in its outer region. Borrowing wave propagation terminology, this region is termed the caustic region. Using scaling laws from sonic boom work, focus factors at the caustic are estimated to vary from 2 to 6 for incoming shocklet strengths of 1 to .01 percent of the free stream pressure level. The situation regarding experimental evidence of the caustic region is reviewed

Higher dimensional theories in physics, following the Kaluza model of unification

This thesis traces the origins and evolution of higher dimensional models in physics, with particular reference to the five-dimensional Kaluza-Klein unification. It includes the motivation needed, and the increasing status and significance of the multidimensional description of reality for the 1990's. The differing conceptualisations are analysed, from the mathematical, via Kasner's embedding dimensions and Schrodinger's waves, to the high status of Kaluza-Klein dimensions in physics today. This includes the use of models, and the metaphysical interpretations needed to translate the mathematics. The main area of original research is the unpublished manuscripts and letters of Theodor Kaiuza, some Einstein letters, further memoirs from his son Theodor Kaiuza Junior and from some of his original students. Unpublished material from Helsinki concerns the Finnish physicist Nordstrom, the real originator of the idea that 'forces' in 4-dimensional spacetime might arise from gravity in higher dimensions. The work of the Swedish physicist Oskar Klein and the reactions of de Broglie and Einstein initiated the Kaluza-Klein connection which is traced through fifty years of neglect to its re-entry into mainstream physics. The cosmological significance and conceptualisation through analogue models is charted by personal correspondence with key scientists across a range of theoretical physics, involving the use of aesthetic criteria where there is no direct physical verification. Qualitative models implicitly indicating multidimensions are identified in the paradoxes and enigmas of existing physics, in Quantum Mechanics and the singularities in General Relativity. The Kaluza-Klein philosophy brings this wide range of models together in the late 1980's via supergravity, superstrings and supermanifolds. This new multidimensional paradigm wave is seen to produce a coherent and consistent metaphysics, a new perspective on reality. It may also have immense potential significance for philosophy and theology. The thesis concludes with the reality question, "Are we a four-dimensional projection of a deeper reality of many, even infinite, dimensions?

The conceptual development of population and variation as foundations of econometric analysis

Economics is a time-bound science. The analytical tools of statistical description and inference, however, were first developed for static comparisons of differences rather than formulation of processes of change. This thesis offers an historical perspective on the dichotomy of logical variation and temporal variation. I examine the interaction of statistical technique with the needs and concepts generated in the study of political arithmetic, observational errors. social physics, natural selection and economic motion. Through these interactions the concept of statistical population changed. There was a shift in emphasis from the assumption of equivalence of constituents and from the mean as a manifestation of truth and divine order to the assumption of deviation and the mean as a typical value in motion. In Darwin's theory of natural selection, differences within a population were the source of evolutionary variation of a species. The quantitative techniques of correlation and regreSSion were developed to test theories of evolution and inheritance. The problems of reconciling logical variation and temporal variation were most prominent in the application of correlation and regression to economic time series data. Differencing observations and calculations of deviations from moving averages were suggested as solutions. The most significant steps were taken in the the formulation of stochastic processes and in the development of errors-in-equations models. With the latter. the statistical properties of residuals rather than of series of observations became important. In building on some of these historical examples I suggest that acknowledgement of complementary statistical populations may enable us to further reconcile logical and temporal variations

Kenyon College Catalog 2013-2014

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