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IDENTIFICATION AND CONTROL OF UNKNOWN MULTIVARIABLE SYSTEMS WITH DEAD TIME
Abstract
Research in the adaptive control of unknown or partially known system spans the last 25 years. Sound theories are being developed to lay a solid foundation in this field. Several approaches can be used to realize the adaptive control systems. Self-tuning regulator and model reference approaches have been used successfully in some applications. During the last decade long standing stability problems have been resolved and progress has been made in convergence theory. Major advances in microprocessor technology make it feasible to implement the adaptive control algorithms on-line. Several practical systems are non-linear. The non-linearity may be due to the inherent nature of the process, saturation of the equipment, etc. Measurements also may be non-linear. Due to the inadequacy of non-linear system theory and knowledge about the process, it is many times not possible to design a suitable controller to meet the performance requirement. A logical way to approach the design is to approximate the system by a suitable linear model and represent all the non-linearities as stochastic disturbances. The self-tuning regulator utilizes linear system theory, stochastic system theory and optimal control theory. Many industrial processes have dead time (transport delay) between the inputs and the outputs. Self-tuners are designed on the basis of known model order and dead time. Wrong assumptions may lead to stability problems. Further, these regulators are more sensitive to dead time than to the model order. If the dead times are varying they have to be identified on-line. A recursive procedure has been developed in this dissertation to identify the parameters and dead time simultaneously on-line. Explicit identification of the above quantities is then used to design a controller using known design procedures. As an example these procedures are applied to a chemical absorber-desorber plant. Illustrative results are presented and discussed. In some instances these self-tuners may not be satisfactory due to the assumed validity of the certainty equivalent principle. Non-linear systems violate this principle. Additional control signals like probing and caution may be needed. These are discussed with reference to a simple example. Finally, general conclusions drawn from this study are presented and some areas are pointed out in which additional research is required.
Subject Area
Systems design
Recommended Citation
GURUBASAVARAJ, K. H, "IDENTIFICATION AND CONTROL OF UNKNOWN MULTIVARIABLE SYSTEMS WITH DEAD TIME" (1983). ETD collection for University of Nebraska-Lincoln. AAI8328172.
https://digitalcommons.unl.edu/dissertations/AAI8328172