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Studier av syre-reglering i biologisk avloppsrening

Hansson, Lennart (1982) In MSc Theses
Department of Automatic Control
Abstract
In this report, the dynamics of an aertor of an activated sludge process is studied. Two control strategies for the dissolved oxygen concentration are tested. One contains either a PI-controller or an on-off controller, the other a self-tuning controller. <br><br> There are two key-parameters in the system, KLa, the total oxygen transfer rate, and OUR, the oxygen uptake rate of the microorganisms in the aerator. The parameters are difficult to obtain from direct measurements. An estimator is derived. The estimates will be calculated from the process output, DO-concentration, and from the input signal, the air-flow rate. <br><br>The estimator is also part of a self-tuning controller. Here, the controller works with a minimem variance... (More)
In this report, the dynamics of an aertor of an activated sludge process is studied. Two control strategies for the dissolved oxygen concentration are tested. One contains either a PI-controller or an on-off controller, the other a self-tuning controller. <br><br> There are two key-parameters in the system, KLa, the total oxygen transfer rate, and OUR, the oxygen uptake rate of the microorganisms in the aerator. The parameters are difficult to obtain from direct measurements. An estimator is derived. The estimates will be calculated from the process output, DO-concentration, and from the input signal, the air-flow rate. <br><br>The estimator is also part of a self-tuning controller. Here, the controller works with a minimem variance algorithm. <br><br>The simulations show, that the estimates contain a bias, if the estimation of the two parameters are done at the same time. Different methods are tested to avoid this problem. Even if bias cannot be avoided, the estimator can be used in a self-tuning controller because the total estimation error is close to zero. To obtain unbiased estimates of the two parameters is important in other aerator control schemes. Therefore different approaches have to be taken. <br><br> The simulations show that an acceptable control can be obtained both with a PI-controller and with a self-tuning controller. (Less)
Please use this url to cite or link to this publication:
author
Hansson, Lennart
supervisor
organization
year
type
H3 - Professional qualifications (4 Years - )
subject
publication/series
MSc Theses
report number
TFRT-5284
ISSN
0280-5316
language
Swedish
id
8849885
date added to LUP
2016-03-28 19:47:23
date last changed
2016-03-28 19:47:23
@misc{8849885,
  abstract     = {In this report, the dynamics of an aertor of an activated sludge process is studied. Two control strategies for the dissolved oxygen concentration are tested. One contains either a PI-controller or an on-off controller, the other a self-tuning controller. <br><br> There are two key-parameters in the system, KLa, the total oxygen transfer rate, and OUR, the oxygen uptake rate of the microorganisms in the aerator. The parameters are difficult to obtain from direct measurements. An estimator is derived. The estimates will be calculated from the process output, DO-concentration, and from the input signal, the air-flow rate. <br><br>The estimator is also part of a self-tuning controller. Here, the controller works with a minimem variance algorithm. <br><br>The simulations show, that the estimates contain a bias, if the estimation of the two parameters are done at the same time. Different methods are tested to avoid this problem. Even if bias cannot be avoided, the estimator can be used in a self-tuning controller because the total estimation error is close to zero. To obtain unbiased estimates of the two parameters is important in other aerator control schemes. Therefore different approaches have to be taken. <br><br> The simulations show that an acceptable control can be obtained both with a PI-controller and with a self-tuning controller.},
  author       = {Hansson, Lennart},
  issn         = {0280-5316},
  language     = {swe},
  note         = {Student Paper},
  series       = {MSc Theses},
  title        = {Studier av syre-reglering i biologisk avloppsrening},
  year         = {1982},
}