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Dead-Time Compensation and Performance Monitoring in Process Control

Ingimundarson, Ari LU (2003) In PhD Theses TFRT-1064.
Abstract (Swedish)
Popular Abstract in Swedish

Avhandlingen består av två delar. Den första delen behandlar reglering av processer med lång dödtid. Avhandlingen ger förslag på hur regulatorer för dessa processer ska dimensioneras och jämför sedan prestanda hos dessa regulatorer med vanliga PID-regulatorer.



Avhandlingens andra del handlar om metoder för automatisk övervakning av reglerkretsar i processindustrin. Två nya metoder presenteras. Båda metoderna är testade i pappersindustrin. Dessa test visar att metoderna fungerar bra och upptäcker när reglerkretsar inte fungerar som de ska.
Abstract
The thesis contains two parts, dead-time compensation and performance monitoring. The first part on dead-time compensation is about robust tuning procedures for dead-time compensating controllers (DTC). Both stable and integrating processes are considered. Simple experiments are performed to obtain process models as well as bounds on the allowable bandwidth for stability. The DTCs used have few parameters with clear physical interpretation so that manual tuning is possible.



In the second part on dead-time compensation the performance of PID controllers is compared to the performance of DTCs. The aim is to answer the question: ``When can a simple dead-time compensator be expected to perform better than a PID?''. The... (More)
The thesis contains two parts, dead-time compensation and performance monitoring. The first part on dead-time compensation is about robust tuning procedures for dead-time compensating controllers (DTC). Both stable and integrating processes are considered. Simple experiments are performed to obtain process models as well as bounds on the allowable bandwidth for stability. The DTCs used have few parameters with clear physical interpretation so that manual tuning is possible.



In the second part on dead-time compensation the performance of PID controllers is compared to the performance of DTCs. The aim is to answer the question: ``When can a simple dead-time compensator be expected to perform better than a PID?''. The performance criterion used is the integrated absolute error (IAE). It is compared for PI and PID controllers and a simple dead-time compensator (DTC) when a step load disturbance is applied at the plant input.



The topic of the second part of the thesis is performance monitoring of lambda-tuned feedback controllers. A lambda tuned loop is a loop with an one-degree-of freedom controller whose set point response is of first order plus dead time. Lambda is the time constant of the set-point response. For these loops a non intrusive performance monitoring methods is described which is thought to be a first indicator of bad performance after which existing diagnosis algorithms could be applied. For online implementation in distributed control systems a simple recursive algorithm to estimate the index is presented. All parameters of the monitoring method are set by using the lambda tuning. The method applies equally to stochastic or deterministic disturbances.



Finally an algorithm to estimate a synthetic gradient of a quadratic cost function is presented. It is demonstrated that the gradient can provide valuable information for maintenance of controllers as the gradient gives information about the disturbances affecting the loop. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Professor Bay Jørgensen, Sten, Denmark
organization
publishing date
type
Thesis
publication status
published
subject
keywords
robotteknik, Automatiska system, reglerteknik, Automation, robotics, control engineering
in
PhD Theses
volume
TFRT-1064
pages
145 pages
publisher
Department of Automatic Control, Lund Institute of Technology (LTH)
defense location
M:B, the M-building, Lund Institute of Technology
defense date
2003-01-31 10:15
ISSN
0280-5316
language
English
LU publication?
yes
id
f2c67a1b-897a-4ed9-9074-1a1ca448644c (old id 20705)
date added to LUP
2007-05-28 11:02:36
date last changed
2018-05-29 10:13:57
@phdthesis{f2c67a1b-897a-4ed9-9074-1a1ca448644c,
  abstract     = {The thesis contains two parts, dead-time compensation and performance monitoring. The first part on dead-time compensation is about robust tuning procedures for dead-time compensating controllers (DTC). Both stable and integrating processes are considered. Simple experiments are performed to obtain process models as well as bounds on the allowable bandwidth for stability. The DTCs used have few parameters with clear physical interpretation so that manual tuning is possible.<br/><br>
<br/><br>
In the second part on dead-time compensation the performance of PID controllers is compared to the performance of DTCs. The aim is to answer the question: ``When can a simple dead-time compensator be expected to perform better than a PID?''. The performance criterion used is the integrated absolute error (IAE). It is compared for PI and PID controllers and a simple dead-time compensator (DTC) when a step load disturbance is applied at the plant input.<br/><br>
<br/><br>
The topic of the second part of the thesis is performance monitoring of lambda-tuned feedback controllers. A lambda tuned loop is a loop with an one-degree-of freedom controller whose set point response is of first order plus dead time. Lambda is the time constant of the set-point response. For these loops a non intrusive performance monitoring methods is described which is thought to be a first indicator of bad performance after which existing diagnosis algorithms could be applied. For online implementation in distributed control systems a simple recursive algorithm to estimate the index is presented. All parameters of the monitoring method are set by using the lambda tuning. The method applies equally to stochastic or deterministic disturbances.<br/><br>
<br/><br>
Finally an algorithm to estimate a synthetic gradient of a quadratic cost function is presented. It is demonstrated that the gradient can provide valuable information for maintenance of controllers as the gradient gives information about the disturbances affecting the loop.},
  author       = {Ingimundarson, Ari},
  issn         = {0280-5316},
  keyword      = {robotteknik,Automatiska system,reglerteknik,Automation,robotics,control engineering},
  language     = {eng},
  pages        = {145},
  publisher    = {Department of Automatic Control, Lund Institute of Technology (LTH)},
  school       = {Lund University},
  series       = {PhD Theses},
  title        = {Dead-Time Compensation and Performance Monitoring in Process Control},
  volume       = {TFRT-1064},
  year         = {2003},
}