Substrate Control in Fed-Batch Cultivations Using a Model-Based Modification of a PI-Controller
(1992)- Abstract
- A fedbatch process shows exponential growth under ideal conditions. To obtain good substrate concentration control it is necessary that the regulator can track an exponentially growing feed demand, and standard PI-control has to be supplemented with an estimated basic dosage to get reasonable control. However, an exponentially growing concentration error is impossible to avoid. An I-term could be interpreted as an observer of a constant demand, and we have proposed to replace it with a model-based observer for an exponentially growing demand. In the resulting controller the integrator is replaced by an unstable pole at s = μ, the specific growth rate, and the initial condition of this term is equivalent to the basic dosage part. The... (More)
- A fedbatch process shows exponential growth under ideal conditions. To obtain good substrate concentration control it is necessary that the regulator can track an exponentially growing feed demand, and standard PI-control has to be supplemented with an estimated basic dosage to get reasonable control. However, an exponentially growing concentration error is impossible to avoid. An I-term could be interpreted as an observer of a constant demand, and we have proposed to replace it with a model-based observer for an exponentially growing demand. In the resulting controller the integrator is replaced by an unstable pole at s = μ, the specific growth rate, and the initial condition of this term is equivalent to the basic dosage part. The regulator can now track the exponentially growing feed demand without error. Pseudomonas cepacia was grown on salicylate as sole carbon and energy source. Salicylate is a toxic substrate, so it is important to have good substrate control. On-line measurement of salicylate concentration was carried out using a filtration system from which cell-free permeate was passed to a flow-through spectrophotometer. Introducing more instability into the controller requires attention to the anti-windup features. No such problems were found during the cultivations or in simulations of the effect of conceivable disturbances like pump-failure, air-bubbles in the spectrofotometer, and low oxygen concentration induced growth-rate reduction. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/8517417
- author
- Holst, Olle LU and Hagander, Per LU
- organization
- publishing date
- 1992
- type
- Chapter in Book/Report/Conference proceeding
- publication status
- published
- subject
- host publication
- Proceedings of the 2nd IFAC Symposium on Modelling and Control of Biotechnical Processes
- language
- English
- LU publication?
- yes
- id
- d3f44ff2-ffe2-407c-b006-4c688a99402c (old id 8517417)
- date added to LUP
- 2016-04-04 14:11:16
- date last changed
- 2018-11-21 21:18:49
@inproceedings{d3f44ff2-ffe2-407c-b006-4c688a99402c,
abstract = {{A fedbatch process shows exponential growth under ideal conditions. To obtain good substrate concentration control it is necessary that the regulator can track an exponentially growing feed demand, and standard PI-control has to be supplemented with an estimated basic dosage to get reasonable control. However, an exponentially growing concentration error is impossible to avoid. An I-term could be interpreted as an observer of a constant demand, and we have proposed to replace it with a model-based observer for an exponentially growing demand. In the resulting controller the integrator is replaced by an unstable pole at s = μ, the specific growth rate, and the initial condition of this term is equivalent to the basic dosage part. The regulator can now track the exponentially growing feed demand without error. Pseudomonas cepacia was grown on salicylate as sole carbon and energy source. Salicylate is a toxic substrate, so it is important to have good substrate control. On-line measurement of salicylate concentration was carried out using a filtration system from which cell-free permeate was passed to a flow-through spectrophotometer. Introducing more instability into the controller requires attention to the anti-windup features. No such problems were found during the cultivations or in simulations of the effect of conceivable disturbances like pump-failure, air-bubbles in the spectrofotometer, and low oxygen concentration induced growth-rate reduction.}},
author = {{Holst, Olle and Hagander, Per}},
booktitle = {{Proceedings of the 2nd IFAC Symposium on Modelling and Control of Biotechnical Processes}},
language = {{eng}},
title = {{Substrate Control in Fed-Batch Cultivations Using a Model-Based Modification of a PI-Controller}},
year = {{1992}},
}