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A new approach to relay-based autotuning PID controllers and their evaluation in pH control of industrial photobioreactors

Caparroz, Malena ; Soltesz, Kristian LU orcid ; Hägglund, Tore LU ; Guzmán, José Luis and Berenguel, Manuel (2025) In Control Engineering Practice 164.
Abstract
This paper presents a novel adaptive autotuning strategy for controlling the pH in microalgae raceway reactors, a critical variable in optimizing biomass productivity under dynamic environmental conditions. The method expands on existing relay-based autotuning principles, tailored to suit the seasonally variable dynamics of microalgae cultivation systems influenced by CO2 injection and photosynthetic activity. The novelty of the proposed approach relies on the use of a relay-based autotuning technique that applies the relay signal to the setpoint and not to the control signal. This method allows for seamless integration into existing control loops without manual recalibration across seasons. Moreover, the method is coupled with a... (More)
This paper presents a novel adaptive autotuning strategy for controlling the pH in microalgae raceway reactors, a critical variable in optimizing biomass productivity under dynamic environmental conditions. The method expands on existing relay-based autotuning principles, tailored to suit the seasonally variable dynamics of microalgae cultivation systems influenced by CO2 injection and photosynthetic activity. The novelty of the proposed approach relies on the use of a relay-based autotuning technique that applies the relay signal to the setpoint and not to the control signal. This method allows for seamless integration into existing control loops without manual recalibration across seasons. Moreover, the method is coupled with a classification algorithm to assess weather conditions, enhancing the reliability of autotuning under fluctuating solar radiation. Using the developed autotuning method, low-order models are identified, and the autotuner is coupled with a Proportional-Integral controller plus a static feedforward compensation to counteract solar radiation disturbances. The designed algorithm has been successfully evaluated
for five consecutive days in a real semi-industrial-scale raceway reactor and compared with a classical PI with a feedforward strategy. The results demonstrate reliable performance across clear and cloudy conditions, offering a scalable and automated solution for adaptive pH regulation in microalgae production systems. (Less)
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author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Control Engineering Practice
volume
164
pages
13 pages
publisher
Elsevier
ISSN
0967-0661
DOI
10.1016/j.conengprac.2025.106520
project
PID Control
language
English
LU publication?
yes
id
b19a046b-293b-4f45-8dd3-d90a28c0b5fe
date added to LUP
2025-07-27 18:42:02
date last changed
2025-09-11 08:51:59
@article{b19a046b-293b-4f45-8dd3-d90a28c0b5fe,
  abstract     = {{This paper presents a novel adaptive autotuning strategy for controlling the pH in microalgae raceway reactors, a critical variable in optimizing biomass productivity under dynamic environmental conditions. The method expands on existing relay-based autotuning principles, tailored to suit the seasonally variable dynamics of microalgae cultivation systems influenced by CO2 injection and photosynthetic activity. The novelty of the proposed approach relies on the use of a relay-based autotuning technique that applies the relay signal to the setpoint and not to the control signal. This method allows for seamless integration into existing control loops without manual recalibration across seasons. Moreover, the method is coupled with a classification algorithm to assess weather conditions, enhancing the reliability of autotuning under fluctuating solar radiation. Using the developed autotuning method, low-order models are identified, and the autotuner is coupled with a Proportional-Integral controller plus a static feedforward compensation to counteract solar radiation disturbances. The designed algorithm has been successfully evaluated<br/>for five consecutive days in a real semi-industrial-scale raceway reactor and compared with a classical PI with a feedforward strategy. The results demonstrate reliable performance across clear and cloudy conditions, offering a scalable and automated solution for adaptive pH regulation in microalgae production systems.}},
  author       = {{Caparroz, Malena and Soltesz, Kristian and Hägglund, Tore and Guzmán, José Luis and Berenguel, Manuel}},
  issn         = {{0967-0661}},
  language     = {{eng}},
  publisher    = {{Elsevier}},
  series       = {{Control Engineering Practice}},
  title        = {{A new approach to relay-based autotuning PID controllers and their evaluation in pH control of industrial photobioreactors}},
  url          = {{https://lup.lub.lu.se/search/files/224181570/Relay_autotuner_CEP.pdf}},
  doi          = {{10.1016/j.conengprac.2025.106520}},
  volume       = {{164}},
  year         = {{2025}},
}