Radiation-Adaptive Hybrid PI+CI Control for pH Regulation in a Raceway Photobioreactor

Radiation-Adaptive Hybrid PI+CI Control for pH Regulation in a Raceway Photobioreactor | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Radiation-Adaptive Hybrid PI+CI Control for pH Regulation in a Raceway Photobioreactor Juan Ignacio Mulero-Martínez, Alfonso Baños, José Luis Guzmán, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9557709/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 6 You are reading this latest preprint version Abstract Maintaining pH within its optimal range is a major challenge in open raceway photobioreactors due to time-varying irradiance, transport delay, actuator saturation, and nonlinear biological dynamics. Conventional control strategies, including fixed-parameter PI controllers, often struggle to provide satisfactory regulation under outdoor operating conditions. This paper proposes a hybrid PI+CI controller for pH regulation in a raceway photobioreactor, in which the reset ratio is adapted online using measured solar irradiance. The design also accounts for the one-sided actuation constraint imposed by CO$_2$ injection, which can decrease pH but cannot actively increase it. The proposed controller is evaluated in a first-principles simulator previously validated against outdoor raceway operation. Simulation results over several days and pH setpoints show that the proposed strategy improves pH regulation and reduces normalized tracking error indices with respect to a PI controller with anti-windup. These results support the potential of irradiance-adaptive reset control as a practical strategy for pH regulation in outdoor microalgae cultivation systems. Hybrid control Reset control Clegg integrator pH control Photobioreactors Process control Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 11 May, 2026 Reviewers agreed at journal 09 May, 2026 Reviewers invited by journal 04 May, 2026 Editor assigned by journal 04 May, 2026 Submission checks completed at journal 04 May, 2026 First submitted to journal 28 Apr, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9557709","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":638497596,"identity":"174b414a-42d8-42d9-a8a6-c94befb71050","order_by":0,"name":"Juan Ignacio Mulero-Martínez","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2ElEQVRIiWNgGAWjYBACxgYILQNiPyBJCw8QMxsACQmibQNpYZMgSgvzjORnDxhzDvPwSx8+Vs27w66Ogb0dvwMZZ6SZGzBuO8wj2ZeWdpv3TLIEA88ZAwJaEswkQFoMzvCY3eZtOyDBIJGD32GMM9K/gbXYA7UUg7XIPyfksByoLTw8ZswQWxgIOKznTZlE4rZ0HokzbMmSc88kS7bx5ODXYtievk3i4zZrOf4e5oMf3u6w4+dnP47fYYYNQCIBbieQx4ZXPRDIozqzgZD6UTAKRsEoGIkAAG0gPADwFbKEAAAAAElFTkSuQmCC","orcid":"","institution":"Polytechnic University of Cartagena","correspondingAuthor":true,"prefix":"","firstName":"Juan","middleName":"Ignacio","lastName":"Mulero-Martínez","suffix":""},{"id":638497597,"identity":"5ff9eba4-ade6-4521-a0b7-1d5a4c4402de","order_by":1,"name":"Alfonso Baños","email":"","orcid":"","institution":"University of Murcia","correspondingAuthor":false,"prefix":"","firstName":"Alfonso","middleName":"","lastName":"Baños","suffix":""},{"id":638497598,"identity":"afbb81b2-09fe-4218-8f39-4e64d43ad624","order_by":2,"name":"José Luis Guzmán","email":"","orcid":"","institution":"University of Almería","correspondingAuthor":false,"prefix":"","firstName":"José","middleName":"Luis","lastName":"Guzmán","suffix":""},{"id":638497599,"identity":"6e55e3f7-9664-4701-a80b-104d067e1bbc","order_by":3,"name":"José Carlos Moreno","email":"","orcid":"","institution":"University of Almería","correspondingAuthor":false,"prefix":"","firstName":"José","middleName":"Carlos","lastName":"Moreno","suffix":""}],"badges":[],"createdAt":"2026-04-28 19:08:46","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9557709/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9557709/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":109067929,"identity":"ee68954a-938b-41ae-a296-b7af3f17c3a5","added_by":"auto","created_at":"2026-05-12 10:02:35","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2834088,"visible":true,"origin":"","legend":"","description":"","filename":"DesignandImplementationofanHybridControllerforanIndustrialRacewayPhotobioreactor4.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9557709/v1_covered_58a6ad37-4ae3-401a-8983-45d2e0071f11.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eRadiation-Adaptive Hybrid PI+CI Control for pH Regulation in a Raceway Photobioreactor\u003c/p\u003e","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-control-automation-and-electrical-systems","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jcae","sideBox":"Learn more about [Journal of Control, Automation and Electrical Systems](https://link.springer.com/journal/40313)","snPcode":"40313","submissionUrl":"https://submission.springernature.com/new-submission/40313/3","title":"Journal of Control, Automation and Electrical Systems","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Hybrid control, Reset control, Clegg integrator, pH control, Photobioreactors, Process control","lastPublishedDoi":"10.21203/rs.3.rs-9557709/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9557709/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Maintaining pH within its optimal range is a major challenge in open raceway photobioreactors due to time-varying irradiance, transport delay, actuator saturation, and nonlinear biological dynamics. 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