Intelligent Control of Refrigeration Systems: Adaptive Fuzzy Strategies for Superheat Regulation
Author
Panneerselvam, Aakash Raj
Term
4. semester
Education
Publication year
2025
Submitted on
2025-09-01
Pages
69
Abstract
The evaporator is a key part of refrigeration and air-conditioning systems because it absorbs heat efficiently. However, its behavior can be hard to control due to nonlinear dynamics and periods of very high gain, where small changes cause large responses. A central challenge is keeping the superheat at the right level. Superheat is how much the refrigerant vapor temperature exceeds its boiling point at the evaporator outlet; it acts as a safety margin to ensure only vapor reaches the compressor. If superheat is too low, liquid refrigerant can enter the compressor and cause damage. If it is too high, cooling becomes less effective and wastes energy. To address this, two advanced control methods are proposed: 1) Adaptive fuzzy-based sliding mode control, which uses rule-based fuzzy logic to adjust settings in real time and maintain stability and performance despite nonlinearities, and 2) Adaptive fuzzy PID control with adaptive gains, a hybrid approach in which fuzzy logic continuously tunes the proportional and integral gains to achieve robust operation across conditions. The goal is an adaptive controller that maintains the desired superheat while handling changes in gain and transport delays, meaning the lag between a control action and its effect. The controller must balance efficiency and protection by keeping superheat as low as possible without allowing liquid to reach the compressor. Key design choices include selecting appropriate gains, mitigating transport delays, and updating control rules on the fly to keep the evaporator running smoothly and efficiently.
Fordamperen er en central del af køle- og klimaanlæg, fordi den står for at optage varme effektivt. Dens ydeevne kan dog være svær at styre, blandt andet på grund af ikke-lineær adfærd og perioder med meget høj forstærkning, hvor små ændringer giver store udsving. En hovedudfordring er at holde overhedningen på det rette niveau. Overhedning er, kort fortalt, hvor meget kølemidlets damp er varmere end dens kogepunkt ved fordamperens udløb; den fungerer som sikkerhedsmargen, så kun damp og ikke væske når kompressoren. For lav overhedning kan sende flydende kølemiddel ind i kompressoren og skade systemet, mens for høj overhedning gør kølingen mindre effektiv og øger energiforbruget. For at løse dette foreslås to avancerede reguleringsmetoder: 1) Adaptiv fuzzy-baseret sliding mode-regulering, som bruger regelbaseret fuzzylogik til løbende at tilpasse indstillinger og sikre stabilitet og ydeevne på trods af ikke-lineariteter, og 2) Adaptiv fuzzy PID-regulering med adaptive forstærkninger, en hybridmetode hvor fuzzylogik kontinuerligt justerer de proportionale og integrale gain for at opnå robust drift under forskellige forhold. Målet er en adaptiv regulering, der holder overhedningen på den ønskede værdi, samtidig med at den håndterer ændringer i forstærkning og transportforsinkelser, altså forsinkelsen mellem en reguleringshandling og dens effekt i systemet. Regulatoren skal balancere effektivitet og beskyttelse ved at holde overhedningen så lav som muligt uden at tillade væske i kompressoren. Vigtige designvalg omfatter korrekt valg af gain, håndtering af transportforsinkelser og løbende justering af regler, så fordamperen kan køre jævnt og energieffektivt.
[This apstract has been rewritten with the help of AI based on the project's original abstract]