Robust Control of Transport Refrigeration System
Author
Kovacevic, Ajdin
Term
4. term
Education
Publication year
2020
Submitted on
2020-01-08
Pages
98
Abstract
Når der dannes is på fordamperens kølespiral i et kølesystem, ændrer anlæggets dynamik sig og gør reguleringen vanskelig. Dette projekt havde til formål at udvikle en robust regulator, som kan holde overhedningen (temperaturen over kølemidlets mætningspunkt) stabil, mens der opbygges is. Som udgangspunkt bruges en virksomhedsmodel af anlægget: et MIMO-system (flere input og flere output) med 14 tilstande, 4 input og 2 output. For at forenkle designet blev modellen afkoblet til to SISO-delsystemer (ét input og ét output). Vi valgte en robust H∞-tilgang, hvor krav til nominel stabilitet og ydeevne samt robust stabilitet og robust ydeevne specificeres med vægtfunktioner. Regulatoren blev realiseret som en PID-regulator (proportional–integral–derivativ) og viste i simulationer, at den fungerer. Ved implementering på det fysiske anlæg viste det sig imidlertid vanskeligt at opnå selv nominel stabilitet. Samlet peger resultaterne på, at den afprøvede robuste styring ikke nødvendigvis løser problemet med is på fordamperen, og at andre løsninger bør undersøges.
When ice forms on an evaporator coil, the system dynamics change and control becomes harder. This project set out to develop a robust controller that keeps superheat (the refrigerant vapor temperature above its saturation temperature) stable while ice builds up. We used a company-supplied model of the system, initially a 14-state MIMO model with 4 inputs and 2 outputs. To simplify design, we decoupled it into two SISO subsystems. We adopted an H-infinity (H∞) robust control approach, in which nominal stability and performance as well as robust stability and robust performance are addressed by choosing appropriate weighting functions. The H∞ controller was implemented with a PID structure (proportional–integral–derivative) and was shown to work in simulations. However, on the real system it was difficult to achieve even nominal stability. Overall, the results indicate that the tested robust control approach may not solve the evaporator icing problem, and alternative solutions should be explored.
[This abstract was generated with the help of AI]
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