Abstract

This project concerns development of a proof of concept self-tuning system for a Mission OS (TM) boiler system. Furthermore, a method to ensure clean combustion, in case of fuel actuator saturation, has been developed. The Mission OS (TM) boiler system is modelled as three separate non-linear models; a model of the Mission OS (TM) boiler, the feed water actuator system and the fuel actuator system. For design of SISO controllers, the complex non-linear models are simplified to integrator models. Both the complex non-linear models and the simple integrator models are verified using measurement data from the boiler system. Controllers are designed to comply with the developed self-tuning scheme, capable of identifying model parameters during the start-up phase of the boiler system. The identified parameters includes fuel actuator servo characteristics, feed water valve characteristics, a curveband, describing the oil/air ratio, used as oxygen level control and pressure build-up characteristics. Based on these parameters, controller parameters are calculated prior to operating the boiler. Control of the fuel actuator system for the Mission OS (TM) boiler system includes Pulse Width Modulation (PWM) position control of oil valve and air damper. To comply with the curveband, in case of PWM saturation, a constrained minimisation problem has been derived and solved by a model predictive reference correction scheme, ensuring steady oxygen level by compliance of the curveband. Finally, to assess potential improvements of the water level control, a Kalman estimator is designed to estimate the mean water level and the unmeasurable steam consumption. The developed methods are verified by simulation and shows satisfactory performance.

Dette projekt omhandler udvikling af et proof-of-concept self-tuning system til et Mission OS (TM) kedelsystem. Ydermere er der udviklet en metode, der sikrer ren forbrænding, selv ved saturering af aktuatorerne i brændstofsystemet. Mission OS (TM) kedelsystemet er modelleret som tre separate ulineære modeller; en model af Mission OS (TM) kedlen, fødevandssystemet og brændstofsystemet. I forbindelse med design of SISO regulatorer, er de komplekse ulineære modeller simplificeret til integratormodeller. De komplekse ulineære modeller og de simple integratormodeller er verificeret mod måledata fra kedelsystemet. Regulatorerne er designet med henblik på anvendelse i det udviklede self-tuning system, som er udviklet til at identificere modelparametre under opstart af kedelsystemet. De identificerede parametre omfatter karakteristik af servomotorer, fødevandsventil, damptrykopbygning samt et kurvebånd, der beskriver olie/luft forhold, anvendt til iltregulering. På baggrund af disse parametre udregnes regulatorparametre, inden kedelsystemet sættes i normal drift. Regulering af brændstofsystemet til Mission OS (TM) kedelsystemet inkluderer pulsbreddemoduleret (PWM) positionsregulering af olieventil og luftspjæld. Opgaven at følge et kurvebånd ved aktuator saturering, er beskrevet som et minimeringsproblem. Minimeringsproblemet er løst ved brug af et modelprædiktivt referencekorrektionssystem, der sikrer konstant iltniveau ved overholdelse af kurvebåndet. Endeligt er en Kalman estimator designet til at estimere middelvandstand i kedlen og det umålbare dampforbrug, med henblik på at vurdere mulig forbedring af vandstandsreguleringen. De udviklede metoder er verificeret gennem simulering og viser tilfredsstillende resultater.

A master thesis from Aalborg University

Structural Optimization and Self-tuning of Marine Boilers