| Abstract | Magistarski rad sastoji se od šest poglavlja. U prvom, uvodnom poglavlju daje se kratki osvrt na značajni tržišni uspjeh dizelskih motora u Europi u posljednjih deset godina (1997 – 2008. g.). Ističu se razlozi tog uspjeha, te se još spominju tri uvodna područja, i to: ekologija, zakonske norme i industrija nafte. U drugom poglavlju dan je kratki pregled teorijskih osnova dizelskog motora i princip njegova rada. Navedene su osnovne definicije fizikalnih veličina, radne značajke i njihove oznake. Veličine poput prosječnog indiciranog tlaka, indicirane korisnosti, efektivne snage motora, faktora viška zraka i slično spominju se gotovo u svim slijedećim poglavljima, te ih je odmah na početku rada bilo potrebno definirati. U trećem poglavlju opisani su svi podsustavi dizelskog motora od kojih će se sastojati cjelokupni matematički model motora. Dan je naglasak na upravljačke komponente (aktuatore, senzore, upravljačko računalo), dok konstrukcijski dio motora poput klipova, klipnjače, bregaste osovine, nije bio u fokusu ovoga rada. Podsustavi koji su detaljnije opisani u ovom trećem poglavlju su: sustav za recirkulaciju (povrat) ispušnih plinova, visokotlačni sustav za ubrizgavanje goriva (engl. common–rail), sustav prednabijanja dizelskog motora temeljen na turbini sa zakretnim lopaticama, te kao posljednji opisan je sustav za elektroničku regulaciju i upravljanje radom dizelskog motora. U četvrtom poglavlju razvijen je matematički model dizelskog motora s prednabijanjem. Kao osnova koristio se usrednjeni model motora (engl. Mean Value Engine Model, u daljnjem tekstu MVEM model) koji je razvijen 1991. godine na tehničkom Univerzitetu u Kopenhagenu. Prvo su matematički opisane sve komponente od kojih se sastoji model motora, a zatim se model implementirao unutar programa za simulaciju dinamičkih sustava MATLAB SIMULI\NK 7.0. Prikazani su i tipični primjeri simulacije postavljenog modela. Peto poglavlje odnosi se na tri projektirana sustava regulacije motora. U regulacijskom krugu ugrađeni su diskretni PI ili PID regulatori. U uvodnom dijelu petog poglavlja, izvedena je prijenosna funkcija diskretnog PID regulatora u Ƶ-području. Regulator se podešava pomoću Takahasijeve procedure zasnovane na oscilacijskom eksperimentu. Prvi projektirani sustav regulacije je uređaj za regulaciju brzine vozila, tzv. tempomat. Poremećajnu veličinu predstavlja postotak nagiba ceste koji se mijenja od +5 % (uspon), pa sve do -5 % (nizbrdica). Simulacijsko ispitivanje projektiranog tempomata provedeno je u četvrtom i petom stupnju prijenosa mjenjača. Drugi projektirani regulacijski sustav odnosi se na regulaciju povrata ispušnih plinova u usisni kolektor motora, tzv. EGR regulacija. Da bi se ova regulacija mogla uspješno realizirati bilo je potrebno u usisni kolektor matematičkog modela motora ugraditi dodatni aktuator koji se naziva elektronička EGR zaklopka. Regulator djeluje direktno na električni EGR-ventil čijim se zatvaranjem, odnosno otvaranjem prigušuje protok ispušnih plinova prema usisu, a indirektno i na EGR zaklopku čijim se zatvaranjem prigušuje protok svježeg zraka iz kompresora i stvara podtlak nužan za ostvarenje povrata ispušnih plinova. Posljednji projektirani regulacijski sustav odnosi se na regulaciju tlaka prednabijanja. Ovaj regulacijski krug je ugrađen u već postojeći simulacijski model uređaja za regulaciju brzine vozila, tzv. tempomata. Rezultat ove simbioze je složeni simulacijski model s dva ugrađena regulatora, jedan za regulaciju brzine vrtnje, a drugi za regulaciju tlaka prednabijanja. Regulator za regulaciju tlaka djeluje na električni aktuator kojim se direktno mijenja napadni kut turbinskih lopatica, odnosno indirektno protok ispušnih plinova kroz turbinu. |
| Abstract (english) | This master's dissertation is composed of six big chapters. The first, introductory chapter renders a brief review of the great market success Diesel engines have had in Europe for the past decade (1997-2008) and states the reasons for such success. Besides, another three areas (ecology, legal standards and oil industry) also mentioned. All three areas are controlled by three particularly powerful lobbies that will have a crucial influence on defining the future of Diesel engine in Europe. The second chapter renders a brief outline of theoretical basics and operating principle of Diesel engine. It states the basic definitions of physical variables, operating characteristics and their symbols. Values such as mean indicated pressure, indicated efficiency, effective engine power, air/fuel ratio etc. are mentioned in almost each of the following chapters, which called for providing their definitions right at the beginning of the paper. The third chapter contains descriptions of all subsystems of Diesel engine the mathematical model will be comprised of. Emphasis is laid on control components, actuators, sensors and control unit, while the structural part of the engine such as pistons, connecting rod and camshaft was not in focus of this paper. Subsystems described in more detail in this third chapter are: exhaust gas recirculation system, common-rail injection systems in passenger cars, turbocharging systems for Diesel engines equipped with variable geometry turbines and, as the last described is the system of Diesel engine control and management. The fourth chapter develops a mathematical model of turbocharged Diesel engines. The Mean Value Engine Model, which was developed at the Technical University of Copenhagen, Denmark in 1991, was used as the basis [33]. First, all components constituting the model of the engine were described mathematically, and then their implementation inside the program for dynamic system simulation followed. MATLAB SIMULINK 7.0 interface was selected for the program. Engine main scheme developed in SIMULINK was also presented in the fourth chapter. After it, the simulation model was started, and then a display of the first preliminary data in the diagrams. The fifth chapter refers to exactly three design systems for engine control. Discreet PI or PID controllers were built in the control circuit. In the introductory section of the fifth chapter, a transfer function of the digital PID controller in Z-area was arranged. The first design control system is a devise for vehicle speed control, the so-called tempomat. Disturb value is the percentage of the road inclination varying from +5% (gradient) to -5% (downward slope). Gradient of 5% is the highest lawful gradient that must not be exceeded at highway construction in all countries within the EU. Testing of the tempomat was conducted in the fourth and the fifth transmission gears. The second design control system refers to the control of exhaust gas recirculation flow back into the engine intake system, the so-called EGR control. For a successfully accomplished control, it was necessary to build an additional actuator, named electronic EGR throttle, in the intake manifold of the mathematical model. Outlet signal from the controller acts directly on the electrical EGR-valve by closing and/or opening of which the throttle exhaust gas flow towards engine intake system is damped; and indirectly on the EGR throttle by closing of which the throttle fresh-air mass flow from the compressor is damped. The last design control system refers to the boost pressure control. This control circuit is built in the existing simulation model of the device for vehicle speed control, the so-called tempomat. The result of this symbiosis is a big simulation model with two inbuilt controllers, one for speed control and the other for boost control. The boost controller acts on the electrical actuator by means of which the turbine vane position is directly changed, that is, indirectly the mass flow of exhaust gas through the turbine. Finally, all control circuits have inbuilt PI or PID controllers that are tuned using the Takahashi procedure for tuning the parameters of digital controllers. |
