Anna G. Stefanopoulou

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In this paper we present the results of the air supply control problem for a Fuel Cell Stack (FCS) power system. In particular, we control the compressor motor in order to regulate (and replenish) the oxygen depleted from the fuel cell cathode during power generation. This task needs to be achieved rapidly and efficiently to avoid oxygen starvation and(More)
Fuel Cells are electrochemical devices that convert the chemical energy of a gaseous fuel directly into electricity. They are widely regarded as a potential future stationary and mobile power source. The response of a fuel cell system depends on the air and hydrogen feed, flow and pressure regulation, and heat and water management. In this paper, we develop(More)
A multivariable control scheme is designed to minimize emission of nitrogen oxides NOx and generation of smoke in a Diesel engine equipped with a variable geometry tur bocharger VGT and an external exhaust gas recirculation system EGR Steady state optimization results in operat ing points where NOx emissions and smoke generation are highly coupled and(More)
Good estimates of vehicle mass and road grade are important in automation of heavy duty vehicle, vehicle following maneuvers or traditional powertrain control schemes. Recursive Least Square with multiple forgetting factors accounts for different rates of change for different parameters and thus, enables simultaneous estimation of the time-varying grade and(More)
Many electromagnetic actuators su2er from high velocity impacts. One such actuator is the electromechanical valve actuator, recently receiving attention for enabling variable valve timing in internal combustion engines. Impacts experienced by the actuator are excessively loud and create unnecessary wear. This paper presents an extremum seeking controller(More)
A Mean Value Model (MVM) for a Homogeneous Charge Compression Ignition (HCCI) engine is presented. Using a phenomenological zero-dimensional approach with five continuous and three discrete states we first model the effects of the Exhaust Gas Recirculation (EGR) valve, the exhaust Rebreathing Lift (RBL), and the fueling rate on the state of charge in the(More)
Lithium-ion battery is the core of new plug-in hybrid-electrical vehicles (PHEV) as well as considered in many 2nd generation hybrid electric vehicles (HEV). In most cases the lithium-ion battery performance plays an important role for the energy management of these vehicles as high-rate transient power source cycling around a relatively fixed state of(More)
Variable valve timing allows improvements of internal combustion engines and can be achieved by camless actuation technology. In this paper we consider an electromechanical valve (EMV) actuator. One of the main problems in the EMV actuator is the noise and wear associated with high contact velocities during the closing and opening of the valve. The contact(More)
A nonlinear fuel cell system dynamic model tha t is suitable for control s tudy is presented. The t ransient phenomena captured in the model include the flow characterist ics and inertia dynamics of the compressor, the manifold filling dynamics, and consequently, the reactant part ial pressures. Character izat ion of the Fuel Cell polarization curves based(More)
Lithium ion batteries should always be prevented from overheating and, hence, thermal monitoring is indispensable. Since only the surface temperature of the battery can be measured, a thermal model is needed to estimate the core temperature of the battery, which can be higher and more critical. In this paper, an online parameter identification scheme is(More)