Robust control of internal states in a polymer electrolyte membrane fuel cell air-feed system by considering actuator properties

Air stoichiometry, pressure, and relative humidity in the air-feed system of a vehicular polymer electrolyte membrane fuel cell (PEMFC) influence efficiency, durability and reliability. It is critical to develop robust control algorithms for these internal states to improve system performance. There is limited extant research on designing robust control algorithms that consider the three internal states as well as the constraints of real actuators, such as an air compressor, a membrane humidifier, and a back-up pressure valve (BPV). This study examines robust control strategies for the three internal states based on adaptive second order sliding mode (ASOSM) and nonlinear proportional-integral (NPI) feedback control algorithms. In the study, control targets are established based on stable properties of the PEMFC system. The study involves proposing and comparing five control strategies that are a combination of NPI and ASOSM algorithms. The following results are obtained: (1) the stable control targets for the three internal states are followed adequately by using an NPI or an ASOSM algorithm and differences only exists in dynamic processes; (2) with respect to the control of air stoichiometry, an NPI algorithm performs better than an ASOSM algorithm as chattering in air stoichiometry can be avoided and the convergence time to the target value is acceptable; (3) with respect to the control of cathodic pressure, an ASOSM algorithm performs better than an NPI algorithm as the overshoots in cathodic pressures can be effectively reduced; (4) with respect to the control of relative humidity, both NPI and ASOSM algorithms lead to a practical bang–bang strategy. The strategy that performs the best among the five strategies is selected, and the robustness of the selected strategy with respect to parameter uncertainties is verified.     

Luminescence Properties of Fullerene

Abstract

The increasing miniaturisation on the field of electronics and information generation requires evaluation of new concepts and technologies. One method to fulfil the demands is use of single molecular units for data storage and processing. The primary research field of our work group are the properties of conducting polymers and switching molecules. The work includes synthesis of new organic materials for molecular electronics as well as the study of conductivity under different conditions, their dynamics upon optical excitation and their suitability for electronic devices. Materials to be studied are, above all, molecules with extended systems of conjugated double bonds. It covers one-dimensional conductors like polyacetylene and related polymers or oligomers whose structure are based on a polyacetylene backbone, but also more complex structures like graphite^[1-4].     

Beulbemessung diskret gelagerter dünnwandiger kreiszylindrischer Stahlsilokonstruktionen nach EN 1993‐1‐6

Buckling design of discretely supported thin‐walled steel silo structures according to EN 1993‐1‐6. This paper deals with the exemplary application of alternative buckling design procedures, as introduced by the new European Standard on buckling of steel shells, to a practical thin‐walled steel silo structure. First the general features of these design procedures as well as relevant issues of structural modelling are outlined. Then the outcomes of the different buckling design procedures are compared to each other and critically evaluated.     

Elektrochemisches Rauschen von Magnesium in organischen Lösungsmitteln

Electrochemical Noise of Magnesium in Organic Solvents The electrochemical noise of the system Mg/n-C₄H₉OH, NaClO₄ is analyzed on different conditions. The suitability of this method is to be investigated for the determination of selfdischarge of galvanic cells. Gravimetric measurements, radiometric methods and visual judgement of anode surfaces are taken for this hitherto. The long-term stability of the system without polarization up to 75 days is confirmed by constant noise amplitude and comparative EIS-measurements. The system activated by constant polarization showed a corrosive attack indicated by an increasing current noise amplitude within some hours. Finally passivation occurred after advanced destruction of the oxidic surface layer. The noise amplitude diminished. Salt deposit caused this event, corroborated by SEM shottings. Analysis of potential noise in nonaqueous electrolytes is inconclusive owing to inherent noise of used reference electrodes of 2. kind.