This paper presents an online diagnosis method for supercapacitors' aging problem. State-of-Health (SoH) estimation is an important feature since aging introduces degradation in supercapacitors' performance, which might eventually lead to their failure. SoH is usually measured by Electrochemical Impedance Spectroscopy (EIS). But, this has to be performed offline and requires interruption of the system's operation. Unlike this method, this paper presents an online diagnosis technique for supercapacitors using an extended Kalman observer as a well-known tool for its particularities and performances to study nonlinear parameters estimation. The main objective of this paper is the online State-of-Health diagnosis based on the supercapacitors aging indicators estimation. Moreover, the proposed online estimation strategy requires only voltage and current measurements, which reduces the number of sensors with respect to other methods. The effectiveness of the proposed online observer is shown through experimental results and robustness to noise is also studied. S 0018-9545 (c)
The aim of this study is to obtain high-quality zinc oxide thin films at room temperature by reactive radiofrequency (rf) magnetron sputtering in an oxygen environment. The films were deposited on glass and silicon substrates at several temperatures, ranging from ambient temperature to 400 °C. In order to have the best results at room temperature we adjusted several deposition parameters such as the O 2 /Ar gas pressure, target-substrate distance, rf power, and gas flow rate. The ZnO samples were characterized by several methods. From XRD measurements it was confirmed that ZnO films are c-axis oriented, the line width and intensity are sensitive to the variation of the growth temperature, and the best results were found at room temperature for our growth conditions. From AFM pictures it is seen that the grain size decreases when the temperature is increased to 400 °C and the surface roughness of the as-deposited films increases with the deposition temperature. All films exhibited excellent transmission (in excess of 90%) in the visible range with a steep fall off in transmission at 375 nm for the samples grown at room temperature. From the absorbance measurements the optical band-gap energy was extrapolated at about 3.25 eV, which closely agrees with the ZnO single-crystal value. Raman backscattering is used to probe the zone center phonons and evaluate the residual stress in the as-grown ZnO thin films from the position of the E 2 high mode.
We report a new design and operation of a microelectromechanical systems (MEMS) differential scanning calorimeter (DSC) for heat-capacity measurements. The sensor consists of a 500-nm silicon nitride membrane supported by four bridges on a silicon wafer. On one side of the membrane, a serpentineshaped platinum layer is deposited and used as both a resistive heater and a thermometer during the DSC measurement. This MEMS design can provide a self-alignment between the DSC cell and the material to be analyzed in order to prevent its deposition on the sloping side walls of the silicon frame. According to FEM calculations, the system exhibits good thermal isolation and high uniformities in the temperature field in the sensing area of the device. To evaluate the use of this calorimetric device for liquid samples, we measure the heat of vaporization of nanoliter-scale water droplets with high preciseness using the calorimeter in both scanning and heat conduction modes.[
2008-0288]Index Terms-Calorimetry, heat capacity, microelectromechanical systems (MEMS).
This paper investigates the control problem for static boost type converters using an high gain state feedback robust controller incorporating an integral action. The robust feature allows to achieve the required performance in presence of parametric uncertainties, while the integral action provides an offset free performance with respect to the desired levels of voltage. The adopted high gain approach is motivated by both fundamental as well as practical considerations, namely the underlying fundamental potential and the design parameter specification simplicity. The stability and convergence analysis has been carried out using an adequate Lyapunov approach, and the control system calibration is achieved throughout a few design parameters which are closely related to the desired dynamical performances. The effectiveness of the proposed control approach has been corroborated by numerical simulations and probing experimental results.
IntroductionThe control of static converters has been the subject of an important research activity over the past decades. This interest is mainly due to the emergence of embedded electronics in everyday life, increasing thereby the need for more efficient converters. Indeed, this type of converter is used for many applications such as laptop computers [1], photo-voltaic [2], vehicular systems [3], fuel cell [4], etc. Furthermore in recent use of electrical devices, the control problem is not the only feature required from the user. There are more and more need of informations on the evolution/aging of the system. In the case of converters, these informations can be obtained by reconstructing voltages and currents thanks to suitable observers.
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