Search

The paper presents a way to obtain an intelligent miniaturized three-axial accelerometric sensor, based on the on-line estimation and compensation of the sensor errors generated by the environmental temperature variation. Taking into account that this error's value is a strongly nonlinear complex function of the values of environmental temperature and of the acceleration exciting the sensor, its correction may not be done off-line and it requires the presence of an additional temperature sensor. The proposed identification methodology for the error model is based on a neuro-fuzzy procedure which process off-line the numerical values obtained from the accelerometer experimental testing for different values of acceleration applied to its axes of sensitivity and for different values of operating temperature. In the sections of the paper are shown the results of the experimental testing of the accelerometer on all the three sensitivity axes, the identification of the error models on each axis by using fuzzy logic techniques combined with adaptive neural-network techniques, and the validation of the obtained models with experimental values. After the training of the neuro-fuzzy developed models for all of the three detection channels was obtained a reduction by almost two orders of magnitude of the acceleration absolute maximum error due to environmental temperature variation. [ABSTRACT FROM AUTHOR]

A way to improve the transient regime of a miniature accelerometer by using a smart control structure to close its loop is here presented. The control structure is developed by using the fuzzy logic techniques and it replaces an electronic block on the feedback path of the closed loop, block that, in the classical architecture, assured the system damping and, in the same time, played the role of elastic link of the accelerometer proof mass. The paper exposes gradually the operating principle of the miniature accelerometer, its mathematical modeling, the results obtained for classical closed loop architecture, the design procedure for the smart closed-loop control structure, and the results of the smart architecture. Finally, a comparative numerical study between the classical and the proposed accelerometer architectures is made [ABSTRACT FROM AUTHOR]

This paper presents some studies concerning hybrid power sources fuel cell, new generation photovoltaic cells with high efficiency and small battery based for High Altitude Pseudo-Satellites (HAPS). HAPS are recent entrants UAS-s in both directions of research of major aviation companies. Their goal is to replace services provided by classical communications and surveillance satellites, which show a high cost, with services provided by much cheaper technology platforms. It is exposed a state-of-the-art in the field of hybrid power sources used on high altitude UAVs and the future trends in the electrical propulsion of aircraft are highlighted. The hybrid power source's primary energy sources are photovoltaic panels and fuel cells. Regarding the problems that arise in the use of fuel cells on board the HAPS are: power / weight ratio; the energy system design according to the size of aircraft considering the use of fuel cell with solar cells; the need to use a regenerative system that allows to achieve flight durations of the order of five years without returning to the ground. An estimation concerning the possibility to obtain a practically unlimited flight duration using photovoltaic cells and regenerative fuel cells is also presented. [ABSTRACT FROM AUTHOR]

In this paper are presented some studies concerning energy conversion systems for High Altitude Pseudo-Satellites (HAPS). In the first part of the paper, a state-of-the-art in the field of energy conversion systems on board of high altitude UAVs together with the identification of future trends in electrical propulsion of aircrafts are shown. The interfacing between the fuel cells and the bus, as well as the bus voltage adjustment is made via the DC to DC converters. Simple type boost converters are lighter, but have a lower gain. On the ground, they require large heat radiators, but at higher altitudes due to low external temperatures the radiators sizes can be lowered substantially. Resonant converters perform much better gain, but contain transformers, which are heavy and thus increases the weight of the aircraft, and thus the energy propulsion required. It is necessary to carry out a study to identify optimal energy balance from the point of view of the entire aircraft. There are also performed critical analyses of few possible constructive solutions, their advantages and disadvantages and some estimations concerning dimensioning of these conversion systems. [ABSTRACT FROM AUTHOR]

This paper presents the modeling and the analysis of boost DC-DC converter using numerical simulations. The intended parameters of the converter are 15V to 30 V, power 1 kW. The modeling is performed first in MATLAB/SIMULINK toolbox SIMPOWERSYS, and after that the electronic scheme is implemented and simulated in MULTISIM 12. The implemented control system is PI type and is realized using as simple as possible components so that the scheme could be used also as didactical laboratory application. The command is a classic PWM one, realized with a 555 oscillator with a frequency of 10 kHz and a linear variable voltage generator using also the 555 circuit. On the feedback one used a differential error amplifier with 741 circuit and a PI controller also with the 555 circuit. One followed both the simulation in MATLAB/SIMULINK, using a average model of the converter and modeling and simulation in MULTISIM which put in evidence the practical problems appeared in the hard implementation. From the numerical simulations one obtained the converters behavior under different loads and the time response at step load variations. The obtained results are realistic and verify the control method proposed. [ABSTRACT FROM AUTHOR]