A solution of UAV localization problem using an interacting multiple nonlinear fuzzy adaptive H_∞ models filter algorithm

The purpose of this research is to improve the robustness of the autonomous system in order to improve the position and velocity estimation of an Unmanned Aerial Vehicle(UAV).Therefore, new integrated SINS/GPS navigation scheme based on Interacting Multiple Nonlinear Fuzzy Adaptive H_∞ Models(IMM-NFAH_∞) filtering technique for UAV is presented. The proposed IMM-NFAH_∞ strategy switches between two different Nonlinear Fuzzy Adaptive H_∞(NFAH_∞) filters and each NFAH_∞ filter is based on different fuzzy logic inference systems. The newly proposed technique takes into consideration the high order Taylor series terms and adapts the nonlinear H_∞ filter based on different fuzzy inference systems via adaptive filter bounds(di),along with disturbance attenuation parameter c. Simulation analysis validates the performance of the proposed algorithm, and the comparison with nonlinear H_∞(NH_∞) filter and that with different NFAH_∞ filters demonstrate the effectiveness of UAV localization utilizing IMM-NFAH_∞ filter.     

MPPT of photovoltaic systems using extremum - seeking control

A stability analysis for a maximum power point tracking (MPPT) scheme based on extremum-seeking control is developed for a photovoltaic (PV) array supplying a dc-to-dc switching converter. The global stability of the extremum-seeking algorithm is demonstrated by means of Lyapunov's approach. Subsequently, the algorithm is applied to an MPPT system based on the "perturb and observe" method. The steady-state behavior of the PV system with MPPT control is characterized by a stable oscillation around the maximum power point. The tracking algorithm leads the array coordinates to the maximum power point by increasing or decreasing linearly with time the array voltage. Off-line measurements are not required by the control law, which is implemented by means of an analog multiplier, standard operational amplifiers, a flip-flop circuit and a pulsewidth modulator. The effectiveness of the proposed MPPT scheme is demonstrated experimentally under different operating conditions.     

Coronal Hole Properties Observed with Sumer

We analyze SUMER spectra of 14 lines belonging to 12 ions, obtained on both sides of the boundary of polar coronal holes as well as at other locations along the limb. We compare line intensities, shifts and widths in coronal holes with values obtained in the quiet Sun. We find that with increasing formation temperature, spectral lines show an increasingly stronger blueshift in coronal holes relative to the quiet Sun at an equal heliospheric angle. The width of the lines is generally larger (by a few km/s) inside the coronal hole. Intensity measurements show the presence of the coronal hole in Ne VIII lines as well as in Fe XII, with evidence for a slightly enhanced emission in polar coronal holes for lines formed below 10⁵ K. This revised version was published online in June 2006 with corrections to the Cover Date.     

EUV Observations Above Polar Coronal Holes

We derive electron temperature and density as a function of height up to 0.2 R_⊙ above the limb in polar coronal holes, using five EUV data sets recorded by the SOHO Coronal Diagnostic Spectrometer between July 1997 and February 1998. Radial T and N distributions, averaged in a 2° to 10° range of position angles, are the same above the North and South coronal holes. They do not show any time variability over a period of seven months. Polar plumes are found to have lower electron temperature and higher density than the interplume lanes. The electron density slope suggests that the proton temperatures are twice as high as the electron temperatures. This revised version was published online in June 2006 with corrections to the Cover Date.     

Novel single-switch converter with power factor correction

A new single-stage single-switch power factor correction converter with output electrical isolation is presented. The configuration of this converter is achieved by combining a flyback circuit and a forward circuit in one power stage. The principle of operation and steady-state analysis of the proposed topology is given. Based on its steady-state operation constraints, a design procedure along with a specific design example is reported. To verify the theoretical analysis of the proposed converter, a design example is given with its PSPICE simulation and experimental results     

Systematic Approach for Classification of Modern Surveillance Radar Systems

Inherent search volume is proposed as a tool for systematic comparison of modern phased-array surveillance radar systems. The advantage of the inherent search volume over the existing approaches based on single-scan and cumulative probability of detection is that the inherent search volume depends only on the unadjustable parameters of the radar. A comparison algorithm based on the inherent search volume criterion is presented.     

Cooperative processing of measurements in multilateral radial–range difference system of passive radiolocation

A study is made to define a procedure of cooperative processing of goniometric and range difference measurements in multilateral system of passive radiolocation. As a result, we worked out the computational algorithms, which implement this procedure. The accuracy characteristics are estimated.     

Open-type mixing device of a bubble structure

Results on the experimental investigation of a novel open-type mixing device with a twophase bubble structure working fluid for gas-droplet jet formation are presented. We study the effect of mode parameters upon velocity fields and droplet atomization obtained at the mixing device outlet.     

High precision gamma-ray spectrometer PGS for Russian interplanetary mission to Mars

The high precision gamma-ray spectrometer (PGS) is scheduled to be launched on the Russian MARS mission in 1996, and to go into an elliptical polar orbit around Mars. The PGS consists of two high-purity germanium detectors, associated electronics, and a passive cooler and will be deployed from one of the solar panels. The PGS will measure nuclear gamma-ray emissions from the Martian surface, cosmic gamma-ray bursts, and the high-energy component of solar flares in the broad energy range from 50 keV to 8 MeV in 4096 energy channels. The first results are presented of development, integration and qualification of the instrument, both for the passive cooler and for the detector with spectrometric electronics.     

Atmospheric drag modelling for orbital micro-debris at LEO altitudes

Data from satellite impact experiments and the scanning of recovered spacecraft offers an extended timebase to examine, using a consistent methodology, the microparticle fluxes. New penetration data from the TiCCE experiment on Eureca /1, 2/ adds to this database and shows that - despite an expected growth in the micro-debris flux - the observed flux is not greater than either LDEF or SMM. The question arises: “is this consistent with the micro particle flux being dominated by space debris or by meteoroids”.

To assist this assessment, numerical modelling using the Gear method /3/ of explicit time integration of the atmospheric drag lifetime of micron dimensioned orbital debris in both circular (LEO) and eccentric (GTO) orbits has been performed for the relevant space exposures. Results are applied to the data to examine whether the recent variations in flux can be attributed to varying levels of, orbital micro-debris caused by atmospheric drag and its changes during the solar cycle.