128 research outputs found
Attitude Estimation and Control Using Linear-Like Complementary Filters: Theory and Experiment
This paper proposes new algorithms for attitude estimation and control based
on fused inertial vector measurements using linear complementary filters
principle. First, n-order direct and passive complementary filters combined
with TRIAD algorithm are proposed to give attitude estimation solutions. These
solutions which are efficient with respect to noise include the gyro bias
estimation. Thereafter, the same principle of data fusion is used to address
the problem of attitude tracking based on inertial vector measurements. Thus,
instead of using noisy raw measurements in the control law a new solution of
control that includes a linear-like complementary filter to deal with the noise
is proposed. The stability analysis of the tracking error dynamics based on
LaSalle's invariance theorem proved that almost all trajectories converge
asymptotically to the desired equilibrium. Experimental results, obtained with
DIY Quad equipped with the APM2.6 auto-pilot, show the effectiveness and the
performance of the proposed solutions.Comment: Submitted for Journal publication on March 09, 2015. Partial results
related to this work have been presented in IEEE-ROBIO-201
Kerr-AdS black hole behaviors from dark energy
We investigate the critical behaviors of four-dimensional Kerr-AdS black holes from quintessential Dark Energy (DE) contributions. Using a moduli space, coordinated by the DE state parameter w and the quintessence field intensity a, we deal with three different (w)-models. By elaborating analytical formulas of relevant thermodynamical quantities denoted by X(w), we find significant similarities and distinctions. Precisely, for the (-1 3)-model, we show that DE contributions stabilize such black holes. For the (-1)-model, however, we get a reversed DE effect. In the (-2 3)-model, Kerr-AdS black holes reveal a resistance regarding the usual DE effects. Exploiting the explicit formulas of such thermodynamical quantities, we give certain physical interpretations for thermal behaviors. Although such relevant distinctions, we show that the (w)-models involve similar universal ratios associated with certain critical thermodynamical quantities. Then, we analyze the photon orbits in the presence of DE
Dual-Band MIMO Antenna with Four CPW Elements using Polarization Diversity for 5G Mobile Communication Networks and Satellite
In this paper, a novel design of compact quad-element MIMO (Multiple Input Multiple Output) antenna for 5G communication networks and satellites is proposed. The four similar elements of this antenna are placed perpendicularly to each other on a 40x40 mm2 FR4 substrate. Each element is fed by a CPW (coplanar waveguide) line. Two slits and an I-shaped slot are etched into the patch, and by varying their parameters; a good matching is achieved in the lower (4.9 GHz) and upper (17 GHz) frequency bands. However, 25 and 30 dB isolations are attained in the lower and upper bands, using the polarization diversity technique and adding stubs on the ground plane. A prototype of the proposed antenna is fabricated and measured. Moreover, the performance of the MIMO antenna is studied in terms of ECC (envelope correlation coefficient), DG (diversity gain), TARC (total active reflection coefficient), realized gain, efficiency, and radiation pattern, validated with the measured results, and showed a good agreement
Impact of ion irradiation-induced interface intermixing on the magnetic and electrical properties of magnetic tunnel junctions
The impact of 400 keV Ar+ irradiation on the magnetic and electrical properties of in-plane magnetized magnetic tunnel junction (MTJ) stacks was investigated by ferromagnetic resonance, vibrating sample magnetometry and current-in-plane tunneling techniques. The ion fluences ranged from 10^12 cm−2 to 5 × 10^15 cm−2. Below 10^14 cm−2, the anisotropy of the Ta-capped FeCoB free layer was weakly modulated, following a decrease in the saturation magnetization. The tunnel magnetoresistance (TMR), along with the exchange-bias and the interlayer exchange coupling providing a stable magnetic configuration to the reference layer, decreased continuously. Above 10^14 cm−2, a strong decrease in the saturation magnetization was accompanied by a loss of the magnetic coupling and of the TMR. We show there is an ion-fluence window where the modulation of magnetic anisotropy can occur while preserving a large TMR and stable magnetic configuration of the MTJ, and demonstrate that the layers surrounding the free layer play a decisive role in determining the trend of the magnetic anisotropy modulation resulting from the irradiation. Our results provide guidance for the tailoring of MTJ parameters via ion irradiation, which we propose as a potentially suitable technique for setting the magnetic easy-cone state in MTJ for attaining field-free, fast, and non-stochastic magnetization switching.publishe
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