782 research outputs found
Yet Another Tutorial of Disturbance Observer: Robust Stabilization and Recovery of Nominal Performance
This paper presents a tutorial-style review on the recent results about the
disturbance observer (DOB) in view of robust stabilization and recovery of the
nominal performance. The analysis is based on the case when the bandwidth of
Q-filter is large, and it is explained in a pedagogical manner that, even in
the presence of plant uncertainties and disturbances, the behavior of real
uncertain plant can be made almost similar to that of disturbance-free nominal
system both in the transient and in the steady-state. The conventional DOB is
interpreted in a new perspective, and its restrictions and extensions are
discussed
Robotic Herding of a Flock of Birds Using an Unmanned Aerial Vehicle
In this paper, we derive an algorithm for enabling a single robotic unmanned aerial vehicle to herd a flock of birds away from a designated volume of space, such as the air space around an airport. The herding algorithm, referred to as the m-waypoint algorithm, is designed using a dynamic model of bird flocking based on Reynolds’ rules. We derive bounds on its performance using a combination of reduced-order modeling of the flock's motion, heuristics, and rigorous analysis. A unique contribution of the paper is the experimental demonstration of several facets of the herding algorithm on flocks of live birds reacting to a robotic pursuer. The experiments allow us to estimate several parameters of the flocking model, and especially the interaction between the pursuer and the flock. The herding algorithm is also demonstrated using numerical simulations
More Proofs for `Determination of Stability with respect to Positive Orthant for a Class of Positive Nonlinear Systems'
This is a supplement material for a published article by the authors.In the published paper `Determination of Stability with respect to Positive Orthant
for a Class of Positive Nonlinear Systems,' IEEE Trans. on Automatic Control, vol. 53, no. 5, pp. 1329-1334, 2008, by the authors, some proofs are omitted due to the space limitation of the journal. In this note, we present those omitted proofs
Enrichment of rare alleles within epigenetic chromatin marks in the first intron
In previous studies, we demonstrated that some sites in the first intron likely regulate gene expression. In the present work, we sought to further confirm the functional relevance of first intron sites by estimating the quantity of rare alleles in the first intron. A basic hypothesis posited herein is that genomic regions carrying more functionally important sites will have a higher proportion of rare alleles. We estimated the proportions of rare single nucleotide polymorphisms with a minor allele frequency < 0.01 located in several histone marks in the first introns of various genes, and compared them with those in other introns and those in 2-kb upstream regions. As expected, rare alleles were found to be significantly enriched in most of the regulatory sites located in the first introns. Meanwhile, transcription factor binding sites were significantly more enriched in the 2-kb upstream regions (i.e., the regions of putative promoters of genes) than in the first introns. These results strongly support our proposal that the first intron sites of genes may have important regulatory functions in gene expression independent of promoters
AoA-based Position and Orientation Estimation Using Lens MIMO in Cooperative Vehicle-to-Vehicle Systems
Positioning accuracy is a critical requirement for vehicle-to-everything
(V2X) use cases. Therefore, this paper derives the theoretical limits of
estimation for the position and orientation of vehicles in a cooperative
vehicle-to-vehicle (V2V) scenario, using a lens-based multiple-input
multiple-output (lens-MIMO) system. Following this, we analyze the
Cramr-Rao lower bounds (CRLBs) of the position and
orientation estimation and explore a received signal model of a lens-MIMO for
the particular angle of arrival (AoA) estimation with a V2V geometric model.
Further, we propose a lower complexity AoA estimation technique exploiting the
unique characteristics of the lens-MIMO for a single target vehicle; as a
result, its estimation scheme is effectively extended by the successive
interference cancellation (SIC) method for multiple target vehicles. Given
these AoAs, we investigate the lens-MIMO estimation capability for the
positions and orientations of vehicles. Subsequently, we prove that the
lens-MIMO outperforms a conventional uniform linear array (ULA) in a certain
configuration of a lens's structure. Finally, we confirm that the proposed
localization algorithm is superior to ULA's CRLB as the resolution of the lens
increases in spite of the lower complexity.Comment: 16 pages, 11 figure
Addendum for "A Study of Disturbance Observers with Unknown Relative Degree"
[Preprint] The paper "A Study of Disturbance Observers with Unknown Relative Degree" [1] by the authors could not include the proofs for Theorem 5 and Theorem 6 due to the page limit. We provide them in this supplementary document, and an example is included with simulation results
Anisotropic Dirac fermions in a Bi square net of SrMnBi2
We report the highly anisotropic Dirac fermions in a Bi square net of
SrMnBi2, based on a first principle calculation, angle resolved photoemission
spectroscopy, and quantum oscillations for high-quality single crystals. We
found that the Dirac dispersion is generally induced in the (SrBi)+ layer
containing a double-sized Bi square net. In contrast to the commonly observed
isotropic Dirac cone, the Dirac cone in SrMnBi2 is highly anisotropic with a
large momentum-dependent disparity of Fermi velocities of ~ 8. These findings
demonstrate that a Bi square net, a common building block of various layered
pnictides, provide a new platform that hosts highly anisotropic Dirac fermions.Comment: 5 pages, 4 figure
Sparse RF Lens Antenna Array Design for AoA Estimation in Wideband Systems: Placement Optimization and Performance Analysis
In this paper, we propose a novel architecture for a lens antenna array (LAA)
designed to work with a small number of antennas and enable angle-of-arrival
(AoA) estimation for advanced 5G vehicle-to-everything (V2X) use cases that
demand wider bandwidths and higher data rates. We derive a received signal in
terms of optical analysis to consider the variability of the focal region for
different carrier frequencies in a wideband multi-carrier system. By taking
full advantage of the beam squint effect for multiple pilot signals with
different frequencies, we propose a novel reconfiguration of antenna array
(RAA) for the sparse LAA and a max-energy antenna selection (MS) algorithm for
the AoA estimation. In addition, this paper presents an analysis of the
received power at the single antenna with the maximum energy and compares it to
simulation results. In contrast to previous studies on LAA that assumed a large
number of antennas, which can require high complexity and hardware costs, the
proposed RAA with MS estimation algorithm is shown meets the requirements of 5G
V2X in a vehicular environment while utilizing limited RF hardware and has low
complexity.Comment: 15 pages, 10 figure
Deformation and fatigue behaviors of carburized automotive gear steel and predictions
The fatigue behavior of carburized components such as automotive transmission gears is very complex due to hardness and microstructure difference, residual stresses and multi-axial stress states developed between the case and the core. In addition, automotive gears in service, commonly used in helical type, are actually subjected to complex stress conditions such as bending, torsion, and contact stress states. This study presents experimental and analytical results on deformation behavior of carburized steels, widely used in automotive gears, under cyclic stress conditions including axial and torsion loadings. Axial fatigue tests and rotating bending fatigue tests are also included. Predictions of cyclic deformation and fatigue behaviors of the carburized steel with two-layer model are compared with experimental results. The carburized steel investigated in this study exhibited cyclic softening under both axial loading and torsional loading. Predicted results with simple two-layer model for the cyclic deformation and fatigue behaviors were comparatively similar to the experimental data
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