170 research outputs found
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Model-Free Control applied for position control of Quadrotor using ROS
In this paper, an intelligent PD (iPD) controller named Model-Free Controller is proposed. Herein, it is used to control the position of a Vertical Take-Off and Landing (VTOL) Unmanned Aerial Vehicle (UAV) Quadrotor. This strategy increases the control performance as well as its robustness level with respect to the classical PD. This is due to the estimation principle provided by the ultra-local model that estimate the unknown disturbances and uncertainties each iteration. The efficiency of the proposed strategy is shown through various numerical simulations where a thorough analysis is provided. Moreover, a comparison study is elaborated between the iPD and the classical PD
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Adaptive fuzzy model-free control for 3D trajectory tracking of quadrotor
This paper presents a novel adaptive control strategy with rejection ability for unmanned aerial vehicles (UAVs), namely fuzzy model-free control (FMFC). It is based on the model-free control (MFC) concept, where the control parameters are tuned online using fuzzy logic. The controller assumes an ultra-local model that can compensate unknown/unmodelled dynamics, uncertainties and external disturbances, ensuring a good robustness level. Moreover, the fuzzy logic system is used to tune online the proportional-derivative terms due to its heuristic aspect. These compensation and adaptation mechanisms allow ensuring good compromise robustness-performance even in the presence of disturbances. Several experiments, using RotorS Gazebo micro aerial vehicle (MAV) simulator, are provided to demonstrate the effectiveness of the proposed controller compared with other techniques. The fuzzy model-free controller shows superior performance without the time-consuming and tedious tuning task
Circulating microRNAs as potential biomarkers of early vascular damage in vitamin D deficiency, obese, and diabetic patients
Vitamin D3 deficiency, obesity, and diabetes mellitus (DM) have been shown to increase the risk of cardiovascular diseases (CVDs). However, the early detection of vascular damage in those patients is still difficult to ascertain. MicroRNAs (miRNAs) are recognized to play a critical role in initiation and pathogenesis of vascular dysfunction. Herein, we aimed to identify circulating miRNA biomarkers of vascular dysfunction as early predictors of CVDs. We have recruited 23 middle-aged Emiratis patients with the following criteria: A healthy control group with vitamin D ≥ 20ng, and BMI 1.5) in high-risk patients for CVDs vs healthy controls. Collectively, our result indicates that four specific circulating miRNA signature, may be utilized as non-invasive, diagnostic and prognostic biomarkers for early vascular damage in patients suffering from vitamin D deficiency, obesity and DM
Dynamical compressibility of dense granular shear flows
It has been conjectured by Bagnold [1] that an assembly of hard
non-deformable spheres could behave as a compressible medium when slowly
sheared, as the average density of such a system effectively depends on the
confining pressure. Here we use discrete element simulations to show the
existence of transverse and sagittal waves associated to this dynamical
compressibility. For this purpose, we study the resonance of these waves in a
linear Couette cell and compare the results with those predicted from a
continuum local constitutive relation
Helicobacter Pylori stool antigens: post and pre-treatment evalutation of two methods performances in adult’s strains in Algeria
Optimal Byzantine Resilient Convergence in Asynchronous Robot Networks
We propose the first deterministic algorithm that tolerates up to
byzantine faults in -sized networks and performs in the asynchronous
CORDA model. Our solution matches the previously established lower bound for
the semi-synchronous ATOM model on the number of tolerated Byzantine robots.
Our algorithm works under bounded scheduling assumptions for oblivious robots
moving in a uni-dimensional space
Rendezvous on a Line by Location-Aware Robots Despite the Presence of Byzantine Faults
A set of mobile robots is placed at points of an infinite line. The robots
are equipped with GPS devices and they may communicate their positions on the
line to a central authority. The collection contains an unknown subset of
"spies", i.e., byzantine robots, which are indistinguishable from the
non-faulty ones. The set of the non-faulty robots need to rendezvous in the
shortest possible time in order to perform some task, while the byzantine
robots may try to delay their rendezvous for as long as possible. The problem
facing a central authority is to determine trajectories for all robots so as to
minimize the time until the non-faulty robots have rendezvoused. The
trajectories must be determined without knowledge of which robots are faulty.
Our goal is to minimize the competitive ratio between the time required to
achieve the first rendezvous of the non-faulty robots and the time required for
such a rendezvous to occur under the assumption that the faulty robots are
known at the start. We provide a bounded competitive ratio algorithm, where the
central authority is informed only of the set of initial robot positions,
without knowing which ones or how many of them are faulty. When an upper bound
on the number of byzantine robots is known to the central authority, we provide
algorithms with better competitive ratios. In some instances we are able to
show these algorithms are optimal
Pattern formation
The Pattern Formation problem is one of the most important coordination problem for robotic systems. Initially the entities are in arbitrary positions; within finite time they must arrange themselves in the space so to form a pattern given in input. In this chapter, we will mainly deal with the problem in the OBLOT model
Multisite campaign on the open cluster M67. III. Delta Scuti pulsations in the blue stragglers
We have made an asteroseismic analysis of the variable blue stragglers in the
open cluster M67. The data set consists of photometric time series from eight
sites using nine 0.6-2.1 meter telescopes with a time baseline of 43 days. In
two stars, EW Cnc and EX Cnc, we detect the highest number of frequencies (41
and 26) detected in delta Scuti stars belonging to a stellar cluster, and EW
Cnc has the second highest number of frequencies detected in any delta Scuti
star. We have computed a grid of pulsation models that take the effects of
rotation into account. The distribution of observed and theoretical frequencies
show that in a wide frequency range a significant fraction of the radial and
non-radial low-degree modes are excited to detectable amplitudes. Despite the
large number of observed frequencies we cannot constrain the fundamental
parameters of the stars. To make progress we need to identify the degrees of
some of the modes either from multi-colour photometry or spectroscopy.Comment: 15 pages, 14 figs, one appendix. Part three in a series of papers
describing results from an extensive multi-site campaign on the open cluster
M6
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