scholarly journals Robotic Active Information Gathering for Spatial Field Reconstruction with Rapidly-Exploring Random Trees and Online Learning of Gaussian Processes

Sensors ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 1016 ◽  
Author(s):  
Alberto Viseras ◽  
Dmitriy Shutin ◽  
Luis Merino
Keyword(s):  
Magnetic Field ◽  
Gaussian Processes ◽  
Complex Dynamics ◽  
Information Gathering ◽  
Random Trees ◽  
Online Information ◽  
Novel Approach ◽  
Path Cost ◽  
The Magnetic Field ◽  
Minimizing Path

Information gathering (IG) algorithms aim to intelligently select a mobile sensor actions required to efficiently obtain an accurate reconstruction of a physical process, such as an occupancy map, or a magnetic field. Many recent works have proposed algorithms for IG that employ Gaussian processes (GPs) as underlying model of the process. However, most algorithms discretize the state space, which makes them computationally intractable for robotic systems with complex dynamics. Moreover, they are not suited for online information gathering tasks as they assume prior knowledge about GP parameters. This paper presents a novel approach that tackles the two aforementioned issues. Specifically, our approach includes two intertwined steps: (i) a Rapidly-Exploring Random Tree (RRT) search that allows a robot to identify unvisited locations, and to learn the GP parameters, and (ii) an RRT*-based informative path planning that guides the robot towards those locations by maximizing the information gathered while minimizing path cost. The combination of the two steps allows an online realization of the algorithm, while eliminating the need for discretization. We demonstrate that our proposed algorithm outperforms state-of-the-art both in simulations, and in a lab experiment in which a ground-based robot explores the magnetic field intensity within an indoor environment populated with obstacles.

scholarly journals Distributed Multi-Robot Information Gathering under Spatio-Temporal Inter-Robot Constraints

Sensors ◽  
2020 ◽  
Vol 20 (2) ◽  
pp. 484
Author(s):  
Alberto Viseras ◽  
Zhe Xu ◽  
Luis Merino
Keyword(s):  
Decision Making ◽  
Collision Avoidance ◽  
Physical Process ◽  
Wind Field ◽  
Complex Dynamics ◽  
Information Gathering ◽  
Distributed Decision Making ◽  
Novel Approach ◽  
Distributed Decision ◽  
Multi Robot

Information gathering (IG) algorithms aim to intelligently select the mobile robotic sensor actions required to efficiently obtain an accurate reconstruction of a physical process, such as an occupancy map, a wind field, or a magnetic field. Recently, multiple IG algorithms that benefit from multi-robot cooperation have been proposed in the literature. Most of these algorithms employ discretization of the state and action spaces, which makes them computationally intractable for robotic systems with complex dynamics. Moreover, they cannot deal with inter-robot restrictions such as collision avoidance or communication constraints. This paper presents a novel approach for multi-robot information gathering (MR-IG) that tackles the two aforementioned restrictions: (i) discretization of robot’s state space, and (ii) dealing with inter-robot constraints. Here we propose an algorithm that employs: (i) an underlying model of the physical process of interest, (ii) sampling-based planners to plan paths in a continuous domain, and (iii) a distributed decision-making algorithm to enable multi-robot coordination. In particular, we use the max-sum algorithm for distributed decision-making by defining an information-theoretic utility function. This function maximizes IG, while fulfilling inter-robot communication and collision avoidance constraints. We validate our proposed approach in simulations, and in a field experiment where three quadcopters explore a simulated wind field. Results demonstrate the effectiveness and scalability with respect to the number of robots of our approach.

scholarly journals Numerical simulations of the emerging plasma blob into a solar coronal hole

2019 ◽  
Vol 489 (2) ◽  
pp. 2769-2774 ◽  
Author(s):  
Anamaría Navarro ◽  
K Murawski ◽  
D Wójcik ◽  
F D Lora-Clavijo
Keyword(s):  
Magnetic Field ◽  
Coronal Hole ◽  
Complex Dynamics ◽  
Hot Plasma ◽  
Magnetic Resistivity ◽  
Plasma Blob ◽  
Parametric Studies ◽  
Magnetic Plasma ◽  
The Magnetic Field ◽  
Solar Coronal

ABSTRACT We numerically simulate emergence of a magnetic plasma blob into a solar coronal hole. This blob may be associated with granulation and therefore it has a weak magnetic field. Two-dimensional simulations are performed using the magnus code which solves magnetohydrodynamic equations, taking into account magnetic resistivity and thermal conduction. As a result of the interaction of the emerging blob with the ambient plasma, the magnetic lines experience reconnection with the blob getting flattened and deformed with time. Additionally, this process launches a vertical outflow of hot plasma and the chromosphere in its response increases its temperature. We perform parametric studies by varying the magnitude of the magnetic field of the blob and observing the net heating of the chromosphere. These studies are inspired by realistic simulations of granulation made with the use of two-fluid joanna code. In these simulations a number of magnetic blobs are detected in the convection zone and in the photosphere. From the numerical results, we conclude that as a result of granulation operating in a solar quiet region the emerging blob may trigger very complex dynamics in the upper regions of the solar atmosphere, and the associated outflows may be a source of heating of the chromosphere and possibly the solar corona.

BOUBAKER POLYNOMIALS EXPRESSION TO THE MAGNETIC PHASE-SHIFT INDUCED IN LEON–VIGMOND 3D-MODEL OF THE HUMAN HEART

2012 ◽  
Vol 12 (01) ◽  
pp. 1250016
Author(s):  
M. DADA ◽  
M. A. AWEDA ◽  
O. B. AWOJOYOGBE ◽  
K. BOUBAKER
Keyword(s):  
Magnetic Field ◽  
Phase Shift ◽  
Human Heart ◽  
3D Model ◽  
Complex Dynamics ◽  
Mathematical Formulation ◽  
Daunting Task ◽  
Boubaker Polynomials ◽  
Heart Modeling ◽  
The Magnetic Field

The heart is simulated as an electrically controlled fluid pump which operates by mechanical contraction. Human heart modeling is undoubtedly a computationally daunting task which must incorporate magnetic, plastic, mechanic and electric patterns. In this paper, a polynomial mathematical formulation for the magnetic field phase shift in a particular heart 3D-model is proposed. The developed model can give an insight into the local and global complex dynamics of the heart magnetic field under controlled excitation as guides to monitoring i.e., the transition from normal to abnormal myocardial activity or collateral dysfunctions. The used protocol allowed handling the boundary conditions in a smooth way.

scholarly journals Study of Train-Side Passive Magnetic Measurements with Applications to Train Localization

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Oliver Heirich ◽  
Benjamin Siebler ◽  
Erik Hedberg
Keyword(s):  
Magnetic Field ◽  
Magnetic Measurements ◽  
Low Cost ◽  
Magnetic Sensors ◽  
Single Chip ◽  
Novel Approach ◽  
Magnetic Signatures ◽  
Navigation Equipment ◽  
Electronic Compass ◽  
The Magnetic Field

Passive magnetic sensors measure the magnetic field density in three axes and are often integrated on a single chip. These low-cost sensors are widely used in car navigation as well as in battery powered navigation equipment such as smartphones as part of an electronic compass. We focus on a train localization application with multiple, exclusively onboard sensors and a track map. This approach is considered as a base technology for future railway applications such as collision avoidance systems or autonomous train driving. In this paper, we address the following question: how beneficial are passive magnetic measurements for train localization? We present and analyze measurements of two different magnetometers recorded on a regional train at regular passenger service. We show promising correlations of the measurements with the track positions and the traveled switch way. The processed data reveals that the railway environment has repeatable, location-dependent magnetic signatures. This is considered as a novel approach to train localization, as the use of these magnetic signals at first view is not obvious. The proposed methods based on passive magnetic measurements show a high potential to be integrated in new and existing train localization approaches.

Observing the galactic magnetic field

1967 ◽  
Vol 31 ◽  
pp. 375-380
Author(s):  
H. C. van de Hulst
Keyword(s):  
Magnetic Field ◽  
Fair Agreement ◽  
Solar Neighbourhood ◽  
Galactic Magnetic Field ◽  
The Magnetic Field

Various methods of observing the galactic magnetic field are reviewed, and their results summarized. There is fair agreement about the direction of the magnetic field in the solar neighbourhood:l= 50° to 80°; the strength of the field in the disk is of the order of 10-5gauss.

Evolution of Large-Scale Coronal Structures

1994 ◽  
Vol 144 ◽  
pp. 29-33
Author(s):  
P. Ambrož
Keyword(s):  
Magnetic Field ◽  
Field Line ◽  
Large Scale ◽  
Coronal Magnetic Field ◽  
Source Surface ◽  
Solar Cycles ◽  
Characteristic Relationship ◽  
The Magnetic Field ◽  
Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

Emergence of Twisted Magnetic Flux Related Sigmoidal Brightening

2000 ◽  
Vol 179 ◽  
pp. 263-264
Author(s):  
K. Sundara Raman ◽  
K. B. Ramesh ◽  
R. Selvendran ◽  
P. S. M. Aleem ◽  
K. M. Hiremath
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Ultra Violet ◽  
Active Regions ◽  
Morphological Properties ◽  
Energy Storage And Conversion ◽  
The Sun ◽  
X Rays ◽  
The Magnetic Field

Extended AbstractWe have examined the morphological properties of a sigmoid associated with an SXR (soft X-ray) flare. The sigmoid is cospatial with the EUV (extreme ultra violet) images and in the optical part lies along an S-shaped Hαfilament. The photoheliogram shows flux emergence within an existingδtype sunspot which has caused the rotation of the umbrae giving rise to the sigmoidal brightening.It is now widely accepted that flares derive their energy from the magnetic fields of the active regions and coronal levels are considered to be the flare sites. But still a satisfactory understanding of the flare processes has not been achieved because of the difficulties encountered to predict and estimate the probability of flare eruptions. The convection flows and vortices below the photosphere transport and concentrate magnetic field, which subsequently appear as active regions in the photosphere (Rust & Kumar 1994 and the references therein). Successive emergence of magnetic flux, twist the field, creating flare productive magnetic shear and has been studied by many authors (Sundara Ramanet al.1998 and the references therein). Hence, it is considered that the flare is powered by the energy stored in the twisted magnetic flux tubes (Kurokawa 1996 and the references therein). Rust & Kumar (1996) named the S-shaped bright coronal loops that appear in soft X-rays as ‘Sigmoids’ and concluded that this S-shaped distortion is due to the twist developed in the magnetic field lines. These transient sigmoidal features tell a great deal about unstable coronal magnetic fields, as these regions are more likely to be eruptive (Canfieldet al.1999). As the magnetic fields of the active regions are deep rooted in the Sun, the twist developed in the subphotospheric flux tube penetrates the photosphere and extends in to the corona. Thus, it is essentially favourable for the subphotospheric twist to unwind the twist and transmit it through the photosphere to the corona. Therefore, it becomes essential to make complete observational descriptions of a flare from the magnetic field changes that are taking place in different atmospheric levels of the Sun, to pin down the energy storage and conversion process that trigger the flare phenomena.

On the Configuration of the Magnetic Field of β CrB

1976 ◽  
Vol 32 ◽  
pp. 613-622
Author(s):  
I.A. Aslanov ◽  
Yu.S. Rustamov
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Radial Velocity ◽  
Magnetic Field Strength ◽  
Complex Shape ◽  
Rotation Period ◽  
Field Variation ◽  
Magnetic Field Variation ◽  
Secular Variations ◽  
The Magnetic Field

SummaryMeasurements of the radial velocities and magnetic field strength of β CrB were carried out. It is shown that there is a variability with the rotation period different for various elements. The curve of the magnetic field variation measured from lines of 5 different elements: FeI, CrI, CrII, TiII, ScII and CaI has a complex shape specific for each element. This may be due to the presence of magnetic spots on the stellar surface. A comparison with the radial velocity curves suggests the presence of a least 4 spots of Ti and Cr coinciding with magnetic spots. A change of the magnetic field with optical depth is shown. The curve of the Heffvariation with the rotation period is given. A possibility of secular variations of the magnetic field is shown.

Materials for Electron Beam Information Storage

1969 ◽  
Vol 27 ◽  
pp. 152-153 ◽  
Author(s):  
D. E. Speliotis
Keyword(s):  
Magnetic Field ◽  
Electron Beam ◽  
Recent Literature ◽  
Electron Beams ◽  
Information Storage ◽  
The Subject ◽  
The Magnetic Field

The interaction of electron beams with a large variety of materials for information storage has been the subject of numerous proposals and studies in the recent literature. The materials range from photographic to thermoplastic and magnetic, and the interactions with the electron beam for writing and reading the information utilize the energy, or the current, or even the magnetic field associated with the electron beam.

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