scholarly journals Magnetometer-Based Drift Correction During Rest in IMU Arm Motion Tracking

Sensors ◽  
2019 ◽  
Vol 19 (6) ◽  
pp. 1312 ◽  
Author(s):  
Frieder Wittmann ◽  
Olivier Lambercy ◽  
Roger Gassert
Keyword(s):  
Magnetic Field ◽  
Real Time ◽  
Video Game ◽  
Homogeneous Magnetic Field ◽  
Inhomogeneous Magnetic Field ◽  
Alternative Methods ◽  
Local Magnetic Field ◽  
Magnetic Field Direction ◽  
Drift Correction ◽  
Time Motion

Real-time motion capture of the human arm in the home environment has many usecases, such as video game and therapy applications. The required tracking can be based onoff-the-shelf Inertial Measurement Units (IMUs) with integrated three-axis accelerometers, gyroscopes,and magnetometers. However, this usually requires a homogeneous magnetic field to correctfor orientation drift, which is often not available inside buildings. In this paper, RPMC (RestPose Magnetometer-based drift Correction), a novel method that is robust to long term drift inenvironments with inhomogeneous magnetic fields, is presented. The sensor orientation is estimatedby integrating the angular velocity measured by the gyroscope and correcting drift around the pitchand roll axes with the acceleration information. This commonly leads to short term drift aroundthe gravitational axis. Here, during the calibration phase, the local magnetic field direction for eachsensor, and its orientation relative to the inertial frame, are recorded in a rest pose. It is assumed thatarm movements in free space are exhausting and require regular rest. A set of rules is used to detectwhen the user has returned to the rest pose, to then correct for the drift that has occurred with themagnetometer. Optical validations demonstrated accurate (root mean square error RMS = 6.1), lowlatency (61 ms) tracking of the user’s wrist orientation, in real time, for a full hour of arm movements.The reduction in error relative to three alternative methods implemented for comparison was between82.5% and 90.7% for the same movement and environment. Therefore, the proposed arm trackingmethod allows for the correction of orientation drift in an inhomogeneous magnetic field by exploitingthe user’s need for frequent rest.

scholarly journals Towards Functional Mobile Microrobotic Systems

Robotics ◽  
2019 ◽  
Vol 8 (3) ◽  
pp. 69 ◽  
Author(s):  
Georges Adam ◽  
Sagar Chowdhury ◽  
Maria Guix ◽  
Benjamin V. Johnson ◽  
Chenghao Bi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Real Time ◽  
Local Magnetic Field ◽  
Force Sensing ◽  
Magnetic Actuation ◽  
Complex Surfaces ◽  
Independent Control ◽  
Dry Conditions

This paper presents our work over the last decade in developing functional microrobotic systems, which include wireless actuation of microrobots to traverse complex surfaces, addition of sensing capabilities, and independent actuation of swarms of microrobots. We will discuss our work on the design, fabrication, and testing of a number of different mobile microrobots that are able to achieve these goals. These microrobots include the microscale magnetorestrictive asymmetric bimorph microrobot ( μ MAB), our first attempt at magnetic actuation in the microscale; the microscale tumbling microrobot ( μ TUM), our microrobot capable of traversing complex surfaces in both wet and dry conditions; and the micro-force sensing magnetic microrobot ( μ FSMM), which is capable of real-time micro-force sensing feedback to the user as well as intuitive wireless actuation. Additionally, we will present our latest results on using local magnetic field actuation for independent control of multiple microrobots in the same workspace for microassembly tasks.

scholarly journals Solitary waves observed in the auroral zone: the Cluster multi-spacecraft perspective

2004 ◽  
Vol 11 (2) ◽  
pp. 183-196 ◽  
Author(s):  
J. S. Pickett ◽  
S. W. Kahler ◽  
L.-J. Chen ◽  
R. L. Huff ◽  
O. Santolík ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solitary Waves ◽  
Correlation Study ◽  
Auroral Zone ◽  
Potential Change ◽  
Local Magnetic Field ◽  
Double Layers ◽  
Magnetic Field Direction ◽  
Field Lines ◽  
Generation Mechanisms

Abstract. We report on recent measurements of solitary waves made by the Wideband Plasma Wave Receiver located on each of the four Cluster spacecraft at 4.5-6.5RE (well above the auroral acceleration region) as they cross field lines that map to the auroral zones. These solitary waves are observed in the Wideband data as isolated bipolar and tripolar waveforms. Examples of the two types of pulses are provided. The time durations of the majority of both types of solitary waves observed in this region range from about 0.3 up to 5ms. Their peak-to-peak amplitudes range from about 0.05 up to 20mV/m, with a few reaching up to almost 70mV/m. There is essentially no potential change across the bipolar pulses. There appears to be a small, measurable potential change, up to 0.5V, across the tripolar pulses, which is consistent with weak or hybrid double layers. A limited cross-spacecraft correlation study was carried out in order to identify the same solitary wave on more than one spacecraft. We found no convincing correlations of the bipolar solitary waves. In the two cases of possible correlation of the tripolar pulses, we found that the solitary waves are propagating at several hundred to a few thousand km/s and that they are possibly evolving (growing, decaying) as they propagate from one spacecraft to the next. Further, they have a perpendicular (to the magnetic field) width of 50km or greater and a parallel width of about 2-5km. We conclude, in general, however, that the Cluster spacecraft at separations along and perpendicular to the local magnetic field direction of tens of km and greater are too large to obtain positive correlations in this region. Looking at the macroscale of the auroral zone at 4.5-6.5RE, we find that the onsets of the broadband electrostatic noise associated with the solitary waves observed in the spectrograms of the WBD data are generally consistent with propagation of the solitary waves up the field lines (away from Earth), or with particles or waves propagating up the field line, which leads to local generation of the solitary waves all along the field lines. A discussion of the importance of these solitary waves in magnetospheric processes and their possible generation mechanisms, through electron beam instabilities and turbulence, is provided.

Morphology of Aluminum Nanopowder Combustion Products in a Magnetic Field in Air

2016 ◽  
Vol 685 ◽  
pp. 516-520 ◽  
Author(s):  
Andrei V. Mostovshchikov ◽  
Alexander P. Ilyin ◽  
Irina K. Zabrodina
Keyword(s):  
Magnetic Field ◽  
Homogeneous Magnetic Field ◽  
Combustion Products ◽  
Inhomogeneous Magnetic Field ◽  
Oxidation Products ◽  
Structural Units ◽  
Electron Microscope Investigation ◽  
Aluminum Nanopowder ◽  
Micron Size ◽  
Thermal Flows

The microstructure of aluminum nanopowder combustion crystalline products in air and the influence of a constant magnetic field (with induction of 0.3 T) on their structures have been studied. It was revealed that in the combustion products of free-poured aluminum nanopowder two-level whiskers are present. Hexagonal single crystals are formed by combustion in air in a homogeneous magnetic field, and in case of inhomogeneous magnetic field (with induction of 0.3 T) faceted elongated crystals of micron size are generated. The crystallites of such structure are formed due to the mass transfer of the combustion products in the direction of thermal flows. Ordered six-sided crystal structures are formed by overcooling the oxidation products by the action of magnetic field and by increasing the mobility of their structural units in recrystallization thermal wave. According to electron- microscope investigation the formation of the faceted crystals is possible with optimal sizes of combustion product particles.

A two-spacecraft study of Mars induced magnetosphere's response to upstream conditions

2020 ◽  
Author(s):  
Katerina Stergiopoulou ◽  
Niklas Edberg ◽  
David Andrews ◽  
Beatriz Sánchez-Cano
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Real Time ◽  
Dynamic Pressure ◽  
Local Magnetic Field ◽  
Mars Atmosphere ◽  
Solar Wind Magnetic Field ◽  
Magnetic Field Magnitude ◽  
Induced Field ◽  
The Imf

<p>We investigate the effects of the upstream solar wind magnetic field on the Martian induced magnetosphere. This is a two-spacecraft study, for which we use Mars Express (MEX) magnetic field magnitude data from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument and Interplanetary Magnetic Field (IMF) measurements and solar wind density and velocity from the magnetometer (MAG) and the Solar Wind Ion Analyzer (SWIA) on board Mars Atmosphere and Volatile EvolutioN (MAVEN), from November 2014 to November 2018. Equally temporally spaced echoes appear in MARSIS' ionograms from which the electron cyclotron frequency and eventually the magnitude of the local magnetic field can be calculated. At the same time solar wind magnetic field data and solar wind parameters from MAG and SWIA respectively are utilized, providing the solar wind input to the Martian system. We make real time comparisons of the IMF and the induced magnetic field in the environment of Mars and we test the ratio B<sub>(MEX)</sub> /B<sub>(MAVEN)</sub>  against various parameters such as the solar wind dynamic pressure, velocity, density, Mach number as well as the Martian seasons, latitudes and heliocentric distances. Additionally, we search for disturbances in IMF which then can be traced in the induced field ultimately revealing the response time of the induced magnetosphere to the solar wind behaviour. <br />MEX and MAVEN measurements combined allow us to investigate the response of the Martian induced magnetosphere to the solar wind magnetic field. Real time comparisons of the IMF and the induced field could help us understand the mechanisms controlling the structure of the Martian induced magnetosphere. </p>

Determining Electromechanical Network Model Parameters of a Piezomagnetic Unimorph Structure With Finite-Element Simulations

2012 ◽  
Author(s):  
Uwe Marschner ◽  
Eric Starke
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Network Model ◽  
Magnetic System ◽  
Magnetic Layer ◽  
Homogeneous Magnetic Field ◽  
Inhomogeneous Magnetic Field ◽  
Model Parameters ◽  
Electromechanical Properties ◽  
Fixed Beam

Two-layer piezomagnetic elements within a homogeneous magnetic field have been well studied. In this paper the effect of an inhomogeneous magnetic field distribution in the magnetic layer on the electromechanical properties of a two-layer element with planar conductor arrangement on top is investigated. Based on static Finite Element (FE) simulations the parameters of its network model are determined. The inductance of the arrangement with and without magnetic layer allows the calculation of the reluctances of the magnetic system. Magnetic field strength and moment of the fixed-fixed beam give the magnetomechanical transduction coefficient, moment and deflection the bending compliance. The dynamic behavior of the electromechanical transducer can be calculated efficiently by the completed network model in sensing as well as actuation direction.

scholarly journals Proton beam velocity distributions in an interplanetary coronal mass ejection

2009 ◽  
Vol 27 (2) ◽  
pp. 869-875 ◽  
Author(s):  
E. Marsch ◽  
S. Yao ◽  
C.-Y. Tu
Keyword(s):  
Magnetic Field ◽  
Coronal Mass Ejection ◽  
Flow Speed ◽  
Local Magnetic Field ◽  
Magnetic Field Direction ◽  
Interplanetary Coronal Mass Ejection ◽  
Magnetic Field Rotation ◽  
Solar Wind Flow ◽  
Field Fluctuations ◽  
Mass Ejection

Abstract. The plasma and magnetic-field instruments on the Helios 2 spacecraft, which was on 3 April 1979 located at 0.68 AU, detected an interplanetary coronal mass ejection (ICME) that revealed itself by the typical signature of magnetic field rotation. The solar wind flow speed ranged between 400 and 500 km/s. We present here some detailed proton velocity distributions measured within the ICME. These cold distributions are characterized by an isotropic core part with a low temperature, T≤105 K, but sometimes reveal a broad and extended hot proton tail or beam propagating along the local magnetic field direction. These beams lasted only for about an hour and were unusual as compared with the normal ICME protons distribution which were comparatively isotropic. Furthermore, we looked into the velocity and field fluctuations in this ICME and found signatures of Alfvén waves, which might be related to the occurrence of the hot proton beams. However, it cannot be excluded that the beam originated from the Sun.

scholarly journals Use of the Relaxometry Technique for Quantification of Paramagnetic Ions in Aqueous Solutions and a Comparison with Other Analytical Methods

2016 ◽  
Vol 2016 ◽  
pp. 1-5 ◽  
Author(s):  
Bruna Ferreira Gomes ◽  
Juliana Soares da Silva Burato ◽  
Carlos Manuel Silva Lobo ◽  
Luiz Alberto Colnago
Keyword(s):  
Magnetic Field ◽  
Analytical Methods ◽  
Visible Region ◽  
Homogeneous Magnetic Field ◽  
Inhomogeneous Magnetic Field ◽  
Metallic Surfaces ◽  
Absorption Bands ◽  
Limit Of Quantification ◽  
Chemical Indicators ◽  
Paramagnetic Ions

We have demonstrated that the relaxometry technique is very efficient to quantify paramagnetic ions duringin situelectrolysis measurements. Therefore, the goal of this work was to validate the relaxometry technique in the determination of the concentration of the ions contained in electrolytic solutions, Cu2+, Ni2+, Cr3+, and Mn2+, and compare it with other analytical methods. Two different NMR spectrometers were used: a commercial spectrometer with a homogeneous magnetic field and a home-built unilateral sensor with an inhomogeneous magnetic field. Without pretreatment, manganese ions do not have absorption bands in the UV-Visible region, but it is possible to quantify them using relaxometry (the limit of quantification is close to 10−5 mol L−1). Therefore, since the technique does not require chemical indicators and is a cheap and robust method, it can be used as a replacement for some conventional quantification techniques. The relaxometry technique could be applied to evaluate the corrosion of metallic surfaces.

scholarly journals On the generation of solitary waves observed by Cluster in the near-Earth magnetosheath

2005 ◽  
Vol 12 (2) ◽  
pp. 181-193 ◽  
Author(s):  
J. S. Pickett ◽  
L.-J. Chen ◽  
S. W. Kahler ◽  
O. Santolík ◽  
M. L. Goldstein ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solitary Waves ◽  
Bow Shock ◽  
Generation Mechanism ◽  
Local Magnetic Field ◽  
Magnetic Field Direction ◽  
Waveform Data ◽  
Background Magnetic Field ◽  
Ion Velocity ◽  
The Magnetic Field

Abstract. Through case studies involving Cluster waveform observations, solitary waves in the form of bipolar and tripolar pulses have recently been found to be quite abundant in the near-Earth dayside magnetosheath. We expand on the results of those previous studies by examining the distribution of solitary waves from the bow shock to the magnetopause using Cluster waveform data. Cluster's orbit allows for the measurement of solitary waves in the magnetosheath from about 10 RE to 19.5 RE. Our results clearly show that within the magnetosheath, solitary waves are likely to be observed at any distance from the bow shock and that this distance has no dependence on the time durations and amplitudes of the solitary waves. In addition we have found that these same two quantities show no dependence on either the ion velocity or the angle between the ion velocity and the local magnetic field direction. These results point to the conclusion that the solitary waves are probably created locally in the magnetosheath at multiple locations, and that the generation mechanism is most likely not solely related to ion dynamics, if at all. To gain insight into a possible local generation mechanism, we have examined the electron differential energy flux characteristics parallel and perpendicular to the magnetic field, as well as the local electron plasma and cyclotron frequencies and the type of bow shock that Cluster is behind, for several time intervals where solitary waves were observed in the magnetosheath. We have found that solitary waves are most likely to be observed when there are counterstreaming (~parallel and anti-parallel to the magnetic field) electrons at or below about 100eV. However, there are times when these counterstreaming electrons are present when solitary waves are not. During these times the background magnetic field strength is usually very low (<10nT), implying that the amplitudes of the solitary waves, if present, would be near or below those of other waves and electrostatic fluctuations in this region making it impossible to isolate or clearly distinguish them from these other emissions in the waveform data. Based on these results, we have concluded that some of the near-Earth magnetosheath solitary waves, perhaps in the form of electron phase-space holes, may be generated locally by a two-stream instability involving electrons based on the counterstreaming electrons that are often observed when solitary waves are present. We have not ruled out the possibility that the solitary waves could be generated as a result of the lower-hybrid Buneman instability in the presence of an electron beam, through the electron acoustic mode or through processes involving turbulence, which is almost always present in the magnetosheath, but these will be examined in a more comprehensive study in the future.

scholarly journals Simulating TeV gamma-ray morphologies of shell-type supernova remnants

2020 ◽  
Vol 498 (4) ◽  
pp. 5557-5573 ◽  
Author(s):  
Matteo Pais ◽  
Christoph Pfrommer
Keyword(s):  
Magnetic Field ◽  
Supernova Remnants ◽  
Large Scale ◽  
Gamma Ray ◽  
Cosmic Ray ◽  
Local Magnetic Field ◽  
Magnetic Field Direction ◽  
Best Fitting ◽  
Gamma Ray Emission ◽  
Fitting Model

ABSTRACT Supernova remnant (SNR) shocks provide favourable sites of cosmic ray (CR) proton acceleration if the local magnetic field direction is quasi-parallel to the shock normal. Using the moving-mesh magnetohydrodynamical (MHD) code arepo we present a suite of SNR simulations with CR acceleration in the Sedov–Taylor phase that combine different magnetic field topologies, density distributions with gradients and large-scale fluctuations, and – for our core-collapse SNRs – a multiphase interstellar medium with dense clumps with a contrast of 104. Assuming the hadronic gamma-ray emission model for the TeV gamma-ray emission, we find that large-amplitude density fluctuations of δρ/ρ0 ≳ 75 per cent are required to strongly modulate the gamma-ray emissivity in a straw man’s model in which the acceleration efficiency is independent of magnetic obliquity. However, this causes strong corrugations of the shock surface that are ruled out by gamma-ray observations. By contrast, magnetic obliquity-dependent acceleration can easily explain the observed variance in gamma-ray morphologies ranging from SN1006 (with a homogeneous magnetic field) to Vela Junior and RX J1713 (with a turbulent field) in a single model that derives from plasma particle-in-cell simulations. Our best-fitting model for SN1006 has a large-scale density gradient of ∇n ≃ 0.0034 cm−3 pc−1 pointing from south-west to north-east and a magnetic inclination with the plane of the sky of ≲10°. Our best-fitting model for Vela Junior and RX J1713 adopts a combination of turbulent magnetic field and dense clumps to explain their TeV gamma-ray morphologies and moderate shock corrugations.

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