scholarly journals Distorter Characterisation Using Mutual Inductance in Electromagnetic Tracking

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 3059 ◽  
Author(s):  
Herman Jaeger ◽  
Pádraig Cantillon-Murphy
Keyword(s):  
Magnetic Field ◽  
Measurement Errors ◽  
Surgical Navigation ◽  
Sensor Arrays ◽  
Medical Robotics ◽  
Mutual Inductance ◽  
Electromagnetic Tracking ◽  
Novel Method ◽  
Transmitter Design ◽  
The Magnetic Field

Electromagnetic tracking (EMT) is playing an increasingly important role in surgical navigation, medical robotics and virtual reality development as a positional and orientation reference. Though EMT is not restricted by line-of-sight requirements, measurement errors caused by magnetic distortions in the environment remain the technology’s principal shortcoming. The characterisation, reduction and compensation of these errors is a broadly researched topic, with many developed techniques relying on auxiliary tracking hardware including redundant sensor arrays, optical and inertial tracking systems. This paper describes a novel method of detecting static magnetic distortions using only the magnetic field transmitting array. An existing transmitter design is modified to enable simultaneous transmission and reception of the generated magnetic field. A mutual inductance model is developed for this transmitter design in which deviations from control measurements indicate the location, magnitude and material of the field distorter to an approximate degree. While not directly compensating for errors, this work enables users of EMT systems to optimise placement of the magnetic transmitter by characterising a distorter’s effect within the tracking volume without the use of additional hardware. The discrimination capabilities of this method may also allow researchers to apply material-specific compensation techniques to minimise position error in the clinical setting.

scholarly journals A virtual platform for real-time performance analysis of electromagnetic tracking systems for surgical navigation

ACTA IMEKO ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 103
Author(s):  
Mattia Alessandro Ragolia ◽  
Filippo Attivissimo ◽  
Attilio Di Nisio ◽  
Anna Maria Lucia Lanzolla ◽  
Marco Scarpetta
Keyword(s):  
Magnetic Field ◽  
Real Time ◽  
Surgical Navigation ◽  
Surgical Instruments ◽  
Accurate Estimation ◽  
Electromagnetic Tracking ◽  
Tracking Systems ◽  
Virtual Platform ◽  
Magnetic Field Generator ◽  
The Magnetic Field

<p class="Abstract">Electromagnetic Tracking Systems (EMTSs) are widely used in surgical navigation, allowing to improve the outcome of diagnosis and surgical interventions, by providing the surgeon with real-time position of surgical instruments during medical procedures. However, particular effort was dedicated to the development of efficient and robust algorithms, to obtain an accurate estimation of the instrument position for distances from the magnetic field generator beyond 0.5 m. Indeed, the main goal is to improve the limited range of current commercial systems, which strongly affects the freedom of movement of the medical team. Studies are currently being conducted to optimize the magnetic field generator configuration (both geometrical arrangements and electrical properties) since it affects tracking accuracy. In this paper, we propose a virtual platform for assessing the performance of EMTSs for surgical navigation, providing real-time results and statistics, and allowing to track instruments both in real and simulated environments. Simulations and experimental tests are performed to validate the proposed virtual platform, by employing it to assess the performance of a real EMTS. The platform offers a real-time tool to analyze EMTS components and field generator configurations, for a deeper understanding of EMTS technology, thus supporting engineers during system design and characterization.</p>

An Adaptive △M-ICCP Geomagnetic Matching Algorithm

2017 ◽  
Vol 71 (3) ◽  
pp. 649-663 ◽  
Author(s):  
Jing Xiao ◽  
Xiusheng Duan ◽  
Xiaohui Qi
Keyword(s):  
Magnetic Field ◽  
Dynamic Environment ◽  
Magnetic Sensor ◽  
Matching Method ◽  
Simulation Experiments ◽  
Matching Algorithm ◽  
Contour Point ◽  
Novel Method ◽  
The Magnetic Field ◽  
Selection Of

In this paper, a novel method is proposed to generate the matching sequence of an ICCP algorithm for aircraft geomagnetic-aided navigation based on the M coding principle. The length of the matching sequence and the selection of the matching points directly affects the performance of the Iterated Closest Contour Point (ICCP) algorithm. This study proposes an adaptive geomagnetic matching method, ΔM-ICCP, to solve the problem of selecting suitable matching lengths, and matching points, when a vehicle is moving in a highly dynamic environment. First, the △M coding principle is adopted to select the matching points based on the information of the magnetic field, the resolution of the magnetic map, and the accuracy of the magnetic sensor. Then, the problem of selecting parameters for the △M-ICCP algorithm is turned into an optimisation problem, which can be solved by a Binary Particle Swarm Optimisation (BPSO) algorithm. Finally, the algorithm is verified through simulation experiments. The proposed algorithm can provide a basis to determine the matching length of the △M-ICCP algorithm and adaptively adjust the algorithm's parameters according to different trajectories. The algorithm is applicable even in the areas where the fluctuations of Earth's magnetic field are not significant.

scholarly journals On the field of force near the neutral point produced by two equal coaxial coils, with special reference to the Campbell standard of mutual inductance

1925 ◽  
Vol 107 (744) ◽  
pp. 716-724 ◽  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Special Reference ◽  
Opposite Direction ◽  
Mutual Inductance ◽  
Common Axis ◽  
The Common ◽  
Small Change ◽  
The Magnetic Field ◽  
A Current

When a current is passed through two equal coaxial coils so that the component of the magnetic fields parallel to the common axis add, there is a circle, mid-way between the two coils, at which the magnetic field is zero. At all points in the plane of that circle lying outside it, the field of force is in one direction, and at all points within the circle it is in the opposite direction. It is evident, therefore, that if a coaxial turn of wire be placed in the plane of the circle, the mutual inductance between the two coils will be a maximum, when the wire coincides with the circle, and any small change in the radius of the turn will affect the value of the mutual inductance only to the second order of small quantities.

The roller chain lubricated with ferrofluids

2018 ◽  
Vol 233 (6) ◽  
pp. 927-935
Author(s):  
Yanjuan Zhang ◽  
Zhengqing Yang ◽  
Decai Li
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Service Life ◽  
Chain Structure ◽  
Lubricating Oil ◽  
Roller Chain ◽  
New Type ◽  
Chain Transmission ◽  
Novel Method ◽  
The Magnetic Field

The sleeve of roller chain periodically squeezes the pin during the process of chain transmission. The lubrication oil located in the gap of the sleeve and pin will be pushed out and cannot be restored automatically. The absence of sufficient lubricating oil can cause friction, wear, and even the roller chain failure between the pin and the sleeve. This article presents a novel method and a new type of chain structure to lubricant roller chain with ferrofluids, which is capable of prolonging the service life of roller chain. The results show that ferrofluids can be remained in the clearance between the sleeve and the pin shaft under the effect of external magnetic field. The ferrofluids that were squeezed out of the clearance can be restored automatically, which ensure the reliability of chain transmission. And the external magnetic field effectively prevents the chain lubrication leakage due to the edge effect of the magnetic field.

scholarly journals Signal Space Separation Method for a Biomagnetic Sensor Array Arranged on a Flat Plane for Magnetocardiographic Applications: A Computer Simulation Study

2018 ◽  
Vol 2018 ◽  
pp. 1-19 ◽  
Author(s):  
Kensuke Sekihara
Keyword(s):  
Magnetic Field ◽  
Sensor Array ◽  
Sensor Arrays ◽  
Signal Space ◽  
Signal Space Separation ◽  
Vector Sensor ◽  
Vector Sensors ◽  
Modified Sensor ◽  
Space Separation ◽  
The Magnetic Field

Although the signal space separation (SSS) method can successfully suppress interference/artifacts overlapped onto magnetoencephalography (MEG) signals, the method is considered inapplicable to data from nonhelmet-type sensor arrays, such as the flat sensor arrays typically used in magnetocardiographic (MCG) applications. This paper shows that the SSS method is still effective for data measured from a (nonhelmet-type) array of sensors arranged on a flat plane. By using computer simulations, it is shown that the optimum location of the origin can be determined by assessing the dependence of signal and noise gains of the SSS extractor on the origin location. The optimum values of the parameters LC and LD, which, respectively, indicate the truncation values of the multipole-order ℓ of the internal and external subspaces, are also determined by evaluating dependences of the signal, noise, and interference gains (i.e., the shield factor) on these parameters. The shield factor exceeds 104 for interferences originating from fairly distant sources. However, the shield factor drops to approximately 100 when calibration errors of 0.1% exist and to 30 when calibration errors of 1% exist. The shielding capability can be significantly improved using vector sensors, which measure the x, y, and z components of the magnetic field. With 1% calibration errors, a vector sensor array still maintains a shield factor of approximately 500. It is found that the SSS application to data from flat sensor arrays causes a distortion in the signal magnetic field, but it is shown that the distortion can be corrected by using an SSS-modified sensor lead field in the voxel space analysis.

scholarly journals Planar Body-Mounted Sensors for Electromagnetic Tracking

Sensors ◽  
2021 ◽  
Vol 21 (8) ◽  
pp. 2822
Author(s):  
Marco Cavaliere ◽  
Herman Alexander Jaeger ◽  
Kilian O’Donoghue ◽  
Pádraig Cantillon-Murphy
Keyword(s):  
Magnetic Field ◽  
Surgical Navigation ◽  
Cost Benefit ◽  
Cost Effective ◽  
Magnetic Sensors ◽  
Electromagnetic Tracking ◽  
Cost Effective Method ◽  
Pcb Manufacturing ◽  
The Cost ◽  
Planar Body

Electromagnetic tracking is a safe, reliable, and cost-effective method to track medical instruments in image-guided surgical navigation. However, patient motion and magnetic field distortions heavily impact the accuracy of tracked position and orientation. The use of redundant magnetic sensors can help to map and mitigate for patient movements and magnetic field distortions within the tracking region. We propose a planar inductive sensor design, printed on PCB and embedded into medical patches. The main advantage is the high repeatability and the cost benefit of using mass PCB manufacturing processes. The article presents new operative formulas for electromagnetic tracking of planar coils on the centimetre scale. The full magnetic analytical model is based on the mutual inductance between coils which can be approximated as being composed by straight conductive filaments. The full model is used to perform accurate system simulations and to assess the accuracy of faster simplified magnetic models, which are necessary to achieve real-time tracking in medical applications.

scholarly journals Magnetic field, frequency and temperature dependence of complex conductance of ultrathin La1.65Sr0.45CuO4∕La2CuO4 films and the organic superconductors κ-(BEDT-TTF)2Cu[N(CN)2]Br

2015 ◽  
Vol 29 (25n26) ◽  
pp. 1542012 ◽  
Author(s):  
V. A. Gasparov ◽  
Xi He ◽  
G. Dubuis ◽  
D. Pavuna ◽  
N. D. Kushch ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Diffusion Constant ◽  
Atomic Layer ◽  
Mutual Inductance ◽  
Organic Superconductors ◽  
Field Frequency ◽  
Bilayer Films ◽  
The Magnetic Field

We used atomic-layer molecular beam epitaxy (ALL-MBE) to synthesize bilayer films of a cuprate metal ([Formula: see text], LSCO) and a cuprate insulator ([Formula: see text], LCO), in which interface superconductivity occurs in a layer that is just one-half unit cell thick. We have studied the magnetic field and temperature dependence of the complex sheet conductance, [Formula: see text], of these films, and compared them to [Formula: see text]-(BEDT-TTF)[Formula: see text] single crystals. The magnetic field [Formula: see text] was applied both parallel and perpendicular to the 2D conducting layers. Experiments have been carried out at frequencies between 23 kHz and 50 MHz using either two-coil mutual inductance technique, or the LC resonators with spiral or rectangular coils. The real and the imaginary parts of the mutual-inductance [Formula: see text] between the coil and the sample were measured and converted to complex conductivity. For [Formula: see text] perpendicular to the conducting layers, we observed almost identical behavior in both films and [Formula: see text]-Br single crystals: (i) the transition onset in the inductive response, [Formula: see text](T) occurs at a temperature lower by 2 K than in [Formula: see text], (ii) this shift is almost constant with magnetic field up to 8 T; (iii) the vortex diffusion constant [Formula: see text] is exponential due to pinning of vortex cores. These results can be described by the extended dynamic theory of the Berezinski–Kosterlitz–Thouless (BKT) transition and dynamics of bound vortex–antivortex pairs with short separation lengths.

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 &amp; 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 &amp; 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.

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