Magnetic Localization Method Research Articles

A Remote Two-Point Magnetic Localization Method Based on SQUID Magnetometers and Magnetic Gradient Tensor Invariants.

In practical application, existing two-point magnetic gradient tensor (MGT) localization methods have a maximum detection distance of only 2.5 m, and the magnetic moment vectors of measured targets are all unknown. In order to realize remote, real-time localization, a new two-point magnetic localization method based on self-developed, ultra-sensitive superconducting quantum interference device (SQUID) magnetometers and MGT invariants is proposed. Both the magnetic moment vector and the relative position vector can be directly calculated based on the linear positioning model, and a quasi-Newton optimization algorithm is adopted to further improve the interference suppression capability. The simulation results show that the detection distance of the proposed method can reach 500 m when the superconducting MGT measurement system is used. Compared with Nara's single-point tensor (NSPT) method and Xu's two-point tensor (XTPT) method, the proposed method produces the smallest relative localization error (i.e., significantly less than 1% in the non-positioning blind area) without sacrificing real-time characteristics. The causes of and solutions to the positioning blind area are also analyzed. The equivalent experiments, which were conducted with a detection distance of 10 m, validate the effectiveness of the localization method, yielding a minimum relative localization error of 4.5229%.

Magnetic Localization Method for Vehicles Based on Transformer

Magnetic positioning is a promising technique for vehicles in Global Navigation Satellite System (GNSS)-denied scenarios. Traditional magnetic positioning methods resolve the position coordinates by calculating the similarity between the measured sequence and the sequence generated from the magnetic database with criteria such as the Mean Absolute Difference (MAD), PRODuct correlation (PROD), etc., which usually suffer from a high mismatch rate. To solve this problem, we propose a novel magnetic localization method for vehicles based on Transformer. In this paper, we cast the magnetic localization problem as a regression task, in which a neural network is trained by equidistant sequences to predict the current position. In addition, by adopting Transformer to perform magnetic localization of vehicles for the first time, magnetic features are extracted, and positional relationships are explored to guarantee positioning accuracy. The experimental results show that the proposed method can greatly improve the magnetic positioning accuracy, with an average improvement of approximately 2 m.

Magneto-oscillatory localization for small-scale robots

Magnetism is widely used for the wireless localization and actuation of robots and devices for medical procedures. However, current static magnetic localization methods suffer from large required magnets and are limited to only five degrees of freedom due to a fundamental constraint of the rotational symmetry around the magnetic axis. We present the small-scale magneto-oscillatory localization (SMOL) method, which is capable of wirelessly localizing a millimeter-scale tracker with full six degrees of freedom in deep biological tissues. The SMOL device uses the temporal oscillation of a mechanically resonant cantilever with a magnetic dipole to break the rotational symmetry, and exploits the frequency-response to achieve a high signal-to-noise ratio with sub-millimeter accuracy over a large distance of up to 12 centimeters and quasi-continuous refresh rates up to 200 Hz. Integration into real-time closed-loop controlled robots and minimally-invasive surgical tools are demonstrated to reveal the vast potential of the SMOL method.

A Poppet Magnetic Localization Method for the Ultraclean Electric Valve Based on Combined Integral and Fitting Model

A Poppet Magnetic Localization Method for the Ultraclean Electric Valve Based on Combined Integral and Fitting Model

Object Localization by Construction of an Asymmetric Isobody of the Magnetic Gradient Tensor Contraction Using Two Identical Permanent Magnets

This paper deals with predictive maintenance of infrastructure objects, focusing on the inspection of bridges. To achieve this goal, unmanned aerial vehicles place measuring units for data collection at different points of the bridge. This work deals with the question of how these measuring units can be found and removed by them later. For this purpose, a magnetic localization method based on the STAR method is presented. In contrast to the STAR method, which only detects the center of a magnetic target, a modified version called SRIOD is implemented here, where the orientation of the magnetic target can also be detected. This is essential information if the unmanned aerial vehicle is to grab the measuring unit with a robotic arm. In this regard, two identical permanent magnets are integrated into the measuring unit, whose gradient tensor contraction of the magnetic flux density distribution has a directed asymmetric surface when considering the contours of constant values. This creates a magnetic invisible reference plane that can be detected with a magnetic gradiometer. The method is verified both in simulation and experimentally in a laboratory setup.

Towards Differential Static Magnetic Localization of Commercial Capsule Endoscopes: An Evaluation Using Different Ring and Cylindrical Magnets

Abstract. Capsule endoscopy is a promising diagnostic tool for the entire gastrointestinal tract. Since a patient swallows the capsules, their size must be sufficiently small. The principal built-in components are cameras, silver-oxide batteries, light emitting diodes, and an antenna for transmitting the video. For diagnosis and treatment, the precise localization of the capsules for specific video frames is required. Recently, static magnetic localization of these capsules with an integrated permanent magnet showed promising results. However, in the state-of-the-art, relatively large magnets compared to the small capsules were used. Therefore, in this extended paper, the localization performance of a recently proposed optimized differential static magnetic localization method for different sized disc and ring magnets was evaluated. The ring magnets were designed for integration with the two batteries of commercial capsules. The magnets were evaluated in static and dynamic scenarios to evaluate the performance of the method in a patient's daily life. It was revealed that the mean position and orientation errors did not exceed 5 mm and 4∘, respectively, for all applied magnets except for the 1.5 and 3 mm long disc magnets. Moreover, the results indicated that the ferromagnetic batteries of capsule endoscopes increase the localization performance when they are centered within a diametrical ring magnet. Overall, it was revealed that the localization performance of the optimized differential method is significantly better than the state-of-the-art even when the magnet volume is significantly reduced compared to previous work. Therefore, it was concluded that 5 mm long disc magnet or a ring magnet are excellent candidates for integration into a commercial capsule for magnetic localization and yield the advantage of being passive magnetic sources.

Calibrated analytical model for magnetic localization of wireless capsule endoscope based on onboard sensing

AbstractWireless capsule endoscopes (WCEs) are pill-sized camera-embedded devices that can provide visualization of the gastrointestinal (GI) tract by capturing and transmitting images to an external receiver. Determination of the exact location of the WCE is crucial for the accurate navigation of the WCE through external guidance, tracking of the GI abnormality, and the treatment of the detected disease. Despite the enormous progress in the real-time tracking of the WCE, a well-calibrated analytical model is still missing for the accurate localization of WCEs by the measurements from different onboard sensing units. In this paper, a well-calibrated analytical model for the magnetic localization of the WCE was established by optimizing the magnetic moment in the magnetic dipole model. The Jacobian-based iterative method was employed to solve the position of the WCE. An error model was established and experimentally verified for the analysis and prediction of the localization errors caused by inaccurate measurements from the magnetic field sensor. The assessment of the real-time localization of the WCE was performed via experimental trials using an external permanent magnet (EPM) mounted on a robotic manipulator and a WCE equipped with a 3-axis magnetic field sensor and an inertial measurement unit (IMU). The localization errors were measured under different translational and rotational motion modes and working spaces. The results showed that the selection of workspace (distance relative to the EPM) could lead to different positioning errors. The proposed magnetic localization method holds great potential for the real-time localization of WCEs when performing complex motions during GI diagnosis.

Magnetic Localization Method of Capsule Endoscope Based on Hybrid Model

Magnetic localization is an effective method for obtaining the pose of a wireless capsule endoscope (WCE) because it is able to provide the position and orientation of the magnet in places where visual methods are not available. In magnetic positioning, the magnetic dipole model is often used to calculate the magnetic field of a magnetic source. However, the magnetic field calculated by the magnetic dipole model introduces positioning errors when a permanent magnet is used as the magnetic source and the size of the permanent magnet cannot be ignored. In this paper, a WCE localization method was proposed based on the combination of the magnetic dipole model and the analytical model. A cylindrical magnet was mounted in the WCE. The magnetic field of the magnet was calculated using the magnetic dipole model and the rough position of the magnet was estimated using the Particle Swarm Optimization (PSO) algorithm; then the magnetic field of the magnet was described using the analytical model and the estimated result of the PSO algorithm was used as the initial value of the Levenberg-Marquardt (L-M) algorithm to calculate the pose of the WCE. Experiments on static and dynamic localization of magnet were carried out in the localization system. The experimental results verified the feasibility of the proposed method.

Characterization of a magnetic localization method based on Hall effect sensor array for microrobot position tracking

Characterization of a magnetic localization method based on Hall effect sensor array for microrobot position tracking

MagnetOFuse: A Hybrid Tracking Algorithm for Wireless Capsule Endoscopy Within the GI Track

Wireless Capsule Endoscopy (WCE) is a well-established diagnostic tool for visualizing the Gastrointestinal (GI) tract. Early diagnosis helps doctors to act beforehand and treat the disease on its earlier stages. Images taken by WCE do not provide location information. However, this data is useful for selecting proper treatment. In this paper, we have introduced a hybrid method called MagnetOFuse to localize the capsule inside the human GI track. The capsule is equipped with four side wall cameras and a magnet. Magnetic localization acquires the capsule’s global position using 9 three-axis Hall effect sensors. However, magnetic localization alone cannot distinguish between the capsule’s motion and the GI tract’s motion. To overcome this issue and increase the tracking accuracy, low-resolution mono-chromatic cameras are installed along the capsule’s side, which are responsible for measuring the capsule’s movement, not the involuntary motion of the GI system. A complete setup is designed to test the capsule and to perform the experiments. The results show that the proposed hybrid method has an average position error of only 3.5 mm and can compensate for the GI tract’s relative movements. Furthermore, environment parameters such as magnetic interference and the nonhomogeneous structure of the GI tract have little influence on our system compared to the available magnetic localization methods.

An hFFNN-LM Based Real-Time and High Precision Magnet Localization Method

Magnet tracking is an emerging tracking method for medical instruments and biological tissues, such as endoscopes and catheters. Traditional magnet tracking technology typically uses an optimization algorithm or heuristic algorithm to estimate the pose of a permanent magnet according to the measured magnetic induction intensity. However, this technology is limited by the high delay and the poor quality of the initial solution. This article proposes a new magnetic localization method, i.e., a hybrid feedforward neural network and Levenberg–Marquardt (hFFNN-LM) algorithm. FFNN provides an adjusted initial solution to the LM algorithm for solving the nonlinear inverse magnetic problem. The hFFNN-LM algorithm is promising for real-time magnetic tracking as it provides satisfactory tolerance for initially estimated parameters and fast search speed. The average single localization time is 1.07 ms. The experimental results show that the proposed method has a very low tracking delay compared to some other popular LM-based methods. The proposed hFFNN-LM algorithm achieves superior localization performances, i.e., the mean position and orientation errors are tested to be 0.70 mm and 0.90°, respectively.

Novel Magnetic Localization Methods for Minimizing the Ellipse Error Based on Tensor Invariants

There are various technology routes for the localization of magnetic targets. Among them, the localization methods based on magnetic gradient tensor invariants have remarkable preponderance. For instance, such invariants are not sensitive to the jitter of the coordinate system, which means this kind of methods can be very suitable for application in moving carriers. Traditional classic method contains ellipse error which cannot be simply ignored. In order to eliminate this error, the general solution of location vector is derived in this letter. And then, three methods for solving the general solution are given. To validate the effectiveness of proposed methods, the localization problem of the measurement array surrounding static target is simulated. In this simulation, the localization results of the traditional method and the proposed methods are analyzed and compared. The conclusions show that the proposed methods successfully remove the ellipse error and improve the localization accuracy.

Innovative Differential Magnetic Localization Method for Capsule Endoscopy to Prevent Interference Caused by the Geomagnetic Field

Abstract. Wireless capsule endoscopy is an established medical application for the examination of the gastrointestinal tract. However, the robust and precise localization of these capsules is still in need of further scientific investigation. This paper presents an innovative differential magnetic localization method for capsule endoscopy to prevent interference caused by the geomagnetic field. The effect of changing the orientation of the capsule on the localization process was also examined. Simulations using COMSOL Multiphysics with the superimposed geomagnetic field were performed. The Levenberg–Marquardt algorithm was applied in MATLAB to estimate the position and orientation of the capsule. Comparing the proposed differential method with the absolute magnetic localization method under ideal conditions, the mean position and orientation errors were reduced by three orders in magnitude to less than 0.1 mm and 0.1∘ respectively. Even if sensor non-idealities are considered, the simulation-based results reveal that our proposed method is competitive with state-of-the-art geomagnetic compensation methods for static magnetic localization of capsule endoscopes. The achieved localization accuracy by applying the differential method is not dependent on the rotation of the localization system relative to the geomagnetic flux density under the made assumptions and the impact of the magnet orientation is neglectable. It is concluded that the proposed method is capable of preventing all interference whose components are approximately equal at all sensors with identical orientation.

Magnetic Tracking of Wireless Capsule Endoscope in Mobile Setup Based on Differential Signals

Magnetic localization methods have been widely studied to provide accurate position and orientation information of intra-body objects, such as wireless capsule endoscopes. However, these methods cannot work well in dynamic scenarios when using a wearable sensor array due to the geomagnetic field. In this article, we propose a novel approach for tracking wireless capsules in a mobile setup based on differential signals from adjacent magnetic sensors. Compared to the previous passive magnetic localization framework, the proposed algorithm can eliminate the interference of the geomagnetic field without introducing other compensation sensors or signals. As a result, the proposed method can be used for wearable sensor arrays without knowing the distribution of the geomagnetic field and the movement of the sensor array in advance. Moreover, the relationship between position error and distance of adjacent sensors has been studied to improve tracking accuracy. Finally, a sensor array with 16 three-axis magnetic sensors is developed. Both static and dynamic experiments have been carried out, whose results verified the effectiveness of the proposed method.

Research on Magnetic localization method of underwater Magnetometer in Single component

In order to solve the problem of single component magnetometer’s localization, a new method is proposed using auxiliary magnetic source. The localization model is designed and multi-direction moving path of magnetic source is optimized, then DE algorithm is adopted to calculate the coordinates of magnetometer. Simulation indicated the method is right and efficient, meanwhile, the result is got in high precision and the influence of marine noise is analysed in localization. The method supplies a novel path for single component magnetometer’s localization in practice.

Enhanced Localization of Robotic Capsule Endoscopes Using Positron Emission Markers and Rigid-Body Transformation

Using positron emission markers for the localization of a robotic capsule endoscope is promising because it does not require onboard space or built-in battery for operation. Further, its compatibility with magnetic actuation is another significant advantage compared with conventional magnetic localization methods reported in the literature. In this paper, we propose a new tracking algorithm based on rigid-body transformation and gamma rays emitted from three positron emission markers onboard to localize an endoscopic capsule operating within the gastrointestinal tract of the human body. Different from traditional rigid-body transformation based on datasets of 3-D points, our method estimates the transformation parameters (e.g., translation vector and rotation angle) from several groups of 3-D lines in order to determine the locations of the markers emitting the gamma rays. Validated by both simulation data using a voxelized phantom in the Geant4 Application for Emission Tomography toolkit and the experimental data collected from a positron emission tomography scanner, the new localization method shows a significant improvement in the tracking accuracy (an average position error of 0.4 mm and orientation error of 1.9°) and the failure rate (18/9600 localization runs), compared to the localization results reported in the literature.

Real-Time Orientation-Invariant Magnetic Localization and Sensor Calibration Based on Closed-Form Models

This paper presents a real-time orientation-invariant magnetic localization method based on a closed-form analytical inverse model. This method requires only a pair of inexpensive 3-axis magnetic sensors to acquire data for solving the unique solution of the inverse problem. Taking advantage of gravity, a permanent-magnet-upright device is designed to maintain a constant magnetic moment direction. An effective calibration method for the sensor orientation is proposed based on orthogonality to assure high performance. Then, a prototype magnetic localization system is developed. An in-depth experimental analysis is presented demonstrating the design feasibility of the tracking system in real time with a cycle-time less than 0.1 ms, and root-mean-square translation and rotation errors of 40 μm for a 40 mm × 40 mm × 50 mm volume and 0.16° for [-10°, 10°], respectively.

A real-time magnetic localization method of underwater non-cooperative magnetic targets based on unscented particle filter

A real-time magnetic localization method based on unscented particle filter (UPF) is proposed to solve the problem for real-time localization of underwater non-cooperative magnetic targets. The state space model of non-cooperative magnetic targets is set up according to its motion characteristic, and the state is estimated in real time by UPF. In order to improve the observability of the system, the particle state is constrained and magnetic moment is inverted by the least square method. The simulation results and ferromagnetic object localization experimental results show that the method is good in localization precision and real-time performance, which can be applied to the real-time magnetic localization in near field.

Long range magnetic localization- accuracy and range study

Undersurface localization systems are accuracy demanding application. Localization methods used for common position estimation in open space or in building cannot be used since they are usually based on RF signal transmission or satellite navigation. Magnetic localization methods are usually the only usable solution. Horizontal directional drilling is one of accuracy demanding application where the operator needs to know exact position of the underground unit with respect to a given point on the surface. Long range surface magnetic localization system will be presented in this paper. This paper will summarize achievable accuracy of magnetic localization and maximal range with respect to given localization error. First results measured with presented system will be presented as well as results from FEM modeling. The influence of target distance, magnetic sensors noise, orientation sensor accuracy and surrounding material will be evaluated and considered in this work.