Hardy's Multi-Quadric method of calibrating a wireless electromagnetic localization system for intestinal micro-devices

A transformerless multilevel inductive power transfer (IPT) system converts a medium-voltage (MV) to a low-voltage (LV) using a multilevel active rectifier and resonant inverters. Excitation coils deliver the output power of the multilevel converter to a common transmitter coil. The transmitter coil then generates an augmented magnetic field to induce load voltages on receiver coils, which can be attached to the bottom of electric vehicles. However, MV isolation between the excitation and transmitter coils should be guaranteed for safe operation. This study presents a new design methodology for MV-isolated excitation coils. Electric fields are analyzed to evaluate the insulation performance of the excitation coil. Additionally, magnetic fields are discussed to design an efficient excitation coil. Based on the analysis, a multi-objective optimization is conducted on the excitation coil with respect to the insulation voltage, core loss, and volume. A 6 kV/6-level IPT system was developed for experimental evaluations. Grid-to-load and coil-to-coil efficiencies of 86% and 90% were achieved using the testbed. Finally, the developed excitation coil passed a 70 kV over-voltage test.

An electromagnetic system was developed to detect the covering depth of steel reinforcing bar (rebar). In this system, a circular coil with the diameter of about 10 cm was used to produce the excitation magnetic field. The frequency of the AC current flow in the excitation coil was 4.2 kHz and the current amplitude was about 20 mA. A coil wrapped around a 1 cm ferrite core was used to detect the induced magnetic field by steel rebar. From the signal amplitude after demodulation, the depth information of the steel rebar was obtained. To detect deeper steel rebar, the big background signal produced by the excitation coil must be compensated. To compensate it, another coil also wrapped around the ferrite core was used. By optimizing the system, the maximum detection depth was about 220 mm. We also measured the resolution of depth measurement. It was about 0.3 mm when the depth was 50 mm, and 0.6 mm when the depth was 80 mm.

In the program of bone surgery robot, we employ an electromagnetic method to locate the position of surgical instruments and surgical sites. In this processing, the key part is to extract the coupling voltage signals that are sensed by the sensing coils as accurately as possible, because it will affect the precision of location directly. However, in the real system, these coupling voltage signals are very weak and be drowned in noises. In this paper, we propose three methods to extract this signal accurately, which are phase lock amplifier, function fitting and Fast Fourier Transformation (FFT). Also we make theoretical analysis and emulation for each method, and show their experimental results. After sedulous comparison, we conclude function fitting is the most suitable method for this system.

According to the sinusoidal coil design theory discussed previously, a slotwise electro-magnetic system can reproduce with high accuracy one and poly-periodical sinusoidal air gap B-field distributions and consequently sinusoidal amplitude modulation as a function of angular position. In the sinusoidal electromagnetic systems discussed previously however there were stationary and rotary coils which necessitate these systems having brushes or special one- or two-phase ring transformers providing magnetic coupling as shown in Fig. 4.9 to transmit an output signal from the rotation coils. In motion control devices there are a variety of miniature electro-magnetic systems which provide a conceptually brushless one- or poly-periodical magnetic coupling. In such a brushless electro-magnetic system there would only be stationary coils (excitation and signaling) and not rotation coils which need brushes. The slotwise sinusoidal electromagnetic system discussed in this and previous chapters is called a silent rotor and stator electro-machine system (silent armature) in classical electrical machine technology. Such systems provide a regular air gap along the air gap circumference (except at teeth irregularity), i.e. specific permeance Go given by equation 3.19 is constantKeywordsMagnetic CircuitBias FieldStationary CoilSecondary CoilExcitation CoilThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

An encircling send-receive type pulsed eddy current (PEC) probe is designed for use in the tube inspection. When bare receive coils, which are located away from the exciter, are used, the peak time of the signal does not change although the distance from the exciter increases. This is because the magnetic fields from exciter coil arrive directly at the receive coil without passing through the tube. Therefore, in this work, both exciter and sensor coils are shielded to reduce the influence of direct fields from the exciter coil. Numerical simulation with the designed shielded encircling PEC probe shows the corresponding increase of peak time as the sensor distance increases. Ferrite and carbon steel shields are compared and found that the ferrite shielding results in slightly stronger peak value and quicker peak time than the carbon steel shielding. Sensitivity of peak value to defect depth variation is also investigated and found that the normalized peak value is more sensitive when the sensor is located closer to the exciter for aluminum tube. In the case of magnetic tube, however, all the characteristics are opposite to those obtained from nonmagnetic aluminum tube.

The demand for accurate localization in complex environments continues to increase despite the difficulty in extracting positional information from measurements are not yet complete. Like any other process, localization also has security requirements. The use of ultra-wideband (UWB) indoor localization systems have recently grown quickly in industries, with a reliable, fast, and have high accuracy performances. In particular, time difference-of-arrival (TDOA) is one of the widely used localization models. However, as TDOA measurement errors increase, the accuracy of the localization decreases. The accuracy of the TDOA measurement is influenced the accuracy of the localization and affected by multiple factors such as time synchronization, errors in sensor positions, missing data is caused by network attack. To reduce the influence of a sensor measurement error in localization, this paper proposes an improved localization algorithm for source localization using deep learning to address a TDOA measurements error or missing data in an asynchronous localization called DeepTAL. Unlike the conventional algorithm, DeepTAL can obtain highly accurate localization data in the presence of TDOA measurement errors or missing data. The algorithm starts with TDOA measurements without time synchronization. A network based on Long Short-Term Memory (LSTM) is then applied to achieve a stronger learning and better representation of the determined target state and TDOA prediction. The network can express features more abstractly at higher levels and increase recognition accuracy. After that, the target node is accurately located by TDOAs. We implement the DeepTAL algorithm on an asynchronous localization system with UWB signals. The experiments show that the proposed DeepTAL algorithm is efficient in improving the localization precision as measurement errors or missing data.

This paper presents a method to design and simulate excitation coil (drive coil) for single-sided magnetic particle imaging (MPI) scanner. Magnetic excitation of the magnetic nanoparticles (MNPs) used as the tracer is paramount so that their non-linear magnetization response will be acquired for image reconstruction. Numerical simulation of the magnetic field produced by the excitation coil in the form of solenoid is carried out in Matlab using Biot-Savart law. The results are compared with that of Ansys Maxwell software simulation and experimental results of the excitation coil having the same specifications. The solenoid simulated has 350 turns of copper wire (0.6mm diameter) and 2A excitation current, produces a magnetic field of around 1.49 mT using Matlab, 1.51 mT using Ansys Maxwell and 1.82 mT experimentally, at the surface of the coil. These magnetic fields values are within the excitation range for MPI, hence sufficient for the MNPs excitation from single-sided scanner topology.

A complete system for dynamic structural identification test under ambient loads is presented. The main objective of these improvements is to achieve significant cost reductions. In this way the system can be suitable for application to a large number of structures within the framework of a comprehensive optimal maintenance program of structures. To achieve this cost reduction of the tests, the following improvements have been introduced: (a) a complete wireless system to acquire sensor data, (b) a wireless localization system that permits referring sensors to a local coordinate system. This localization system has been the object of recent patent, and ( c) finally, further developments of software aimed to diminishing human intervention in the structural identification process. In case of standard bridge monitoring the application of above improvements can achieve the generation of an automatic identification report. This goal is to be attained eventually, and to which the described developments contribute. Therefore these improvements can reduce engineer's intervention mainly to propose general guidelines for a suitable sensors placement.

With the advancement of robotics in medicine in recent years, diverse and promising applications for ferromagnetic continuum robots (FCRs) have been introduced. These robots utilize an electromagnetic actuation system for movement and control, which leads to reduced tissue damage, significantly shorter surgery durations, and improved patient recovery times. Recent research in FCR modeling highlights the critical challenge of developing a dynamic model to assess system behavior in real-time, crucial for maximizing benefits in medical applications. In this paper, the geometric discretization method and Lagrange’s principle are used to derive the dynamic equations of a FCR under the influence of an external magnetic field. This approach enables the examination of the system’s behavior at any given moment, providing a suitable foundation for designing various controllers based on the model. Given the electromagnetic system used in steering the FCRs, an analysis of the magnetic field in both ideal and real conditions is conducted to enhance reliability for medical applications. Simulation results indicate that the robots deform in a direction different from the magnetic field direction, demonstrating non-planar deformation characteristics. Furthermore, comparison with experimental data demonstrates that the theoretical framework accurately predicts the robot’s deformation, with calculation errors less than 5%.

To track a capsule endoscope, a novel measuring method based on alternating magnetic field is presented. The signal-to-noise ratio of the magnetic sensor decreases sharply with the increasing tracking distance. Thus, a magnetic generator with automatic gain regulation is designed to improve the localization precision. It is composed of a microcontroller, a DA converter, a timer, a waveform synthesis circuit, a power amplifier, a sequence control circuit and excitation coils. First, the wireless magnetic sensor measures the strength of the magnetic field produced by the magnetic generator. Via radio frequency communication, the measured result is feedback to the comparator of the microcontroller. According to a deviation obtained by comparing the measured results with the reference value, the microcontroller outputs a digital signal to the DA converter to control the magnitude of the exciting current. The prototype of the system was developed and the experiment was performed. The experiment shows that the magnetic field generator can automatically adjust the strength of the exciting signal.

Based on the principle of primary excitation magnetic field counteraction, in this paper a new type of excitation coil named two-arm Archimedean spiral coil (TAASC) is designed and first introduced into biomedical magnetic induction tomography coil system to improve the coil system sensitivity. The primary voltage and the scaled level map of secondary voltage perturbation for the TAASC are calculated through theory and simulation. The coil system sensitivity curves when using the TAASC as excitation coil are tested at different positions, electrical conductivities and frequencies by simulation experiments. As a control, all the theoretical calculations and simulation experiments are conducted again for the circular excitation coil. The results show that the primary excitation magnetic field can be markedly counteracted while the secondary induction magnetic field perturbation is nearly at the same order of magnitude, and the coil system has a bigger sensitivity with an improvement factor of 103 to 104 by using this new type of TAASC as excitation coil, compared with the common circular excitation coil. The simulated results are in good agreement with the theoretical results.

ABSTRACTHelicopter electromagnetic (HEM) systems are commonly used for conductivity mapping and the data are often interpreted using an isotropic horizontally layered earth model. However, in regions with distinct dipping stratification, it is useful to extend the model to a layered earth with general anisotropy by assigning each layer a symmetrical 3 × 3 resistivity tensor.The electromagnetic (EM) field is represented by two scalar potentials, which describe the poloidal and toroidal parts of the magnetic field. Via a 2D Fourier transform, we obtain two coupled ordinary differential equations in the vertical coordinate. To stabilize the numerical calculation, the wavenumber domain is divided into two parts associated with small and large wavenumbers. The EM field for small wavenumbers is continued from layer to layer with the continuity conditions. For large wavenumbers, the EM field behaves like a DC field and therefore cannot be sensed by airborne EM systems. Thus, the contribution from the large wavenumbers is simply ignored.The magnetic fields are calculated for the vertical coaxial (VCX), horizontal coplanar (HCP) and vertical coplanar (VCP) coil configurations for a helicopter EM system. The apparent resistivities defined from the VCX, VCP and HCP coil responses, when plotted in polar coordinates, clearly identify the principal anisotropic axes of an anisotropic earth. The field example from the Edwards Aquifer recharge area in Texas confirms that the polar plots of the apparent resistivities identify the principal anisotropic axes that coincide well with the direction of the underground structures.

Magnetorheological elastomer (MRE)-based base isolation system has been proposed to compensate for the drawbacks of the existing passive-type base isolation system. MRE is one of smart material with magnetorheological (MR) effect that can change the stiffness and damping ratio in real time when the magnetic field is applied. The conventional MREbased base isolation system has inter-place between MRE and electromagnetic system. This is determined in consideration of the deformation of MRE, resulting in loss of magnetic flux density and excessive volume of MRE-based base isolation system. Since the strain of the MRE should be considered to be 100 % as base isolation system, the size of the base isolation system becomes large and the practical applicability is remarkably reduced. In addition, the loss of the magnetic flux density increases according to the size of the inter-space between MRE and electromagnetic system. Therefore, a new type of electromagnetic system is proposed to address these problems. In this study, an electromagnetic system which can move with MRE by separating it to the laminated type is proposed. MRE-based base isolation system with the laminated electromagnetic system occupies a small volume compared to the conventional MRE-based base isolation system and can form magnetic closed loop which can minimize the loss of the magnetic flux density. The numerical simulation was performed to compare the proposed electromagnetic system and the conventional MRE-based base isolation. From the numerical simulation, the lab-scale experiment was carried out and the proposed method can be utilized to improve the reality of MRE-based base isolation system.

The casing inspection tool was introduced to the oil industry in 1960, and since that time a number of logs have been recorded in various areas of operation. The purpose of this paper is to report results thus far obtained with this corrosion-detecting tool. To properly evaluate results of interpretation procedures as developed through field use, interpretation principles as a result of laboratory and field experience, actual field results in various areas and recommended operating procedures. Examples of various casing inspection logs are presented along with follow-up well information necessary to properly evaluate results of interpretation techniques. Principle of Operation The casing inspection log uses a method of measuring the effect of eddy currents on a magnetic field. The instrument consists of two radial coils, an exciter coil and a pick-up coil. Fig. 1 is a block diagram of the instrument. The exciter coil is fed from an AC source at the surface, and the resulting magnetic field sets up eddy currents in the casing wails. These eddy currents cause the magnetic field to be attenuated and shifted in phase, and the resulting magnetic field is detected by the pick-up coil. The pickup signal is amplified and transmitted to the surface by modulating a 3 kc carrier. In the surface instrument the carrier is separated from the exciter voltage, amplified and demodulated. At this point the signal is a true reproduction of the bottom-hole signal from the pick-up coil. The phase of this signal is compared with the phase of the exciter voltage, and the resulting phase shift is recorded on a strip-chart recorder. The theory of eddy currents indicates that phase shift is determined by four factors: casing wall thickness, frequency, magnetic permeability and resistivity of the metal. The basic phase-shift equation which follows shows that the phase shift is directly proportional to casing wall thickness. (1) where phi = phase shift, D = depth, mu = magnetic permeability, p = resistivity in micro-ohmcm, andF = frequency in cycles/sec. The factors of magnetic permeability and resistivity of the metal are practically always unknown for any joint of casing, and logs run thus far indicate that these factors vary considerably among types of casing and manufacturers. There are also indications that stresses placed upon casing as set in wells seem to affect magnetic permeability of the metal. This problem is minimized by using a reference joint to arrive at a metal thickness scale, and using that reference joint for all subsequent logs recorded in the same well. To detect small corroded areas, a differential pick-up coil is used. The log obtained is linear with respect to wall thickness, with an exaggerated indication of small non-conformities. Equipment The down-hole tool is illustrated in Fig. 2. Centralizing springs are used at the top and bottom of the tool to minimize wear on the two coil housings. The tool has been designed to withstand normal well temperatures of 350F and pressures of 20,000 psi. It has been operated in wells to 13,500 ft. The construction and operation of the tool are such that satisfactory results can be obtained with any type of well fluid. In the surface control panel the phase angle is measured by a transistorized phase detector. A linear output voltage which is proportional to the phase angle is produced to drive a strip-chart recorder pen in the surface equipment. P. 377ˆ

Stress and strain measurement of the large helical device during coil excitation