Orthogonal Coils Research Articles

Misalignment‐tolerant coupling cell of 2‐D modular WPT system for charging area simplified extension

Abstract2‐D modular wireless power transfer (WPT) system needs to have stable output when coil misalignment occurs. In order to improve the misalignment tolerance of the system coupling unit, this article proposes a magnetic coupling structure based on the LCC‐S compensation topology by combining a rectangular coil with two sets of mutually orthogonal solenoidal compensation coils. The rectangular coil is used to receive the vertical magnetic flux, and the two sets of compensating coils are used to receive the magnetic flux in the directions of X‐axis and Y‐axis on the horizontal plane, separately. The receiving side of the 2‐D wireless power transmission array cells cascaded half‐bridge rectifiers to connect each group of coils. This arrangement effectively compensates for the voltage drop of the rectangular coil caused by positional offset in any direction, so that the output voltage of the receiving side remains stable. The article firstly establishes the equivalent circuit model of the proposed design and deduces in detail the relationship equations between the output characteristics of the system and each influence factor. Secondly, the magnetic coupling structure is designed by finite element electromagnetic simulation software, and the total equivalent mutual inductance fluctuation of the proposed design is verified to be within 3.9% over the range of 2‐D transmission array cells. Finally, a 150 W experimental platform is built to verify the misaligment‐tolerant of the proposed design in the range of 2‐D transmission array cells. The experimental results show that the output voltage fluctuation of the proposed design within 4.27% at all directional offsets. Moreover, the stable output performance can be obtained in the case of vertical and rotational misalignment.

Densely sampled stimulus-response map of human cortex with single pulse TMS-EEG and its relation to whole brain neuroimaging measures.

Large-scale networks underpin brain functions. How such networks respond to focal stimulation can help decipher complex brain processes and optimize brain stimulation treatments. To map such stimulation-response patterns across the brain non-invasively, we recorded concurrent EEG responses from single-pulse transcranial magnetic stimulation (i.e., TMS-EEG) from over 100 cortical regions with two orthogonal coil orientations from one densely-sampled individual. We also acquired Human Connectome Project (HCP)-styled diffusion imaging scans (six), resting-state functional Magnetic Resonance Imaging (fMRI) scans (120 mins), resting-state EEG scans (108 mins), and structural MR scans (T1- and T2-weighted). Using the TMS-EEG data, we applied network science-based community detection to reveal insights about the brain's causal-functional organization from both a stimulation and recording perspective. We also computed structural and functional maps and the electric field of each TMS stimulation condition. Altogether, we hope the release of this densely sampled (n=1) dataset will be a uniquely valuable resource for both basic and clinical neuroscience research.

The configuration and detection characteristics of a 3D holographic LWD instrument antenna system based on multi-component EM induction theory

In order to improve the precision of electromagnetic resistivity logging, while ensuring the reliability of boundary detection and anisotropy identification, this study starts from the theory of multi-component electromagnetic induction. Through deriving the formula of component responses, the analytical expressions of electromagnetic wave fields are obtained for various coil pairs of azimuthal instruments. A 3D holographic LWD instrument antenna configuration is constructed, with co-planar and non-coplanar, tilted and orthogonal coil combinations, all components of the magnetic field tensor Hxx,Hxy,Hxz,Hyx,Hyy,Hyz,Hzx,Hzx,HzzHxx,Hxy,Hxz,Hyx,Hyy,Hyz,Hzx,Hzx,Hzz are successfully resolved. With the combination of some or all components, functional signals are generated for specific detection objectives. Numerical simulation of the response of those signals shows that the distance of boundary detection and anisotropy identification capability are superior to traditional geo-signals. The response relationship shows that as the contrast of the formation resistivity decreases and the well deviation angle increases, the anisotropy identification capability gradually strengthens, and the signal strength and identification capability are better at frequency in the range of 400–600 kHz. The proposed antenna configuration has the potential to significantly enhance formation evaluation and to improve geo-steering capability, contributing technology-wise to the optimal landing trajectory and best wellbore position, resulting in cost saving and maximize oil & gas production.

Design of continuous repeater power transmission coil for wireless power transfer system for EVs with consideration of vehicle deviation

In recent years, EVs have become increasingly popular around the world, and research on wireless power supply technology for EV driving has progressed accordingly. In order to realize this wireless power transfer system for EVs on a real scale, it is necessary to lengthen the power transfer section per power transfer unit and to secure a sufficient power transfer section with a small number of power transfer units as a whole. To solve this problem, the single coil method, in which one coil is lengthened, has been proposed. However, as the coil length increases, resistance loss increases and efficiency decreases. Therefore, a repeater coil system has been proposed. In this in-transit power-feeding system, it is necessary to consider transient phenomena when the EV to be fed deviates from the feeding lane. Therefore, we propose a new repeater coil configuration on the transmission side that assumes a no-load condition. In this study, a new repeater coil system combining rectangular coils and orthogonal coils is proposed, which enables stable feeding of power to EVs by rectangular coils and response to transient phenomena. A comparison was also made with the single coil method that has been studied previously.

Detecting and recovering critical mineral resource systems using broadband total-field airborne natural source audio frequency magnetotellurics measurements

Airborne geophysical methods offer a substantial advantage compared to ground-based techniques in exploring territories of different sizes, ranging from entire metallogenic provinces to the deposit scale, including those hosting critical minerals. An airborne method with measurements of natural magnetic field variations, known as audio frequency magnetotellurics (a passive field method), significantly increases the depth of investigation and expands the resistivity detection range compared with some controlled-source primary-field methods. We describe the technical solutions used in an airborne electromagnetic passive system with a mobile sensor of the total magnetic field variations and the stationary sensor of electric field variations, and its applications to recovering the complex geology of hydrothermal-magmatic systems often associated with critical minerals. The system’s ability to explore depths, typically beginning from the near-surface and down to 1–2 km, by recording responses in three orthogonal inductive coils over a broad bandwidth from 22 Hz to 21,000 Hz allows for mapping resistivities across a broad range. This capability is crucial for obtaining more comprehensive exploration models. Field case studies of the natural field system include application in exploring for unconformity uranium mineralization, along with other associated minerals, epithermal gold and polymetallic-bearing structures, and ferromanganese and polymetallic deposits formed in a continental rift valley. An extra case study involving kimberlites was incorporated as a proven example of the natural field system’s capability in conducting near-surface and deep investigations. The case histories illustrate the airborne natural electromagnetic field technology capabilities in recovering geoelectric models and their specific patterns.

Axial magnetic quadrupole mode of dielectric resonator for omnidirectional wireless power transfer

To achieve omnidirectional wireless power transfer (WPT) with high efficiency, a high Q-factor transmitter generating homogeneous magnetic field is crucial. Traditionally, orthogonal coils of different shapes are used to realize transmitters. In this paper, we develop an omnidirectional magnetic resonant WPT system based on a dielectric disk resonator with colossal permittivity and low loss operating at the axial magnetic quadrupole mode. The constant power transfer efficiency of 88% at the frequency of 157 MHz over the transfer distance of 3 cm for all azimuth angles of a receiver is experimentally demonstrated. The possibility of multi-receivers charging is also studied demonstrating a total efficiency of 90% regardless of azimuth angle between two receivers with respect to the transmitting disk resonator. The minimized exposure of biological tissues to the electric and magnetic fields as well as a low specific absorption rate is observed that makes the WPT system safer for charging with higher input power.

A composite decoupling method of the 2D WPT transmitter array based on the compensation topology and orthogonal coupling

Typical dynamic wireless power transfer systems use a long-track transmitter (Tx) coil or multiple segmented Tx coils, producing a limited efficient charging area. To improve charging flexibility, the two-dimensional (2D) transmitter array is adopted. However, the cross coupling between Tx coils will exist in multiple directions, resulting in the degradation of system performance. Therefore, this paper presents a composite decoupling method for the 2D wireless power supply array based on the compensation topology and orthogonal coupling. The compensation topology eliminates cross coupling between electrically connected Tx coils, while orthogonal coils decouple Tx coils without electrical connection. Compared with traditional methods, the proposed decoupling method can eliminate cross coupling between Tx coils in multiple directions. Additionally, it reduces the cost of inverters and decoupling inductors significantly. The transmitter array is configured with three operation modes to stabilize system power transmission. The effectiveness of the proposed method is verified through the experiment.

Biplanar quadrature coil for versatile low-field extremity MRI

Biplanar magnets offer extended flexibility in MRI, particularly appealing due to unmatched accessibility to the patient. At low field strength (<0.2 T), such geometries could be particularly suitable for interventional settings or purpose-built applications such as musculoskeletal imaging. In the proposed work, we present a dual-channel, biplanar coil array for low-field MRI featuring almost fully open access when sited in a biplanar magnet. The proposed detector relies on the assembly of two orthogonal biplanar coils (single transmit channel, two receive channels in quadrature) respectively interfaced with custom inductive couplers. Simulations of the B1 field in each element were performed before the quadrature coil was built and used at ∼ 0.1 T (4.33 MHz). Once assembled, the best performance in our setup was achieved in undermatched conditions in place of conventional 50-Ω matching. Phantom images display the extended coverage of the quadrature coil, with similar SNR from each individual biplanar coil. The combined images show an expected SNR gain of 2 that confirms good decoupling between the two channels (−36 dB). To the best of our knowledge, the proposed coil represents the first implementation of a biplanar geometry at low field and the first quadrature detection for a biplanar design. The open design and overall good sensitivity of our biplanar design enabled fast and quasi-isotropic 3D imaging with (1.6 × 1.6 × 2.2) mm3 resolution in vivo in human extremities.

Simulation and Control Design of a Midrange WPT Charging System for In-Flight Drones

Drones, or unmanned aerial vehicles (UAVs), have emerged as an indispensable tool across numerous industries due to their remarkable versatility, efficiency, and capabilities. Notwithstanding all these traits, drones are still limited by battery life. In this paper, we propose a genuine in-flight charging method without landing. The charging system consists of three orthogonal coils, among which the receiving coil is connected to the drone. The development of the model for wireless dynamic charging systems is achieved by integrating the receiver trajectory and velocity in the model. Furthermore, the model is significantly enhanced by introducing the concept of the positioning mutual coupling function for the receiver trajectory; thus, it is possible to simulate a genuine continuous trajectory for UAVs and link it to the systems’ total input power consumption. The developed control algorithm can direct the magnetic field resultant to track the exact trajectory of the drone. The real-time simulation of the multiparameter discrete extremum-seeking control (ESC) algorithm on the (DSP) F28379D hardware shows that the input power is maximized up to 12 W in a response time of 2 ms for a drone-hovering velocity of 8 m/s without any feedback.

Experimental Study of a Room-Temperature Shimming Technology Employing Genetic Algorithm for NMR/MRI Superconducting Magnets

We present a recently developed shimming method that uses a system of room-temperature (RT) orthogonal shimming coils to improve the spatial field homogeneity of high-resolution nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) superconducting magnets. Conventional RT shimming methods require recursive routines of field mapping and RT shim coil current adjustments, which lead to a less effective and time-consuming process. In this paper, we introduce a new RT shimming method that utilizes a process of gradual and automatic search to find an optimal operating point with a genetic algorithm (GA), a type of optimization technique. The proposed algorithm is capable of determining the optimal set of currents for a system of shimming coils to create the best spatial field homogeneity by minimizing the NMR spectral linewidth. We used a commercial 600-MHz NMR magnet with a full NMR spectral linewidth at half maximum (FWHM) of 2.2 ppm, as determined by an NMR test sample contained in a cylindrical glass tube with a diameter of 5 mm to demonstrate that the shimming method can improve the FWHM to 0.15 ppm. The results demonstrate the strong potential of the proposed RT shimming methodology for the auto-shimming process of NMR/MRI applications.

A Novel Electromagnetic Positioning Prototype System With Simplified Receiver for Interventional Surgery Application

To meet the need of 3D positioning of surgical instru-ment in interventional surgery and the requirement of smaller size sensor for the narrow blood vessels, a new electromagnetic posi-tioning model is proposed with simplified receiver. Based on the electromagnetic theory and geometry principle, the electromag-netic field transmitter with groups of three orthogonal coils and the simplified receiver with smaller size than existing sensors are designed. Then, using Biot-Savart Law, the distance between re-ceiving end and geometric center of orthogonal coils is calculated, and the spatial coordinate of receiving end is computed with the spherical intersection formula. To further reduce the positioning error, a two-round accuracy improvement algorithm is designed for selecting the optimal topology of coil groups at the transmitter end and fitting correction of the calculated distance. We imple-ment the prototype system and perform both simulation experi-ments and actual experiments. The results show that our proposed new electromagnetic positioning method with simplified receiver has higher accuracy and stronger stability, compared with the tra-ditional positioning approach of three-coil transmitter and three-coil receiver.

Thermal modeling of the cylindrical electromagnets in transient and steady-state modes

PurposeAn excessive increase in temperature will reduce the lifespan and even burn the coil. The variety of materials in the structure of the electromagnet along with its multi-layer winding creates a complex and heterogeneous thermal structure. There are very few researches that are completely focused on the thermal analysis of electromagnets. The purpose of this paper is to provide an accurate, yet fast and simple method for the thermal analysis of cylindrical electromagnets in both transient and steady-state modes. For this purpose, a thermal equivalent circuit (TEC) is presented based on the nodding approach.Design/methodology/approachThe results of TEC analysis of cylindrical electromagnet, for two orthogonal and orthocyclic winding coil technologies, were compared with the results of the thermal simulation in COMSOL. The authors also built a laboratory model of the cylindrical electromagnet, similar to those analyzed and simulated, and measured the temperature in different parts of it.FindingsThe comparison of the results obtained from different methods for the thermal analysis of the cylindrical electromagnet indicates that the proposed TEC has an error of less than 2%. The simplicity and high accuracy of the results are the most important advantages of the proposed TEC.Originality/valueComparing the information and results related to winding schemes, indicates that the orthogonal winding has less cost and weight due to the shorter length of the wire used. On the other hand, orthocyclic winding generates lower temperature and has more lifting force, and is simpler to implement. Therefore, in practice, orthocyclic winding technology is usually used.

Multi-component induction logging detection characteristics of the fracture azimuth and dip angles and the fast extraction methods of fracture distribution parameters

In the field of log interpretation of tight sandstone and shale reservoirs, it is difficult to quantitatively evaluate the fracture distribution parameters (fracture azimuth angle and fracture dip angle) near the borehole. Multi-component induction logging can measure the apparent resistivities of the reservoir in different directions by an orthogonal coil system, which lays a foundation for the quantitative evaluation of the fracture distribution parameters near the borehole. First, we derive the finite element equations for numerical calculation from the Maxwell equations for the time-harmonic field and construct a three-dimensional (3D) vector finite element numerical algorithm for the fractured formation. Second, we quantitatively analyze the multi-component induction logging detection characteristics of the fracture azimuth and dip angles. Third, we establish a fast extraction method of the fracture azimuth angle based on coordinate system rotation and an analytical calculation method of the fracture dip angle using the combination of cross components and coplanar components of multi-component induction logging. Finally, we use field data to test the fracture distribution parameter extraction method, and the fracture dip and azimuth angles calculated by multi-component induction logging are consistent with those calculated by borehole imaging logging, which realizes the fast extraction of the distribution parameters of fractures in tight sandstone and shale reservoirs.

Design of Two Orthogonal Transmitters With Double L-Type Ferrite for the Wireless Charging System in Unmanned Aerial Vehicles

This article proposes a wireless charging system based on a novel magnetic coupler with high coupling capacity for recharging the unmanned aerial vehicles (UAVs). The novel magnetic coupler includes two transmitters and one receiver, in which the transmitters consist of double orthogonal rectangular coils and double orthogonal L-type cores and the receiver is an air-cored receiving coil perpendicular to one coil of the transmitter and parallel to the other coil of the transmitter. The magnetic flux is concentrated in the receiving coil as much as possible while guaranteeing the magnetic flux operation space away from a UAV body by coil structure itself. A prototype of the UAV wireless charging system based on the novel magnetic coupler is built and tested. The experimental wireless charging system designed for Phantom 4 RTK can deliver 102 W at a dc-to-battery efficiency of 91.02% at the maximum output power point, which is adapted to the wireless charging in UAVs.

Rotating alternating current field measurement testing system with TMR arrays for arbitrary-angle crack on nonferromagnetic pipes

Nonferromagnetic pipes are widely used in power plants such as fluid transportation and heat exchanger devices. Due to the severity of the environments, including corrosion, high temperature, etc, they are subject to surface arbitrary-angle cracks. In view of this background, this paper proposed a rotating alternating current field measurement (RACFM) testing system for arbitrary-angle cracks on nonferromagnetic pipes. The RACFM pipe detection model is established and the unidirectional excitation coil and the orthogonal excitation coils are simulated separately. The testing system and the probe with tunnel magneto resistance sensor arrays and flexible orthogonal excitation coils are built to detect cracks at different angles on the pipe. The simulation and experimental results reveal that the RACFM detection system has high sensitivity for arbitrary-angle cracks on the outer surface of the pipe, and it can effectively measure the lengths and angles of the cracks.

Modelling and Control Design of a Non-Collaborative UAV Wireless Charging System.

This study proposes an analytical model of a WPT system with three orthogonal transmitter coils organised to produce a concentrated and controlled omnidirectional magnetic field suited for charging a moving, rotating load, providing maximal energy transfer without receiving end feedback. In order to create a realistic 3D WPT simulation system and a precise controller design, the mutual coupling values in terms of the receiver angular positions are modelled using the Ansys software. In using the established model of the 3DWPT system, an extremum seeking control (ESC) is used to maximize the power transfer utilizing the input power as an objective function assigned with specified parametric values defining the WPT model. The output power transmitted by the sending-end coils to a load of a moving UAV rotating in orbit is displayed. According to simulation results, when the receiver UAV speed is close to 2250 deg/s, the controller can accomplish a maximum power transfer of 2.6w in almost 1ms.

A Three-Dimensional Orthogonal Receiving Coil for In Vivo Microrobot Wireless Power Transmission Systems

Approaches to studying electromagnetic induction in weak coupling have recently received attention in robotics since they could be used to supply energy to robots, allowing robots to diagnose and treat diseases in the human body. A three-dimensional orthogonal receiving coil connected in parallel, with a size of 13 mm × 13 mm × 13 mm, for an intestinal examination microrobot is designed in this article. Based on the defined attitude functions, we build and verify the stability and effectiveness of the proposed coil model through both analytical calculation and simulation analysis. In addition, to supply enough power to the microrobot, the number of turns of the receiving coil is optimized, considering both the electrical coil parameters and the limited space inside the robot. Then, an evaluation of the proposed 3D orthogonal receiving coil is presented in the bench tests. The results show that the power transmission efficiency can reach as high as 9.6%, with 1271 mW. This paper also uses a curved pipe to simulate the robot’s movement with the designed coil in the tortuous intestine. The average speed is 0.97 mm/s, with the path covering 180°. The experiments illustrate the excellent performance of the wireless power transmission, even when the positions of the two induction coils are constantly changing.

Two-Dimensional Position Tracking Using Gradient Magnetic Fields

In this work, a two-dimensional (2D) position-detection device using a single axis magnetic sensor combined with orthogonal gradient coils was designed and fabricated. The sensors used were an induction coil and a GMR spin-valve sensor GF807 from Sensitec Inc. The field profiles generated by the two orthogonal gradient coils were analyzed numerically to achieve the maximum linear range, which corresponded to the detection area of the tracking system. The two coils were driven by 1-kHz sine wave currents with a 90° phase difference to generate the fields with uniform gradients along the x- and y-axis in the plane of the tracking stage. The gradient fields were detected by a single-axis sensor incorporated with a digital dual-phase lock-in detector to retrieve the position information. A linearity correction algorithm was used to improve the location accuracy and to extend the linear range for position sensing. The mean positioning error was found to be 0.417 mm, corresponding to the relative error of 0.21% in the working range of 200 mm × 200 mm, indicating that the proposed tracking system is promising for applications requiring accurate control of the two-dimensional position.

Underwater Electromagnetic Guidance Based on the Magnetic Dipole Model Applied in AUV Terminal Docking

To address the poor effect of optical/visual guidance used in AUV terminal docking with strong background light and turbid water quality, an underwater electromagnetic guidance method based on the magnetic dipole model is proposed in this paper. According to the magnetic dipole model, the electromagnetic field of 1 kHz frequency generated by the coil in the range of terminal docking is the near field, where the position can be figured out through the amplitude and phase information of three orthogonal magnetic field intensity vectors. A triaxial-coil magnetometer with three orthogonal coils and a method for extracting the amplitude and phase information of the induced voltage are presented in this paper. According to Faraday’s law, the amplitude and phase information of the induced voltage of a triaxial-coil magnetometer replace the information of magnetic field intensity in relation to positioning. The underwater positioning results show that the average positioning error within 6 m can reach the centimeter level. Five underwater terminal docking tasks were carried out, and four of them were successfully completed, which verified the feasibility of the proposed method.

The Delta Robot-A long travel nano-positioning stage for scanning x-ray microscopy.

A new stage design concept, the Delta Robot, is presented, which is a parallel kinematic design for scanning x-ray microscopy applications. The stage employs three orthogonal voice coils, which actuate parallelogram flexures. The design has a 3 mm travel range and achieves rms position jitter, integrated from 1 Hz to 1 kHz, of 2.8 and 1.3 nm perpendicular to the beam and 5.6 nm along the beam direction with loads up to 350 g. The Delta Robot design process used a mechatronics approach of iterative modeling and simulation to develop the system and validate performance. The design considerations, design process, stability, and operational performance on the hard x-ray nanoprobe at Diamond Light Source are presented.