Flat Coil Research Articles

Radio-Frequency ‘Magnetic-Field’ Probes Based on the Single Layer Flat Coil Oscillators - New Type of SFCO-Sensors for Bio-Medical Investigations

The physical principles and advantages of the use of a new class of the SFCO sensors (radio-frequency ‘magnetic-field’ probes) for the investigation of biomedical signals are discussed. The perspectivity of their application for the investigation of dynamic changes of dielectric characteristics of tissues and the medium of the organism is demonstrated. Data related to the registration of the state of the human vascular system by the use of such sensors are presented.

Design and modeling of a linear speed sensor with a flat type structure and air coils

This paper presents the design and modeling of a linear eddy current speed sensor with a flat type structure and an air coil configuration. The theory of the eddy current speed sensor is based on utilizing the speed component of the induced currents in a solid moving conductor under stationary or alternating source fields. The stationary part comprises one rectangular excitation coil and two antiserially connected rectangular pick-up coils on the left and right sides of the excitation coil in the direction of the trajectory of the moving part. The moving part is considered firstly as a rectangular conductive ferromagnetic solid iron plate, and secondly as a rectangular aluminum plate. A 3D analytical model using Fourier series is developed to analyze the linear speed sensor in Cartesian coordinates. In addition, the 3D numerical finite element method is used for simulations of the linear speed sensor, and the results are compared with the results for analytical methods. The effects of iron permeability on the speed sensor are calculated for a rectangular ferromagnetic solid iron bar or conductor. The experimental results are presented for a linear speed sensor for a rectangular ferromagnetic solid iron plate and also for a rectangular aluminum plate, at variable speeds. The calculation and the experimental results show that the speed sensor outputs differ completely for solid iron conductive plates and for aluminum conductive plates, due to the different electrical conductivities and magnetic permeabilities.

Determination of Heat Transfer Coefficient for the Air Forced Cooling Over a Flat Side of Coil

Abstract The paper deals with the analytical and experimental determination of the forced convection heat transfer coefficients over the flat coil module. In the analytical part, the forced convection coefficients at different wind speeds are calculated based on various known equations of the forced convection heat transfer coefficient with unheated starting length. The experimental part presents the description of the test: loading the coil with DC current and measurements of the coil temperatures with thermal sensors while it was inside a wind tunnel. Based on the measurement, the convection coefficients were determined. In the final part, the experimental and analytical results are compared. It is found that the accuracy of the analytical results is more precise in highly turbulent flows.

Flat Spiral Coil Design for Higher Riveting Force and Energy Saving in the Electromagnetic Riveting Process

AbstractElectromagnetic riveting (EMR) belongs to the green manufacturing process, which has the advantages of low noise, no pollution, and large riveting force. In this paper, the influences of structural parameters of a flat spiral coil on riveting force and energy saving were investigated, and the cross-section geometry, base angle, and height of the coil section were designed. The EMR simulation models with fully coupled electromagnetic–thermal–mechanical were built in ls-dyna software, and the riveting force was adopted to assess the performances of different types of coils. The results showed that the riveting force given by trapezoid cross-section coil was the largest compared with rectangular, pentagonal, and circular types. Moreover, the increase in the base angle and height of the coil section had a positive effect on improving the riveting force and energy saving. In addition, weights analyses showed that the contribution rates of three structural parameters (length of the bottom edge, base angle, and height) of the coil to energy saving were 0.5231, 0.2347, and 0.2422, respectively. In general, the riveting force was improved and discharge energy was saved by adjusting geometric parameters of the coil. The research could provide guidance for the coil design in the EMR process.

A Full-Tensor Superconducting Gravity Gradiometer System Composed of Levitation-Type Accelerometers

In this paper, a superconducting gravity gradiometer system that is designed to measure full-tensor gravity gradients based on levitation-type component accelerometers without using mechanical springs is presented. All components of the gradiometer system are made of a superconducting material, niobium. Working principles are the flux quantization and the perfect diamagnetism of the superconductor. Each component of the gravity gradient tensor is obtained from the differential gravity measured by using two accelerometers, each of which is composed of a cubic test mass, a flat sensing coil, and a flat counter coil to balance the repulsive force of the sensing coil and ambient gravity. The measured signals are amplified by using superconducting quantum interference devices. The full-tensor gradiometer system consists of three perpendicularly aligned sets of gradiometers, each of which measures one diagonal and two off-diagonal components. The details of the structure of the system, the dynamics of the gradiometer, the transfer function, the common mode rejection, and the optimum conditions are discussed.

Optimal Design of Gap Sensor for High-Speed Maglev Train

The gap sensor plays an important role in high-speed maglev train which is able to measure the variation of trains’ suspension gap. The magnetic fields distribution is different clearly when the sensor is opposite to different position in a tooth-groove period of stator railway. The fluctuation of equivalent inductance leads to the slot-effect. The slot-effect is an important factor affecting the stability of the high-speed maglev train suspension control system. The distribution of magnetic field intensity of the flat rectangular coil in different gaps and positions is analysed, and the mechanism of slot-effect is revealed. A new coil is proposed in this paper and this optimized coil can create a smaller slot error than the flat rectangle coil. The simulation results show that the slot error of optimized coil is always less than the error of original coil in any gap distance. The slot error is reduced by half at the working air gap from 8mm to12mm. The slot error of the optimized coil reaches a maximum at 2mm and reaches its minimum at the rated suspension gap 10mm.

Magnetic Augmented Self-sensing Flexible Electroadhesive Grippers

Current electroadhesion (EA) grippers cannot be used to lift objects with limited contact areas. Current electromagnetic adhesion (MA) grippers cannot be used to grip nonferrous materials. Here, we combine EA and MA into a monolithic, electrically controllable, flexible, and hybrid electro/magneto-adhesive (E/MA), to offer EA grippers augmented with magnetoadhesion and MA grippers augmented with electroadhesion. This E/MA was achieved by exploiting two intertwined coplanar coils inspired by Tesla's flat bifilar coil. By appropriate electrical connections an electromagnetic field is generated – driving magnetic attraction—or an electric field is generated—delivering electroadhesion—or both fields can be generated simultaneously. As a result, the E/MA grippers cannot only be used to lift ferrous and nonferrous materials, but also low-density objects, such as office paper clips. We also present a customized capacitance measurement method to enable an autonomous material handling system without embedding external sensors. E/MA grippers have the potential to expand the capabilities and impact of soft robotics and industrial gripper systems.

AC Resistance Reduction of a Flexible Wireless Power Transmission Coil Using Magnetic Path Control Technology at 13.56 MHz

To reduce the size and weight of wireless power transfer devices, lightweight, thin, and highly efficient power-transmitting and power-receiving coils are required. In this paper, we describe a spiral-shaped flexible flat wire coil with reduced ac resistance, which is suitable for being mounted on electric tools and smart phones. A method for reducing the ac resistance of a flexible coil for wireless power transfer at high frequencies is required. The proposed flexible coil uses magnetic path control technology to suppress the skin and proximity effects by applying a magnetic material to the coils. The proposed coil reduces the ac resistance by 18% at 13.56 MHz in the ISM band, and improves the Q value of the coil by 27%. As a result, the transmission efficiency improves by 1.3% when the distance between the coils in 10 mm.

Thermal Performance of Plastic Receiver in Solar Collector

A plastic tubes used as absorber of active flat plate solar collector (FPSC) for heating water were studied numerically and experimentally. The set-up is located in Babylon (republic of Iraq) 43.80 East longitude and 32.30 North latitude with titled of 450 toward the south direction. The study involved three dimensions mathematical model for flat coil plastic absorber which solved by FLUENT-ANSYS-R.18 program. Experiments were conducted at outdoor conditions for clear days on January and February 2018 with various water volume flow rates namely (500, 750, 1000, 1250, and 1500 Liter per hour LPH) on each month for Reynolds number range of (1 x 104 to 5 x 104) through the receiver. The experimental results showed improvement in absorber input - output temperature difference, collector efficiency, and water storage temperature; the maximum input - output temperature difference is 3.1 °C, the maximum collector efficiency is 79%, and the maximum water storage temperature is 67 °C. The comparison validates a good agreement between the numerical and experimental results at variable operation conditions with maximum deviation of 4.2%. Also the experimental results were compared with previous study for similar condition and gave a good improvement.

Method for enhancement of spatial resolution of eddy current imaging

We propose a method for spatial resolution enhancement of eddy current images obtained by magnetic induction 2D scanning. A measurement technique based on a scanning differential source of an alternating magnetic field combined with a receiver is considered. A flat spiral coil is used as a receiver. The dimensions of the receiver and source coils are larger than or comparable with the dimensions of the objects under study. We represent an electrically conductive object as a set of small diameter conductive coils with a specific current induced by an external source. The method proposed solves the forward and inverse problems for linear coefficients describing the distribution of small coils representing a flat conductive object of arbitrary shape. This method was verified numerically and experimentally. The visualization of the object at a range of 15 mm with appropriate spatial resolution is shown experimentally at a frequency of 30 kHz. This method could be applied for the non-destructive testing and visualization of metallic objects.The novelty of the proposed method lies in the fact that it provides the ability to use probe coils with sizes much larger than inhomogeneities. We also proposed a method for calculating the hardware function of the system and solving the inverse problem. Detailed object visualization with sizes smaller than the probe system of the coils is provided. The possibility of increasing the resolution by seven times at a noise level of 0.1% is shown numerically.

Design and Fabrication of Flat Coil Spring Motioning Bicycle

Design and Fabrication of Flat Coil Spring Motioning Bicycle

Computer modeling of electrical coil characteristics dedicated for helmet-mounted cueing systems with magnetic method

Paper presents the importance of the helmet-mounted cueing systems in the field of flight safety increasing and mission execution effectiveness. There are presented the selected helmet systems used in the foreign and domestic solutions, utilizing the magnetic method. An original method of pilot’s helmet angular position determination utilizing the magnetic field from single flat coil and quaternion calculus is presented. The valuable elements are given mathematical relationships describing the characteristics of the magnetic field generated by selected types of electric coils as well as the results of simulation tests and the laboratory experimental verification of a flat coil model (designed in the Air Force Institute of Technology - AFIT) with a given number of coils.

Integrated structure and precision control of flat voice coil actuator for non‐contact satellite

The disturbance caused by actuator is an important factor affecting the performance of the high-precision payload, and a new actuator is urgently required for the non-contact satellite. First, a flat voice coil actuator (VCA) with high precision and high bandwidth is proposed for the non-contact ultra-quiet satellite, and the principle of the eddy current sensor is analysed. Second, an optimised integrated structure is proposed with the flat actuator to output high-precision forces and the eddy current sensor to measure the distance of the displacement. The mathematical model of the VCA is established, and the precision of output force is studied. Third, the attitude control using six actuators in Stewart configuration is discussed, and the compensation method of unbalanced torque is provided. Finally, physical test is taken on the principle prototype, and numerical simulations are implemented to verify the effectiveness of the integrated structure and the control methodology.

Electromagnetic Forming Analysis of the Al 99.0 Sheet with Tools of Different Configurations

Electromagnetic forming is an advanced manufacturing procedure, characterized by the fact that the tool carrying the deformation force does not touch the workpiece. This paper presents research regarding the electromagnetic forming of Al 99.0 (EN AW-1200) sheet with coils, having different configurations. The purpose of the research was to find the flat spiral coil configuration that ensures maximum deformation of the workpiece. Flat spiral coils with different gaps between the coil and the workpiece, and coils with different number of windings were tested. The influence of these parameters was monitored on the maximum strain of the free bulged parts. The analysis of the results obtained for different configurations of the flat spiral coils allowed the selection of the significant parameters that influenced the electromagnetic forming process of the Al 99.0 flat workpiece, which aimed to elaborate the mathematical model and to optimize the investigated process.

Effect of electromagnetic induction spectroscopy of screw crack implant on electromagnetic signal strength

Abstract Screws in bone implant are widely used in medical technology which focus on stabilizing and supporting the broken bone in means of healing. Improvement in bone implant are required in order to ensure better healing process because some failures may happen due to the crack of the screw implant. Previous studies showed there are lack of investigation on screw crack detection in bone screw implant. Early detection of screw implant loosening is crucial for faster repairing and a healthy ready-to-operate. The purpose of this study is to investigate the received signal strength of electromagnetic field induction on implant screw by employing a single channel magnetic induction spectroscopy using flat spiral coil sensor. This study also to evaluate the screw implant under the action of electromagnetic field induction. The electromagnetic method is choose to be implement using the COMSOL Multiphysics’s simulation software. The magnetic induction spectroscopy technique was used in this study to evaluate the received signal strength data for the different screw crack and non-crack. In this study, a high-cycle fatigue test using the flat coil sensor was performed in order to monitor cracks in Titanium Ti-6Al-4V screw.. The results suggested the feasibility of the proposed electromagnetic induction spectroscopy.

Wireless Power Transfer With Magnetic Resonator Coupling and Sleep/Active Strategy for a Drone Charging Station in Smart Agriculture

Drones can be used in agriculture applications to monitor crop yield and climate conditions and to extend the communication range of wireless sensor networks in monitoring areas. However, monitoring the climate conditions in agriculture applications faces challenges and limitations, such as drone flight time, power consumption, and communication distance, which are addressed in this study. Wireless power transfer (WPT) can be used to charge drone batteries. WPT using a magnetic resonant coupling (MRC) technique was considered in this study because it allows high transfer power and efficiency with tens of centimeters, power transfers can be achieved in misalignment situations, charging several devices simultaneously, and unaffected by weather conditions. WPT was practically implemented based on a solar cell using a proposed flat spiral coil (FSC) in the transmitter circuit and multiturn coil (MTC) in a receiver circuit (drone) for the alignment and misalignment of two coils at different distances. FSC and MTC improved power transfer and efficiency to 20.46 W and 85.25%, respectively, at 0 cm with the loaded system under alignment condition. In addition, the two coils achieved appropriate transfer efficiencies and power for charging the drone battery under misaligned conditions. The maximum power transfer and efficiency were 17.1 W and 71% for the misalignment condition, at an air gap of 1 cm between two coils when the system was loaded with the drone battery. Moreover, the battery life of the drone was extended to 851 minutes based on the proposed sleep/active strategy relative to the traditional operation (i.e., 25.84 minutes). Consequently, a 96.9% battery power saving was achieved based on this strategy. Comparison results showed that the proposed system outperformed some present techniques in terms of the transfer power, transfer efficiency, and drone battery life. The proposed WPT technique developed in this study has been proven to solve the misalignment issue. Thus it offers a great opportunity as a key deployment component for the automation of farming practices toward the Internet of Farming applications.

Coupled thermo-electromagnetic model of a new robotic high-frequency local induction heat treatment system for large steel components

A new robotic high-frequency local induction heat treatment system is studied. The system is designed to perform on-site local heat treatment on large steel components such as hydropower turbine runner. A flat spiral coil is moved by a robot arm over the area to treat. A fast numerical model is developed to predict the temperature distribution and system settings. Several numerical strategies are proposed to minimize the computation time. The model combines an equivalent circuit with thermal finite elements and the electromagnetic mutual impedance method. A simple approach based on the concept of complex permeability is proposed to model hysteresis losses. The computed power losses in the RLC circuit and the temperature field in flat paramagnetic and ferromagnetic workpieces are compared with experimental measurements. Results confirm the accuracy of the coupled thermo-electromagnetic model.

A comparative study on the effects of boundary constraints on electromagnetic sheet forming

This paper investigates the effect of boundary constraints on the plastic deformation behavior of a ∅458 circular sheet metal in an electromagnetic forming process. Both experiments and simulations were conducted on a flat spiral coil system. In the experiments, two different boundary conditions were imposed on the workpiece flange by utilizing a blank holder with and without a draw bead to control the draw-in of the flange. Both the final profile and thickness distribution of the workpiece are sensitive to the boundary constraint, due to the varied draw-in material flow. Furthermore, according to the morphology characteristic of the deformation profile, three typical deformation stages can be recognized, where the thickness reduction at the sheet center only occurs in the first and third stages. This work provides a better understanding of the deformation behavior in the electromagnetic sheet-forming process under varied boundary constraints, which is fundamental for the further development of this process.

Theoretical evaluation of the screening-current-induced magnetic field in superconducting coils with tape wires

We theoretically investigate the physical mechanism of the screening-current-induced field (SCIF) in solenoid coils wound with superconducting tape wires. We derive the direct relationship between the SCIF and the magnetization of tape wires, and a scaling law for the SCIF and the coil dimensions is demonstrated. A simple analytical expression of the SCIF is obtained as functions of current load factor, tape wire width, and the coil dimensions. We verify that the published data for the precise numerical computation of SCIF are roughly fitted by our theoretical results for flat coils where the height is smaller than the outer diameter.

The Plasma Ionization Mechanism for a Radio Frequency Ion Thruster with a Flat Coil Inductor

A model of discharge for a radio frequency (RF) ion thruster with a flat induction coil is proposed. The configuration of magnetic fields and currents in 3D geometry is described. The skin layer boundary is determined by the condition at which the azimuthal current in plasma becomes zero under a transformer coupling with the inductor. Variation of radial magnetic field and azimuthal current at the generator driving frequency induces currents at the driving and second harmonic frequencies. Plasma becomes ionized due to magnetized collisional plasma electrons in mobile current layers. With operation at the optimal driving frequency, magnetic field of a definite sign fills the entire gas-discharge space in the course of convective diffusion within the current half-cycle. In the next half-cycle, it is filled with magnetic field of the opposite sign. Ohmic losses in the current layer are compensated in the course of field annihilation. The concentration of particles captured by the mobile layer was determined from the equality of “frosted” electron flows entering and leaving the layer in the course of single coulomb collisions with scattering at the pinch-angle. The azimuthal current of the fundamental harmonic component is determined by mobile layer currents outside the skin layer. The power losses are compensated by magnetic energy. The simulated results are compared with experimental data. The model of physical processes in radio frequency discharge with a flat induction coil has substantial peculiarities as compared with the discharge model using a cylindrical induction coil.