Spiral Coil Research Articles

High-Impedance Wireless Power Transfer Transmitter Coils for Freely Positioning Receivers

In this letter, a wireless power transfer (WPT) system based on two high-impedance coil (HIC) - cable loop antennas with a modified shield - as transmitters (Tx)s and a spiral coil as a receiver (Rx) is proposed and discussed. Utilizing features of HIC at its parallel-circuit resonance frequency, we design the Tx in a way that in the absence of the Rx, the input impedance of the Tx is very high compared to the case when the Rx is near the Tx. This feature offers a possibility for free positioning of the Rx over an array of Txs and auto self-activation and de-activation of the Txs, leading to highly efficient performance. To verify the proposed solution, we have designed, fabricated, and experimentally tested a WPT system based on two HICs as Txs and one Rx. The proposed system operates in a high-frequency range (around 280 MHz) in the near-field coupling regime. The measured averaged efficiency of the prototype is higher than 93%. The proposed system is simple, cheap, and does not require any control circuit system for tuning the system when the receiver position changes.

Optimization of Bio-Implantable Power Transmission Efficiency Based on Input Impedance

Recently, the inductive coupling link is the most robust method for powering implanted biomedical devices, such as micro-system stimulators, cochlear implants, and retinal implants. This research provides a novel theoretical and mathematical analysis to optimize the inductive coupling link efficiency driven by efficient proposed class-E power amplifiers using high and optimum input impedance. The design of the coupling link is based on two pairs of aligned, single-layer, planar spiral circular coils with a proposed geometric dimension, operating at a resonant frequency of 13.56 MHz. Both transmitter and receiver coils are small in size. Implanted device resistance varies from 200 Ω to 500 Ω with 50 Ω of stepes. When the conventional load resistance of power amplifiers is 50 Ω, the efficiency is 45%; when the optimum resonant load is 41.89 Ω with a coupling coefficient of 0.087, the efficiency increases to 49%. The efficiency optimization is reached by calculating the matching network for the external LC tank of the transmitter coil. The proposed design may be suitable for active implantable devices.

Fundamental Study on Equivalent Circuit Model of Spiral Coil for Low Frequency Band

In recent years, wireless power transmission technology has attracted a lot of attention. By using wireless power transmission, it is possible to easily supply power to tablets and smartphones without connecting to a cable. However, the impedance of spiral coils is difficult to derive from the external form and it is difficult to assume the impedance at the design stage. In this study, the impedance is derived based on the equation of electromagnetism with the addition of a geometric approach. As a result, we have derived a formula that makes the computational process more theoretical and easier than the conventional one.

A Novel Machine Learning Approach to Classify and Detect Atrial Fibrillation Using Optimized Implantable Electrocardiogram Sensor

There are some constraints such as external electrodes, a failure to capture most paroxysmal atrial fibrillation (AFib), low power transfer efficiency (PTE) for 24/7 charging technology, a short period of monitoring, and automatic detection of AFib in conventional electrocardiogram (ECG) sensors. To overcome these constraints, an implantable ECG sensor with a 2-coil inductive link with maximum power transfer efficiency (PTE) is designed to continuously monitor patients and efficiently detect AFib using global covering rule discovery and the minimum description length (MDL) algorithm. Among different combinations of ECG coils, the square spiral-square spiral coil demonstrates the maximum PTE, 56.23%, at the resonant frequency of 13.56 MHz and it is used in the implantable ECG sensor. The QRS complex from ECG signals of twenty-nine AFib patients is detected using different operation methods (DOM). The MDL algorithm is used to group 12 features of heart rate variability (HRV) parameters. The global covering rule discovery is proposed as a novel classification technique of AFib in ECG data. The average classification accuracy was 96.67 ± 7.03, and then the average recall, precision, F1-measures, and an average number of generated rules were 97.08 ± 6.23, 97.08 ± 6.23, 96.57 ± 7.23, and 7.9 ± 0.32, respectively. We found that the NN50, pNN50, and LF parameters can distinguish the AFib patient better than a healthy one. Among these parameters, pNN50 showed that it is greater than 34.75 in 41.38% of patients. The optimized implantable ECG sensor with a maximum PTE of 56.23% along with novel AFib detection and classification methods is suitable for its implementation in future implantable ECG sensors.

Transmission Characteristics of Wireless Power Transmission Using a Cone Spiral Coil

Transmission Characteristics of Wireless Power Transmission Using a Cone Spiral Coil

Spiral coil beneath fingertip enhances tactile sensation while tracing surface with small undulations

ABSTRACT We found that a spiral coil placed beneath a fingertip enhances tactile sensation while tracing small undulated surfaces. Hence, we investigated the mechanism underlying the enhanced tactile sensation. We evaluated the amplification effect quantitatively to demonstrate that the coil increases the tactile sensation in the finger pad. Specifically, we installed a strain gauge between the spiral coil and the fingertip to measure the strain corresponding to the curvature of a skin surface that undergoes deformation when tracing the surface. Then, to determine the enhancing mechanism of tactile sensation by the coil, we modeled the coil while moving on a surface with irregularities. The corresponding simulation results show that the inclination of the coil elements changes while moving on uneven shapes. Furthermore, as the distance between the tips of adjacent coil elements increases (reduces), the shape (or curvature) of the skin varies, and the skin on the fingertip attached to the coil expands (contracts) along the lateral direction. Therefore, the lateral strain on the fingertip is amplified by the coil moving on an undulated surface, thus enhancing tactile sensation.

Approach to Choose of Optimal Number of Turns in Planar Spiral Coils for Systems of Wireless Power Transmission

Correct choice of coil parameters for resonant circuits in inductive power transmission systems is a relevant problem, as it significantly influences the efficiency and transmitted power in the systems and provides for optimization of these parameters. This paper presents a methodology of calculation of geometrical and electrical parameters and approach to choose the optimal number of turns in planar coils used in the wireless power transmission (WPT) system with parallel resonant circuit. Formulas are derived for calculation of active resistance and inductance of the coil, normalized to the specified design parameters of the coil. Connection is made between the design and electrical parameters of the coil, which allows choosing the optimal number of turns according to different criteria and guard conditions. The examples of practical use of the chosen approach with transmitting and receiving coils of WPT system are presented. The obtained results show that efficiency and transmitted power in the system are higher when using the coils with the calculated number of turns. The proposed approach may be used in selection of optimal design of loop coils in systems with fixed frequency, and in systems, whose operational frequency depends on the parameters of the resonant circuit.

Experimental Study of the Guided Wave Directivity Patterns of Thin Removable Magnetostrictive Patches.

The characteristics of removable magnetostrictive thin patches are investigated for the generation of guided waves in plates. The directivity patterns of SH, S0 and A0 modes have been measured in a thin metallic plate for different combinations of static and dynamic magnetic field directions. This used different coil geometries such as racetrack and spiral coils to generate the dynamic magnetic field, as well as separate biasing static magnetic fields from permanent magnets. This arrangement generated signals via both Lorentz and magnetostrictive forces, and the resultant emitted guided waves were studied for different dynamic and static magnetic field directions and magnitudes. It is demonstrated that different guided wave modes can be produced by controlling these parameters.

Thromboxane Synthesis and Platelet Protein Release During Simulated Extracorporeal Circulation

Platelet secretion induced by certain soluble aggregating agents is associated with thromboxane formation. Activation of platelets by artificial surfaces may involve similar biochemical pathways. Therefore, we monitored platelet release and formation of thromboxane B2. the stable end-product of thromboxane A2, during simulated extracorporeal circulation where contact between blood and synthetic surfaces is extensive. Fresh heparinized human blood was recirculated for 2 hr at 37°C at 1 liter/min in circuits (0.95 sqm) constructed of standard silicone rubber components (0.1 sqm) and a spiral coil membrane oxygenator (0.85 sqm). Within 2 min of recirculation, plasma levels of the platelet-specific protein, low-affinity platelet factor 4 (LA-PF4) rose from <1.5% to 11 % ±3% SEM of that which was released by triton X-100, indicating significant release of platelet α-granule contents. This occurred despite the absence of detectable thromboxane B2 in plasma (<0.5 pmole/ml). Between 2 and 15 min, plasma levels of LA-PF4 increased from 11% to 42% ± 3%, and plasma thromboxane B2 concentrations rose to 3.2 pmole/ml. Subsequently, thromboxane B2 levels continued to rise to 9.8 pmole/ml by 2 hr. Thromboxane B2 was not detected in blood from donors who had ingested aspirin, and the extent of platelet secretion was reduced by about 50% (25% at 2 hr). Thus, although a component of platelet granule release during extracorporeal recirculation appears to be associated with thromboxane synthesis, considerable release of LA-PF4 may occur by thromboxanβ-indβpen-dent pathways.

Energy Scavenging From Low Frequency Vibrations Through a Multi-Pole Thin Magnet and a High-Aspect-Ratio Array Coil

The challenges of developing a micro electromagnetic power generator are to increase the flux density from the thin permanent magnet and reduce the resistance of the micro high-winding-density coil. To overcome these challenges, we propose a novel MEMS power generator for low-frequency-vibration energy harvesting employing a 16-poles thin magnet plate and a high-aspect-ratio spiral micro array coil. Transient magnetic analysis has proved that the multi-pole magnet thin plate (8.9 × 8.9 × t0.5 mm) magnetized by laser assisted heating helps increase the output power from the generator compared with the unidirectional one. The high-aspect-ratio spiral micro array coil (width: 80 µm, thickness: 160 µm, total turns: 144) fabricated by the combination of multilayer SU-8 micro moldings, copper plating, and silver paste screen printing is beneficial for increasing coil density and reducing resistance, thus improving output power. The vibration experiment showed that in terms of no consideration of spring and guideway structure, when the magnet is directly vibrated by an actuator, the induced voltage, generated power, and power density were 1.63 mV, 0.12 µW and 1.03 µW/cm3, respectively at an excitation frequency of 10 Hz with an amplitude of 2 mm. When a 3D-printed cantilever beam was adopted as the spring and guideway structure for the resonant prototype, the counterparts were 8.48 mV, 3.34 µW and 5.22 µW/cm3, respectively at 38 Hz and 2 mm excitation (corresponding to a vibration acceleration peak of 11.6 g).

Optimal Design of Planar Spiral Coil for Uniform Magnetic Field to Wirelessly Power Position-Free Targets

A large circular transmitter (power pad) is often utilized for inductively wireless charging so that the power receiver can position itself freely within the power pad. However, the uneven magnetic field distribution leads to the impedance mismatch and the variable transferred power due to the misalignment between a receiving coil and a relatively large transmitter coil. In this paper, the effects of the turn numbers, trace spacing, and coil size on the uniformity of magnetic field distribution over a planar spiral coil (PSC) are investigated based on an analytical model. Then, the genetic algorithm is used to optimize the trace width and spacing of a ten-turn PSC with the fixed outer and inner diameters, whereas the magnetic field is numerically calculated by HFSS software. The geometrically optimal PSC is obtained with the trace width approximately equal to trace spacing for each turn by minimizing the coefficient of variation (COV) of magnetic field within an effective charging area over the coil. The results showed that the simulated and measured COVs of magnetic field were 0.130 and 0.121, respectively, which are obviously less than that of the uniformly spaced regular coil and show a little less than that of the optimally spaced coil with fixed trace width. Therefore, the trace spacing is a major consideration to achieve the uniform magnetic field, whereas the trace width variation is applied to refine the evenness of field. It is also expected that the proposed GA-based optimization is well applied to design other Txs with conformable shape in inductively WPT systems for stable power delivery regardless of the receiver positions.

A brief review: basic coil designs for inductive power transfer

The inductive power transfer (IPT) has contributed to the fast growth of the electric vehicle (EV) market. The technology to recharge the EV battery has attracted the attention of many researchers and car manufacturers in developing green transportation. In IPT charging system, the coil design is indispensable in enhancing the EV battery charging process performance. This paper starts by describing the two charging techniques; static charging and dynamic charging before further presents the IPT system descriptions. Afterwards, this paper describes a brief review of coil designs which discusses the critical factors that affect the power transmission efficiency (PTE) including their basic designs, design concepts and features merits. The discussions on the basic coil designs for IPT are of the circular spiral coil (CSC), square coil (SC), rectangular coil (RC), and double-D coil (DDC). Furthermore, the significant advantages and limitations of each research on different geometries are analyzed and discussed in this paper. Finally, this paper evaluates some essential aspects that influence the coil geometry designs in practical.

Experimental and CFD investigation of spiral tube heat exchanger

In this paper, the thermal, hydraulic and thermodynamic performances of heat exchanger with spiral coils are placed cascading on the cylindrical shaped shell inside the heat exchanger. Tube side pressure drop and exergy efficiency are considered as a hydraulic and thermo hydraulic performance whereas overall heat transfer coefficient (U), effectiveness are considered as thermal performance. The tube side flow rate varies from 2 to 6 lpm and shell has two flow rates 4 lpm and 10 lpm. Flow conditions are varied and conducted the experiment to find the best flow rate inside the spiral heat exchanger. From the experiment results effectiveness, nusselt number, prandtl number, heat transfer rate, overall heat transfer coefficient and exergy efficiency, to validate the outlet temperature CFD analysis were performed on various flow rates. The experiment results are good in agreement with CFD results. Shell side flow rate of 10 lpm gives higher efficiency for the different flow rates of tube side from 2 to 6 lpm.

PCB-Embedded Spiral Pattern Pick-Up Coil Current Sensor for WBG Devices

This paper proposes a current sensor for wide bandgap (WBG) devices. The current of a power semiconductor device is mainly measured using a Rogowski coil, an active current transformer, and a coaxial shunt resistor. The Rogowski coil and active current transformer are not suitable for the current measurement of surface mount WBG devices due to their operating principle. The coaxial shunt resistor causes parasitic inductance. Since WBG devices are more sensitive to parasitic inductance than silicon devices, parasitic inductance may affect circuit operation. To overcome these problems, this paper proposes a printed circuit board (PCB)-embedded spiral pattern pick-up coil current measurement for WBG devices. The proposed pick-up coil has high mutual inductance compared to the conventional pick-up coil, so the measurement sensitivity is high. In addition, there is no need for additional processing outside the PCB. Experimental results using a double pulse tester circuit are provided to verify the performance of the proposed current sensor.

Experimental study on deep hole drilling of GH4169 alloy

GH4169 alloy material has good corrosion resistance, radiation resistance and other excellent properties, and has been widely used in aerospace and other manufacturing fields. At the same time, due to its severe machining hardening phenomenon and high cutting force during machining, it is also one of the typical difficult-to-machine materials, and the deep hole drilling of GH4169 alloy has been rarely studied. In this paper, the deep hole drilling test of GH4169 is studied, and BTA system is adopted in the test, the wear and failure modes of the cutting tool, and the change of chip morphology were analyzed. Results showed that the middle cutter tooth wear focused on central blade, the wear of the center tooth occurs mainly at the tip of the cutter tooth, the wear of edge tooth mainly occurs at the arc of the tool tip where the main cutting edge is connected with the secondary cutting edge: the chips produced by the central cutter tooth are mostly short and small c-shaped chips, the chip produced by the middle tooth is not easy to break the chip, most of which are elongated spiral chip, the cuttings produced by the edge tooth are not easy to discharge, and most of them are hard spiral coils.

Study on the Integration of Flue Gas Waste Heat Desulfurization and Dust Removal in Civilian Coal-fired Heating Furnace

To put the policy of civil coal governance environment, the clean and efficient use of technology and civilian cainuanlu practical application within consideration, this paper designed a set of flue gas desulfurization dust removal integration of recovery of waste heat from flue gas treatment system, in order to achieve the recovery of waste heat of flue gas and reduce cainuanlu particulate matter and sulfur dioxide emissions. The flue gas treatment system mainly used the structure of the spiral coil heating and stainless steel tube, and will recovery the smoke waste heat ; There are three dust removal processes: the strainer mesh filtration of the entire unit, adsorption of modified activated coke and water spray cleaning; Desulfurization part was designed to operate the easy drawer cabinet structure, using the modified adsorption properties of activated coke processing SO2 in flue gas. The experimental results show that the processing system of dust removal and desulfurization efficiency is at 80%.

Liftoff Tolerant Pancake Eddy-Current Sensor for the Thickness and Spacing Measurement of Nonmagnetic Plates

The liftoff spacing distance between the eddy current (EC) sensor and the test piece will influence the detected signals and accuracy of the measurement. Various techniques including novel sensor designs, features (liftoff point of intersection, liftoff invariance phenomenon), and algorithms have been proposed for the compensation of error caused by the liftoff effect using the EC sensor. However, few of these have directly measured the liftoff spacing distance, particularly for the distance up to 15 mm. In this article, a liftoff tolerant pancake sensor has been designed. By analyzing the sensitive region of the magnetic vector potential change (due to the test piece), the receiver of the sensor is designed as a circular spiral pancake coil with a large mean radius and span length (the difference between inner and outer radius). Experiments on the inductance measurement of three different nonmagnetic samples have been carried out using both the designed pancake sensor and the previous triple-helix sensor. From the experiment results, the detected signal of the designed sensor has been proven much larger than that of the triple-helix sensor. Besides, simplified algorithms have been proposed for the measurement of the liftoff spacing and thickness of non-magnetic samples when using the proposed pancake sensor. Results show that the liftoff spacing and thickness can be measured with a small error of 0.14 mm (absolute error under 209.66 kHz), and 1.35% (relative error, under low working frequencies of 142, 238, and 338 Hz) for the liftoff spacing from 1 to 15 mm.

Cylindrical condenser in a liquid cleaning device

The article presents the results of theoretical substantiation and experimental confirmation of the effectiveness of non-reactive technologies for cleaning liquids. The method of research includes the main theoretical provisions of the process of coagulation treatment of water taking into account modern trends of its development, modern methods of using this process of water purification, laboratory and production studies on natural waters using the developed device of non-reactive water treatment. Studies of sediment kinetics when settling water after its coagulation showed that the deposition time was reduced – from 30–40 min (without additional treatment) to 8…10 min when treating a coagulant solution in a spiral coil and to 3…5 min when treating in a spiral coil with electrostatic field application.

A Magnetic Dipole Resonator for Magnetic Coupled Resonance Wireless Power Transmission

This paper proposes a magnetic dipole structure Resonator for the magnetic coupled resonance wireless power transmission (WPT). The various characteristics are investigated by using simulations. To investigate the advantage of the proposed structure coil, a same geometric size traditional single-layer spiral coil is used for the power transfer characteristics Comparison. Due to the proposed structure, if the magnetic dipole resonator needs to be resonated at the same frequency with the traditional spiral coil, the larger number of turns is needed. This causes the resistance of loss to dramatically increase, thus decreasing the power transfer efficiency. To solve this problem, the tightly coupled parallel-connected coil structure was used. Depending on the characteristics of the tightly coupled parallel-connected coil structure the proposed magnetic dipole resonator can offer significantly reduced resistance with very little self-inductance loss. Simulation results show that compare to the same resonance frequency traditional single-layer spiral coil, a magnetic dipole resonator contributed by the tightly coupled parallel-connected coil structure can increase the Q factor by approximately 54.3%. Moreover, the simulation evaluation results confirmed that the proposed resonator can also dramatically improves the system power transfer flexibility performance.

Influence of Working Fluid on a Novel Solar Pond Coil

Abstract A design configuration and selection of working fluid for solar absorption remain critical for high performance of energy harvesting process in solar pond. In this study, heating and pressure loss characteristics in a novel designed spiral-coil geometry pertinent to salt-gradient solar pond (SGSP) is examined and the thermal performance of nanofluids in the coil is assessed. Nanofluids possessing graphene, functionalized graphene nanoplatelet (fGnP), and graphene oxide (GO) at 0.06% volume concentration are considered as the working fluids in the system. In order to achieve a novel design of a spiral coil, the circular cross-sectional geometries with aspect ratios (AR) of 0.5, 1, and 2 are incorporated in the analysis. The selection of the aspect ratios of 0.5, 1, and 2 results in elliptic, circular, and oval cross sections of the coil, respectively. The findings reveal that heat transfer enhances and pressure loss reduces via increasing the mass flowrate. This is due to the formation of a stable secondary flow which causes mixing enhancement while shortening the thermal entry length. Circular and elliptic cross sections resulted in the maximum and the smallest normalized average Nusselt numbers, respectively, for low rates of flow. This is because of thermal resistance created under the large surface area-to-volume ratio; however, this effect varnishes for high mass flowrates. Graphene oxide and functionalized graphene nanoplatelet have the highest and the lowest normalized average pressure drops, respectively, for all flow rates.