Magnetic Poles Research Articles

磁気式アブソリュートエンコーダの高精度化

The purpose of this study is to develop an absolute track recording method to develop a higher accuracy magnetic absolute encoder. Shortening the magnetic pole distance is effective to achieve higher accuracy, but the absolute position misdetection due to attenuation and interference of the magnetic signal on the absolute track decrease the accuracy. Therefore, a magnetic pole array and its decoding method are developed to solve the problems of magnetic signal attenuation and interference by increasing the magnetic pole spacing without allowing three or more identical magnetic poles in succession. When the magnetic pole distance is shortened, the magnetic signal of the absolute track of the developed method detects the absolute position with a larger sensor gap than the existing method. At the magnetic pole distance realized by the developed method, interpolation errors are reduced, confirming the high accuracy of the magnetic absolute encoder.

A Multipole Magnetoactive Elastomer for Vibration-Driven Locomotion.

Smart materials such as magnetoactive elastomers (MAEs) combine elastic and magnetic properties that can be significantly changed in response to a magnetic field and therefore offer enormous potential for applications in both scientific research and engineering. When such an elastomer contains microsized hard magnetic particles, it can become an elastic magnet once magnetized in a strong magnetic field. This article studies a multipole MAE with the aim of utilizing it as an actuation element of vibration-driven locomotion robots. The elastomer beam has three magnetic poles overall with the same poles at the ends and possesses silicone bristles protruding from its underside. The quasi-static bending of the multipole elastomer in a uniform magnetic field is investigated experimentally. The theoretical model exploits the magnetic torque to describe the field-induced bending shapes. The unidirectional locomotion of the elastomeric bristle-bot is realized in two prototype designs using magnetic actuation of either an external or an integrated source of an alternating magnetic field. The motion principle is based on cyclic interplay of asymmetric friction and inertia forces caused by field-induced bending vibrations of the elastomer. The locomotion behavior of both prototypes shows a strong resonant dependency of the advancing speed on the frequency of applied magnetic actuation.

Rotor Position Estimation Method Based on Harmonic Signal for a Wound-Field Synchronous Starter/Generator in the Low-Speed Region

During on-load starting process of an aviation wound-field synchronous starter/generator system, accurate rotor position information is required. Mechanical position sensor is susceptible to interference, increasing volume and weight, so online rotor position estimation is more desirable. Harmonics of main exciter (ME) caused by rotating rectifier are analyzed, and the 5th harmonic is used creatively to estimate rotor position in this paper. In this method, by performing coordinate transformation on stator current of ME, rotor position increment is extracted and obtained through a low-pass filter. Meanwhile, taking advantage of the unidirectional conduction characteristics of rotating rectifier, a new idea to estimate initial rotor position is also proposed. In this approach, pulse signal is injected into the stator winding of main generator (MM) every fixed electrical angle, then the maximum and minimum current response correspond to that of MM's S and N pole respectively. Finally, combine initial rotor position and position increment, continuous rotor position of MM can be gained. The proposed methods avoid dependence on the saliency of MM, require no high-frequency signal injection and do not need secondary magnetic pole identification. Effectiveness and advantages of the proposed method are verified on the test.

Dusty plasmas above the sunlit surface of Mercury

Above the sunlit surface of Mercury, the properties and formation of dusty plasmas are investigated. It is demonstrated that the dusty plasmas are formed for subsolar angles exceeding approximately 76° due to photoelectric and electrostatic processes. As a result, the dusty plasmas are present in the polar regions of Mercury, characterized by latitudes of about 70° and above. The formation of dusty plasmas is also possible for lower latitudes, but only where the surface profile allows it. Plasmas above the sunlit surface of Mercury consist, in particular, of photoelectrons, electrons, and ions of the solar wind, and also charged dust particles. The distribution functions of photoelectrons near the surface of Mercury, as well as the altitude dependences of the number densities of dust particles, their charges and sizes, as well as electric fields, are obtained. The calculations are carried out which correspond to the position of Mercury at aphelion and perihelion of its orbit for the situations of dusty plasma location in the vicinity of magnetic poles of Mercury and in other regions. It is shown that there are qualitative differences between the dusty plasma systems of Mercury and the Moon related to the fact that Mercury has a magnetosphere and Mercury's orbit is one of the most eccentric of all planetary orbits in the Solar System. The effects of magnetic fields can slightly influence the dust particle transport and, correspondingly, the expansion of the region of the existence of dusty plasmas above the surface of Mercury due to the effect of dust particle transport is not so significant as at the Moon. Furthermore, due to the presence of Mercury's magnetosphere, the solar wind is important for the formation of dusty plasmas at Mercury only in the vicinity of the regions of the magnetic poles. In other regions of Mercury, in contrast to the situation at the Moon, the solar wind does not influence significantly the dusty plasma properties. The dusty plasma parameters are different in the cases of aphelion and perihelion of the orbit of Mercury.

Parametric study on circularly abrupt magnetic flux density changes of electromagnetic energy harvesters via simulation

Energy harvesting has long been widely studied. In this paper, we systematically investigate the output performances of rotating electromagnetic energy harvesters (EMEHs) with different magnetic pole pairs and coil parameters via simulations. Different numbers of magnetic pole pairs obviously affect the abrupt magnetic flux density (MFD) change and the further output voltage. Hence, we set up finite element (FEM) models of proposed harvesters to compare the output voltage under different numbers of the magnetic pole pairs p in the same coil parameters conditions. Subsequently, to further study how the coil parameters affect the voltage and power of EMEHs, we conduct simulations using different coil heights h and wire diameters d with the same magnet array. The results of the magnet simulation indicate that in a certain volume, EMEHs yield a maximal output voltage of about 12.2 V in the case of p=4. In the best contrast, EMEHs produce a peak output power of about 26.36 W under the excitation of 180 rad/s. This study will be of great significance in improving power in the field of harvesting electromagnetic energy.

Research on the influence of trapezoidal magnetization of bonded magnetic ring on cogging torque

Abstract In this article, the influence of trapezoidal magnetization method on cogging torque of permanent magnet motor is studied. First, the structure is analyzed by analytical method to explain its mechanism of reducing cogging torque. Then, in order to verify the effectiveness of the formula, a six-slot four-pole motor is introduced for finite element analysis. Through comparison of the original structure motor, the magnet skew structure motor, and the trapezoidal magnetic pole structure motor, it demonstrates that the trapezoidal magnetic pole structure motor can effectively reduce the Cogging torque and does not produce additional axial electromagnetic force. Finally, a magnetizing fixture with a trapezoidal magnetic pole structure is made to magnetize the magnetic ring. The magnetized magnetic ring is installed on the motor, and the Cogging torque, Back EMF, etc., are tested. The test results are in good agreement with the simulation results. This method can be used to optimize the cogging torque of the permanent magnet motor.

An Estimation of the Geometrical Structure of Polar Cap and Emission Property of Radio Pulsar: A Treatment from an Analytical Approach

Pulsars are believed to be one of the most interesting objects in the universe. The emission mechanism of pulsars is still a conundrum to physicists, as there is no completely acceptable theory that can establish a consensus between theory and observation. Pulsars possess a gigantic magnetic field, to the order of 1012 Gauss, and generate a very powerful radio beam from the magnetic pole. However, the powerful radio beam is generated by some complicated coherent plasma processes and acceleration in the pulsar magnetosphere. The location of the origin of the radio waves has been predicted to come out exclusively from the polar cap zone, whose boundary is defined by the footprint of the last open field line. However, in this paper, we mainly try to generate the shape of the polar cap structure from an analytical solution and discuss how it gets distorted for different geometrical parameters due to the presence of perturbation such as polar cap current flow. Also, apart from that, we try to emphasize understanding the variation of radio emission height and polarization angle with respect to different geometry-related parameters as well as with frequency.

Design of Permanent Magnet-Assisted Synchronous Reluctance Motor with Low Torque Ripple

Permanent magnet-assisted synchronous reluctance motors (PMSRMs) have been widely used in household appliances, national defense and the military, due to their advantages of low cost and high efficiency. However, their excessive torque ripple cause a series of problems, such as high vibration and noise. To solve this problem, this paper first considers the important factor that causes the torque ripple—the cogging torque. Firstly, the generating principle of the cogging torque is analyzed, and a method combining magnetic pole migration and the stator auxiliary groove is proposed. On this basis, considering the position, width, depth, quantity and shape of the auxiliary groove, the Taguchi method is used to optimize the proposed improved structure. Finally, a new motor structure that can minimize torque ripple is obtained. Compared with the original structure, the cogging torque is reduced by 57.6%, the torque ripple is reduced by 38%, and the electromagnetic torque is only reduced by 1.6%.

A study of a modified design of dumbbell-shaped flux switching tubular linear generator for regular wave energy conversion

Wave energy converters (WEC) use indirect drive hydraulic or turbine-type power take-off (PTO) mechanisms which consist of many moving parts, creating mechanical complexity and increasing the installation and maintenance costs. Linear generator-based direct drive wave energy converters could be a solution to overcome this problem, but the efficiency of the single conventional linear generator is not high enough, and it cannot work satisfactorily in the low-frequency range.In this paper, a novel dumbbell-shaped flux-switching linear generator has been proposed and studied as a power take-off unit for ocean wave energy conversion. The linear generator has a dumbbell-shaped stator, and the design is ameliorated by placing the permanent magnet rings of longitudinally alternating magnetic pole directions in the slots of its stator outer surface and is separated by thin wall steel ring shoulders. The linear generator also has a dumbbell-shaped translator. The stator is hollow where the translator slides inside axially inducing current in the coil. A long permanent magnet is inserted inside the hollow steel dumbbell core of the translator and a copper coil is wound around the outer surface of the moving translator core. The addition of permanent magnets on the outer slots of the stator is found to increase the output power significantly. To facilitate the investigation, the modified generator design has been compared to the conventional linear permanent magnet generator for their performances using the finite element method, as both machines are different in their structures. The results show that the double dumbbell-shaped flux-switching linear generator gives higher power output, magnetic flux density, branch current, and induced voltage. The double dumbbell-shaped flux-switching linear generator is then placed in a cylindrical buoy and investigated in a wave energy converter in the ocean environment. The hydrodynamic response of the cylindrical buoy has been investigated through ANSYS AQWA. The dynamic differential equations of the wave energy converter have been developed and solved for regular waves using Matlab codes. The peak output voltage, power, and the relative displacement of the linear generator translator with respect to the stator fixed with the buoy have been calculated through the Fourier Transform in the frequency domain using a Matlab code and through numerical integrations in the time domain using a Matlab Simulink code. The results in the time and frequency domains are compared and verified with each other. The relative displacement between the translator and stator buoy has been used as motion input of the ANSYS Maxwell simulation model, and the output voltage results of the ANSYS Maxwell simulation model have been compared and verified with those of the Matlab simulation models. The linear generator design in the wave energy converter under the regular wave excitation is further optimized for the maximum ratio of the peak output power to peak cogging force using the central composite design-based response surface method (RSM). The ANOVA analysis is used to validate the response surface model where its R2 coefficient of 99.93% has indicated an excellent fit. The methods and results differ from those presented in previous studies.

SEPARATION OF MAGNETIC ANOMALIES USING FRACTAL METHOD IN THE ESFORDI REGION FOR IRON EXPLORATION, CENTRAL EAST OF IRAN

Link for citation: Amin Karimi Kalvarzi, Aref Shirazi, Adel Shirazy, Amin Beiranvand Pour, Ardeshir Hezarkhani, Hamed Nazerian, Timkin T.V., . Voroshilov V.G. Separation of magnetic anomalies using fractal method in the Esfordi region for iron exploration, central east of Iran. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 3, рр. 197-209. In Rus.
 The relevance of research is determined by the possibilities of measuring the potential magnetic field, which has self-similar (fractal) properties, as well as a practical tool for prospecting and exploration of iron ores. In the Esfordi area, this method was used by us for the first time to identify, separate and interpret geophysical (magnetic) anomalies. The main aim of this thematic and practical study is the qualitative interpretation of geophysical data, the application of new methods in the prospecting and exploration of mineral deposits, modeling the geological environment and forecasting new promising areas. Object: Esfordi region, Yazd province, Iran. Methods. To obtain additional information about the subsurface, magnetometric data were used with their interpretation by the RTP (reduction to the north magnetic pole) method. For modeling purposes, an artificial sample was made, consisting of a sphere, a cube and a cuboid, and it was found that the fractal method can be used to separate anomalies for unipolar models (cube and cuboid). Results. The results of the study were applied to the Esfordi region, where it was found that at a survey scale of 1:100000, there is a direct relationship between the fractal method and the 3D model, which can be used to locate iron ore mineralization.

Research on the torque performance for two multi-pole bilayer magnetorheological fluid couplings

This paper studies on the permanent magnets configuration on the transmission torque of the multi-pole bilayer magnetorheological (MR) coupling. Based on the electromagnetic field theory, the magnetic circuit models of traditional permanent magnet array (TPMA) and Halbach permanent magnet array (HPMA) are established, and the magnetic flux density within the MR fluid working gaps has been derived in order to evaluate the merits of the designed MR coupling. A 3D FE magnetic-fluid analysis has been necessary following the initial conceptual analysis, in order to study the influence of key parameters on the transmission torque. The results show that the transmission torque of the MR coupling with Halbach permanent magnet array is 33.45% higher than that of the ordinary permanent magnet array, with a same structure size. For the MR coupling with Halbach permanent magnet array, the unilateral magnetic focusing effect is better with the increase of the residual flux density of the secondary magnetic pole as well as the radial length of magnetic pole. And the single side magnetic focusing effect is the best when the main magnetic pole is 15°. The influence of the magnetic pole angle on the transmission torque has been further studied.

Investigation of different types of winding in counter-rotating double-rotor axial flux permanent magnet machines

ABSTRACT The choice of the winding type has a significant effect on the performance characteristics of the machine, efficiency, weight of the required wire, ease of winding, etc. The purpose of this paper is to investigate the effect of winding type as well as the polarity of magnets on both sides of the stator core on the back electromotive force (Back-EMF) of the counter-rotating double-rotor axial flux permanent magnet generator (CRDR-AFPMG). The winding type influences the produced voltages of the generator. Hence, in this paper, several types of windings, such as the first type of shifted winding, the second type of shifted winding, and the independent winding are investigated to produce three voltages with the same amplitudes and 120 degrees of phase differences. However, it has been found that, among the studied windings, only the second type of shifted winding and independent winding produces three voltages with similar amplitudes and 120 degrees of phase difference. Finally, the suitable type of winding for the proposed machine will be determined, and the performance of the case study machine will be evaluated by finite element (FE) simulation. JMAG designer software is used for this purpose.

Study on finishing inner wall of Co[sbnd]Cr alloy cardiovascular stent tube via novel atomized CBN/metal spherical magnetic abrasive powders

In this study, in order to solve the problem that the inner wall of the cardiovascular stent is difficult to polish, the magnetic abrasive finishing (MAF) method is used to finish the inner wall of the CoCr alloy tube that is used for the manufacture of the cardiovascular stent. The surface defects such as wrinkles, cracks and pits generated in the production process are removed, and the internal surface roughness is decreased to obtain better surface quality. Firstly, aiming at the problem of poor performance of traditional magnetic abrasive powders (MAPs), “gas-solid two-phase double-stage atomization and rapid solidification” is proposed and a novel atomized CBN/metal spherical MAPs with different sizes are successfully prepared. This MAP is used for MAF of the inner wall of CoCr alloy cardiovascular stent. Secondly, the slotted magnetic pole is designed according to the numerical simulation, and the MAF setup for the inner wall of ultra-fine and ultra-long tubes is developed. Finally, the orthogonal experiment is carried out with surface roughness as the evaluation index. Through the analysis of range theory, the order of the apparent degree of each process parameter on surface roughness is as follows: tube rotational speed > feed speed of magnetic pole > MAPs filling quantity > MAP particle size. According to the result, a model of surface roughness prediction based on whale optimization algorithm (WOA) and least squares support vector machine (LSSVM) is constructed. The interaction between tube rotational speed and other process parameters is analyzed based on the model fitting results, and the process parameters are optimized. The result show that MAF technology can effectively remove the defects of the inner wall of the CoCr alloy cardiovascular stent tube and accurately predict the surface roughness. After MAF under the optimized process parameters, the surface roughness Ra decreases from 0.485 μm to 0.092 μm.

Investigation of Spherical Al2O3 Magnetic Abrasive Prepared by Novel Method for Finishing of the Inner Surface of Cobalt-Chromium Alloy Cardiovascular Stents Tube.

In this investigation, spherical Al2O3 magnetic abrasive particles (MAPs) were used to polish the inner surface of ultra-fine long cobalt-chromium alloy cardiovascular stent tubes. The magnetic abrasives were prepared by combining plasma molten metal powder and hard abrasives, and the magnetic abrasives prepared by this new method are characterized by high sphericity, narrow particle size distribution range, long life, and good economic value. Firstly, the spherical Al2O3 magnetic abrasives were prepared by the new method; secondly, the polishing machine for the inner surface of the ultra-fine long cardiovascular stent tubes was developed; finally, the influence laws of spindle speed, magnetic pole speed, MAP filling quantities, the magnetic pole gap on the surface roughness (Ra), and the removal thickness (RT) of tubes were investigated. The results showed that the prepared Al2O3 magnetic abrasives were spherical in shape, and their superficial layer was tightly bound with Al2O3 hard abrasives with sharp cutting; the use of spherical Al2O3 magnetic abrasives could achieve the polishing of the inner surface of ultra-fine cobalt-chromium alloy cardiovascular bracket tubes, and after processing, the inner surface roughness (Ra) of the tubes decreased from 0.337 µm to 0.09 µm and had an RT of 5.106 µm.

Characteristics and FEA verification of the attraction between like magnetic poles

The attraction between unequally sized like magnetic poles is characterized herein. Finite element analysis (FEA) simulation has verified that attraction can occur between like poles. Between two unequally sized like poles with various dimensions and alignments, a turning point (TP) appears on the curves of force vs. distance between them, which is caused by the localized demagnetization (LD). The LD plays a role far before the distance between the poles reduces to the TP. The LD area may have a changed polarity, making the attraction possible and not in violation of basic laws of magnetism. Here, the LD levels have been determined using FEA simulation, and the factors affecting the LD have been explored, including the geometry, the linearity of the BH curve, and the alignment of the magnet pairs. Novel devices can be designed with attraction between the centers of such like poles and repulsion when off-center.

Enhancement of Piezoelectricity by Novel Poling Method of the Rare‐Earth Modified BiFeO3–BaTiO3 Lead‐Free Ceramics

AbstractIn piezoceramics, the Curie temperature (TC) and piezoelectric coefficient (d33) are often inversely proportional, so it is very difficult to optimize high piezoelectricity and TC simultaneously. In addition, the high and temperature‐insensitive piezoelectric strain coefficient (d33*) with small hysteresis is also a longstanding obstacle in the development of lead‐free ceramics. In this work, a facile approach of donor doping strategy is adopted to replace Ba2+ with Yb3+, Y3+, Sm3+, and Nd3+ as a result, a high TC of 450 °C and outstanding d33 of 422–436 pC N−1 is achieved by a novel magnetic poling method. Thermally‐stable and outstanding piezoelectric strain performance (d33* ≈ 520–550 pm V−1 and ΔST ≈ 10%) with small strain hysteresis (H < 20%) results are highly encourageable in lead‐free ceramics. The main factors contributing to high piezoelectricity are the morphotropic phase boundary, suppression of defect charges by donor doping, thermal quenching, mesoscale nanodomain size, and novel poling method. The excellent piezoelectric performance and high TC of this work are superior to those of state‐of‐the‐art piezoceramics. The synergistic approaches of compositional design strategy and novel poling process in this work are highly beneficial for temperature‐insensitive piezoelectric sensor and actuator applications.

Iterative Parallel–Serial Detection Structure Using MAP Algorithm for Bit-Patterned Media Recording Systems

In bit-patterned media recording (BPMR), data are modulated into the magnetic poles and stored in the magnetic islands. Thus, to increase the areal density (AD) of the storage device, we should reduce the distance between the magnetic islands. This leads to a two-dimensional (2-D) interference, wherein each island is affected by the neighboring islands. Therefore, to handle the 2-D interference, we proposed a parallel–serial structure of the detection based on the maximum <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$a$ </tex-math></inline-formula> posteriori (MAP) algorithm. The equalized received signal was fed to two branches in parallel. One branch was in the order of horizontal and then vertical detections, and the other was in the reverse order of vertical and horizontal detections. With the MAP algorithm, the serial structure of two branches can improve the bit error rate (BER) performance of the detection. Moreover, we can extract the extrinsic information from the output of the MAP algorithm of two branches and create the iteration of the parallel structure. The original signal was restored with higher accuracy after each iteration. The simulation results showed that the iterative parallel–serial detection structure using MAP improved the BER performance compared to those in previous studies with only parallel or serial structures.

Study of the Effect of Magnetic Abrasive Finishing on the Material Removal of AA1100 Aluminum Alloy

This study evaluates the performance of magnetic abrasive finishing (MAF) of aluminum alloy in terms of achieving materials removal (MR). A vertical milling machine is used to perform the finishing process using a developed MAF unit that consists of an inductor made out of a 150 mm long and 20 mm diameter iron core wound with 1500 turns and 0.5 mm copper wire. The commutator and magnetic pole are attached at the top and bottom of the inductor, respectively. The required current is supplied using a DC power supply. The South Pole workpiece is a 100×50×3 mm3 plate of AA 1100 aluminum alloy, whereas the magnetic pole represented the North Pole. Pole rotational speed, applied current, and abrasive finishing time was selected as input parameters of the MAF with three-level of (270, 600. 930 rpm; 0.5, 1, 1.5 Amp; 6,9,12 min). The L9 orthogonal array of the Taguchi method was utilized to examine the impact of each independent input. The obtained results clarify that applied current was the most effective factor in terms of its contribution (63.16%) in the produced MR, followed by time finishing and rotational speed.

Overview of Key Technologies for Torque Ripple Suppression in Four- Wheel In-Wheel Motor Drive Electric Vehicles

Aims and Objectives: The stability control of the four-wheel hub motor-driven electric vehicle is of great significance to the safety of the driver during the driving process, and the torque fluctuation is an important factor that affects the stability control of the vehicle. Therefore, this paper reviews the key technologies and difficulties of torque ripple suppression for in-wheel motor-driven electric vehicles from two aspects: rational design of the in-wheel motor structure to suppress the torque fluctuation of the motor and the in-wheel motor torque control distribution strategy. Methods: Through the analysis of the structural characteristics of the motor, the structural optimization design of the pole slot, cogging, core shape, and magnetic pole shape is used to suppress the torque fluctuation of the motor, and the methods of previous scholars are unified and explained; From the motor control strategy, summed up the scholars in the motor torque ripple suppression method strategy; From the perspective of motor torque control allocation strategy, a series of related strategies are elaborated. The previous researchers proposed the neural network PID electronic differential speed torque comprehensive control strategies, electronic differential control algorithms based on sliding mode control, automotive electronic stability program control algorithms based on hierarchical coordinated control strategies, and other control strategies and algorithms. Results: Based on the theoretical model, the theoretical model is verified and tested through software simulation or test platform. The errors of all simulation and test results in the literature and the theoretical model are within the acceptable range. Conclusion: The theoretical model has been verified on the software simulation or test platform, which proves the feasibility and effectiveness of the theoretical model, thereby suppressing torque fluctuations and improving the stability of the vehicle. Finally, the development direction of the key technology of torque ripple suppression for four-wheel in-wheel motor-driven electric vehicles has been prospected.

INCREASING THE EFFICIENCY OF THE SURFACE-MOUNTED ULTRASONIC ELECTROMAGNETIC-ACOUSTIC TRANSDUCER ON ACCOUNT OF THE MAGNETIC FIELD SOURCE

Model studies were carried out using the COMSOL Multiphysics package, aimed at ensuring the forming of a permanent magnet magnetic field at a considerable distance to a ferromagnetic product from its pole, which is necessary to create efficient portable ultrasonic electromagnetic-acoustic transducers of thickness gauges and testing and diagnostic devices. It is theoretically shown and experimentally confirmed that for portable measuring ultrasonic devices it is expedient to set the height of the permanent magnet at about 60 mm and the cross section of the magnet pole 50x50 mm2. At the same time, with a gap between the magnet pole and the product of about 30 mm, the value of the normal component of the magnetic field induction near the surface of the object is about 0.3...0.4 T, which is sufficient for thickness gauging or diagnostics of ferromagnetic products using the ultrasonic pitch-and-catch method. References 19, figures 8.