Journal of the Japan Society of Applied Electromagnetics and Mechanics
Online ISSN : 2187-9257
Print ISSN : 0919-4452
ISSN-L : 0919-4452
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Showing 1-30 articles out of 30 articles from the selected issue
Special Topic: The 28th MAGDA Conference in Oita (MAGDA2019)
[Academic Papers]
  • Touichirou KIMURA, Shinnosuke OOKAWA, Kunihisa TASHIRO, Hiroyuki WAKIW ...
    2021 Volume 29 Issue 1 Pages 1-6
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     The purpose of this study is discrimination of differences in metal plating condition. The sensor coil is placed away from the discrimination target by 0.5 mm, and the time derivative of the current flowing the coil is measured while the step voltage is applied to the coil. Maximum value of the time derivative of the current and the time at the maximum value are extracted from the measured current waveform, and used as inputs to SVM for discrimination. As a result, the plating and the plating peeling states can be discriminated. However, the number of metal foils, which corresponds to differences in peeling conditions, con not be discriminated 100 %.

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  • Gun KURODA, Suguru MOTOTANI, Kae DOKI, Akihiro TORII
    2021 Volume 29 Issue 1 Pages 7-12
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     In this study, we control the received voltage via wireless communication in the wireless power transfer applied to a small mobile robot. We developed the robot powered by 85 kHz band wireless power transfer system via coupled magnetic resonance. However, the received voltage fluctuated when the robot moves or the electronic load changes during power supply. In this case, converters are generally used on the secondary side to control the received voltage. However, in the case of the small robot, they cannot be mounted due to the limitation of weight and installation space. Therefore, we apply wireless communication to control the received voltage with a DC-DC converter of primary side. From the experiment results, the proposed wireless feedback method improves the voltage fluctuations caused by the movement of the robot by 0.5 V or less. For electric load fluctuation, the relationship between the delay time and the voltage fluctuation is evaluated.

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  • Kayo MATSUHASHI, Yuhei OZAWA, Kunihisa TASHIRO, Hiroyuki WAKIWAKA, Tsu ...
    2021 Volume 29 Issue 1 Pages 13-18
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     The purpose of this report is to design a magnetic guiding device for guiding capsule endoscopes. The goal is to obtain 17 mT at a distance of 100 mm from the guiding device. Furthermore, the device needs to be lightweight. Two magnetic guiding devices were proposed. The one with 4 magnets arranged was 1475 g, and the one with donut type was 1229 g. In both cases, a magnetic flux density of 17.1 mT was obtained at a distance of 100 mm. However, the magnitude of the magnetic gradient was different, and the magnetic force obtained was 5 mN for the 4 cylindrical magnets and 5.9 mN for the donut type.

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  • Misuzu YONEYAMA, Masaya WATADA, Akira MORI
    2021 Volume 29 Issue 1 Pages 19-25
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     Ultrasonic screening for breast cancer tends to be affected by the skill of the examiner. In this study, we will develop an auxiliary device for breast examination for the purpose of acquiring ultrasound images with unclear tumor size and position. In this paper, we examined the design of auxiliary equipment and the control system. Moreover, the operation result on the breast phantom using the produced functional testing machine and the evaluation result of the system are shown.

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  • Shogo OGATA, Naoto YAMAZAKI, Takeo ISHIKAWA
    2021 Volume 29 Issue 1 Pages 26-31
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     As the quality characteristics of electric power steering (EPS) motors, the high average torque, small torque ripple, and small cogging torque are required. This paper proposes a slot-less permanent magnet (PM) synchronous motor for EPS motor, which has theoretically 0 cogging torque. Magnet volume and coil volume are determined by 2-D finite element (FE) analysis. The 3-D FE analysis shows that it has the average torque of 2.667Nm and the torque ripple of 0.053Nm. Therefore, it is verified that the proposed motor has a great decrease of torque ripple.

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  • Naoya SODA, Yoshitaka ICHIGE
    2021 Volume 29 Issue 1 Pages 32-38
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     Magnetic property of an electromagnetic steel sheet which is used for an iron core of electrical machinery and apparatus changes due to the external stress. Although several researches under out-of-plane stress are reported, those all are investigations for a measurement sample. An investigation of magnetic property by applying stress to an iron core of electrical machinery and apparatus directly is very important for future electrical machinery and apparatus development. Additionally, magnetic flux density B and magnetic field intensity H are vector quantities and a spatial phase angle θBH is between those. The spatial phase angle θBH is an important factor to calculate iron loss. Therefore, in this paper, local vector magnetic measurement in iron core of EI type reactor under out-of-plane stress is reported. The iron core is non-oriented electrical steel sheet. As a result, it is clarified that iron loss decreases because the phase difference θBH decreases by applying of stress from out-of-plane.

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  • Iwanori MURAKAMI, Yiming CHO, Naoto YAMASHITA
    2021 Volume 29 Issue 1 Pages 39-44
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     In this study, we developed a method to control vibration of a superconducting magnetic bearing flywheel using a repulsive levitation system that combines permanent magnets and coils. Generally, in the repulsive type magnetic levitation system using only permanent magnets, the repulsive force in the levitation direction is strong, but it is unstable in other directions. Therefore, the pinning effect of high-temperature superconductors is used to increase the stability. However, the resonance in the radial direction was large, and countermeasures were required. Thus, we propose a method to suppress the amplitude by changing the radial stiffness. In this method, we changes the current applied to the coil inserted between the repulsion magnets. This makes it possible to change the radial stiffness. Vibration is controlled by changing the stiffness at resonance point. The above vibration control method was verified by experiments, and the usefulness of this proposal was clarified.

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  • Wataru SAITO, Kenta TAKEI, Wataru KITAGAWA, Takahuru TAKESHITA, Yoshio ...
    2021 Volume 29 Issue 1 Pages 45-51
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     Recently, ultra-compact electromagnetic actuators are used in high temperature fields, and special applications in industry. However, the size and required thrust differ depending on the purpose and application used, therefore it is necessary to redesign an electromagnetic actuator suitable for each application. In addition, there are problems such as demagnetization of a permanent magnet used for an actuator in a high temperature field and generation of a very large EMF (electromagnetic force) by coils. Therefore, I design a stackable electromagnetic linear actuator and various the characteristics by electromagnetic analysis.

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  • Yuto UEDA, Toru MASUZAWA, Masahiro OSA
    2021 Volume 29 Issue 1 Pages 52-57
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     In previous research,the homopolar magnetic bearing and the maglev motor using the magnetic bearing were developed for application to an artificial heart. Implantable VAD is subjected to acceleration due to patient movement. For this reason, magnetic bearings must have acceleration resistance performance that allows the rotor to float stably without contact against external acceleration. In this pepar, the acceleration resistance performance of the magnetic bearings and maglev motor was calculated. After that, the acceleration performance of two real machines of magnetic bearing and maglev motor ware evaluated by applying acceleration to the magnetic bearing by sinusoidal excitation using a vibrator. As a result, it was confirmed that the acceleration resistance performance of the magnetic bearing and maglev motor almost coincided with each other in the calculation and real machine experiments.

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Special Topic: The 32nd Symposium on Electromagnetics and Dynamics
[Academic Papers]
  • Yuichiro KAI, Tomoyuki NOMAGUCHI
    2021 Volume 29 Issue 1 Pages 59-64
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     Magnetic properties of motor cores are deteriorated due to residual stress and outside load during manufacturing process. In this paper, new stress-relief annealing method of ring cores will be suggested by applying an induced magnetic field. The temperature distribution and temperature characteristic on the surface of the ring core is examined by changing the lamination number of the ring core. In addition, the ring core which cut by punching, wire discharge and laser process are annealed and the magnetic properties of these cores before and after the annealing is evaluated.

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  • Kenta TAKEI, Wataru KITAGAWA, Takaharu TAKESHITA, Yoshio FUJIMURA
    2021 Volume 29 Issue 1 Pages 65-71
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     This paper describes the design of small-sized and high thrust electromagnetic actuator, and the optimization of the mover aimed at the lightweight of the mover. The proposed electromagnetic actuator is used for the hotmelt applicator. The stackable electromagnetic actuator has been designed so that the electromagnetic actuators with various characteristics can be configured because the hotmelt has different properties for each main component. Moreover, in order to improve the characteristics of the electromagnetic actuator, it is considered useful to reduce the mass of the mover according to the equation of motion. In this paper, the permanent magnet volume has been reduced and resin has been interposed as a spacer to reduce the weight on the mover. As a result, the proposed model can obtain the same thrust as the conventional model and the response can be improved.

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  • Yui TANAKA, Tomotaka MURASHIGE, Wataru HIJIKATA
    2021 Volume 29 Issue 1 Pages 72-77
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     The purpose of this research was to propose synchronous control of the pump flow rate with the natural heart by estimating heartbeat and estimated a pump flow rate without using additional sensors. In this study, we have developed a disturbance observer to estimate heartbeat for estimating the radial thrust, which is the force generating on the impeller by the blood flow in the blood pump. The pump flow rate was also estimated from the radial thrust by experimentally determining the relationship between the pump flow rate and the radial thrust. The validation test was conducted using a simple mock circulation loop, and the heartbeat and the pump flow rate were successfully estimated by the proposed method. Our results concluded that using the heartbeat and pump flow rate estimation system proposed in this study enabled synchronous control with simulated natural heart in a simple mock circulation loop.

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  • ―Fundamental Consideration on Vibration Characteristics of Stationary Continuous Steel Plate―
    Ryo NAKASUGA, Yasuhiro NARAWA, Sora ISHIHARA, Ryo YAMAGUCHI, Takayoshi ...
    2021 Volume 29 Issue 1 Pages 78-84
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     The continuous steel plate production line extends several kilometers long, and during that time the steel plate is transported in contact with rollers. The surface quality of the steel plate deteriorates due to the friction caused by the contact between the steel plate and the roller. Therefore, we proposed a non-contact guide system for traveling continuous steel plates. High guidance performance could be obtained by installing the electromagnet along with the shape of the traveling steel plate. However, it has not been analytically obtained the shape of the continuous steel plate. In this study, we calculated the static shape of the steel plate with a thickness of 0.3 mm and analyzed the response when a disturbance was applied to the steel plate. In addition, the vibration characteristics of the continuous steel plate were examined by inputting disturbance from an electromagnet to the stationary continuous steel plate.

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  • Takumi IEMOTO, Akio GOFUKU, Naoto YOKOMITSU, Nagayoshi KASASHIMA, Tomo ...
    2021 Volume 29 Issue 1 Pages 85-91
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     An electromagnetic-type spherical motor rotates by the electromagnetic force worked between a rotor with permanent magnets and a stator with electromagnets. The torque map control method proposed by Kasashima, et. al., can control a spherical motor to rotate in any direction by adjusting the currents to excite electromagnets. The measurement of relative rotor posture to stator is necessary for the torque map control method because the currents to excite electromagnets to rotate the rotor around a specified rotation axis depend on relative rotor posture. A posture measurement technique of the rotor using Hall sensors is studied. A prototype posture measurement device developed is arranged Hall sensors in a mesh format to cover some part of the rotor in order to measure magnetic field generated by permanent magnets. It is necessary to estimate the position of permanent magnets of the rotor for the measurement of rotor posture. However, the permanent magnet position may not be estimated if there is an error in the distance measurement between Hall sensors and permanent magnets calculated from the output values of the Hall sensors.

     This study addresses the problem of the distance measurement error by applying least squares method to trilateration. The developed rotor posture measurement system is evaluated by rotor posture measurement experiments at various rotational speeds not only around the orthogonal coordinate axes but also an oblique axis.

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  • Takafumi MIYAKE, Katsuhiro HIRATA, Noboru NIGUCHI, Kazuaki TAKAHARA, H ...
    2021 Volume 29 Issue 1 Pages 92-97
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     Magnetic geared motors attract attention due to its low-speed and high-torque characteristics and contactless torque transmission. However, the gear ratio is at most 10 because it depends on the pole-pair ratio between rotors, and the increase of the number of pole pairs decreases the torque density. In order to solve this problem, an axially-differential magnetic-geared motor that is axially combined a magnetic geared motor with a magnetic gear has been proposed. It can increase the gear ratio up to approximately several hundred without the increase of the number of pole pairs. In this paper, the performance of the axially-differential magnetic-geared motor is investigated by carrying out measurements on a prototype and 2-D finite element analysis.

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  • Hironori SUZUKI, Katsuhiro HIRATA, Noboru NIGUCHI, Kazukai TAKAHARA
    2021 Volume 29 Issue 1 Pages 98-104
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     Magnetic-geared motors attract attention as a type of low-speed and high-torque motor. However, the maximum torque is limited by the maximum transmission torque between rotors. In order to solve the problem, a magnetic-geared motor with field coils was proposed. On the other hand, the magnetic-geared motor has a complicated stator structure due to its field coils, and low productivity. Therefore, in this paper, we propose a magnetic-geared motor using a superimposed field current which can increase its maximum transmission torque and its control method. The improvement of the maximum transmission torque due to the superimposed current and the effectiveness of the proposed control method are verified using 2-D finite element analysis.

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  • Tomoki OKINAGA, Takahiko YAMAMOTO, Kohji KOSHIJI
    2021 Volume 29 Issue 1 Pages 105-110
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     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.

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  • Atsuki SHIINA, Muhammad Nur Hakimi bin MOHAMAD KAMAL, Kazuki OGAWA, Ta ...
    2021 Volume 29 Issue 1 Pages 111-117
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     Contact conveyance by roller is carried out on the thin steel plate production line. The surface of the thin steel plate was scratched, and the quality of the steel plate deteriorates. Therefore, non-contact magnetic levitation conveyance of thin steel plate using the attractive force of electromagnets has been proposed. On the other hand, the levitation stability of thin steel plates has been improved by applying a magnetic field in the horizontal direction to suppress the deflection of the thin steel plates. We also have studied a curved magnetic levitation system using the flexibility of thin steel plates. In this study, we constructed electromagnetic levitation system which has vertical levitation control system with tilted electromagnet and horizontal positioning control system by electromagnet installed in horizontal direction. We performed transportation experiment of the bending levitated steel plate and investigate the effect of bending for transportation performance. From the results, the different tendency from previous study for levitation stability was obtained.

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  • Genu TAKAHASHI, Nanako OKUNO, Takamichi HIRATA, Akira MORI, Masaya WAT ...
    2021 Volume 29 Issue 1 Pages 118-123
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     Currently, 9.6 million people die from cancer worldwide each year. Therefore, there is a need to find effective cancer treatments. In this study, we investigate the application to cancer treatment by performing plasma irradiation experiments on cells. We generated plasma under atmospheric pressure and is equal to the temperature of the atmosphere, therefore it is possible to irradiate the living body. In this study, first, normal cells derived from mice are irradiated with atmospheric pressure plasma to investigate their effects on cell proliferation and apoptosis. Apoptosis is the death of cells characterized by the regular fragmentation of nuclear chromatin DNA and the fragmentation of the cell itself through the cascade of signals through the mediation of various functional proteins in the cell. In addition, the effects of atmospheric pressure plasma irradiation of human-derived cancer cells on cancer cells were investigated in terms of both proliferation ability and gene expression of inflammatory cytokines.

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  • Keigo NISHIDE, Akira HEYA, Katsuhiro HIRATA
    2021 Volume 29 Issue 1 Pages 124-129
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     Magnetic bearings (MBs) levitate and suspend rotors. MBs have some advantages such as low friction, no wear, and no risk of fluid pollution because they can suspend rotors without mechanical contacts and lubricants. To avoid increasing the size of systems, triaxial active control magnetic bearings (triaxial AMBs) have been proposed. We proposed the triaxial AMB without permanent magnets which has an asymmetric structure. It is specially designed for high-temperature turbomachines. However, the triaxial AMB has interference characteris-tics when it suspends a rotor in the radial and thrust direction simultaneously. In order to solve this problem, the position control system with a non-linear compensator is proposed. The compensation characteristics are changed by current and rotor displacement. It is proved that the compensator can suppress the interference. However, it is not clarified how the position controllability changes when the compensation characteristics change. We investigate the position controllability when the compensator has different characteristics.

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  • Natsumi TSUGUTA, Hironobu YONEMORI
    2021 Volume 29 Issue 1 Pages 130-136
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     In this paper, we discuss the acoustic noise generated when driving an IH cooker with a power supply that including high-frequency noise. Because, the acoustic noise generated from the IH cooker is on the order of kHz, which causes health damage to users. Examples include headache, nausea, dizziness, and discomfort. In this study, we clarify the data that contributes to the formulation of guidelines on acoustic noise specific to IH cookers. We conducted an acoustic noise measurement focusing on the amplitude and frequency components of the noise contained in the power supply. The measurement results were compared with the environmental standards announced by the Ministry of the Environment. As a result, we have clarified the conditions for generating acoustic noise that exceeds environmental standards.

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  • Takeshi OKUYAMA, Ryohei NIWATA, Mami TANAKA
    2021 Volume 29 Issue 1 Pages 137-142
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     It is important to evaluate the mechanical properties of the fingertip skin, which is one of the factors affecting the tactile sensation. In this paper, in order to quantify the mechanical properties of the stratum corneum of the fingertip, a fingertip measurement system using optical coherence tomography (OCT) was developed and the Young's modulus of the stratum corneum of the fingertip was measured using the fingertip measurement system. First, a fingertip measurement system using OCT was constructed. Then, it was devised the method to detect the stratum corneum of the fingertip from the tomographic image of contact area between the fingertip and the acrylic plate. As a result, the proposed method successfully detected the stratum corneum from tomographic images. Next, the fingertip was pressed against the acrylic plate with various pressing forces, and the thickness of the stratum corneum at the fingertip is measured. From the measurement results, the Young's modulus of the stratum corneum of the fingertip could be calculated. Finally, the measurement was performed by changing the position of the fingertip pressed against the acrylic plate, and the Young's modulus of the stratum corneum of the fingertip was calculated under each condition. It was confirmed that the Young's modulus of the stratum corneum differs depending on the position of the fingertip.

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  • Takeshi OKUYAMA, Kenichi TAKAHASHI, Kenta SUZUKI, Shinichi NISHIMURA, ...
    2021 Volume 29 Issue 1 Pages 143-148
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     In this paper, focusing on tactile imitation of wood using resin-printing, the important factor in tactile imitation is investigated by sensory evaluation and tactile sensor measurement. Some wood imitation samples made by resin-printing the wood grain and wood samples were used in the experiment. First, the surface of wood samples and wood imitation samples were measured by using tactile sensor system by using piezoelectric film as sensory material. The variance of the sensor output and the mean power frequency were calculated as the evaluation parameters of the sensor outputs. Next, sensory evaluation experiments were performed, and wood feeling for each sample are clarified. Finally, by compared among the evaluation parameters obtained from the sensor output and the results of the sensory evaluation. It was found that the variance is an important factor in the tactile imitation of wood.

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  • Tomoki CHIKAMATSU, Taiki SANO, Mitsuhide SATO, Tsutomu MIZUNO, Shigemi ...
    2021 Volume 29 Issue 1 Pages 149-154
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     As the conventional eddy current type rail displacement sensor has a small distance (liftoff) from the railhead top surface to a sensor, there is the possibility that a sensor wakes up trouble and malfunction for a collision with the snow and the gravel. As the conventional triangle coil has low Q level, a change of the impedance to depend on rail displacement for when I raise a liftoff is not provided enough. Therefore, the problem that the detection precision of the rail displacement falls to occurs. In this article, I improved a Q level by becoming examination, the high frequency of the drive circuit of the coil structure and enabled measuring it at 50mm that was conventional double size by a liftoff.

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  • Keiri MAESHIRO, Yasuhiro HORI, Yasuyoshi KANEKO, Shigeru SAKUMA
    2021 Volume 29 Issue 1 Pages 155-160
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     A magnet alignment method using permanent magnets is useful as a positioning method for power transmitting and receiving coils in WPT. However, mounting permanent magnets on the power transmission / reception coil has the problem of causing magnetic saturation of the soft magnetic material. In this paper, by canceling out the magnetic field of the permanent magnet mounted on each of the power transmitting and receiving coils, the adsorption power is improved while suppressing the magnetic saturation. As a result of the power supply experiment, the power transmission efficiency of the power transmitting and receiving coil equipped with this method was improved by up to 26% compared to the state of magnetic saturation without the method.

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  • Fumiya KITANO, Hidetoshi UCHIKATA, Kojiro MATSUSITA, Motoki SHIGA, Min ...
    2021 Volume 29 Issue 1 Pages 161-167
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     This paper present a simultaneous optimization of the mechanism and control when two six degree of freedom robot arms in the cooperate button pushing task by combining reinforcement learning and genetic algorithm. The proposed optimization system uses a genetic algorithm to optimize the mechanism and reinforcement learning to optimize the control. The length of each link is changed to the length represented by the gene, and the target is to press six buttons in cooperation with two robot arms. The results are evaluated and optimization is performed by repeating crossovers and generational changes. As a result, it was confirmed that not only the control is optimized, but also the mechanism is optimized to achieve efficient and coordinated task achievement.

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[Technical Papers]
  • Kiyoshi YAMAGUCHI, Toru MASUZAWA, Masahiro OSA, Eisuke TATSUMI
    2021 Volume 29 Issue 1 Pages 168-175
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     A compact axial-gap type maglev motor has been developed for use in pediatric ventricular assist devices (VADs). The developed maglev motor consists of a top stator, a bottom stator and an impeller which is magnetically levitated with 5-degrees of freedom posture control. The motor is 22 mm in outer diameter and 33.6 mm in total height. In this study, design change of stator windings and material change of stator core were investigated to improve motor energy efficiency due to reduction of electrical losses. Energy consumption of the improved maglev motor and magnetic suspension performance were evaluated. Increase in turn numbers of smaller diameter windings reduced the copper loss of the drive line cable due to reduction of required excitation current. Magnetic powder core material effectively reduced the eddy current loss. The energy consumption of the improved motor sufficiently decreased at design operating speed of the maglev pediatric VAD without deterioration of the magnetic suspension performance.

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Regular Paper [Academic Papers]
  • Hao SUN, Masatsugu TAKEMOTO, Satoshi OGASAWARA
    2021 Volume 29 Issue 1 Pages 176-185
    Published: 2021
    Released: May 12, 2021
    JOURNALS FREE ACCESS

     Conventional 5-axis active control system usually has a thrust magnetic bearing (TMB) with a disk rotor and two radial magnetic bearings (RMBs) as the rotor's suspension part. However, considering for the motor part, the number of the units in the 5-axis active control system increases, which resulting in not only the cost increases, but also length of the rotor increases and makes rotor's resonance frequency lower. In order to decrease the units of the entire system, one 3-axis active control T+RMB type magnetic bearing whose suspension force can active control thrust-axis and radial-axis as the suspension part is widely used. However, as a real problem, in applications such as turbo molecular pumps, even though T+RMB is applied as the suspension part of the system, the permanent magnets to generate a bias magnetic flux, leads to the deterioration of assembly during the insertion and removal of the rotor. In order to solve this real problem, a research of magnet-less 3-axis magnetic bearing with cylindrical rotor will be investigated in this paper. What is more, two types of magnet-less structure will be proposed and examined by suspension force and system loss. Finally, the structure with the better performance will be introduced, and the excellent characters of the magnet-less 3-axis magnetic bearing with cylindrical rotor will be shown in 3D-FEM.

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