During the design phase of magnetic bearing centrifugal compressors, a time-domain simulator for the magnetic bearing control system is employed to evaluate the feasibility of magnetic levitation control. Proper modeling of the plant model is critical for simulator development. Especially, axial magnetic bearing actuator uses solid material, necessitating consideration of frequency characteristics due to eddy currents. This paper proposes a method to model axial magnetic bearing actuator using magnetic field analysis based on design information. The effectiveness of the proposed model was confirmed by comparing the responses of a simulator adapted with the proposed model and the actual machine when subjected to a specified input.

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To decrease the size of magnetically levitated pediatric ventricular assist device, we proposed a Single-Stator type magnetic levitation motor (SS-Motor). SS-Motor is constructed by combining Self-Bearing Motor stator with 22 [mm] outer diameter (D22-SBM) and magnetic attract unit with no control, no power supply. In this paper, we examined the structure and specific dimensions of the magnetic attract unit in SS-Motor by using 3D magnetic field analysis (JMAG Designer), based on the requiring performance as a Magnetic levitation motor. We decided optimal model, made magnetic attract unit constructed by permanent magnet with radial magnetize and 3 type yokes. In result, it was confirmed that the magnetic attract unit has the necessary performance to achieve magnetic levitation by combining D22-SBM. By substituting Double-Stator type magnetic levitation motor to SS-Motor with using our Magnetic attract unit and D22-SBM, size of pediatric VAD machine will decrease about 10 [mm].

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To reduce the size and cost of active magnetic bearings, a six-salient-pole active magnetic bearing (6-pole AMB) has been proposed. In the 6-pole AMB, the magnetic circuits of the x- and y- axes are magnetically coupled, making the calculation more complex. Previously, sequential quadratic programming (SQP) was adopted for optimal current calculation, and its effectiveness was experimentally confirmed. In this paper, when a coil failure occurs and the current in the failed coil becomes zero, the remaining coil currents are calculated using SQP. The SQP-based analysis shows that when the number of the failed coils is fewer than three, the coil currents required to generate the reference force can still be obtained. Experimental results demonstrate that stable magnetic levitation can be achieved even when up to three coils have failed.

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High-speed response in control systems is essential in fields such as robotics, precision machinery, and medical devices. Digital controllers using microcontrollers or DSPs often suffer from processing delays due to A/D and D/A conversions and discrete-time computation, which can cause instability in lightweight and fast-responding systems. This study explores high-speed control computation using analog electronic circuits that operate in continuous time and are free from such delays. A small magnetic levitation system was employed as an experimental example requiring rapid feedback control. Numerical simulations were conducted by introducing control delays to determine the stability limit. Based on the results, an analog feedback controller was designed and implemented. Experimental results showed that the proposed analog control circuit achieved stable levitation of a small neodymium magnet. These findings demonstrate that analog electronic circuits provide an effective approach for realizing high-speed control computation in systems where response delay critically affects stability

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Contact conveyance by roller was carried out on a thin steel plate production line to assess damages to the surface of the plates, and scratches were noted, thus reducing their quality. Therefore, modified non-contact magnetic levitation conveyance of thin steel plates using the attractive force of electromagnets is proposed to improve the levitation stability by applying a magnetic field in the horizontal direction to suppress the deflection during conveyance. We also studied a curved magnetic levitation system that considers the flexibility of thin steel plates. In this study, we constructed an electromagnetic levitation system having a vertical levitation control system with tilted electromagnets that induce the sheet to curve slightly, and a horizontal positioning control system using electromagnets installed in the horizontal irection to prevent sliding during transport. From the results, the levitation performance was improved by increasing the tance　between the centers of the horizontal electromagnets.

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This study proposed a new rotor structure that combines the high torque density of an internal permanent magnet (IPM) motor with the high output characteristics of a wound-field motor. In the proposed motor, the rotor consists of multiple units in the axial direction and was fixed to a shaft. The central unit adopted the structure of an IPM motor, whereas the upper and lower units utilized the magnetic circuit advantages of a wound-field motor. The magnetic flux generated by the field windings arranged centrally was supplied to the upper and lower units through the shaft. The proposed motor was expected to leverage the advantages of both IPM and wound-field motors. In this study, numerical verification was conducted to obtain the magnetic characteristics of the proposed motor and compared them with those of conventional motors to demonstrate its advantages.

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This study focused on a thermoacoustic generator, which a linear generator without a spring mechanism was connected to a branch tube of "a loop-type thermoacoustic engine with the branch tube, and proposed a system adds feedback control of displacement and velocity on the piston surface of the linear generator to the voltage". For the proposed system, numerical calculations were performed to investigate the feasibility of changing the specific acoustic impedance and operating the thermoacoustic generator. The numerical results showed that the specific acoustic impedance of the linear generator could be changed to an arbitrary value using the proposed system, and that the thermoacoustic generator could operate over a wide range. Furthermore, the system exhibits the potential to achieve efficiency comparable to that of conventional linear generators equipped with spring mechanism.

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This paper proposed a novel motor structure designed for electric-vehicle applications. The proposed motor aims to achieve both magnet volume reduction and torque ripple suppression, which are critical performance challenges for electric-vehicle motors. Previous research addressed these objectives by proposing an IPM-SynRM configuration, which combines a synchronous reluctance motor (SynRM) and an internal permanent magnet (IPM) motor units axially. However, this motor was unsuitable for automotive applications because its magnetic characteristics differ between the rotational and counter rotation directions. The proposed motor resolved this issue using numerical optimization, thereby the dependence on the rotation direction. In this study, the magnetic characteristics of the proposed motor were calculated through numerical analysis and compared with those of a conventional motor. The results demonstrated that high magnetic characteristics can be achieved regardless of the rotation direction while maintaining the advantages of the conventional motor.

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Most materials heated by microwaves contain water. As water's temperature rises from 0°C to 100°C, its permittivity decreases from 88 to 56. During this process, the electromagnetic field within the heating chamber undergoes complex changes, causing extreme fluctuations in reflected waves. In this study, we developed a precisely designed elliptical heating chamber and an automatic adjustment mechanism that efficiently heats the target material while simultaneously reducing reflected waves during the heating process. This achieved a heating efficiency exceeding 80%.

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The purpose of this paper is to present a study on capsule endoscopy (CE) for the early detection of gastrointestinal cancers. Although CE is considered minimally invasive, its movement is governed by peristalsis and gravity, making active control difficult. To address this issue, a method for the external guidance of CE using a cylindrical magneti guiding magnet is proposed. In this study, the effects of geometric variations of the cylindrical magnet on the magnetic field distribution are analyzed, with emphasis on weight reduction and operational efficiency. The results demonstrate that the cylindrical magnet provides a more uniform magnetic field and enables weight reduction without sacrificing magnetic force.

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Transcutaneous energy transmission system (TETS) is a system that wirelessly supplies power to a ventricular assist device (VAD). However, it faces the issue of high-frequency patient leakage current flowing within the body during use. Therefore, this study prototyped a TETS driven by a medical AC-DC converter and inverter circuit, applying circuit balancing with leakage current suppression effects. Leakage current measurements were performed under conditions that simulated variations in the VAD load and patient posture (upright and supine). The result showed that when supplying 15 W of power to the VAD at 400 kHz, there was no difference in leakage current values regardless of load changes. Furthermore, the maximum leakage current during upright posture was 2.35 mA, while during supine posture was 7.15 mA. Although the leakage current during supine position was approximately three times higher than during upright position, it remained below the regulation value of 10 mA.

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High-frequency isolation transformers are used to suppress high-frequency patient leakage currents generated in medical equipment. This study analyzed the coil-to-coil capacitance and power transmission efficiency when varying the number (1 or 3) and size (φ25.3 mm or φ34.0 mm) of ferrite cores used in the high-frequency isolation transformer. Analysis results showed that using three φ25.3 mm cores (S3) yielded coil-to-coil capacitance C of 2.84 pF and power transmission efficiency η of 97.85 %. Furthermore, when using three φ34.0 mm cores (L3), C was 4.18 pF and η was 97.21 %, indicating that increasing the number of ferrite cores reduced C. When this high-frequency isolation transformer was inserted into the transcutaneous energy transmission system, for S3, the high-frequency patient leakage current Ip was 6.50 mA and the power transmission efficiency η' was 72.35 %. For L3, Ip was 6.61 mA and η' was 72.92 %, both falling below the regulation value of 10 mA.

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Irreversible electroporation (IRE) had been studied as an effective treatment for pancreatic cancer. However, if the cancer recurs, reoperation may be required. We propose an implantable IRE system to reduce the invasiveness of reoperation. The proposed system transmits power wirelessly to the implanted circuit and steps up the voltage to 3 kV. High voltage generates a large electric field during wireless power transmission, which causes stimulation and heating effects in the biological tissues around the coil. Therefore, it is necessary to design a system that applies a high voltage at the treatment site and transmits power at a low voltage in the transcutaneous transformer. In this study, the stimulation and thermal effects in biological tissues were simulated when the outer diameter of the receiving coil of the transcutaneous transformer was varied. Furthermore, the voltage was measured and simulated at each point of the system. As a result, for Type B (outer diameter: 50 mm), the maximum effective value of Ein was 105.0 V/m, and the maximum local SAR was 1.88 W/kg. Both the stimulation and thermal effects were below the limit values.

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Needle dislodgement was the most frequent serious incident during hemodialysis in 2021, yet clinically useful detection systems remain unavailable. Based on interviews with former healthcare professionals regarding the conditions required for a clinically useful system, blood leakage sensors were considered suitable but often generated false alarms in response to non-blood fluids. We propose a method using a sensor exploiting blood–skin optical reflectance differences and conducted experimental verification to evaluate its effectiveness. The results suggest that the proposed detection principle could be effective in clinical settings.

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In this paper, we developed a hybrid magnetorheological transmission for flow balance control of total artificial hearts. The transmission consists of input and output shafts, magnetorheological fluid, permanent magnets, and an electromagnet with adjustable current. A motor rotates the input shaft of the transmission. The transmission transfers the torque to the output shaft that rotates with decelerated rotational speed according to the apparent viscosity of the magnetorheological fluid. In this study, a downsized model was designed by modifying the magnet arrangement and adjusting the dimensions, resulting in a 33% reduction in thickness and a 39% reduction in weight. Experimental results demonstrated that the proposed transmission achieved the target speed reduction ratio of 0.9 with the power consumption of 0.65 W. Furthermore, the transmission ratio successfully tracked the target speed reduction ratio by PI control scheme.

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We propose a compact and flat maglev motor for pediatric ventricular assist device. In previous research, a maglev motor with an outer diameter of 22 mm and a height of 11.3 mm has been developed, and pump drive with non-contact impeller suspension was indicated. The motor was redesigned using finite element method three-dimensional magnetic field analysis to improve anatomical compatibility during device implantation. This study investigated new geometries of the motor and developed a maglev motor with an outer diameter 25 mm and a height of 7.3 mm. The axial attractive force and rotating torque of the new motor were evaluated. At an air gap of 1.3 mm, the axial attractive force per unit current was 1.72 N/A. When the motor was rotated at 3000 to 4000 rpm, the rotating torque was 6.58 mNm/A.

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A contribution ratio analysis of the influencing factors of the electro-permanent magnet was conducted, and an estimation formula for the adsorption force was proposed. By employing the Latin square design in combination with the finite element method, it was determined that the dominant factors are the diameter of the permanent magnet and its residual magnetic flux density. These two parameters account for 87.4 percent of the contribution to the adsorption force. When AlNiCo-5 and NdFeB-N35 permanent magnets were used with an air gap of 0.1 mm, the obtained adsorption force was 11.7 N. The adsorption force was found to be proportional to the residual magnetic flux density and to the square of the magnet diameter. Consequently, the adsorption force can be predicted using the magnet diameter, residual magnetic flux density and air gap.

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To address the challenge of suppressing low-frequency road noise inside compact vehicle, this paper proposes an active noise control (ANC) scheme that generates control sound by directly driving the roof panel with a giant magnetostrictive actuator (GMA). To select the optimal excitation position, we conduct roof-panel excitation experiments and analyze the radiated sound using a power spectral density (PSD)–based energy metric, thereby identifying the position with the highest reproduction quality of the input signal. We then compare, on an LMS-based ANC system, the noise reduction achieved at the optimal position versus the panel center. Results show that placing the GMA at the optimal position substantially increases noise reduction. This confirms that GMA placement critically influences ANC performance and that the PSD-based procedure effectively guides excitation-position selection. The proposed approach provides a practical method for choosing excitation points in ANC systems for compact vehicle.

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Wireless power transfer via magnetic resonant coupling can supply power to a robot located several meters away from a transmitter coil. However, when the distance between the transmitter coil and the robot or power consumption of the robot is changed, the input impedance varies and causes power reflection. Then we propose an impedance matching system using a driver coil and soft magnetic material. We apply bias magnetic field to soft ferrite to control path of magnetic flux generated by driver coil actively, and the coupling coefficient between the driver coil and the transmitter coil changes to match impedance. The result of experiment showed that input impedance could be changed by using bias coil.

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Wireless power transfer is a promising technology that eliminates the need for electrical contacts, thereby enhancing flexibility and convenience in power delivery. In the electromagnetic induction method, it is common to connect capacitors to coils, and various circuit topologies have been proposed. Among these, the series-none compensation has attracted attention because it enables a reduction in component count while maintaining efficiency comparable to that of the series-series compensation under conditions of high magnetic coupling and high Q-factor. However, the relationship between the primary and secondary Q-factors required for achieving high efficiency has not been sufficiently investigated. In this study, the transmission characteristics were theoretically and experimentally analyzed when a low-Q coil was used on the secondary side. The results indicate that the efficiency degradation caused by a decrease in the secondary Q-factor is relatively moderate. Furthermore, by considering the relationship between the primary and secondary Q-factors, it was demonstrated that system weight reduction can be achieved while maintaining high efficiency

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Reducing the weight of aircraft is of great value both economically and environmentally. The use of Carbon Fiber Reinforced Thermo Plastics, which uses thermoplastic resin, enables materials to be fused together, enabling high-rate production. One heating method for fusion is induction heating, which uses the electromagnetic induction effect of a coil. When heating carbon fiber (CF) cloth, it is important to heat the fusion surface uniformly. To determine the fusion conditions for eddy current analysis and heat conduction analysis, electrical resistivity is required. Because the temperature of CF cloth changes during electromagnetic induction heating, it is very important to understand the temperature dependence of electrical resistance. This paper reports the effect of temperature on the electrical resistance characteristics of CF cloth.

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This paper reports on the fabrication and stabilization of a horizontal style non-controlled magnetic levitation motor. The destabilizing force in the axial direction was offset by arranging two sets of Ring Halbach Arrays and HOPG disks facing each other. A rotation speed of 200 rps was obtained by suppressing the radial whirling motion of the rotor with a permanent magnet attached to the end of the rotor shaft and eddy currents generated in a copper block adjacent to it. The estimated braking force of the copper block due to eddy currents was calculated using a model in which eddy currents are considered to be the sum of virtual circular currents.

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Multi-degree-of-freedom motors can be constructed as compact and high-speed systems capable of performing complex movements and achieving direct-drive operation. Therefore, they are expected to find applications not only in the manufacturing field but also in nonmanufacturing fields such as medical and nursing care. This study aims to increase the degrees of freedom of linear motors by developing an XYθz planar actuator capable of simultaneously realizing translational motion along the X-Y axes and 360-degree rotational motion around the Z-axis. This paper proposes a configuration in which the rotor uses a wound field and demonstrates the principle of maintaining a constant magneticpole direction of the rotor during Z-axis rotation. Magnetic-field analysis is conducted to show the electromagnetic force characteristics for translation and Z-axis rotation. Operational simulation is performed based on the relative positions of the stator and rotor magnetic poles. Based on these results, the feasibility of simultaneously driving Z-axis rotational motion and X-Y axis translational motion was examined

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