There is rotational iron loss under the V-junction in the yoke in an actual transformer because not only alternating magnetic field but also rotational and elliptical magnetic field are generated. The rotational iron loss can not be grasped in the standard magnetic measurements because it is assumed that the vectors of magnetic flux density B and magnetic field strength H are scalar quantity in them. We have proposed a two-dimensional vector magnetic measurement technique which can measure the B-vector and H-vector that are in the different directions，additionally，which can grasp the rotational iron loss. There is also phase difference θBH between the B-vector and the H-vector. The iron loss is calculated by the inner product between the B-vector and the H-vector. Therefore，the iron loss increases depending on the θBH. We controlled the θBH by fining the magnetic domain，and developed a new electrical steel sheet，and named “a vector magnetic characteristic controlled electrical steel sheet” which can reduce the iron loss. This paper presents the detail measured results from a vector magnetic characteristic controlled electrical steel sheet.
This paper is concerned with the development of micro magnetic fluid diaphragm driven by alternating magnetic field. The micro magnetic fluid diaphragm is composed of a ring-shaped permanent magnet and kerosene-based magnetic fluid. The response characteristics on the relations between input and output signals were examined by using a photodiode detector system and a digital high-speed video camera system. Sinusoidal, triangle, square, and saw tooth waves as input signals were examined. The magnetic fluid device showed good responses even at the frequency f0=1000 Hz in alternating field.
Behavior of micrometer-size magnetic particles in a simple shear flow of magnetorheological fluids is investigated by using numerical simulation. Hybrid simulation method which combined both HSMAC method and discrete particle method based on the simplified Stokes dynamics is performed. Behaviors of magnetic particles in shear flows between two parallel plates are simulated. Chain-like clusters appear and they are combined each other to form wall structure in the presence of magnetic field in the static state. In the weak shear flow, such clusters move with flow, however, magnetic particles are rearranged as layered sheet-like structure in the rather strong shear flow.
We propose a novel magnetic gear with a high torque density and a huge gear ratio despite the small number of magnet poles. This magnetic gear combines a magnetic flux harmonics gear with a magnetic paradox planetary gear by replacing all planetary gears with steel pole pieces. Its structure and operating principle are described, and the effectiveness of the proposed gear is verified by 3-D finite element analysis.
This paper describes the influence of the pole number of our claw pole magnetic-geared generator on electric-generating performances and torque characteristics through the 3-D finite element analysis. It was found that the high efficiency and output voltage can be realized by reducing a pole number while satisfying JIS.
This research aims at realization of a battery free remote controller by switch type magnetostrictive-power generator using an iron-gallium alloy (Galfenol). The principle of power generation is based on parallel beam structure of Galfenol plate and yoke, by which input mechanical energy by pushing button is converted to electrical energy via free vibration. Our proposing controller consists of the generator, power conversion circuit (rectifier and capacitor), DC-DC converter and wireless module. In order to maximize the energy at the capacitor, the conversion circuit should be designed by considering equivalent model of the generator, coupling of mechanical and electrical circuit. We identified the parameters of the model by measurements of displacement and vibration, which the parameters were used to design the conversion circuit by LTSPICE, conventional circuit simulator. The combinations of capacitors in rectifier circuit providing the maximum energy at simulation and experiment were coincident, which verifies the validity of our design method. The operating condition of converter and module was investigated and twice of switch operation of combined system could send wireless sensor signal.
A miniaturized magnetically levitated motor which can actively control 5-degrees of freedom (5-DOF) of impeller postures has been newly developed for a paediatric ventricular assist device (VAD). Developed motor consists of a top stator, a bottom stator and a levitated impeller that is set between the both stators. The diameter and the height of the motor are 28 mm and 41 mm, respectively. Magnetic field analysis with finite element method was performed in order to design the geometry of motor permanent magnets and a stator. Corners of the motor permanent magnets were cut to produce sinusoidal distribution of magnetic flux density and to reduce the cogging torque. The developed maglev motor produces sufficient suspension force and rotates the levitated impeller up to a rotating speed of 6000 rpm with sufficient posture control performance.
This paper presents a novel one degree-of-freedom (1DOF) actively positioned bearingless motor. The advantages of the proposed bearingless motor are a compact axial length and high radial stiffness compared with conventional 1DOF bearingless motors. In the proposed bearingless motor, single-drive bearingless motor (SDBM) concept has been adapted. Both torque and axial suspension force are regulated independently by only one three-phase inverter and one displacement sensor. Therefore, the single-drive bearingless motor is low cost and small size. Only axial direction z-axis is actively positioned. The other axes, radial movements x and y, and tilting movements θx and θy, are passively stabilized. In this paper, a structure and principle of the active axial force generation in a novel bearingless motor are presented.
We have proposed a variety of magnetic-geared motors. Among them, magnetic-geared motors with permanent magnets in the high-speed rotor and stator slots are superior to the others in terms of the transmission and excitation torques. In this paper, we compare 2 types of magnetic-geared motors which have permanent magnets in the stator slots. The characteristics are compared using finite element analysis coupled with vector control. Finally, the computed characteristics are verified by carrying out measurements on a prototype.
The purpose of this study is investigating efficacy of a magnetic cam which can drive without contact. In general cams, existence of contact between a cam disk and a cam follower causes frictional wear and needs lubrication. On the other hand, the magnetic cam is composed of a cam disk whose rim is a permanent magnet and a magnetic cam follower. It drives by repulsion between magnets of the disk and the follower. Therefore, contact of the system can be removed. Evaluating effectiveness of a magnetic cam system, we derived an equation of motion of the cam follower and conducted numerical calculation of it. As a result, it is confirmed that the magnetic cam system can convert rotational motion into reciprocating motion at low rotational speed. Thus it can be concluded that a magnetic cam is useful at low rotational speed.
A magnetic gear transmits torque without contact. The torque just before the gear idling defines the maximum transmission torque of the magnetic gear. The maximum transmission torque of the magnetic gear is defined by the strength of magnet and the gap between gears at the stage of design. In this paper, we focus on the adjusting method of the maximum transmission torque at the time of use. The adjusting method is to change the facing length of the magnet gears by shifting the one of gears in the axial direction. Thus, we reveal the relationship between the torque and the facing length and the relationship between the torque and the gear gap. The limit torque can be assigned on basis of the obtained relationship.
In recent years, several manufacturers have marketed ultra-compact electric vehicles. We suggest active seat suspension (ASS) to improve the ride comfort by the bad road run as a high value-added product. We used a voice coil motor, which is a kind of linear motor as an actuator of ASS. The ultra-compact electric vehicles are different from a normal car and the frequent riding into to the narrow way and bad road occurs. There are lot of steps and small obstacles on a road surface, and the aggravation of the ride comfort of the vehicle is expected by the comparatively low-speed run. In this study, we focused on the neck electromyogram and seat acceleration when fall from the bump. As a result, we suggested control method of the ASS considering the neck feeling of burden.
Itch is an unpleasant sensation associated with various disease, and can trigger scratching. Management of itch and scratching is important for treatment of disease. Therefore, quantitative and objective evaluation of itch and scratching is demanded. This work aims to develop the sensor system for evaluating the scratching motion. For the purpose, we focus on scratch sounds induced by scratching motion and, propose a nail mounted sensor system . In the sensor system a small microphone is attached on a nail for measuring scratching sounds. First, for investigating the relationship between the scratch sounds and the mechanical characteristics of human scratch motion, the artificial skin model made of polyurethane was used as a scratched object. The measurement system that can measure force and a motion of fingertip during scratching was constructed. Using the measurement system, various kinds of human scratch motions and sounds were measured. By signal processing of the scratch sounds, the several sound features were calculated and characteristics of scratch motions were extracted. Then, correlation coefficients between sound features and scratch motion properties were calculated. From the results, two pairs of the parameters were found as the most adequate parameter pair to evaluate the mechanical characteristics of human scratch motion. And using these parameters, “scratch evaluation map” was proposed as a method to evaluate the mechanical characteristics of human scratch motion. From the results, it was found that the developed sensor system has possibility to evaluate the mechanical characteristics of human scratch motion by the scratch sounds.
Compared to mechanical bearings, superconducting magnetic bearings (SMB) have various merits, because they are able to support a rotor without physical contact. However, SMBs have a problem of making the rotor amplitude larger near the critical rotational speed because of their low damping. Therefore, it is necessary to reduce the amplitude with considering effect of the nonlinearity on dynamics in passing through the critical rotational speed in applications. We proposed a new method of reducing the resonant amplitude of a rotor supported by a SMB using axial translation of the rotor. We adopted an idea that the distance between the superconductor and the rotor can be tuned variably using electromagnetic force exerted by an electromagnet so that the natural frequency of the rotor in the horizontal direction can be changed. Tuning the electromagnetic force when the rotational speed is near the critical rotational speed, it is expected to reduce the resonant amplitude of the system.
This paper presents an energy strage and wireless power transmission system for energy harvesting. This system consists of sabonius windmill, rotating module and magnetic energy harvesting module. The sabonius windmill converts the wind energy to rotation energy of both the windmill and rotating module. The rotating module also can provide the power to the magnetic energy harvesting module with magnetic energy. From experimental results, the storage enegy of the system, provided power to the load and energy losses in the system are considered. Compared with a DC generator, advantages of the system are discussed.
Mostly a technique of resistance heating is using for the heat treatment of aluminum alloy casting. The resistance heating consumes more electrical power. So we have proposed a method to deal with the aluminum alloy casting using induction heating (IH) capable of rapid heating. This system is expected to be applied to the industry. Therefore, the system used in factories actually, is required to have equivalent temperature rise to the resistance heating oven. Because of, elucidate the differences with resistance heating oven and to prove that it has the equivalent or more. We clarify the problems of the indirect heating IH method described in previous studies, we propose a system of the heating method as an improvements. As the results of the comparison and consideration of conventional method and proposed method, we clarified that the proposed method is superior. We report a study carried out about the system of induction heating type indirect heating oven.
We measured magnetization characteristics, magnetostrictive characteristics, modulus of elasticity when we applied compression stress to the magnetostriction materials such as glassy alloy sprayed sample. We calculated an electromechanical coupling factor from three numbers. The electromechanical coupling factor is used as a target for effective utilization of the energy. It is the ratio between input electrical energy and mechanical energy. In addition, we measured magnetostriction when we applied tensile stress by glassy alloy sprayed sample. And we checked whether there was one of what kind of difference in comparison with compression stress applied it.
In recent years, interest in energy harvesting is increasing with the increase of demand of energy. Variety of technologies of electric power generation have being developed by many researchers. One of them is technology of electric power generation using the piezoelectric material. Authors have proposed the flexible piezoelectric device (FPED) which used the piezoelectric film (PVDF) and have been developing the power generation technology using the FPED, which utilized abundant ocean energy. Validation of the theoretical analysis method for FPEDs, via experimental means, is needed in order to achieve future cost effective design optimisations. As the method of installing the device, Authors are thinking how to set up horizontally the device in the sea. Therefore, author have developed a theoretical analysis method along its installation method. In this paper, the results that examined flexible piezoelectric device which installed in the sea floor and generate electricity from the sea wave is reported.
The maximum magnetic flux leakage from a crack is obtained when the direction of the magnetic flux is orthogonal to the longitudinal direction of the crack. In magnetic-particle testing with a yoke method, since we usually cannot predict the direction of the crack to be detected, it is necessary to perform the testing at least two times by changing the direction of magnetization. In a rotating magnetic field type magnetizer using three-pole coils (three-phase alternating current), omnidirectional crack can be detected by a single testing. However, directions of the weak magnetic flux density appear at positions far from the center of the magnetizer, and the rotating magnetic field becomes no homogeneous distribution. In this research, it was considered to split each magnetic pole in the magnetizer to generate the uniform rotating magnetic field. The distribution of the rotating magnetic flux density was evaluated with a finite element method analysis, and an optimal disposition angle of the split coil was discussed. In addition, a multi coil magnetizer was developed to generate the uniform rotating magnetic field more widely.
In recent years, guided wave gathers attention as means of nondestructive inspection of wire ropes. In this paper, we investigate propagation configurations of guided waves generated by Electromagnetic Acoustic Transducers (EMATs) by analysis, numerical calculation and experiments. From results of magnetic field numerical analysis, we found that the Lorentz force and the magnetic flux density generated by EMATs distribute over surface element wires of peripheral strands near EMAT's coils. From experimental results of arrival times of received signals, we calculated the propagation velocity of guided waves. The velocity shows that guided waves are mainly propagated as Longitudinal(0,1)-mode (L(0,1)-mode). Thus, we conclude that guided waves are propagated through each element wire of a peripheral strand near EMAT's coils mainly as L(0,1)-mode.
Wireless sensor networks (WSN) are effective to detect peat and forest fires which can give significant damages in environment and economics. To determine optimal network topology of WSN, one has to know characteristics of electromagnetic wave propagation in forest. In this work, the attenuation constant of waves is evaluated from complex permittivity and basal area of the forest using homogenization technique. It is possible to evaluate the attenuation constant from the measured permittivity of tree trunks and the basal area.
This paper presents two-dimensional magnetostriction analysis using a numerical method of two-dimensional magnetostriction (E&S-W model) on transformer model core. In order to reduce vibration and acoustic noise of transformer, it is necessary to evaluate the magnetostriction on the magnetic core. The two-dimensional magnetostriction on electrical steel sheet has been measured. The E&S-W model has been suggested in order to estimate the two-dimensional magnetostriction under non-sinusoidal magnetic flux condition. It is possible to analyze the two-dimensional magnetostriction on magnetic core using vector magnetic characteristics analysis and the E&S-W model. In this method, the distribution of peak-to-peak two-dimensional magnetostriction and the relationship between magnetic flux density vector and principal magnetostriction of expansion and contraction were made clear. The distribution of peak-to-peak two-dimensional magnetostriction was not similar to the distribution of maximum magnetic flux density.
Research on the robot inside the body equipped with various features, such as therapeutic function and self-propelled capability within the capsule endoscope is performed. Research on Wireless Power Transfer for robot inside the body to act sufficient in the body is performed, because internal battery has a limit of the capacity. It is necessary to reduce an electromagnetic field because electromagnetic field is generated from a Wireless Power Transfer. Power transmission in the Wireless Power Transfer depends largely on the quality factor of the coil and the transmission frequency. In this paper, it is shown that it is possible transmission power of 30 mW in the range of 300 mm × 300 mm × 180 mm, while reducing an electromagnetic field in the frequency 700 kHz.
In order to avoid the drive line infection of implantable devices and the surgical treatment for battery replacement, an intravascular micro turbine generator using blood flow, has been proposed and developed. The micro generator consisting of a micro turbine, a magnetic fluid (MF) seal, a stent, and an electrical generator is inserted by catheter into a descending aorta, which is able to reduce the invasiveness to patients. The experimental results using a prototype generator placed in a mock circuit loop showed that the resisting pressure of the MF seal was more than 25 kPa at 2,000 rpm and the generated power was 0.12 mW under a pulsatile flow condition.
An innovative Bi-Ventricular Artificial Heart (IB-Heart) has been successfully developed with a single magnetically suspended motor. The device has auto flow regulation function which reacts to atrial pressure change in order to balance the flow rate of left and right pump. The zero power control is adopted to control axial position of levitated impeller in the IB-Heart. The rate of change of the axial position of the impeller on the atrial pressure change is the key factor of this device's flow regulation function since the flow rate of the pumps is regulated with axial position changing of the levitated impeller. The flow regulating ability of the IB-Heart and the relationship between the rod cross-sectional area and the flow regulation function was investigated. The maglev motor was redesigned with 3-D magnetic field analysis to improve the flow regulation function.
A transcutaneous energy transmitting system (TETS) enables a cable-free supply of electric power through the skin to a ventricular assist device. This carries a lower risk of infection than cable-based power supplies because there is no skin penetration. However, the magnetic field emitted from a TETS exceeds the standard set by CISPR 11. We proposed a three-phase transcutaneous transformer that produces lower magnetic fields. The three-phase transcutaneous transformer comprises three pairs of transformers and is driven by three-phase alternating current. We measured and analyzed the magnetic field strength and its distributions with a method-of-moments-based simulator. The measurement results showed that the maximum magnetic field Hmax from a conventional transcutaneous transformer is 41.82-50.98 dBμA/m which exceeds the CISPR 11 standard level. However, Hmax from the three-phase transcutaneous transformer is 13.44-21.82 dBμA/m, which is well below the CISPR 11 standard level. It is clear that the three-phase transcutaneous transformer is a powerful way to effectively decrease the magnetic field around a TETS.
A novel blood pump with magnetically levitated impeller has been developed to recover cardiac function of acute heart failure patients. The pump assists patients' heart and the impeller's rotational speed are changed based on synchronizing with heart beat in order to increase coronary flow of patients' heart. Impeller levitation stability of the pump operated in pulsatile mode was evaluated with a mock circuit filled with water. In the pulsatile mode, the rotational speed was changed from 800 rpm to 1800 rpm with a beat rate of 60 bpm. Maximum axial displacement of the impeller is 22 % of the blood gap between the impeller and casing. Characteristics of hemolysis of the pump were examined within in-vitro hemolysis tests. NIH value of the maglev pump is about half time of it of a commercial based extracorporeal pump in constant speed operation. Even NIH value operated in the pulsatile mode is about two times of the commercial based pump's one and it is acceptable range for clinical usage. The developed maglev pump indicates sufficient impeller levitation stability and hemolysis property.
Transcutaneous energy transmission is a noninvasive method for supplying power to an implantable artificial heart. However, it is necessary to continue energy transmission using a transcutaneous transformer during bathing because an implantable battery is not yet commercially available. In this study, we evaluated the electromagnetic safety, transmission efficiency, and temperature rise of two types of transformers (air-core-flat type and externally coupled type) immersed in various conductive liquids, with the assumption of bathing and sweating. It was found that, as the liquid conductivity increased, the transmission efficiency decreased; and as the transmission frequency increased, the efficiency decreased significantly. When the transformers were immersed in 0.9% NaCl solution with the assumption of bathing and sweating, the transmission efficiency of each transformer was higher than 94.4% for a transmission frequency of 400 kHz, and the temperature rise was less than 0.3°C. These findings indicate that our transcutaneous transformers can transmit energy to artificial hearts even when immersed in 0.9% NaCl solution.
We have been investigating the mechanical cell stimulation because it has the possibility to enhance cell function without any chemical and biological material. In this paper, a newly developed cell stimulation system using magnetic beads attached on the cell wall is presented. The magnetic beads are attached on cultured cells in advance and an alternating magnetic field produced by the electric magnet is exposed onto the cells attached the magnetic beads. The beads are vibrated with the magnetic field and the cell wall received the vibration stimulation. Basic performance of the stimulation system is evaluated in this paper. The system can produce an attractive force of 30 pN onto the beads and can vibrate the beads up to a vibration frequency of 80 Hz with an oscillation amplitude of 450 nanometers. The vibration of the magnetic beads on the cultured cells with a vibration frequency of 10 Hz was observed successfully with human mesenchymal stem cells.
Past magnetic property measuring methods such as the single sheet test (SST) and the Epstein method cannot quantitatively evaluate magnetic properties of an actual stator core that shows complex shape. Therefore, we are researching the stator winding excitation method as a new method to evaluate magnetic properties (iron loss and maximum magnetic flux density at a tooth) of an actual stator core after each manufacturing process. This method can directly measure them using a dummy rotor and a three-phase stator winding. To actualize this method, we constructed a new measuring system that consists of an iron loss measurement system and a multichannel data acquisition system. According to our experimental result using the proposed iron loss measurement system, the iron loss of the actual stator core that completed all manufacturing processes was about 2.3 times larger than an iron loss of an unprocessed electrical steel sheet. In addition, the proposed multichannel data acquisition system shows observation results of the magnetic flux density waveform and of maximum magnetic flux density at each tooth of the shrink fitting processed actual stator core. From our observation result, maximum magnetic flux density at each tooth was influenced by the compressive stress of a frame.
Bearingless motors are required in semiconductor manufacturing, space applications, and medical devices as centrifugal pumps, reaction wheels and artificial hearts, respectively. Two-axis actively regulated bearingless motors have the advantages of low cost and small size compared with five-axis ones. The axial vibration is a serious problem in two-axis actively controlled bearingless motors because the axial direction is passively stabilized. In this paper, one of the factors of the axial vibration with open-loop speed regulation is found. A block diagram of axial movement and d-axis current with interference is shown. In the experiments, the axial vibration suppression is realized. Therefore the stable magnetic suspension is successfully achieved at 1200 r/min.
In order to improve efficiency of electric equipment, it is necessary to use a high-quality magnetic material and to fully utilize the magnetic properties without deterioration. It is known that the iron loss of the amorphous material is about one-third of that of the grain oriented electrical steel sheet. However, the amorphous material has a large magnetostriction. The magnetic characteristics were usually deteriorated by the compressive stress. Therefore, it is necessary to understand the magnetostriction characteristics of the amorphous material in detail. In this paper, the magnetostriction of amorphous material is clarified.
This paper discusses high frequency acoustic noise generated by an IH cooker. Mechanism of high frequency acoustic noise generation is clarified by the experimental study. Recently, influence of the electromagnetic wave on the human body is worried. The symptoms; user of home electronics appliances feels; are headache and nausea. There is a report that some users who are using IH cooking heater also feel these symptoms. We have discovered that the high frequency acoustic noise, which is generated from an IH cooker, indicates strong-level sound pressure. High frequency strong acoustic noise must not be ignored, because its danger on our health is reported scientifically and medical standpoints. Then, it becomes necessary to examine the suppressing method of high frequency acoustic noise. In this paper, generating mechanism of the high frequency (20 kHz ∼) acoustic noise is made clarify by the experiments. Further, we have experimentally cleared that the lid of a pan has important effect on the suppression of the high frequency acoustic noise.
We have developed an electromagnetic shift unit for automated manual transmission. Since the shift unit is strong and low in cost, it is suitable for commercial vehicles. However, there is a problem that the controllability of the shift unit is not enough due to large inductance of the electromagnet. In this report, PD control, sliding mode control and energy evaluation control(EEC), which we propose in this report, were applied to control simulation of the shift unit, and we verified which control is the most suitable for the electromagnetic shift unit. The result confirmed that EEC excels other control methods. The above investigation has proven the validity and usefulness of EEC.
The authors have researched and developed a highly precise positioning device that uses a piezoelectric element (PZT) and a lever mechanism, which is used to increase the displacement amplitude. Because this device uses elastic deformation of a hinge structure, the resonance peak is very high. Therefore, we attached a damper composed of visco-elastic material (VEM) and a restriction plate to reduce this phenomenon. However, at low range of the frequency response, the gain was reduced by several decibels. We clarified that this damper was the factor to cause an overshoot by identifying a high order model and performing detailed analysis in the previous paper. However, the precision was limited because we modelled a gain reduction area in the first-order phase lag element. In this research, we suggest a method to model the gain reduction part in the high-order phase lag element and demonstrate the effectiveness of the model by experiments. Moreover, we demonstrate the practicality of a simple control system design method for technological advances by experiments on perturbation induced by setting the load mass.