Bearingless canned motor pumps, which employ 5-axis active electromagnetic control, have been developed. In this paper, two types of 5-axis active control type bearingless canned motor pump are introduced and explained about the difference of each structure. One is a conventional structure which was investigated in the past research, the other is a novel structure which was newly proposed. One of the most important difference between these two types is the machine size. To realize miniaturization, the structure of suspension stator core was optimized to insert radial gap sensors into slots. In addition, suspension rotor cores were also used as gap sensor targets. Thus, the area of the radial gap sensors and the gap sensor targets which was arranged to the both ends of the electromagnetic machine could be deleted. Furthermore, a passive thrust magnetic bearing was effectively inserted in the dead space of an active radial magnetic bearing arranged at the buttocks side. As a result, the whole machine size could be miniaturized. Although the machine size was miniaturized, the experimental results demonstrated that the proposed novel structure has enough output power and suspension force. In addition, the proposed structure could reduce the flow loss, because the rotor length was decreased through the miniaturization. Accordingly, whole input power also could be reduced. In this paper, these advantages will be shown by the pump experiments with water.

View full abstract

　A rotor supported by a superconducting magnetic bearing (SMB) shows complicated behavior because of nonlinear magnetic force. In a large-scale system, magnetization distribution of its rotor can be non-uniform. This non-uniformity can cause some nonlinear vibrations of the rotor. In this study, we investigated dynamical behavior of a rotor whose geometric and magnetic centers were not identical. We derived its equations of motion and found out that they had nonlinear terms including quadratic terms. It can be noted that these terms can cause nonlinear vibration such as superharmonics and subharmonics. We experimentally verified our prediction and confirmed appearances of the 2nd and the 3rd order superharmonics and the 1/3-order subharmonics due to the nonlinearity of the magnetic force.

View full abstract

　These years, as we require the comfort at the time of boarding, it is proposed the active control engine mount (ACM), which is the equipment for automobile vibration suppression. For one of the ACM control methods, we use the Filtered-x least-mean-square (Filtered-x LMS) adaptive control system because of the simple structure. Before we use this control method, we need the transfer model that changes controller's output voltage into ACM's thrust. But because of time-related deterioration, the model has errors, which cause system's instability. So, in this paper, we will propose the LMS adaptive control algorithm which does not have to get the transfer model in advance.

View full abstract

　This paper presents vector magnetic characteristic analysis of PM motor by using complex E&S modeling taking account of stress effect. It is well known that the magnetic properties of the electrical steel sheets are generally deteriorated due to influence of mechanical stress. However we can reduce iron losses under limited stress conditions in past researches. A low iron losses PM motor designed by taking account of stress effect is presented.

View full abstract

　There is a method to excite by a square wave as a simple method of the brushless DC motor drive. The simplest method is 120 ° excitation method used the Hall sensor output. But the method has part inferior in terms of efficiency. However, the efficiency can be clearly improved by extending excitation angle or advancing current phase angle, in spite of square wave excitation. In this paper, we measure the motor efficiency using these methods, and inspect their validness experimentally.

View full abstract

　This paper proposes a mesh-less numerical analysis method employing magnetic moment method and particle method for magnetic fluid motion and magnetic phenomena. A basic idea in this method, the magnetic fluid motion is calculated by particle method, the magnetic field distribution and magnetic forces on the each particle are analyzed by magnetic moment method. The magnetic moment method analyzes magnetic field by dividing only ferromagnetic materials into fine elements. In this case, the elements of ferromagnetic materials are replaced with particles in particle method. The method not used calculation points on air and mesh for analyzing magnetic field. Therefore, reshaping of mesh on moved and divided fluids is not required, the analysis is robust over shift of topology. In this paper, an algorism of coupling the methods and analyze result of basic models are shown.

View full abstract

　Recently, human body communication (HBC) which uses a human body as a signal transmission medium has drawn considerable attention as a promising technology to realize efficient and safe body area networks (BANs). However, in order to gain benefit from useful services based on so-called “big data”, the HBC needs connect to external wireless networks such as personal or local area network (PAN or LAN), because the HBC network is confined around the body. In this paper, utilizing wearable electrodes for HBC at a MHz-band as an antenna for wireless PAN and LAN at a GHz-band was propose. Furthermore, the reflection characteristics, electric field distributions and radiation efficiencies of the wearable electrodes in the broad frequency range of 5 MHz to 5.5 GHz were also investigated. As a result, the wearable electrodes, without any additional antenna elements or slits, showed the resonances at 1.03 GHz and 1.93 GHz with radiation efficiencies of 50.2 % and 39.5 %, respectively, for the wireless PAN and LAN. It is confirmed that the electrodes are usable not only for the HBC at MHz-band, but also for PAN and LAN at GHz-band.

View full abstract

　We have proposed and investigated body area networks using magnetic coupling between coils worn on a human arm, and confirmed that the transmission characteristics were improved more than 20 dB compared with those of the conventional human body communication using electrodes in contact with the body. However, the human arm will be bent with various angles in daily life. In this paper, transmission characteristics between the transmission and receiving coils worn on the bent arm and electromagnetic field distributions around the coils and arm were analyzed and investigated. As a result, the transmission characteristics were stable and hardly influenced against bending the human arm with various angles.

View full abstract

　Previously we have succeeded in developing the ECT sensor called “Flat ∞ coil”. This sensor is improved of the ∞ coil which is developed by our laboratory in 2013. Flat ∞ coil sensor is composed of the two spiral type exciting coil and one sensing coil. This sensor is so high sensitive and has the versatile capability e.g. it is able to detect the not only flat surface defect but also curved surface defect compared with conventional ∞ coil.
　This paper concerns with an optimization of the flat ∞ coil. Optimization of this flat ∞ coil fully depends on the 3D finite elements methods. According to the 3D finite element simulation results, we have successfully carried out the optimum size of two exciting coils and a sensing coil.

View full abstract

　Guided waves can propagate along waveguides with low attenuation. Therefore, guided waves are expected to be used for non-destructive testing especially of wire-ropes. Because of complexity of the wire-rope structure, it has not been known completely how guided waves propagate in wire-ropes. So we conducted two experiments of guided waves transmitted and received by Electromagnetic Acoustic Transducers (EMATs) in order to investigate the characteristics of guided waves propagation in wire-ropes. First, we measured the propagation time of guided waves in a wire-rope, in a core strand, and in an element wire, respectively. From the results, we calculated respective group velocities and compared them with each other. Second, we rotated the magnets of the receiver EMAT for a core strand and measured the amplitude of received waves. Obtained results show that non-axisymmetric distribution of the wave amplitude rotates with the same pitch as the helicity of an element wire. From the experimental results, we verified that L(0,1)-mode can be propagated along the element wires of peripheral strands.

View full abstract

　The evaluation of magnetic properties of fatigue-damaged specimens of electromagnetic steel sheets have been investigated. In low-cycle fatigue tests, plastic deformation occurred all over the specimen. In macro-magnetic measurement using B-H analyzer, magnetic properties such as iron loss were remarkably deteriorated. By observing magnetic domain structure using magneto-optical Kerr microscope, the width of magnetic domain decreased and the distribution of magnetic domain became random. In high-cycle fatigue tests, magnetic properties were also deteriorated in fatigue-damaged and especially in fatigue-cracked specimens. By observing specimen surface using laser scanning microscope some grains around notch or fatigue crack were plastically deformed. And in these plastically deformed grains, the width of magnetic domain decreased and the distribution of magnetic domain became random. Then the change of magnetic domain structure in plastically deformed region seems to be the main cause of deterioration of the magnetic properties both in low-cycle and high-cycle fatigue damaged specimens.

View full abstract

　Magnetic hysteresis loop (MHL) and thermoelectric power (TEP) measurements were performed in isothermal aged Fe-1.0wt.%Cu alloys with different cold-rolling ratio. Coercivity decreased and TEP increased with increasing aging time. Isothermal ageing causes recovery of dislocation microstructures and formation of Cu precipitates. Based on the different relationship between micro-structures and two physical parameters (coercivity and TEP), a simple model for estimating the hardness of Fe-Cu alloys was developed. This study demonstrates the feasibility of the combined electromagnetic techniques for non-destructive evaluation of copper-precipitation hardening in steels with high dislocation density.

View full abstract

　In this paper, we investigate the characteristics of a novel magnetic-geared induction motor, in which the rotors synchronize with the rotating magnetic field produced by the coils. The operational principle that the high-speed rotor is driven as an induction motor and the low-speed rotor is rotated as a magnetic gear is described and the characteristics are computed using 3-D finite element method. In addition, the computed characteristics are verified by carrying out measurements on a prototype. The rotation speed was not decreased although loads were increased. This inherent behavior was verified by the measurements.

View full abstract

　The development of multiple degree-of-freedom actuators is expected in robotics and industrial machinery fields. There remain, however, some problems in terms of the torque density, control method, and sensing systems. Under the circumstances, we are studying on a 3-degree-of-freedom outer rotor spherical actuator and its control method. We have also confirmed the characteristics employing 3D-FEM. In this paper, genetic algorithm is employed to search for the optimal stator pole arrangement which has the maximum torque constant (Instead, minimum mean current with a constant torque). Then, the effectiveness of the optimization is verified through the comparison of the mean current controlled to generate a constant torque between the optimized and the initial models.

View full abstract

　Linear oscillatory actuators using a DC motor converts a rotational motion into a linear motion. The actuator we previously proposed is difficult to assemble and its armature sometimes can collide with the rotor during operation because the armature is sandwiched between two rotors. In this study, we propose a linear oscillatory actuator that has a new structure. The new structure of this actuator solves the above problems because the armature is inserted inside the rotor. Also, we verified that the performance of the new actuator is equivalent to the previous model through FEM analysis and dynamic simulation.

View full abstract

　A linear motor attracts attention as a driving source for long-distance transportation system in the vast factory. This system is asked for a high acceleration, a high deceleration, a large thrust and a good controllability. Working process of the products are scattered in a multiple areas, the conveyance of the products between the process is important. When moving the products to the next processing, the mover is stopped. Then is unloaded the product from the mover. Also, the product is loaded on the mover that is moved to next processing. Thus, the mover repeats the “Stop and Go” which leads to a decrease in transport efficiency. This paper reports a parallel synchronous drive method for transportation system of PM-LSM. This method synchronizes the mover of the two LSMs. One assumes the main-line connecting the inter-processes and the other assumes the sub-line of each processing. Because both movers in the synchronized state is the same inertia, conveyance material may be moved without the mover stops. We tested the various driving of this method by simulation.

View full abstract

　The aim of this work presented here is to demonstrate that the ultrasonic guided wave testing system using electromagnetic acoustic transducers (EMAT) is able to detect the inner corrosion of steel pipes. Both excitation and reception of the guided wave is carried out with EMAT in this system, promising the practical guided wave testing system. First of all, theoretical background of the guided wave and EMAT are reviewed. Dispersion curve of the group velocity are calculated from a set of characteristic equation. Principle of the guided wave excitation and reception with EMAT is also discussed. Second, three dimensional guided wave testing simulator is developed and details of the guided wave testing system is delivered. Finally, simulation and experimental results are compared and discussed. Steel pipes with artificial inner corrosion are tested with torsional guided wave mode and the sensitivity to the corrosion is evaluated.

View full abstract

　Glassy alloys have exceptional soft magnetic properties. It has an advantage that shaping is possible by thermal spraying method and ideal coercive force of Glassy alloys is zero as same as other amorphous metals. Glassy alloy's magnetic properties will be improved by control of internal stress and grant of induced magnetic anisotropy with heat treatment. In this paper, we fabricated ring and cylinder samples of two kinds Glassy alloys and evaluated its magnetic property. As a result, we found the relative permeability of ring samples is about 400 and that of cylinder samples is about 120. Residual magnetization of cylindrical magnetic shield is about 0.10 mT. Transverse shielding factor for AC magnetic field is about 10.

View full abstract

　For quality control of Nd-Fe-B sintered magnets motor, a prototype prediction and screening tool applying less than 400kA/M magnetic field for Neodymium Magnet without Magnetization and measuring flux density distribution with hall sensor array was developed . And co-relationship between flux density distribution after applied less than 400kA/m magnetic field and flux density distribution after applied 4800kA/m magnetic field was observed.
　As the result, we confirmed the possibility of prediction and screening approach for Neodymium magnet without magnetization using the above co-relationship.

View full abstract

　Magnetic fluid tuned liquid column damper (MF-TLCD) is a kind of semi-active damper that uses magnetic fluid as its working fluid. An MF-TLCD alters the natural frequency of the magnetic fluid column that forms the resident liquid inside the MF-TLCD by applying a magnetic field. We quantitatively investigated the damping coefficient generated by the flow of magnetic fluid, which is strongly related to the damping performance. Three kind of U-pipes that have each different shape ((1) conventional (2) equipped with an orifice (3) curved fluently) were prepared and single-degree-of-freedom oscillation was performed with each those pipes. Finally, we discussed the effect to the damping performance of MF-TLCD induced by various damping coefficient subjected to magnetic field and configurations of those U-pipes.

View full abstract

　There are individual variations on the motor threshold (MT) and therapeutic effect in clinical treatment using transcranial magnetic stimulation (TMS)．These variations may result from the difference of individual brain anatomies. In this study, we built numerical brain models individually from six subjects, and calculated the distributions of eddy currents induced by TMS. The brain models were built from individual MRI data with segmenting into gray matter, white matter, and cerebrospinal fluid. The location of the figure-eight stimulator coil was recorded using a binocular infrared camera when the stimulation response of twitch observed over 50 % of trials. The eddy current distributions were obtained using an originally developed solver based on the scalar potential finite difference (SPFD) method. The results showed different distributions of the eddy current density between each brain models. The average eddy current density in the primary motor cortex was 17±6.9 A/m² for the stimulus intensity corresponding to the MT. Assessment of the relationship between the eddy current density, stimulus conditions, and brain anatomy would help understanding of the mechanism of the varying MT. The developed model enabled us to compare the numerical results with experiments. Experiments have shown that a displacement of stimulator coil from the appropriate location causes an increase in the MT. This phenomenon was observed also in our simulations.

View full abstract

　This paper presents a real-time positioning system for indoor use, which utilizes ultrasonic waves. Many existing systems were prevented from real-time applications by long detection time and calculation time. The proposed system utilizes multiple frequencies of ultrasonic waves, which lead to the reduction of positioning interval and system complexity. We developed our prototype system with Arduino Uno, and achieved 30 ms of the positioning interval.

View full abstract

　In the transport system of a thin steel plate production line, the quality of the plate surface deteriorates over time because of contact with rollers. However, when a flexible thin steel plate is targeted for levitation, levitation control becomes difficult because the thin plate undergoes increased flexure. To solve this problem, we propose a levitation of a flexible thin steel plate that is bent to an extent which does not induce plastic deformation. In this paper, to elucidate the bending levitation performance, ultrathin steel plate with a thickness of 0.18 mm is levitated and the relationship between tilt angle of electromagnets, standard deviation of displacement and levitation probability is evaluated. Furthermore, shape of steel plate is analyzed using finite difference method and effective levitation angle is estimated. As a result, when levitating thin steel plate at the optimal tilt angle of electromagnets attained by finite difference method, desirable levitation performance can be achieved.

View full abstract

　The extracorporeal blood pump with magnetically levitated motor has been developed to recover cardiac function of acute heart failure patients. Rotation and levitation of the impeller are controlled by feedback of rotating angle, axial position and tilt angles that are detected by hall sensors and gap sensors. Establishment of sensorless control is required because these sensors will cause lower reliability of the blood pump. In this paper, a sensorless motor control is studied for the magnetically levitated blood pump. Rotating speed and angle is estimated based on the back-EMF calculated directly from the motor voltage and current. The levitated impeller is rotated stably using the sensorless motor control when the axial position of the impeller is shifted and the motor speed is changed as a step. The settling time of the rotation speed is 0.094 seconds when the rotation speed is changes from 600 rpm to 3000 rpm and vice versa.

View full abstract

　We have developed a small, thin, maglev ventricular assist device (VAD), which can be implanted under the thorax muscle layer like a pacemaker. Radial position of a levitated impeller and its rotation are actively controlled by radial type self-bearing motor. An Axial position and tilt motion, stabilized passively with self-restoring characteristics of permanent magnets, are measured by using the three laser displacement sensors to evaluate the performance of the passive stability. Irregular motion of axial position and tilt angle of the levitated impeller caused by irregular hydrodynamic force are observed in higher flow rate condition and shut off condition. The impeller posture aligned in horizontally with increasing rotational speed due to the gyroscopic effect.

View full abstract

　In this study, we propose a magnetically driven micro valve made of magnetic composite with thick negative photoresist SU-8 and magnetic particles. It is able to fabricate a magnetically driven element using simple processing method based on micromachining technology by magnetic composite. To evaluate performance of the proposed microvalve, driving test under the external magnetic field was carried out. A prototype of the microvalve has the flow rate reduction rate of about 60%, and pressure resistance of 9 kPa.

View full abstract

　A noncontact transfer method using a combination of ultrasonic levitation with flexure traveling wave has some advantages in clean environment and simple device configuration. This paper deals with the introduction of a two-dimensional transfer device using the ultrasonic levitation and its fundamental characteristics, and the measurement of generated pressure on the vibration plate. A prototype of the two-dimensional transfer device with four bolted Langevin transducers was constructed. Thrust by the flexure traveling wave was observed. The wavelength of the traveling wave of the vibration agreed with that of the pressure in a local area. Vortexes were observed all over the vibration plate. The sum of the vortexes caused driving force of the carried plate.

View full abstract

　Linear resonant actuators (LRAs) have been used and studied because of high efficiency. However, the amplitude of LRAs severely decreases when external loads are applied. As a solution to this problem, we have proposed an external load estimation method using two signals of the back-EMF. However, the proposed method was effective only under unipolar drive. This paper proposes load and amplitude estimation method for LRAs using two back-EMF signals under bipolar PWM feedback control. The effectiveness of this method was verified through 2-D FEM analysis of our code.

View full abstract