A magnetic fluid (MF) seal enables mechanical contact-free rotation of a shaft and hence has excellent durability. The performance of an MF seal, however, decreases in liquids. We developed an MF seal that has a ‘‘shield’’ mechanism. Factors limiting the seal life and their solution methods were studied. Factors limiting seal life were MF flowing away and mixing of MF with liquids. Two types of shield were placed in MF seals installed in rotary pumps. Long-term durability tests were conducted. The MF seal with a small cavity space shield showed a longer life (116+ days, ongoing) while the MF seal with a large cavity space shield failed after 28, 31 and 30 days. The use of an optimally designed-shield prolongs an MF seal life by preventing the MF from flowing away and mixing with liquids.
An artificial heart to which magnetic levitation technology is applying can suspend an impeller without contact has been researched and developed to achieve high durability and good blood compatibility. This paper introduces self-bearing motor and magnetically levitated centrifugal blood pump using it under development at National Institute of Technology, Ibaraki College. The self-bearing motor is a magnetic levitation motor whose stator has both motor and magnetic bearing functions. The plus minus two pole algorithm is adopted to levitate and rotate the rotor. Radial position of the rotor is controlled actively, and axial position of it is passively stable within the thin rotor structure. A magnetically levitated centrifugal blood pump using the radial type self-bearing motor has been developed for use as an implantable artificial heart. At the operating condition with a flow rate of 5 L/min against a pressure of 100 mm Hg, the oscillation amplitude in radial direction was 0.014 mm. And, the total power consumption was 7.2 W.
Transcutaneous energy transmission (TET) systems can wirelessly supply energy to implantable ventricular assist devices. The energy is transmitted by a transcutaneous transformer through the mutual inductance of two coils i.e. one placed inside the body and the other outside the body. This paper focuses on mechanisms and key features of three types of transcutaneous transformers that were developed by the author. In addition, the impact of electromagnetism on human tissue surrounding air-core-type transcutaneous transformers, and electronic equipment in living organisms were investigated.
We have been studying a bi-directional transcutaneous communication system (TCS) for a totally implantable artificial heart system. We have already developed a TCS using magnetic coupling and a TCS using near-infrared light. The both TCSs has an advantage to be free from unauthorized access from the outside, but they have both merits and demerits. To overcome the disadvantages, we are developing a TCS using intra-body communication technology that uses a human body as communication medium. The TCS using intra-body communication can communicate in both directions between everywhere on surface of the body and everywhere inside the body. And in this study, we are developing a tissue-induced electrode using titanium-mesh to apply a communication current into the body for an implantable communication unit. The TCS using intra-body communication technology is one of promising methods for realizing a TCS for the totally implantable artificial heart system.
The magnetic resonant wireless power transfer system with a function of human tracking has been proposed in order to supply the electrical energy to a power assist robot suit. A simple and fast algorithm using the gradient ascent to calculate optimal coil position based on the position and attitude of a receiver coil was developed. Simulation results showed that the optimal coil positions and attitudes of the transfer and repeater coils were calculated within 0.1 s. Even the receiver coil moved with a speed of 1 m/s, the algorithm could give the coil positions within the sufficient time to keep the high transfer efficiency. The simulated optimal coil position was compared with the experimentally measured optimal position and they showed good agreement each other.
In this study, the relationship between material removal and shear stress from fluid, and the processing pressure on micro-ordered precision processing for inner surface of cylinder utilizing a magnetic compound fluid were investigated. The amount of processing has a local maximum and a local minimum at increasing rotational speed of permanent magnet tool. This cause was discussed with an absorption force between magnetic particles and a circumference force of magnetic cluster. In addition, the amount of processing was clarified to be correlated to the shear stress and the processing pressure respectively. It was also clarified that the characteristics of processing amount and processing pressure were divided into low and high rotational speed regions of the tool.
A transcutaneous energy transmitting system (TETS) enables wireless non-penetrating power supply to ventricular assist device. Design of a transcutaneous transformer embedded in a biological tissue has not been studied. Conduction and displacement currents flowing between transmitting and receiving coils may increase in simulated biological tissue as compared to when a TETS’ transformer is placed in air. Therefore energy transmission efficiency is decreased. In this study, we focused on the impedance between transmitting and receiving coils and proposed an equivalent circuit in simulated biological tissue. To evaluate the validity of the proposed equivalent circuit, we compared the transmission efficiency of the measured values with the values derived from the proposed equivalent circuit. Using the proposed equivalent circuit, these values are in good agreement below 2 MHz. It is confirmed that our proposed equivalent circuit is useful to design a transcutaneous transformer embedded in a biological tissue.
Transcutaneous energy transmission systems (TETS) that supply power to ventricular assist devices have been developed. The air-core transcutaneous transformer is coated with insulating materials, however, the high-frequency leakage current (HFLC) flows because capacitive coupling may be electrically connected between the air-core transcutaneous transformer and the human body. We proposed that high-frequency isolation transformer as a way to suppress HFLC. In this study, attenuation rate of HFLC was measured according to the change of the number of turns of the high-frequency isolation transformer (HFT). As a result, HFLC was 4.2-6.9 mA when the number of turns HFT was 6 turns. TETS which uses 6 turns of HFT satisfies the restriction value of JIS T 0601-1. However, in the 3 turns HFLC was increased to 13 mA and the temperature rise of the HFT was 20 degrees because of the core loss due to high magnetic flux density. It was confirmed that our HFT is compact, lightweight, low heat generation, and is suitable for TETS for ventricular assist device.
In order to improve magnetic properties of Fe-based amorphous magnetic materials (Fe-Si-B), effects of tensile stress applied to specimens during heat treatment were studied. The heat treatments were implemented to 60 mm ×350 mm sheet samples with an electric furnace. The temperature was controlled to be a reference temperature lower enough than the crystallization temperature and the retention time was changed. The tensile stress depending on the attached weights was also changed from 9.8 MPa to 49.0 MPa per 9.8 MPa step. After and before the heat treatments under tensile stress, the magnetic properties of the samples were measured by using a single sheet tester (SST). As a result, it was found that the iron loss was decreased and the permeability was increased by the heat treatment under tensile stress. However excessive tensile stress showed weak effect on the magnetic property improvement.
The efficient construction method of mild hybrid is to minimize the mechanical loss by directly connecting the engine and the assist motor. The shape of the motor to be directly connected to the engine output shaft has a flat structure with a diameter of 250 to 300 mm and an axial length of 60 to 90 mm, and various multipolar PM motors have been proposed in order to obtain high output and high power generation. As a slot pole combination, it is known that a combination of 8-9 is good, but it was said to be impractical due to the problem of magnetic imbalance due to eccentricity. For large diameter motors, it is possible to configured with 16-18, twice the basic configuration. In this paper, we propose an IPM motor with 16 - 18 - combination for mild hybrid considering performance and low vibration during startup and power generation. The usefulness of 16 poles and 18 slots combination and the cogging torque · torque ripple reduction structure were clarified by finite element analysis.
Recently, many medical electronic devices have been developed that can be implanted deep inside the body. These devices are designed to transmit information collected from deep inside the body for receiving antennas outside the body. Therefore, we proposed a wireless information transmission system that transmits datum from deep inside the body to the outside using capacitive coupling. In this study, we designed LC impedance matching circuit at the receiver front end and performed analog and digital information transmission test using simulated human body made of NaCl solution. As a result, received voltage is increased by about 20mV by inserting impedance matching circuit (analog transmission and digital transmission) at the carrier frequency of 2.5MHz. In addition, the transmitting voltage that can be demodulated that it was 500 mV when impedance matching circuit was inserted.
This paper presents an electromagnetic vibration generator for harvesting walking energy, which is used a con-centrated flux array. This array is arrangement of magnets which concentrates magnetic fluxes on one side of the array and prevents the magnetic saturation in the yoke. The generation electricity in walking is calculated with the acceleration which is measured on leg. By comparing the calculated electric power of the proposed and the conventional generator which uses N-S array, we clarified that the proposed generator produces 14% higher power than the conventional generator.
In automobiles, multi axis vibration is generated because there consists of many mechanical parts. In previous study, the vibration was actively controlled by using some linear oscillatory actuators. So, we propose a 2 degrees of freedom linear oscillatory actuator to control the vibration, that achieves downsizing and weight saving. In this paper, the construction and operation principle of the proposed actuator are described. Next, the teeth shape is discussed for increasing constancy of thrust against mover’s position. Finally, it is clarified that the characteristics are enough for actively controlling undesirable multi axis vibration, through analyzed results.
In this research, to improve the transmission characteristics, we proposed introducing a parasitic relay coil without a power source, as a relay device, and investigated transmission characteristics and electromagnetic field distribution. From the results, it was confirmed that the insertion of the relay coil between the transmitting and receiving coils improved the transmission characteristics by up to 8.9 dB, except when the relay coil was located close to the trans-mitting or receiving coils. In addition, it was also confirmed that the magnetic field excitation in the transmitting coil was induced by the relay coil and this enabled effective transmission to the receiving coil. Thus, the effective improvement in the transmission characteristics by introducing the relay coil was confirmed.
The purpose of this paper is to present the technique of how to stabilize the temperature in an industrial oven. The conventional ovens in industries use the electric heaters for increasing the temperature in the oven and may use a blower to blow out the exceeded heat. When the controlled temperature is higher than the set point, the blower may blow out the exceeded heat more than expected that make the temperature is difficult to control and stabilize. In this case, the thermoelectric devices are used to solve these problems. The thermoelectric modules can use to increase or decrease the temperature by inverting the polarity of the thermoelectric module supplied voltage. The designed system consists of a 1,000 watts halogen light bulb, six 60 watts and two 240 watts thermoelectric modules and a microcontroller. The halogen light bulb and the thermoelectric modules are used to heat the oven temperature at the beginning of the heating process for making the temperature increase to the decision set point. The eight thermoelectric modules are used to stabilize the temperature at the set point. The testing results show that the closed-loop response of the temperature or the proposed oven system is significantly better than the oven that uses only the halogen lamp in term of heat overshoot.