This commentary article discusses the overview of my study on “Superconducting levitation mechatronics” which consists of “Superconducting magnetic levitation” and “Superconducting magnetic bearing”. In the study, many superconducting applications and systems are proposed and improved. In the study on hybrid magnetic bearing, the stiffness, rotation speed, etc. are discussed and improved. In the study on flywheel energy storage system, the rotation speed, energy storage system, etc. are discussed and improved. In the study on superconducting actuators, the stiffness, magnetization, etc. are discussed and improved. In the study on superconducting magnetic bearing with superconducting coil, the stiffness, damping coefficient, etc. are discussed and improved. In the study on levitation system with superconducting coil, the superconducting persistent current, application to levitation system, etc. are discussed and improved.
Magnetic levitation using bulk superconductors provides smooth motion without frictional resistance and is therefore being considered for a variety of mechanical systems, such as bearings, energy storage flywheels and linear-drive transport systems. Various transport systems based on bulk superconducting magnetic levitation have been studied, ranging from small demonstrations to large railways. This paper introduces some examples of research into the application of bulk superconducting magnetic levitation and describes one of them, a magnet arrangement for rails that controls the roll angle of a levitating body. Transport systems using superconducting magnetic levitation are often at risk of derailment due to the shuttle tilting backwards from the bank angle. To mitigate this problem, this study investigates an alternative rail magnet arrangement that can improve the stability of levitated transport systems by inducing a forward inclination of the bank angle. The results can be used to enhance the safety of various transport applications that rely on magnetic levitation technology.
The recent status of research and development is discussed from the viewpoint of industrialization of high temperature superconducting bulk as a compact magnetic field generator or magnetic levitation device. It is expected that various high magnetic field equipment and non-contact magnetic levitation utilizing the superconducting performance that can be greatly improved in combination with refrigerators will widely spread.
As an example of magnetic levitation application using superconductivity in the railway field, an initial study of the non-contact support of an aerodynamic vehicle model by magnetic levitation is presented. In consideration of handling and safety, the test apparatus consisted of an electromagnet in the magnetic field generator, which served as the ground track, and a superconducting bulk in the model car. The test results showed that the cooling time of the superconducting bulk at 77 K was more than 10 hours, which was sufficient for operation, but the levitation height and magnetic stiffness during levitation were not sufficient for the target specifications. In order to obtain the required levitation height and stiffness for the test apparatus, it was found necessary to use multiple superconducting bulk materials and to improve the magnetic circuit configuration of the magnetic field generator.
This paper proposes an axial type bearingless motor using zero power control as a low-cost magnetic bearing as-suming temperature drift at low temperatures. A bearingless motor is a motor that functions as a bearing and can support the rotor without contact. The proposed bearingless motor is a one-degree-of-freedom axial type bearingless motor that is actively controlled only in the axial direction of the rotor using an eddy-current displacement sensor. Other degrees of freedom are passively controlled with permanent magnet bearings. In addition, zero-power control is used to solve the problem of temperature drift, in which the output of the eddy-current displacement sensor changes depending on the temperature. As a result, a bearingless motor with only one eddy current displacement sensor and requiring no sensor calibration from room temperature to liquid nitrogen temperature has been developed, and its drive has been verified by experiments using liquid nitrogen.
Magnetic levitation systems using high-temperature superconducting bulk materials have stable levitation characteristics without control, but since the non-contact support results in low damping, an increase in resonance amplitude can be an issue in application. As a method to suppress the resonance, this review focuses on the use of two types of dampers, i.e., electromagnetic shunt dampers and gyroscopic dampers, which are a type of dynamic vibration absorber, and explains their principles and suppression effects based on our research results. Numerical calculations and experiments have confirmed that both types of dampers are effective in reducing resonance amplitude when the parameters are set appropriately. It was also confirmed that they can be effective in suppressing nonlinear resonance. Optimization guidelines still need to be studied.
This report discusses a superconducting magnetic bearing (SMB) for use in a space-borne mission. The SMB consists of a permanent magnet and an array of bulk superconductors. The industrial use of SMB on the earth has been extensively studied, but its use in the space environment is less explored. A passive levitation system like SMB does not require any maintenance, unlike a conventional mechanical bearing, which makes it an attractive technology for space usage. On the other hand, resources in a satellite environment tend to be limited in mass and power. As a result, the design and the operation of the SMB also have to meet these constraints. We describe the pros and cons of the space use of SMB. Then, we will introduce the current development status of SMB for Cosmic Microwave Background polarimeters by focusing on the electromagnetic analysis using a finite element method.
The soft heating method, which is one of the heating methods of hyperthermia, is a safe heating method that can control the attainable temperature of the heating element by using the Curie temperature of the magnetic material. As the heating element, we have proposed an LC booster-type heating element in which a thermosensitive magnetic material, a metallic ring, and an LC resonator are arranged in this order toward the outside. However, in this configuration, the coil conductor of the LC resonator part is exposed to the living tissue, and it is not suitable for implanting in the body. To solve the problem, we suggest the element of new configuration reversing the arrangement of the metallic ring and the LC resonator. In this study, we made a prototype to confirm the characteristics of power consumption and temperature profile with changing number of turns. As a result, we could clarify the heating characteristics of the element.
In the triaxial active magnetic bearing (AMB) with an asymmetric structure, interference occurs when it suspends a rotor in the radial and the thrust direction simultaneously. In order to solve this problem, a position control system with a nonlinear compensator has been proposed, but the degradation of its control performance due to disturbance fluctuations remains an issue. Therefore, we propose a variable structure type non-linear control system (VSTNCS) that improves control performance during disturbance fluctuations by varying controller characteristics based on disturbance estimation. First, this paper describes that the accuracy of disturbance estimation when impulse and sinusoidal disturbances are applied is sufficient to use the proposed control system. Next, the effectiveness of the proposed control system with respect to the conventional control system is clarified when the same disturbances are applied.
This paper describes a proposal for low-temperature cooking of foods using dielectric heating and its heating characteristics. Low-temperature cooking by boiling takes time for the inside of the foods to reach the desired temperature because the food is heated through the hot water. Dielectric heating, on the other hand, can directly heat the inside of the foods and reduce the cooking time. In this study, we measured the specific heat, dielectric constant, and electrical conductivity of salmon, which is an example of a heated sample, and calculated the temperature increase due to dielectric heating. The sample was heated for 10 minutes using a dielectric heating device, and its cross section was photographed by a thermocamera to measure the internal temperature. The maximum and average temperatures of the salmon were confirmed from the images taken, demonstrating the usefulness of dielectric heating.
In recent years, demand for thin steel plate used in the manufacture of automobiles and household electrical appliances has been increasing. Since contact conveyance using rollers, etc. is used in the manufacturing and plating processes of thin steel plates, quality deterioration such as distortion and surface scratches of thin steel plates has become a problem. As a solution to this problem, magnetic levitation technology has been proposed to grip and transport thin steel plates in a non-contact method. However, thin steel plates have low bending rigidity and deflection occurs during levitation. Deflection causes thin steel plates to oscillate in complex shapes, making levitation unstable. In this report, a magnetic levitation system that levitates thin steel plates in an orientation that minimizes the moment of inertia relative to gravity was proposed, and experimentally investigated the possibility of levitation.
A three-degree-of-freedom linear oscillatory actuator (3DOF-LOA) is expected to reduce the size and weight of haptic devices. However, it is difficult to simplify magnetic circuits and structures because of the need to generate forces in various directions in three dimensions. To solve this problem, we have proposed a novel 3DOF-LOA consisting of two permanent magnets and three coils wound in layer. This paper describes verification experiments of the proposed actuator. The detent force and the thrust force characteristics are measured and compare with the analytical results. Then, the dynamic behavior is investigated when a sinusoidal current is applied. As a result, it was revealed that the actuator is driven as the proposed operating principle.
We have constructed a maglev control system consisting of microcomputers and PWM amplifiers to miniaturize the digital control system of a ventricular assist device (VAD). The maglev control's high-speed arithmetic processing capability is essential to realizing the maglev control's stability. Unfortunately, the microcomputer has limited arithmetic processing capability. We evaluate the effect of the control frequency on the maglev control's stability with the control simulation and experiments. Simulation results showed that the control system oscillated and became less stable as the control frequency was reduced. The control frequency at which instability occurred was estimated to be 1.5 - 4 kHz from the phase margin and gain crossing frequency. When the vibration performance of the actual machine was evaluated for each control frequency, the axial vibration amplitude was maximum around the control frequency estimated by the simulation. Therefore, the actual machine and control system used in this experiment required a sampling frequency of 1.5 - 4 kHz or higher.
In recent years, there has been a demand for further performance improvement of internal combustion engines from the viewpoint of reducing environmental impact. The combustion state of an engine is affected by the parameters of the dynamic valve system, such as the opening and closing timing and the lift of the intake and exhaust valves. The valve motion is constant because it depends on the cam geometry, and depending on the engine operating conditions, fuel consumption and power output are affected. Therefore, our research group focused on an electromagnetic valve driven system (EVDS). In this study, four models were created to improve the magnetic circuit of a linear actuator. To investigate the thrust characteristics of these actuators, electromagnetic field analysis was performed using the finite element method. In addition, electromagnetic field analysis was conducted using materials with different saturation magnetic flux densities to investigate the effects of changing the yoke material on the magnetic flux flow and thrust.
The continuous steel plate production line of the steel mill is several kilometers long, and the continuous steel plate is transported by contact support by rolls. In such a continuous steel plate transfer line by rolls, problems such as deterioration of surface quality due to contact between the steel plate and the roll can be mentioned. In our research group, we were able to obtain high induction performance in experiments by installing the electromagnet on the side of the steel plate on the path to convey the electromagnet. However, the shape of the steel plate has not yet been obtained analytically. Therefore, we are focusing on multibody dynamics and studying the optimal placement position of electromagnets. In this research, the restoring force of electromagnet unit in off‐plate direction was changed according to steady current. When the steady current increased, the vibration of continuous steel plate could be suppressed by the electromagnet unit. This tendency could also be obtained by free vibration experiments. From these results, the effectiveness of the proposed electromagnetic guideway was shown.
This study aims to prevent passive (classical) heatstroke, which is common among the elderly, in order to maintain physical function and support activity and participation in the elderly from the perspective of ICF. In this paper, we report on the measurement of body surface temperature and subcutaneous temperature using a medical silicon mannequin that simulates the biological characteristics of the elderly, reproducing the environment in which passive (classical) heatstroke, which is common in the living environment of the elderly, is likely to occur. In addition, we report on an experiment to verify the effect of a jacket with a built-in electric fan on suppressing the rise in body temperature in an environment prone to passive (classical) heatstroke.
In production lines for thin steel plate, which are widely used for industrial products, contact conveyance is performed by rollers. However, quality deterioration due to contact between the thin steel plate and the roller has become a problem. Therefore, non-contact magnetic levitation transportation of thin steel plates using the attractive force of electromagnets has been proposed. So far, we have studied the levitation performance of a magnetic levitation system that combines a horizontal positioning control system and a curved magnetic levitation system. However, the levitation stability of the levitation performance of the magnetic levitation system, which combines the horizontal positioning control system and the curved magnetic levitation system, when the bending angle of the steel plate is changed has not been sufficiently studied. Therefore, in this report, we experimentally investigated the effect of the bending angle of the thin steel plate on the levitation performance.
In this study, we compare three designs of half-wave rectified excitation PM motors, possibly for use in variable speed drive applications. Each proposed motor has a different ratio of permanent magnet excitation to total field excitation (hybridization ratio). The hybridization ratios are selected based on the dominance of magnetic flux contribution to the air-gap by the permanent magnet or field winding excitation. In order to investigate the effect of hybridization ratio on motor performance, a comparison study has been conducted at base speed, low-speed and high-speed region. The comparison is performed using the finite element method.