Mouthguard type sensors have been developed to monitor the healthcare-related information. In order to realize a battery-less sensor system, we propose a sheet form generator driven by occlusal force to supply electrical power for mouthguard type sensors. The proposed generator is made by stacking an electret and a dielectric elastomer. It converts mechanical energy applied by occlusion to electrical energy by electrostatic induction. In this study, the generator sheet was designed and its ability of power generation was evaluated experimentally. The prototype generator achieved 6.2 μW under the force equivalent to occlusal force. The generated power was 190 times as large as that of piezoelectric type. Although the achieved power is not sufficient to provide energy for mouthguard sensors so far, the output power will be improved by optimizing shape of dielectric elastomer and surface voltage of electret. The experimental results sufficiently support the possibility to realize the battery-less sensor system.
In the purpose of environmental conservation and energy saving, demands for high torque and high energy density drive motors at low speed are increasing, and vernier motors utilizing the magnetic gear effect are attracting attention. This paper presents a new stator module type vernier motor, which is applicable amorphous magnetic material effectively as a stator core material in order to reduce loss at high speed operation. For the purpose of clarifying the effect of application of amorphous wound core, the efficiencies of motors made of amorphous magnetic material, non-oriented electrical steel sheet and oriented electrical steel sheet are investigated by using finite element analysis. The results show that the proposed model is effective to improve efficiency of the vernier motor utilizing amorphous magnetic material.
Magnetic properties of a ferromagnetic material change with the applied stress, which is one of the magnetome-chanical effects. The classical Jiles-Atherton model (CJA model) is a typical magnetic hysteresis model at free stress, which describes the hysteresis using the concept of the impedances to domain wall motion caused by pinning effects. However, when a direction of applied magnetic field is reversed before reaching saturation, the minor hysteresis loops obtained from the CJA model can have negative slopes, which is a non-physical behavior. To improve accuracy of the match between CJA model and the experimental results, many kinds of modified hysteresis model based on CJA model have been suggested. Nevertheless, there are few studies suggesting the modified Jiles-Atherton model which can express the stress dependence of hysteresis loops and improve accuracy with experimental results. This paper suggests a Hybrid modified Jiles-Atherton model (HJA model) for centered hysteresis loops of SM490A including both major and minor loops taking into account of tensile stress dependence. In this model, the differential susceptibility shifts with reference to the last reverse magnetic field, and only one constant parameter of CJA model is replaced by a logistic function of magnetization. Additionally, we introduce stress dependence into each parameter of HJA model. As a result, it is shown that the centered hysteresis loops of SM490A under tensile stress can be expressed by the HJA model with good accuracy in both minor and major loops.
A light-driven ﬂying balloon has been fabricated using multi-walled carbon nanotube (MWNT) composite ﬁlms, of which thickness and density are approximately 6 µm and 0.5 mg/cm2, respectively. The shape of balloon is a regular tetrahedron with approximately 11 cm length on a side. By irradiating light using a tungsten lamp to the balloon, the balloon can be levitated like a hot-air balloon because the temperature of MWNT ﬁlm is rapidly increased and the temperature of air inside the balloon is gradually increased. We conﬁrmed that the maximum levitation height is ap-proximately 14 cm during light irradiation. The balloon developed in this study could be utilized for a ﬂying platform of autonomous ﬂying monitoring system.
Countries with rapidly growing economies are building numerous skyscrapers, where safe and high-speed elevators are important elements. Therefore, the authors have proposed an elevator with magnetorheological fluid damper (i.e., MRF damper) to improve the elevator safety. If a disastrous earthquake occurs, many elevators stop at the nearest floor to evacuate passengers. However, in reality, passengers are sometimes trapped in an elevator during seismic vibrations. In this paper, we use an elevator-simulator that consists of a semi-active MRF damper, a spring and verify experimentally whether the proposed MRF damper can absorb strong vibrations of elevators caused by earthquakes.
A compact maglev motor has been developed for pediatric ventricular assist devices (VADs). The maglev motor consists of a top stator, a bottom stator and a levitated impeller which is suspended with 5-degrees of freedom control. The maglev motor has an outer diameter of 22 mm and a total length of 33.6 mm. The maglev motor has been improved by magnetic circuit refinement to enhance magnetic suspension characteristics and reduce power consumption. In this study magnetic suspension performance of the improved maglev motor during pumping was evaluated. The developed maglev pediatric VAD indicated sufficient pump performance to regulate a flow rate of 0.5-2.4 L/min against a pump head pressure of 100 mmHg at a rotating speed of 4000-5000 rpm. The maximum oscillation amplitudes were successfully suppressed less than 0.05 mm in axial direction and 0.16 mm in radial direction. The results indicated that the improvement of the motor significantly contributes to enhance the magnetic suspension and rotation performance.
Purpose of this study is to clarify iron loss distribution on laminated stator core by an interlocking by means of a heat-measurement method with a thermography camera. This method has been applied to the surface mounted permanent magnet (PM) motors, which are removed stator windings, to measure temperature distributions on the stator surface during the PM rotor is rotating. Because the stator cores have no the interlocking, the previous study could not evaluate the influences of interlocking on the iron loss distribution of the stator core. The core loss of the stator core increases due to the interlocking laminations. To design a stator core having low iron loss for a high efficiency motor, the causes of increasing core losses including the interlocking lamination should be analyzed in detail. In this paper, how to evaluate iron loss distribution on stator core by interlocking by means of a heat-measurement method and the evaluated results are reported.
Multi-Degree-of-Freedom (Multi-DOF) actuating systems are composed of several single-DOF motors, which results in large, heavy and complicated structures. In order to solve these problems, various multi-DOF spherical actu-ators have been actively studied. However, the spherical actuator requires many current phases. In this paper, in order to reduce the current phases, a spherical actuator with auxiliary poles is proposed. The proposed actuator can rotate in 3-DOF with 5 current phases. Finally, the torque characteristics of the proposed actuator are evaluated through 3-D FEM analyses.
Power converter used for switching power supplies is required to be smaller and more efficient. As the switching frequency increases and converter size reduced, the core loss will increase and have significant impact to the converter efficiency and temperature. The authors proposed magnetic composite material and evaluated them exhibited a lower core loss than Ni-Zn ferrite in MHz band. Among evaluation of magnetic material, accurate measurement of the core loss is especially important to development of magnetic material. However, the classic two-winding method is limited to low frequency band and high core losses because it is sensitive to phase discrepancies. In this paper, the Measurement method of the core loss evaluation of magnetic composite material utilized the inductive cancellation method proposed as the core loss measurement method in MHz band. From the experimental result, the magnetic composite material using 2.6 µm amorphous powder exhibited core loss of 1.0 W/cm3 at 10 MHz and 10 mT.
Hypoxic Ischemic Encephalopathy (HIE) is a brain disorder. In this research, we developed HIE model rats aiming at examining the functional recovery of HIE by plasma. As a result of evaluation using X-ray CT was confirmed that only the model rats had a high X-ray absorption amount in the brain. In this paper, a region with a high X-ray absorption amount is called a high-density area. Individuals confirmed in the high-density area had cerebral edema and the like which are symptoms of HIE. However, there was a problem that the degree of progress of symptoms could not be judged merely by a high-density area. In this paper, we focused on the luminance value of high density area of HIE model rat and analyzed X - ray CT data. As a result, it was possible to obtain the luminance value distribution of indi-viduals to be control.
A number of automobiles have been fitted with electric motors and their inverters. In order to reduce the space of motors, we have proposed a motor with two controllable rotors, which consist of 2 rotors and 1 stator. However, the previous motor was difficult to be practically used due to its complicated structure. Therefore, we proposed a novel motor with 2 controllable rotors. In this paper, the computed characteristics by carrying out measurements on a prototype are verified. First, the cogging torque and back-EMF are measured. Finally, the N-T characteristics are measured under vector control.
The author made prototype an uncontrolled magnetic levitation motor using a permanent magnet and graphite. The author derived the equation for obtaining the diamagnetic magnetic force of isotropic graphite and anisotropic graphite. The calculated results by the formula well agreed with the measured values. Furthermore, it was found that the diamagnetic magnetic force distribution in the X axis direction of isotropic graphite and anisotropic graphite are different. This suggests that the diamagnetic magnetic force generation mechanism in the X axis direction is different.
This paper reports on the step response characteristics of an electromagnetic suspension which utilizing an opposite drive mechanism using magnets and coils that move continuously in opposite directions was verified by prototype. It was shown that damping time is shortened by operating the opposite drive mechanism, and the electric power about 2 times can be obtained. Moreover, it was confirmed that the damping force and the electric power corresponding to the electric load could be obtained in the actual running test in which the electromagnetic suspension is mounted on the small electric vehicle.