International Journal of Applied Electromagnetics and Mechanics

Preface to the Proceedings from the 16th International Symposium on Applied Electromagnetics and Mechanics (ISEM 2013) special issue.

A mathematical model is developed with an interest to examine the effects of the transverse magnetic field on the thermocapillary convection in a liquid bridge of silicon-oil-based ferrofluid under zero gravity. The mass conservation level set method is used to capture the motion of the free surface. The obvious effects of the transverse magnetic field on the flow and temperature distributions as well as surface deformation are detected. The transverse magnetic field affects not only the velocity level inside the liquid bridge but also the velocity level on the free surface. Moreover, the present results prove that it is necessary to take the surface deformation into account in the study on the thermocapillary convection.

One buckled simply supported giant magnetostrictive material (GMM) thin film laminated beam model subject to axial magnetic excitations is proposed. The magnetostrictive force is simplified as a harmonic excitation. Applying the Hamilton principle and Galerkin approach the model is expressed as a one dimensional vibrating model with parametrical excitation. The multi-scales method is used to obtain the approximation of the solution when the vibration is around the buckled position and the amplitude of the oscillation is small. With the help of the undermined fundamental frequency method and normal form theory the Melnikov approach is improved to calculate more precise threshold value of the amplitude of excitation leading to chaos. The numerical simulation shows the performance of the new Melnikov approach is much better than the traditional way.

Ultrasonic Systems are useful for inspecting ceramic materials because ultrasonic waves are easily propagated in such materials. Conventional ultrasonic testing (UT) methods cannot easily identify internal defects. This study built a visualization system for detecting and reconstructing internal defect images using probe array UT. Internal defect images were reconstructed by applying truncated singular value decomposition. We investigated how the sampling frequency and truncation index affect the reconstructed defect images.

The primary objectives of this work are about the experimental study on the nonlinear electromechanical behaviour of the macro fiber composite(MFC), and to analyse the affecting factors of the inconstant parameters d33 and d31 which can arouse nonlinearities of MFC. Both longitudinal and transverse output strains are measured by actuating the MFC specimen under different DC voltages and a range of peak-to-peak sinusoidal voltages (VPP) at various frequencies, which can investigate how the voltage amplitude and frequency affect nonlinear hysteretic behavior. The experimental results of both DC voltages and AC voltages indicate that the relationship of the applied voltage and output strain displays nonlinear hysteretic behavior. The responses of the AC voltages also indicate that hysteresis nonlinearity behaviour of the MFC actuator is sensitive to the varying voltage amplitude and frequency. The higher the voltage and frequency are, the more obvious the hysteresis phenomenon are.

Stochastic bifurcation characteristics and optimal control of giant magnetostrictive film (GMF)-shape memory alloy (SMA) composite plate subjected to in-plane stochastic excitation were studied in this paper. Nonlinear difference item was introduced to interpret the hysteretic phenomena of both GMF and SMA, and then the nonlinear dynamic model of GMF-SMA composite plate subjected to in-plane stochastic excitation was developed. The stochastic stability of the system was analyzed, and the condition of stochastic Hopf bifurcation was discussed. The reliability function of the system was solved from backward Kolmogorov equation, and then the probability density of the first-passage time was obtained. Finally, the stochastic optimal control strategy was obtained in stochastic dynamic programming method. Numerical simulation shows that the stability of the trivial solution varies with bifurcation parameters, and stochastic Hopf bifurcation appears in the process; the reliability of the system is improved by stochastic optimal control, and the first-passage time is delayed. GMF-SMA composite plate combines the advantages of both GMF and SMA, and can reduce vibration through passive control and active control effectively. The results of this paper are helpful to application of GMF-SMA composite plate in engineering fields.

In order to be able to develop a deterioration sensor based on the inherent magnetic phase in type 304 stainless steel (SUS304 steel), the relationships between the magnetic properties of SUS304 steel and the martensite structure induced in it by tensile deformation were investigated using the electromagnetic impedance (EMI) method, optical microscopy, and the equivalent inclusion method. The results showed that the martensite fraction and internal stress had the greatest effect on the magnetic properties of SUS304 steel in the low tensile strain range. On the other hand, in the high tensile strain region, the changes in the shape and orientation of the martensite particles owing to tensile deformation had the most significant effect on the magnetic properties of SUS304 steel.

In this paper, an electrodynamic vibration suppressor is proposed that can be used to suppress the main component of structural vibrations. This suppressor includes three main parts: an electrodynamic actuator, a power amplifier and a vibration controller. The intrinsic characteristics of the electrodynamic actuator were studied. After proposing a variable-step feedback harmonic cancellation algorithm, a controller was developed on the basis of this algorithm. To verify the effects of the suppressor, an experiment was conducted on a slender cylinder shell. The results show that the vibration was reduced by approximately 73%.

Experimental study on the dynamic behaviour of magnetic fluid micro bridges under the effect of static and alternating magnetic fields was conducted using a high-speed video camera system. Two needle-shaped NdFeB permanent magnets were used to generate the static magnetic field, and Helmholtz coil was used to generate alternating field. Harmonic motion of magnetic fluid bridge was observed. It was found that the amplitude in the vibration of magnetic fluid bridge depends on the strength of alternating magnetic field at the constant frequency. Phenomena of filament thinning and breakup in a capillary bridge of magnetic fluid under the alternating magnetic fields were revealed.

In combining infrared (IR) thermography and the finite element method (FEM), a method is proposed for electromagnetic-thermal coupling analysis of an electromagnetic shaker armature assembly. IR thermography is used to obtain the temperature field of the armature assembly. Based on the lumped capacitance principle, this temperature field is then used to determine local convective heat transfer coefficients. FEM analysis of electromagnetic-thermal coupling is then performed using the obtained coefficients. The validity of this method is demonstrated by comparing measured and calculated transient temperature fields.

A magnetic gear can transmit a torque and a motion without the contact by the magnetic force. Today a magnetic gear are studied about increasing transmit torque and decreasing cogging torque. The property of the positioning is another significant property in use of a motion transmission by magnetic gears. Therefore it is important to measure the positioning property. The purpose of this research is to check the relationship between the number of the magnet of the gear and positioning property. Then we have developed three types of gear which have a different number of teeth severally. By using the developed three types of gear, the average and the standard deviation are calculated from experimental results. We reveal the influence of the number of the teeth to positioning property in several operation conditions.

This paper deals with the vibration control of a cantilever honeycomb sandwich plate by using Macro-Fiber Composite (MFC) piezoelectric actuator. Firstly, the honeycomb plate is equivalent to an orthogonal anisotropic plate. Secondly driving force and bending moment formulas of MFC actuator are derived based on the constitutive relations of the piezoelectric material, the equivalent parameters and bend deformation theory. The result reveals that driving force and bending moment not only depend on the driving voltage and piezoelectric strain constants (d33), but also have relationship with the elastic modulus of honeycomb plate. To simulate the vibration of cantilever honeycomb plate structure, the governing equation of the plate bonded with MFC actuators is derived. Finally, the vibration by proportional derivative (PD) control of system with MFC actuator is simulated. The results show that better control performance is obtained by using MFC actuator when system under impulse excitation and steady state sine excitation. The vibration amplitude is diminished over 75% under PD control.

In this study, vibration isolation of a plate is investigated by using an electromagnetic shunt damping vibration isolator. The isolator consists of a box-shaped spring, a permanent magnet, an electromagnet, and a shunt circuit. The two ends of the electromagnet connect the negative resistance shunt impedance to constitute a circuit. In principle, the negative resistance shunt impedance could improve the damping force by canceling the inherent resistance of the electromagnet. The governing equation of the plate is established according to Hamilton's principle and Galerkin's method. The numerical simulation is conducted and the result demonstrates that the isolator with the negative resistance shunt circuit is able to dampen the vibration of the plate. What's more, an interesting phenomenon is that the negative resistance shunt influences the natural frequencies of the coupling system.

This paper presents small pumps to transport liquid crystal, herein called a liquid crystal pump. The mechanism of liquid crystalline flow by applying an electric field to the liquid crystal is used to generate one-directional flow in a pump. In this study, the pressure-flow rate characteristics of the pump were measured and the relationships between the non-dimensional flow rate and pressure of the pump were obtained. In addition the silicone oil is also used to compare the flow phenomenon with the liquid crystalline flow under application of the electric field. The structure of a liquid crystal pump is simple and the size can be decreased by further research. So our pump has a good possibility for use in cooling system because it makes no noise and no mechanical vibrations.

In this work, a non-contact ultrasonic method based on laser generation and EMAT (electromagnetic acoustic transducer) detection is proposed for residual stress measurement. A numerical method based on finite element model is established to simulate the laser-generated ultrasound in pre-stressed media to determine the capability and sensitivity of this method. Finally, the laser-EMAT ultrasonic method isstudied to measure the residual stress in bearing balls to assess the fatigue level of the bearings.

This paper presents the dynamic characteristic analysis of a small sized permanentmagnet (PM) type stepping motor with newly structured claw-poles. First, the motor parameter is derived by PM analyzing torque and back-EMF using the 3-D finite element analysis (FEA) taking account magnetization of PM. Next, the dynamic characteristic of a small sized motor is calculated by magnetic circuit equation coupled with 3-D FEA. Specially, we propose a test method of step response for a small sized PM type stepping motor using a position sensitive detection (PSD) sensor. From the simulation and test results, it is shown that the proposed dynamic characteristic analysis method has usability for a very small sized motors.

In this paper we propose a new method using finite elements modelling to predict the impact of stranding and compacting process on a conductor electrical resistance. The experimental work has highlighted the complexity of physical phenomenon within the conductor caused by elastic and plastic deformations and inters-strands electrical contact resistance. In reality, electrical performance of a conductor depends on the nature of the material and its metallurgical state, on the mechanical pressure and electrical conductance of inter-strands contact areas. For these reasons, mechanical models have been developed in Abacus software to study different parameters involved in the stranding and compacting process to determine the actual conductor shape, strands actual deformations, residual stresses and contact pressure, etc. The deformed geometries were exported to COMSOL Multi-physics software using ECAD IMPORT module. DC simulations were, then, performed to analyze the electrical resistance of the conductor. Finally, the results obtained by simulation have been compared to the measurements to determine the accuracy of the models.

The problem of inability to calibrate due to uneven thickness in automatic ultrasonic testing used for the upset region of the drill pipe was studied. A water-immersion ultrasonic testing system was established to accomplish the inspection for this area and provide the defects information for post process. A real-time tracking method based on surface reconstruction was present to ensure all of the artificial defects to be accurately detected. An adjusting algorithm for the data was performed to update the detecting results, so that the fitted curve was favorable for calibration. A sample pipe with through-holes was test with the system. The experimental results showed that all of the artificial defects could be detected after surface reconstruction and the adjusted data could provide the basis for the quantification of flaw, all of which had proved the data adjusting algorithm to be effective.

For free and random vibrations of weakly damped systems, a one-to-one relationship between vibration modal shapes of dynamic mechanical systems and linear compound matrix, and a one-to-one relationship between modal responses and principal components are demonstrated using the concept of modal coordinates. Based on this theoretical link, a novel time-domain structural system three-dimensional statistical operational modal analysis technique is proposed then. Numerical simulation processing results show that, the new PCA based method is insensitive to Gauss measurement noise, and enables to identify main contribution modal shapes and eigenfrequencies from the displacement response-only in despite of system boundary, load type, and load position.

In this paper, a system for supplying electric power and signal transmission wirelessly for the hydrostatic loading device is put forward. The electric power supplying and signal sending module of the system adopt contactless transmission method, which is commonly called CPT (contactless power transmission). Energy, with the form of a certain frequency of magnetic field, gets through the austenitic stainless steel. Being used as the chamber of the system, the austenitic stainless steel has the same relative magnetic permeability as the vacuum. After travelling through the chamber wall, energy is captured by the coil inside the chamber. Then it is converted into DC power and sent to the loads inside the chamber [1]. Signal processing and sending module converts the analog signals into digital ones and restore them. Data consisting of signals is sent out from the chamber with the form of magnetic wave. Devices outside the chamber receive the data and recover it.

In this paper, a simple and low-cost method for improving the performance of the neural microelectrodes is reported. The electrochemical polymerization of conducting polymer PANI and MnO _2 (manganese dioxide) were performed to modify the surface of the microelectrode

sites, then the morphology and electrical properties of the coated microelectrodes were investigated to analysize the influence of MnO _2

doping on the PANI coating. Results show that, the surface morphology of PANI coating was improved by MnO _2 doping. Compared to the electrode with PANI, the charge injection capacity of the electrode with PANI-MnO _2 increased by about 7-fold and the impedance decreased

to the original 1/6 (@ 1 KHz). The electrical properties were more stable and excellent with PANI-MnO _2 coating.

A flexible piezoelectric device is proposed that can generate power from vibrations produced by vehicles or plants. The results of an experiment on a small and flexible piezoelectric power generator are presented herein. Forced vibration experiments were performed, and the results for the relationship between output power and vibration characteristics are discussed.

A nondestructive method that evaluates the distribution of plastic strain using an ultrasonic wave would be useful for estimating a structure's state prior to crack development. The authors have proposed an ultrasonic wave measurement method by combining an EMAT and PVDF, in which the couplant is not needed if a contact-type PVDF sensor is used.

This paper reports on the comparison and examination of adhesion-type and contact-type PVDF sensors combined with an EMAT for ultrasonic wave transmission.

Pulsed eddy current testing was carried out to inspect wall thinning. An excitation coil with a relatively small footprint was developed and used. An algorithm based on convolution and deconvolution operations was established to evaluate local wall-thinning.

Springs are used for various purposes, particularly for vibration control and the removal of machines. However, the use of a spring generates high amplitude at the resonance point; therefore, it is difficult to eradicate vibration from all frequency bands. To solve this issue, the variable rate spring was developed, which is composed of a magnetic spring. This variable rate spring can change the spring constant. Basically, the natural frequency of the vibration system fluctuates with changes in the spring constant. As a result, the problem can effectively be resolved by changing the resonance point and eradicating the vibration. The variable rate spring is composed of a magnetic spring and a compression spring; the utility of this spring was verified by an experiment.

According to the Lenz's Law, eddy-current essentially exists in MFL(magnetic flux leakage) testing due to the relative movement between steel pipe and excitation coil, apparently affecting the MFL signals with the testing speed rising. Hence, the constitutive equation of eddy-current in the steel pipe was established by using Lenz's Law and it was found that: eddy-current in the arriving zone has the different direction from excitation current, resulting in the reduction of magnetization intensity; but they have the same direction in the leaving zone, where the magnetization intensity is enhanced; and there is few eddy-current formed in the center; besides, the eddy-current density has direct proportion to the testing speed. Further, the effect on the MFL signal was investigated and it was shown that not only the magnitude but also the features are altered. Finally, a confirmation for the aforementioned analysis was conducted by numerical simulations.

To evaluate the rotor temperature field of a high speed permanent magnet synchronous generator (PMSG), an electromagnetic-eddy current-thermal coupled field model is constructed using 2D Time-stepping Finite-Element-Method(FEM). In the model, the electromagnetic field and the temperature field have the same meshed grids to make a node-to-node data transmission and are solved independently. The data transmission ensures the coupling of the fields and the solve order of these fields is controlled by an external program. Temperature-dependent parameters, for example conductivity, can be set in the model. Windage loss of the rotor calculated by empirical formulas is loaded to the temperature field. Distribution of the rotor temperature is obtained by a calculation example of a 100 kW, 45000 r/min microturbine generator. Experimental data are used to show the validity of the proposed model which is helpful to the thermal design of the high speed PM generator.

For the ultrasonic guided wave testing technology based on the magnetostriction effect, the structure of the sensor has a significant influence on its detectability. A structure for enhancing the received signal strength by encircling a magnetic concentrator around the coil is studied in this work. Based on theoretical analysis, influences of the magnetic permeability of the magnetic concentrator and the electrical conductivity on the signal strength are analyzed. Experiments are presented to verify the analysis.

Commutation angle is a key design criterion when brushless DC (BLDC) motors sensorlessly operate based on the detection of back electromotive force(EMF) zero-crossing and must be designed significantly less than 30 electrical degree. The paper describes a detailed investigation on the commutation angle of brushless DC motors with 120° voltage source inverter. Analytic method is applied to analyze the influence factors. The proposed design principles can provide a clear guide for the adjustment of system parameters. Then two criteria and an estimation method based on approximate anlytical solution of commutation angle are presented with experimental validation.

Electromagnetic acoustic transducer (EMAT) has been used in many industrial areas due to its non-contact nature. However, the longitudinal wave EMAT is rarely employed because it is difficult to be generated. An improved longitudinal wave EMAT is proposed in this paper. By inserting the copper sheet between the coil and the test specimen, the eddy currents induced in the test specimen are changed and the components of the eddy currents for generating the shear wave are effectively suppressed. The performance of the EMAT is tested by the experiment.

The authors present a new compact coplanar interferometer for application in an IFM system with 4 bits that operates in a frequency band from 5 to 6 GHz. This interferometer consists of a couple of coplanar two-way Wilkinson power dividers connected to two CPS lines with different signal delays. This interferometer presents smaller dimensions when compared to other designs. Details of this compact coplanar interferometer are provided along with a comparison between theoretical, simulated and measured results.

In its current state, the wide acceptance of the Magneto-Optical Imaging (MOI) technique is hindered due to noise, lack of recordable results, and impossibility of data post-processing. This paper presents some add-ons made to a commercial MOI system to ease the image interpretation, archiving and reporting of the results. In addition, a few image processing techniques are also employed in an attempt to perform automatic flaw detection. The recording capability of the MOI instrument output images was addressed by digitizing the video signal in video or image files. To help with the identification of the damage location and distance between images, a rotary quadrature encoder was mounted onto the MOI scan head. The use of the encoder allowed the identification of the inspection location with respect to a reference position, such as the beginning of the scan. Moreover, it allowed saving images at fixed intervals, which were then stitched into a single image, thus simplifying the post inspection analysis process. Both live and post-inspection image processing capabilities were made available. Implemented image processing included background subtraction, de-noising, contrast adjustment and morphological operation, among others. Contrast stretching transform and background subtractions were found to be among the most powerful techniques that could be used in simplifying the image interpretation.

The aim of the present study is to develop a motor-generator that fits into a microturbine generator (MTG) system with a power density of 500 W class considering the DC load. The performance evaluation of the motor-generator is performed by back-to-back tests according to AC and DC load to evaluate the power generating characteristics. The power generating characteristics simulation is compared with the experimental results. The analysis results are in accord with the experiment results considering AC and DC loads. The slot model is determined by several characteristics, such as size constraint and the mechanical and electrical performance results between slot and slotless models.

This paper presents the characteristic analysis of the two-degree-of-freedom cylindrical actuator that can move in rotary and linear direction. The actuator uses the permanent magnet that is magnetized in axial direction so that the polarity in rotary and linear direction is generated alternately. When the rotary coil or the linear coil is excited, the mover moves by the principles of PMSM or PMLSM, respectively. As a result, the torque and the thrust are almost out of interference. It was confirmed that the actuator can move in rotary and linear motion independently. Moreover, the iron loss of the mover is smaller than that of the stator in rotary and linear motion, and the hysteresis loss is much larger than the eddy current loss.

In recent years, solid-state devices made their way in the development of electromagnetic non-destructive evaluation (NDE) probes. This fact was evidenced especially for pulsed eddy current, where magneto-resistive and Hall effect devices are used as sensing elements. Their low frequency range and small surface area are suitable to improve the detection of buried and small discontinuities. Although their properties are expected to enhance detectability over simple induction coils, this was still to be proven or demonstrated in a comparative study. This work compares the sensing capabilities of an induction coil to those of two solid-state devices: giant-magneto-resistive (GMR) and Hall effect sensors. All of them are used as detectors in pulsed eddy current probes that have the same excitation mechanism, a ring-type copper coil driven by a constant amplitude square waveform. While the excitation part of the probe is fixed, the sensing components are inter-changeable. Although both induction coils and solid-state sensors output a voltage value as an indication of the magnetic field they are detecting, the voltage for pick-up coils is directly proportional to the rate of change of the magnetic flux. For solid-state sensors the output is in direct relation to the detected magnetic field. Under this study, all three sensing elements are used to detect the driving coil's magnetic output (magnetic field or flux) in air, on planes perpendicular and parallel to the face of the driver coil. The results obtained by all three sensors are quantitatively compared. Then the sensing devices are inserted in the inner space of the driving coil and, subsequently, used for detection of artificially made defects. Finally, the results are compared in terms of magnetic field sensitivity and inspection performance.

An improved version of a coaxial sample holder with continuous inner conductor for measuring the shielding effectiveness of planar films is presented. Keeping the design idea of the previously realized version of inner conductor split in two parts that are screwed on the sample under test, new aspects are: presence of tapered transitions, compact realization, and overall small size (total length less than 150 mm; maximum diameter of the cylindrical device of 48 mm). The theoretical only TEM mode maximum frequency is about 5 GHz. The assembly of the device is easy, as it is the sample preparation. Experimental data have been get in the range 0.1 MHz–3 GHz by using a vector network analyzer. The reliability of the system has been proved by using, as reference samples, copper and aluminium thin films deposited by DC magnetron sputtering on kapton substrates. Films with different thicknesses have been prepared, with values around a few hundreds of nanometers, as measured by using a surface profiler. The shielding effectiveness experimental data of the used reference samples are reported and are well in agreement with the theoretical values.

The objective of the present study is to handle the optimum design of PMs excited TFLMs to transfer for high speed and heavy-load robots which transfer LCD glass panels to maximize thrust force and to minimize attraction force, thrust force ripple ratio, and attraction force ripple ratio. The predicted performance of the optimized TFLM is in accord with the 3-D FEM results. The static thrust force by test is performed to compare simulation results. The estimated error is within 4.1%, and the developed prototype is operated for 3 m/s by synchronous control driver to control both 4,000 N class TFLMs. Experimental validation is successfully performed to verify the design and analysis by optimum design.

Stress corrosion cracks may develop between fasteners in the aluminum inner wing spars of F/A-18 (CF188 Hornet) aircraft. These fasteners secure carbon-fibre/epoxy composite wing skin, of varying thickness (8 to 21 mm), to the spar. Inspection of the spar through the wing skin is required in order to avoid wing disassembly. A pulsed eddy current system that uses principal component analysis and discriminant analysis to identify cracks has been field tested at the USN North Island facility. The results show that the system can accurately identify cracks in real time throughout the wing. The method is far faster than X-ray radiography and, because it is very portable, can be readily deployed to second or first line facilities. Issues that need to be addressed to improve the performance of the system are identified and potential solutions are examined.

This paper presents a switched smart antenna system, designed to provide a reliable communication between a Center for Integrated Operation of a distributor of electric power and automation devices such as electrical switches remotely controlled. The smart antenna system is controlled by an electronic device which sets de direction of the main lobe of an antenna array to the automation device.

Computed tomography system for in situ NDE of degradation bridges is under development, with portable 950 keV/3.95 MeV X-band linac as x-ray source. Collimator is adopted to reduce scattered X-ray noise and 3D model can be built from sectional images so that it becomes possible to evaluate mechanical characters of bridges referring to structural analysis with reduced stiffness. Furthermore, considering limitation of projection angle range during in situ scanning, reconstruction technique with incomplete projection data is studied with experimental data.

This paper proposes a design method considering an irreversible demagnetization, the largest problem of the single-phase LSPM using ferrite on start-up. A parameter satisfying maximum output is extracted from the equivalent circuit in steady state, which is used to determine number of turns and shape. Here, back electromotive force and maximum output are selected as design variables for minimizing the effect of demagnetization and size, and the optimal design point is determined with consideration on the efficiency and maximum output of the single-phase motor.

In this paper, the analysis method is proposed to analyse the performance of the interior permanent magnet synchronous motor (IPMSM) considering the thermal characteristic. An accurate motor characteristic analysis is conducted by presenting the changes in circuit parameter due to the temperature rise and connecting them to thermal equivalent circuits. The arbitrary motor is selected to compare the test results and analysis results to validate the proposed characteristic analysis method.

According to the lift-off effect of eddy current testing, a ferromagnetic absorbing coating thickness gauge was proposed in this paper. After comparison, hyperbolic regression model was adopted to estimate the relationship between the detecting coil impedance and the absorbing coating thickness. An efficient probe with high quality factor and temperature compensation was developed. At the same time, a novel and more flexible calibration method was designed in this paper to improve the measurement accuracy. The experimental results show that the thickness measurement error is less than 0.02 mm, which proves the validity of this absorbing coating thickness gauge.

A rotor slot shape of induction motor for electric vehicle is optimized by FEM with the numerical techniques. To optimize the rotor slot shape, two objective function and 3 variables are defined, and the optimization algorithm is developed. To verify the program, 4 poles 44 kW induction motor is modeled, simulated and analyzed by the program. The optimized rotor slot shape result makes reasonably good improvement to increase torque and efficiency of the motor performance.

This study deals with the dynamic characteristic analysis of a Linear Induction Motor (LIM), using a finite element method in which a moving mesh technique is considered. The focus of this paper is to show the suitability of an on-line observer system for position sensorless control of a LIM under phase asymmetry, saturation and iron loss.

Comparisons are given both from the angle of the observer and that of the proposed FEA method of a linear induction motor. The position control system is realized, and the effectiveness of the observer system for the flux angle is verified by experimental results.

This paper deals with characteristics evaluations for PM magnetization with a stator coil in a post-assembly Line Start Permanent Magnet Motor (LSPMM), using a coupled Finite Element Method (FEM) and Preisach modeling. The focus of this paper is characteristics analysis, relative to magnetizing direction and the quantity of permanent magnets due to eddy currents which occurr in the rotor bar during post-assembly magnetization and which effect Nd-Fe-B magnets.

A new identification method for impact loads is proposed based on the transient statistical energy analysis theory. The load identification problems of structure subjected to single excitation are classified into three cases according to the completeness of load location information and subsystem response set. The input energy of impact load and the load location is firstly identified from the averaged vibration energy responses of subsystems according to energy balance equation for three cases. The load amplitude spectrum is thereafter derived under the assumption of constant value of itself from the identified input energy within each analytical frequency band. Finally, the time history of impact load is further determined for the given load time domain waveform using a developed fitting method. The experimental studies of impact load identification are conducted on a plate-shell assembled structural system. The results show that the location and input energy of impact load can be identified with fairly accuracy using the presented identification method. Besides, both the load spectrum and time history of impact load have good agreements with the measured ones.

This paper investigates optimal design of shoe shape so as to reduce cogging torque of variable-flux (surface permanent magnet synchronous motor) SPMSM using two type of magnets. First, it suggests numerical analysis method of cogging torque of motor organized by two types of magnet. With the numerical method, it designs shoe shape of stator that cogging torque is minimized. Finally, it verifies effectiveness of design using the finite-element analysis.

Non-destructive evaluation (NDE) techniques are indispensable for inspection of damage in structures of carbon steel, which is widely used in many industries. In this paper, experimental and numerical studies were conducted to investigate the electromagnetic property variations of carbon steel Q195 due to plastic strain by using the 4-probe potential drop method and ECT aiming at NDE applications. A series of specimens were fabricated and uniform global plastic strains of different levels were introduced to the specimens by tensile testing. 4-probe potential drop measurements were carried out to obtain the conductivity information at first. It is found that the macro conductivity is not affected significantly by the plastic strain once taking into account the influence of the cross-sectional area reduction of the specimens. Combining the results of numerical analysis using a code of A_r formulation with the measured ECT signals, the permeability of specimens with various plastic damages was evaluated through inverse analysis. It is proved that the ECT signal change due to plastic damages is mainly caused by the variation of permeability, which gives a good possibility to evaluate the plastic damage with a magnetic NDE method.

Magnetic Incremental Permeability (MIP) method practiced as a NDT technique to evaluate the material degradation is based on the eddy current testing in addition to a low frequency bias magnetic field generated by an electromagnetic magnet. To clarify the mechanism of MIP and to find optimal probe design, a numerical method to simulate MIP profile is important. In this paper, a simulation scheme and a numerical code are developed for MIP of ferromagnetic material based on the simulated polarization strategy and the reduced vector potential formulae. Experiments are also conducted for test-pieces of carbon steel to demonstrate the validity of the proposed scheme.

In this paper, a numerical method is proposed for simulating dynamic response of a ferromagnetic structure immersed in a strong magnetic field aiming at applications to the in vessel Tokamak structure of RAFM steel. The magnetic damping coupling effect and the magnetic stiffness coupling effect are considered in the numerical simulation. For simple, the static magnetic field is supposed very strong and the material is considered saturated in this work, i.e., the material is of air permeability but with a strong residual magnetization. To demonstrate the validity of the numerical method, the dynamic response of a ferromagnetic plate immersed in a transient transverse magnetic field with in-plane magnetic field component is simulated with the developed numerical code and compared with the simulated results with ANSYS. The good consistency of numerical results and simulation results demonstrated the validity of the proposed method and the corresponding numerical code.

The electromagnetic shunt damping absorber (EMSDA) is developed based on electromagnetic shunt damping mechanism. The governing equation of planar vibration system equipped with the EMSDA is derived. An optimization method is presented to determine the main working parameters of EMSDA on the basis of the built theoretical model. The objective function minimizing the response variance of system under white noise excitation is formulated. The particle swarm optimization algorithm is employed in optimization. The simulated and experimental studies on vibration control by use of EMSDA are conducted. The results show that the electromagnetic shunt damping absorber can attenuate significantly the structural vibration.

Viscous, magnetization and damping properties of magnetic compound fluids containing fibrous material such as alpha-cellulose were investigated experimentally. It is shown that adding fibrous material to magnetic functional fluids is effective on increasing viscosity on the fluid while the amplification ratio of damping force in the presence of magnetic field against damping force in the absence of magnetic field decrease with increase of volume fraction of the fibrous material.

The recently developed macro fiber composite (MFC) actuators are widely used in a variety application due to their high performance, flexibility and durability when compared with the prior actuators. This paper aims to model and compute the effective electromechanical properties of MFC actuators using the finite element method (FEM) and verify the accuracy the model through the experimental test. The results indicate that the FEM results are in good agreement with the experimental data. It demonstrates that the finite element(FE) model is effective to predict the electro-elastic properties of MFC when the electric field is applied.

Multilayered Tubular Structures (MTS) such as pipeline are widely employed in such industrial fields as nuclear energy, petroleum, etc. It is vital to non-destructively evaluate MTS periodically before catastrophic accidents take place. As one of the advanced Electromagnetic Nondestructive Evaluation (ENDE) techniques, Pulsed Eddy Current Testing (PECT) has been found advantageous over the other ENDE methods regarding evaluation of integrity of MTS. In this paper, a fast forward model of PECT inspection of MTS is proposed based on the analytical modeling, namely the Extended Truncated Region Eigenfunction Expansion (ETREE). The closed-form expressions of PECT signals of 3D magnetic field and coil Electromotive Force (EMF) have been formulated. The proposed model has been verified by Finite Element Modeling (FEM) and experiments. The advantages of the model in terms of high computational speed and accuracy have been identified.

Fast and accurate crack detection techniques are required for the eddy current non destructive testing, especially in the case where a large amount of environmental noise exists. This paper presents a robust inverse solution for accurate shape reconstruction of natural cracks. A robust formulation is employed to deal with the uncertainties caused by the noise in the eddy current testing signals. The proposed method is capable of producing more robust results than the conventional formulation in terms of the statistical analysis of the reconstruction tests.

To calculate the complex permeability of soft magnetic composites, two-dimensional analytical models with and without the defects were used for the complex case. The relation of the complex permeability with the frequency, component size ratio δ and inclusion particle size is deduced. The results show that the effect of the defects is even more pronounced for the complex permeability. The complex permeability is a function of the component size ratio δ and the size of the inclusion. Increasing the component size ratio δ causes a decrease of the complex permeability at the same frequency. With the increase of inclusion particle size when the component size ratio keeps constant 0.01, both of the real and imaginary parts increase. In addition, the theoretical method is tested by the experimental results, which can be used to design parameters before the experiment.

Electrical error which contains amplitude error, function error and zero error has a direct impact on accuracy of resolver when resolver is used as a angle measuring device in control system. Harmonic interference existing in the output electromotive force (EMF) of signal windings is the main influencing factor of function error. Therefore, the reduction of harmonic interference will greatly weaken function error. In this paper, an axial flux variable-reluctance (AFVR) resolver with short pitch distributed winding is put forward on the basis of former variable-reluctance resolver. By the analyses of finite element method (FEM), high order harmonic of output EMF makes the distortion of EMF waveform and causes errors. Furthermore, the change regulation of high harmonics in the output EMF is got. The optimization analysis is done to rotor shape, pole-pairs and each group teeth number of this new resolver. Through FEM analysis and discussion on the optimized AFVR resolver, the analytic results show that the influence of harmonic interference is seriously weakened, and measurement accuracy is upgraded.

This paper discusses high frequency acoustic noise generated by an IH cooker. Mechanism of the high frequency acoustic noise generation is clarified by experimental study. Recently, influence of the electromagnetic wave on the human body is worried. They symptoms some users of home electronic appliances feel are headache and nausea. There is a report that other 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 clarified by the experiments.

Companies of power transmission lines and telecommunications need to know the condition of their structures. However, there are ones which are buried or encased in concrete below-ground. Nondestructive techniques are essentials to investigate the condition of the rods used to anchor guy cables in guyed towers. A connector and a matching circuit have been designed to allow a network analyzer to apply and receive high frequency signals on these rods and, furthermore, to be able to identify corrosion or holes on an anchor rod using a promising nondestructive technique. High frequency analysis have been done on the results provided by simulations and experimental tests through the reflected signals that come in the input port of the connector and matching circuit. The high frequency connector, named CHAAF, was fabricated and tested.

This paper proposes an inversion procedure, based on radial wavelet basis function (RWBF) neural network, to reconstruct 3-D defect profiles from magnetic flux leakage (MFL) data. The architecture of the neural network, the adaptive training algorithm and the reconstruction process are presented. Defects reconstructed from both simulated and experimental MFL data, together with comparison with two other inversion methods, demonstrate the efficiency and accuracy of the proposed inversion procedure.

Their small size together with a remarkable field sensitivity are the most prominent features of present-day GMR sensors paving the way for various applications in automated non-destructive testing (NDT). This work presents a prototype for fast and automated magnetic testing of roller bearings. A local magnetization unit excites the magnetic field inside the bearing. As a result of a design study and the following wafer fabrication the probe was equipped with NDT-adapted GMR sensor arrays in which 48 elements measures the field response. The detection of artificial and 40 μm deep defects could be resolved with a SNR better than 20 dB. In addition, we report of first results of a POD (Probability of Detection) analysis using GMR sensors to investigate bearings with EDM (electronic discharge machining) notches having depths down to 10 μm. Finally, we estimate successfully the depth of a 57 μm notch from the measured data.

Since the excitement of gecko free-walk on a smooth surface is discovered with the cause of Wan der Waals force, researchers have focused on the development of biomimetic gecko tape. Hierarchical structure and anisotropic adhesion are two of the spotlights. However, little work has been done on integration of these two parameters. This paper presents a model design of orientated micro-and nano-arrays including three levels of setae, branches and spatulae. Finite element method is applied for compression shear test simulation. The anisotropic property is controllable due to the hierarchical surface design.

The electrical impedance tomography is a widely investigated problem with many applications in physical and biological sciences. A new nondestructive method of the flood embankment dampness was tested. The basic information about the built measuring system, including the prototype equipment is given. The setup was used to determine the dampness of the test flood blank on a specially built model. The forward problem solution (in the electrical impedance tomography) is solved by the determining potential distribution inside the region under given boundary conditions. The full information about region is considered, This problem is solved by Laplace's equation. The level set methods with the Chan-Vese model were applied in the inverse problem for the image reconstruction.

In the case of one phase failure, the switched reluctance motor(SRM) will behave nearly the same, both in open circuit and in short circuit failure. This means, that the machine will understand the two faults in the same way which makes the SRM faults detection and diagnosis a more challenging task. This paper presents a diagnosis method based on pattern recognition analysis to detect and to classify automatically the electrical faults, short- and open-circuit under any level of load of the studied system: redundant three-phase power converter fed 6/4 SRM. The phases making a pattern recognition diagnosis of SRM, the training and the decision. The training phase consists in determining the pattern vector and the optimal kernels design (the separating classes) by Time-Frequency Representation (TFR). The training data is carried out using a set of fault scenarios, between healthy, single and combined faults, in terms of torque measurement at different load level, in order to deduce the fault severity. The second phase, consists in associating an unknown pattern with one of the defined classes, according to the "k-nearest neighbors" (knn) decision rule, associated with Kalman estimator to tracking of various operating modes and to predict the evolution of the call out of the knowledge database for a given operating mode in order to realize a preventive maintenance. The experimental results prove the efficiency of pattern recognition methods in condition monitoring of reluctance machine.

Recently, permanent magnetic actuator (P.M.A.) is widely used to drive the mechanism of vacuum circuit breaker (V.C.B.). This paper deals with the optimal design of P.M.A. for V.C.B. using the response surface method(R.S.M.). First, the dynamic characteristics of the initial P.M.A. model, such as the holding force, exciting current, and action complete time, are calculated by coupled electrical-mechanical problem based on finite element method (F.E.M.). In order to verify the validity of numerical results obtained from finite element analysis (F.E.A.), the calculated dynamic characteristics of the initial P.M.A. model are compared with no-load test results. Next, using the R.S.M., the initial P.M.A. model is optimized to improve the dynamic characteristics. Finally, in order to verify the validity of the P.M.A. model optimized by using the R.S.M., the dynamic characteristics of the optimized P.M.A. model are calculated by using F.E.A. and compared with those of the initial P.M.A. model.

In order to meet the engineering requirement of gas pipeline inline inspection for cracking defects, a new ultrasonic guided wave (GW) method based on electromagnetic acoustic transducer (EMAT) has emerged. In consideration of the large amount of original inspection data and the limited capacity of the storing device, the research on rapid and large ratio data compression is needed. This paper proposes a new large ratio data compression method based on subsection adaptive method (SAM) and wavelet neural network (WNN) algorithm. The influences of parameter selection on the compression quality, speed and ratio and the method of enhancing the compression speed of this method is studied. The experiment results indicate that compared with the traditional WWN compression algorithm, the proposed method has higher compression quality and speed, and a large compression ratio of 110:1 is achieved by the proposed method. It is thus suitable for gas pipeline crack inline inspection based on EMAT-generated GW.

Lorentz force eddy current testing is a novel nondestructive testing technique which can be applied preferably to the identification of internal defects in non-ferromagnetic moving conductors. This paper describes the comparison of this new technique with well-known eddy current testing. Measurements and numerical simulations have been done for both techniques for artificial subsurface defects in a test specimen made of Aluminum alloy moving with constant velocity.

Different phases which exist in a duplex stainless steel (DSS) affect mechanical as well as electromagnetic properties. Therefore, an eddy current (EC) technique can be utilized to detect phases inclusions. In order to evaluate and identify the amount of deleterious phases it is important to assess the impact of electromagnetic properties of material on a measuring signal. This paper presents a study on the influence of DSS properties changes caused by a sigma (σ) phase on signal measured by an EC transducer. The results of an analytical and numerical analysis are presented. The analytical modeling allows to identify the electromagnetic properties and evaluate the amount of σ phase in the tested material.

This paper presents a new eddy current modeling approach in which the edge field contribution for a finite width conducting plate is accounted for. The 3-D steady-state analytic eddy current model accounts for the source field contributions from oscillatory as well as translational velocity motional effects. The paper discusses the modeling inaccuracies caused by neglecting the source field contributions on the edges of the conductive plate. The new modeling approach is validated by comparing the analytic calculations with a 3-D steady-state finite element analysis model.

This work presents the development of a new approach to EMAT finite element method (FEM) simulations by using a novel coupled electromagnetic-mechanical equation system. Validation is performed within the limits of the un-coupled equations using commercially available FEM codes. The advantages and drawbacks of the new method versus the traditional un-coupled approach are evaluated for various EMAT patterns. Numerical FEM analyses use a sparse direct solver with either Euler or Crank-Nicolson implicit time integration methods.

A measuring system is presented to improve the volumetric strain measurement in hydrostatic pressure environment for a hydro-compression loading test. The measuring system consists of a new triaxial extensometer, a novel contactless signal transmission system and an IPT (inductive power transfer) equipment. By the extensometer, triaxial deformations of foam specimen can be measured directly, from which the volumetric strain is determined. Sensitivities of the triaxial extensometer are predicted using a simplified analytical model, and verified through experimental calibrations. To avoid the punching and lead sealing techniques on the pressure chamber for hydro-compression loading and transfer the strain data of the triaxial extensometer effectively, a new modus of contactless differential signaling is developed in this paper for elimination of noise caused by the IPT.

This paper deals with tweezers for a mass detection during micromanipulation. It measures 52 mm × 30 mm × 10 mm and weighs 37 g. Each finger consists of a bimorph piezoelectric actuator with a stainless steel tip. One of the tweezers working as a vibrator was oscillated at its resonance frequency, and another working as a grasper opened and closed the gap between the tips of the bimorph piezoelectric actuators. The simulation model that represents the contact of two beams and a lumped mass as springs was described. The resonance frequency was increased when the tweezers grasped an object. The relationship between the mass of the object and frequency was obtained experimentally. Because the charge generated by the piezoelectric effect also affected the resonance frequency, the frequency change in the experiments was smaller than that in the simulation.

In this paper the mechanical deflection of steel bars, of different length, in a flux focusing magnetic gear is studied. The mechanical deflection is caused by the magnetic attraction between the steel bars and the inner and outer rotor magnets of the magnetic gear. An iterative magnetomechanical approach using commercial finite element analysis software has been adopted. Two different diameter magnetic gear models with different axial lengths have been modeled and the deflection has been calculated for each model. Experimental verification for one model is also shown. The paper shows that when operating with a small air-gap and long axial length the mechanical deflection can become significant.

In this paper, forced vibration experiments on flexible piezoelectric devices operating in both air and water environments are discussed. Validation of the theoretical analysis method for such devices, via experimental means, is needed in order to achieve future cost effective design optimisations. In aim of this, numerous devices of differing dimensions are manufactured and tested, in various operating conditions, with comparison and discussion to simulation results provided.

The paper describes the alternative designs and performances of a single-phase moving-magnet linear oscillating actuator (LOA) which has been developed for orbital friction welding. The influences of the pole ratio on the performance of the LOAs are investigated and the optimal parameters have been identified with reference to the thrust force characteristics. It can be illustrated that a quasi-Halbach magnetized LOA, in which the magnets are assembled on a nonmagnetic mover yoke, represents the best electromagnetic performances. Finally, the predicted thrust force-current characteristic of quasi-Halbach magnetized LOA is validated by measurements on a prototype actuator.

This paper proposes to use a statistical approach for classifying the contamination level of insulators used in high voltage transmission lines. This studied case considers the voltage applied on glass insulators used in a chain of six elements of a 69 kV power line. When submitted to high voltage, the insulators radiate radio frequency signals up to frequencies of some GHz. In this frequency range the signal can be detected using portable antennas, and then be applied to post processing. These received spectra are analyzed by statistical methods, mean and standard deviation, and the cross relation between them is used to classify the pollution level in insulators. To reduce complexity and cost a simple data processing using the mean and the standard deviation are used. Two types of glass insulators are considered: clean or polluted, and to cover the entire frequency range from 30 MHz to 1 GHz two types of antennas were needed. The results obtained with the mean and the standard deviation show that the first 100 MHz bandwidth can be used for statistical of the insulator pollution level.

The axial flux permanent magnet (AFPM) machine is widely used in many applications due to its advantages. But the conventional AFPM machine has the major problem such as the deformation and unbalanced air gap occurred because of the large magnetic attraction force between the rotor and the stator. For these problems, the magnetic attraction force must be accuractly calculated in the process of the design step of the mechanical parts. Thus, this paper proposes the analysis method to compute the magnetic attraction force of AFPM machine considering a unbalanced rotor structure. The quasi 3D model with a different air gap condition is introduced to analyze the magnetic flux density and the magnetic attraction force due to the eccentricity of rotor structure. To validate the proposed analysis process with the quasi 3D model, 3D FEM analysis is performed to compare the results. As results, the proposed analysis results was obtained the similar results to 3D FEM analysis results. The proposed method is applied and estimated to the 130 kW AFPM generator.

In general, a lot of computing time is needed to analyze the transient characteristics of a power transformer with complex geometry by field-circuit coupling method. This paper proposed a modified 2-D model and an efficient field-circuit coupling technique of a power transformer in order to reduce the computing time. To analyze the transient electromagnetic force acting on each disk of transformer windings, we made 2-D axisymmetric model. First, the transient current equation considering the residual flux was solved to get the inrush current. Next, the transient electromagnetic force due to the inrush current is obtained by applying finite element method (F.E.M.) to the modified 2-D model. The proposed method will be useful for the structure design of the power transformers.

The aim of this study was to investigate the possibility of using electromagnetic radiation in the terahertz frequency range for testing of polymer composites. Glass, natural and basalt fiber reinforced polyester composites as well as sandwich structures after fatigue tests were evaluated. We examined detection abilities of detects and inhomogeneities occurred during bending process at various amounts of load cycles. Extraction and monitoring of proposed parameter enables accurate evaluation of composite structures condition.

Pulsed eddy current (PEC) testing has attracted researchers' interest because the pulsed excitation comprises a broad band of frequencies and the response signal provides more information about defect than traditional eddy current testing. Various features have been extracted from PEC signal for defect characterization. In this paper, we extract frequency-domain features and propose defect characterization scheme for identifying defect's location, radius, and height.

This paper describes 2 types of 2 DOF magnetic suspension systems which suspend two iron balls or an iron stick type object. Both suspension system controls 2 DOF of suspended object(s). The magnetic suspension forces are controlled by a generator of magnetomotive force. This suspension system must control two degrees of freedom without mechanical contacts. In iron stick suspension system, a vertical displacement and a horizontal rotation of the object should be controlled. This paper proves the feasibility of these noncontact suspension systems. A theoretical analysis will be done on the model of these suspension systems and numerical simulations carried out for confirmation of performances.

Cross-wound eddy current sensors have been used for years in the non-destructive testing industry for surface detection of cracks on steel components. The conventional sensor, which is a three dimensional transmit-receive structure comprising two orthogonal coils, can't be directly translated to a flat winding suitable for printed circuit board (PCB) manufacturing. This paper describes a method that makes it possible, through the use of finite element modeling (FEM), to reproduce the cross wound sensor response on a flexible printed circuit board. As a second step, an innovative compact PCB made cross-wound eddy current array (ECA) structure is presented and demonstrated experimentally.

This paper presents the concept of determining the optimum frequency of coil supply in inductive-dynamic drive. As a criterion to obtain the sought frequency, the smallest value of reduced stress in the disc was assumed while maintaining the desired dynamics. The disc stress is determined on the basis of solution of vibrating thin plate equation. Magnetic pressure acting on the disc is obtained from a hybrid circumferentially-field model (CI-FI).

This paper presents the proposal of the hybrid circumferential-field model of an electrodynamic actuator. The field model uses the inductor current as the input data which is obtained from the circumferential model or experimentally. The field model implemented using the FLUX program makes it possible to easily determine the pressure distribution acting on the disc. The results have been verified experimentally.

Magnetic fluid tuned liquid column damper (MF-TLCD) is a new semiactive damper. This device can exhibit high damping effect by tuning its natural frequency to the excitation frequency. In this study, the vibration characteristics of a magnetic fluid under a static magnetic field were investigated by linear analysis and experiment with single-degree-of-freedom oscillation. Moreover, MF-TLCD was installed within a structure and oscillated in double-degrees-of-freedom. It was confirmed that MF-TLCD could achieve high performance compared with the conventional TLCD by controlling the magnetic field.

An experimental study in ultrasonic propagation characteristics of a magnetic fluid under AC magnetic fields was conducted. Sound velocities in a magnetic fluid increased with elapsed time of the AC magnetic fields. Moreover, rapid decreases in sound velocities in a magnetic fluid were observed when the AC magnetic fields were stopped. These results were similar to those for DC magnetic fields. Dependence of frequencies and magnitudes of AC magnetic fields on sound velocities in a magnetic fluid was observed. Moreover, anisotropy was found in each frequency of the AC magnetic fields.

This study investigates the behavior of two-layer sloshing using a magnetic fluid and silicone oil. To obtain basic relations, a linear theory is employed. After obtaining those relations, theoretical values of free-surface displacement, resonant frequency, and resonant pressure amplitude are compared with experimental results. Experimental data are obtained using a laser sensor and four pressure transducers. Free-surface displacement is measured by the laser sensor. Resonant frequency is measured by both the laser sensor and pressure transducers. Resonant pressure amplitude is recorded by the pressure transducers. The results demonstrate that the theory employed in this study is effective as a first estimation of two-layer sloshing. However, to describe the behavior of a two-layer magnetic fluid sloshing more precisely, a nonlinear analysis that considers magnetic force is necessary.

This study is an investigation on the effect of a chamfered orifice inlet on magnetorheological (MR) fluid subjected to shock loading. Three different orifices (without chamfer, chamfered at 60°, and chamfered at 120° on the inlet area) are used. MR fluid is subjected to shock loading, and a magnetic field is generated on the orifice area. Experiments are conducted by measuring piston displacement and damping force. Piston velocity is calculated from the piston displacement data. The results indicate that a chamfered orifice inlet affects the piston stroke, piston velocity, and damping force. The characteristics of piston velocity between the orifice without chamfer and the chamfered orifices are different. The post-peak decrease in piston velocity in the chamfered orifices is more refined than that in the orifice without chamfer. However, the chamfered shape in the orifice inlet reduces the shock loading performance of MR fluid.

An improved vector cross-entropy (CE) method is proposed to provide a potential candidate for solving multi-objective inverse problems with a large number of variables. To balance the exploitation and exploration searches, the whole iterative process is divided into two phases: diversification and intensification phases. Different parameter evolutionary mechanisms of the probability density functions (pdfs) are proposed for different phases. To speed up the convergence rate, a dynamic evolutionary mechanism is proposed. To enhance the diversity of the sampling points, a mutation manipulation is introduced. The ZDT test functions and a high frequency inverse problem are used as the case studies to testify the effectiveness and efficiency of the proposed method.

The magnetic nanoparticles in AC alternating magnetic fields will produce a large amount of heats due to the Néer relaxation. Magnetic Fluid Hyperthermia (MFH), based on this mechanism, offers a new breakthrough and has a promising potential in tumor treatments. The temperature field distribution in the treatment and neighbor regions has a significant effect on the therapeutic result. Therefore, it is essential to control the temperature in the treatment region in a proper range (42°C∼90°C) while to guarantee a sharp gradient in the boundary of the treatment and normal regions. This study provides an automatic shape design methodology using the Finite Element Analysis (FEA) of the electromagnetic-temperature Coupled Field (CF) and a multi-objective Particle Swarm Optimization (MOPSO), to realize sufficient uniformities in the temperature field distribution while to ensure the enough temperature gradient in the cancer boundary.

To develop an efficient robust optimal method for numerical solutions of inverse problems, a metaheuristic based on ant colony optimization(ACO) algorithms is proposed. In accordance to robust design specifications, the algorithm iterative procedures are redesigned, and the methodology and mechanism for reducing the heavy computational burdens associated with robust performance computations are introduced. To validate the feasibility and showcase the merits, of the proposed method, it is used to solve an engineering inverse problem with promising results.

This paper proposes a new magnetic-geared generator, which has a novel permanent magnet arrangement whereby the permanent magnets are embedded into the high-speed rotor and the stator slots, for direct-drive wind power generation systems. The operational principle is described and the performance is verified by using finite element analysis.

In Japan, midwives perform Japanese hands-on (perineal support), which is important to prevent perineal tears and to deliver safely. However, it is difficult for trainee midwives to acquire the procedures. Therefore, the advanced delivery simulator that enables the midwives to evaluate the skill objectively is demanded. In this paper, for realizing the delivery simulator, we focus on the pressure of midwives' fingers and palms during Japanese hands-on. Fundamental experiments were carried out using flexible pressure sensors. In experiments, six experts perform the Japanese hand-on using normal delivery phantom. From the analysis of pressure profile, the cooperation of the left and right hand was investigated.

Palpation is a simple diagnosis method that doctors examine body and organs of patients by feeling with their hand. However, palpation is not objective because the palpation sensitivity depends on skill and experience of doctors. Therefore, an objective method for measuring tactile information is required. In this study, a palpation sensor system for detecting a lump is proposed and fabricated. Fundamental characteristics of the sensor are examined by using measuring objects made of polyurethane resin and aluminium rods as a lump. A peak waveform appears in the sensor output when the sensor is above the lump. In addition, the measuring objects using the silicone cylinder are made in place of aluminium rod. Also, the experiment is done, and the features of peaks are investigated. From the results, it is confirmed that the sensor is available to detect the lump.

This study describes the development of a sensor system for measuring human scratching motion. In order to measure the scratching motion, we focus on the mechanical vibration between the nail and the skin that is scratched. Scratching sounds, induced by the vibration, change according to the scratching intensity or the skin condition. Therefore, the information on the scratching sounds can help us to evaluate the characteristics of scratching. In this study, a nail-mounted compact microphone sensor for measuring human scratching sounds is designed and fabricated. First, the ability of the proposed sensor to measure scratching sounds is investigated. The feasibility of this sensor has been verified. Next, the power spectrum density is calculated from the sensor output to investigate the characteristics of the scratching sounds according to the scratching intensity. It was found that frequency components increased with an increase in the contact force during scratching. The results suggest that it is possible to evaluate the scratching intensity by using the proposed sensor system.

This paper presents a nondestructive evaluation algorithm for locating, discriminating, and evaluating inner and outer diameter (ID and OD) corrosion on a small-bore pipe by means of a bobbin-type magnetic camera that uses arrayed solid-state Hall effect sensor elements for measuring alternating magnetic fields. The proposed magnetic camera system is used to experimentally measure artificial ID and OD hole-type cracks on a small-bore copper alloy pipe over a low-frequency range (2–8 kHz). The measured amplitude signal is analyzed to determine both the position and type of crack. The volumes of the cracks are estimated with standard deviation of 0.77 mm ^{3} to be in the range 1.00–9.01 mm ^{3} .

Inclusions in steel are entrapped foreign materials, which may be metallic or non-metallic. The inclusions disrupt the structural homogeneity of the steel and affect its mechanical properties. Moreover, nonmetallic inclusions such as calcium and magnesium can be propagated as narrow cracks in steel strips after the rolling process. In this paper, we propose the use of magnetic flux leakage testing involving the fusion of images obtained by arrays of linearly integrated Hall sensors (LIHaS) and linearly integrated giant magnetoresistance sensors (LIGiS) for inspecting inclusions in steel strips. In the proposed method, the normal (Bz) and tangential (Bx) components of the magnetic leakage field around an inclusion are detected by means of LIHaS and LIGiS, respectively. The images of the magnetic leakage field were obtained at different scanning (magnetization) directions relative to the rolling direction. The Bz and Bx images of the inclusion are then combined by using image fusion technique to enhance the detection of the inclusion. The effectiveness of the proposed image fusion technique was experimentally verified by using LIHaS and LIGiS images of an inclusion in a cold-rolled steel strip.

Plastic deformation, as a type of micro-damage caused by external loads such as earthquake, is necessary to be evaluated by using an efficient non-destructive evaluation technique in order to guarantee the structural safety. In this paper, the feasibility of the pulsed eddy current testing method for evaluating the plastic deformation in an austenitic stainless steel has been studied through experiments and simulations. Moreover, the electromagnetic property variations due to plastic deformation have also been investigated.

To date, the majority of artificial hearts have been nonpulsatile types. Natural hearts, however, are pulsatile, and the long-term biocompatibility of the nonpulsatile types has not been confirmed. We set out to develop a magnetic pump with a pulsatile flow. Because it is pulsatile, we were able to make this pump as small and compact as a natural heart. It consists of a motor, a bellows, and a permanent magnet. The pulsatile flow artificial heart relies on magnetic force. To determine the basic characteristics of the pump, we measured the flow, pressure and magnetic force. We describe the structure of the pump, it's manufacturing method, and it's principle of operation. The use of the bellows allows us to realize a structure where the fluid chambers and drive are separate. When the pump pulsated at 0.6 [Hz], the rate of flow was 0.618 [l/min]. The differential pressure between inflow and outflow was 3.5 [kPa]. The magnetic attractive force was 243.4 [N] and the magnetic repulsive force was 67.3 [N]. We confirmed that the pump was able to pump water by pulsating steadily.

MRI systems have technical challenges in interference with metals and high cost because of the use of strong magnetic field. Ultralow-field MRI is an emerging technique enabling measurement of samples containing metals due to low resonant frequencies, as well as saving cost due to its simplified coil system. We developed a compact SQUID system for ultralow-field MRI equipped with a magnetic shield box of 1 × 1 × 1.5 m. Oscillating magnetic fields were applied to the pick-up coil of SQUID from an external coil with a magnetic flux density equivalent to magnetic resonance signals from water of 10 ml. The SQUID successfully detected external magnetic fields of 3.08 × 10 ^{-12} T.

This paper reports a utility of the design method that conducts thermo-magnetic coupling analysis by using a heat equivalent circuit and describes evaluation results of relationship between losses and temperature rise based on magnetic properties. We manufactured and tested prototype motors that were designed with thermo-magnetic coupling analysis and found that reduction of copper loss become of particular importance in order to reduce temperature rise, and total losses of motors.

A palpation is a useful method to detect cancer and to evaluate skin or under skin conditions. However, the palpation is a skillful method. Doctor's mental and physical conditions affect diagnoses by the palpation. Additionally, it is hard to share the feeling of palpation with other people because palpation is subjective skill. Therefore, the development of the sensor that can measure the skin and under skin condition of the body like softness as a doctor's palpation is demanded. In this paper, we focus on a haptic perception mechanism of human for evaluating the softness. Six objects are made to conduct sensory tests. The silicone rubber part of the objects has two kinds of thickness and three kinds of Young's modulus. Relationships between physical properties of evaluated objects and the softness that human feel in active touch are investigated. After that, to control the contact condition between objects and finger, a passive touch evaluation system is fabricated. Using the system, relationships between the stiffness of the objects and evaluated haptic softness are investigated under passive touch condition.

The paper presents some optimization approaches to the electromagnetic wave focusing in heterogeneous biological tissue model. The model of human arm was used for investigation. The possibility of focusing of electromagnetic wave optimisation is strongly connected with investigation of electromagnetic wave propagation through complicated heterogeneous biological structure. Firstly we concentrated on the influence of particular structures thickness on scattering parameters value which gives us information about transmission and reflection of electromagnetic wave on interfaces of structures which differ by dielectric parameters. The next simulation showed the influence of water bolus placed on the arm model surface on values of SAR and consequently the possibility to avoid the overheating of upper region of arm model in the process of microwave hyperthermia. The next step connected with possible optimisation of electromagnetic wave focusing showed the influence of metamaterial structure placed in the front of microwave patch antenna used in role of microwave hyperthermia applicator on the electromagnetic wave focusing. The simulations were done for various numbers of metamaterial structures and various distances from arm model. Finally we simulated the focusing accuracy in the case when the combination of water bolus with metamaterial structure was used.

The paper deals with some methods for relative permittivity of dielectric materials measurement and with the relevant techniques. In addition to current methods of measurement evaluation on vector network analyser our new approach gives also information about possibility of the use of classical methods for evaluation of application at vector network analyser as a faster source of basis for computations. In the paper also an attention to a situation is paid when it is problematical to determine the unknown permittivity of solid material by usual methods.

Multilayered magneto-impedance microsensors (Finemet/Copper/Finemet) were elaborated by microfabrication process using bi-layers lift-off method. A post-annealing step was carried out at 300°C for 1h under magnetic field, which led to induce a longitudinal or transversal anisotropy in the magnetic films. A method based on a double amplitude demodulation was proposed for the sensitivity characterization corresponding to the AC magnetic field measurement capability. According to these alternating magnetic field characterizations, the sensitivity, the linearity and the bandwidth of the microsensor were obtained. The highest sensitivity is around 4200 Ω/T and the measurable sensor bandwidth reaches up to 300 kHz. The sensor presented no hysteresis since a DC bias field larger than anisotropy field is applied.

Magnetic susceptibility is the inherent property of materials. Magnetic resonance imaging as a kind of non-invasive testing technique may measure the magnetic field distortion induced by the imaging object and consequently calculate its magnetic susceptibility distribution. Conventionally, magnetic susceptibility mapping is performed in three-dimensional mode with the requirement of multi-slice scanning. In the condition of long objects that have uniform distribution along one direction, two-dimensional phase image of the cross section might be enough to estimate the susceptibility. In this study, we adjust susceptibility mapping algorithm into a two-dimensional mode and evaluate the possibility of using a single-slice image to estimate the magnetic susceptibility. Simulation was performed to validate the algorithm in both ideal and noise-imposed conditions. MRI experiment was performed by using copper, graphite and iron oxide at different concentrations. The results suggest that it is possible to measure the susceptibility of a long object by a two-dimensional image.

NOTES (natural orifice translumenal endoscopic surgery) allows for exceedingly minimally invasive surgery but has high requirement for dexterity, force capabilities and safety of tools. Researchers have proposed some flexible instrument used in surgeries. However, little work has considered the safety problem of the instrument to human tissues due to the absence of controllable flexibility and insufficient force capabilities. This paper presents a design of a flexible and stiffness changeable mechanism which can serve as a tunnel for NOTES tools. Furthermore, the flexible and the stiffness changeable properties are evaluated by FEM analysis.

Soft tissue injuries remain as problems in the application of clamping devices due to overload. Clamping devices with constant force or pressure is desired to solve the problem. This paper proposed a C-shaped component using superelastic shape memory alloy (SMA) sheet to realize constant force clamping. Optimization design of the component was carried out with computational simulation. Numerical results show that approximately constant force can be obtained by varying the initial shape, the end width and the end thickness of the SMA sheet.

Constant-stress phenomenon is an unique property of shape memory alloys (SMAs) and could be widely used in designing surgical devices. It is easily obtained by stretching a SMA wire, but for SMA strips little work has been done. This paper presents a design of constant-force elements by bending superelastic SMA strips. The numerical results show its feasibility for practical use.

This paper proposes a Sensorless Field Oriented Control for surface mounted permanent magnet synchronous motor combining two approaches for different rotor speed ranges. The active flux observer is applied at low speed and combined with a back-EMF observer at high speed. This combination allows for an improvement of the rotor position estimation for a large speed range and is therefore resulting in a higher stability of the sensorless control scheme when compared to the conventional back EMF method. The presented approach is discussed based on simulations.

We have developed a high-frequency pulsed power generation system using either ten or twenty MOSFETs in series. The operation principle of the circuit was elucidated, and the experimental results confirmed the operation of the developed circuit. When twenty MOSFETs were used, repetitive operation was achieved at an output voltage of 10 kV and a frequency of 1 kHz. A preliminary experiment on underwater pulsed electrical discharge is performed, and the occurrence of underwater pulsed electric discharge was confirmed.

Superconducting technology has been significantly improved since the superconductor Y-Ba-Cu-O was discovered. This technology has been applied to many medical image-processing applications such as magnetoencephalogram (MEG) and magnetic resonance imaging (MRI). Because the superconducting phenomenon occurs at extremely low temperatures, liquid helium or liquid hydrogen is essential to obtain a low-temperature environment. In addition, it is well known that the decompression of the liquid helium creates superfluid helium. This phenomenon improves the performance of the superconducting devices. For that reason, a vacuum pump, which can be used at a cryostat, is required.

In this paper, we propose a motor that has a small size and simple structure for use in the cryostat. The proposed motor consists of an axial self-bearing motor, superconducting magnetic bearings, and permanent-magnet repulsive-type passive magnetic bearings. The design of the motor and control method is introduced. The experimental results show that the proposed motor has a high possibility for high-speed rotation at extremely low temperatures.

Magnetostrictive (MS) materials exhibit a large strain and a high energy-density, because of their large MS coupling coefficient. In particular, an MS actuator that uses Terfenol-D generates great-force and strain. The efficiency of an MS actuator is highly dependent on the pre-stress, magnetic field intensity, magnetic bias and thermal expansion. The specific type or shape of permanent magnet (PM) needed for a given magnetic bias is determined using numerical simulation. According to magnetic field the heat created by resistance influences the thermal expansion. This paper proposes the optimal exterior PM for achieving a magnetic bias and minimizing the ohmic heat effect with a geometric composite of an electromagnet considered to be a practically precise MS actuator.

We proposed a microprocessing method using a magnetic compound fluid for the inner surface of a tube made of a material that is difficult to cut, and clarified the processing characteristics and magnetic field distribution of the tool. The tool inserted into the tube comprises a stack of ring-shaped permanent magnets with spacers between them. There is an almost proportional relationship between the amount of material removed and the processing time, and the processed surface acquires a mirror finish. Moreover, for tools with shorter permanent magnets, the circularity is improved by processing.

Prosthetic socket is the only channel for load transfer between limb stump and prosthetic limb, so its design is most important in meeting the requirements of comfort and function. In order to improve comfort and functionality of the upper-limb prosthetic socket, this paper presents a novel design concept of the socket in which the areas and working time of compression can be alternated in needs. A physical model of prosthesis socket with four pressure-adjustable chambers driven by a vacuum pump was designed to form pressure units in the socket to simulate its function in changing compression loads.The effectiveness of the design was proved by experiments.

In this paper an approach is proposed for the taking into account of the displacement of the probe in the finite element simulation of eddy current testing. The proposed approach allows to reduce the difficulties associated to the finite element meshing. The computations are performed using two finite element formulations. Two test ECT problems are proposed. Numerical results are compared with experimental data.

This paper deals with the comparative numerical study of repulsive forces acting on a rectangular aluminum plate by using two methods of magnetic levitation (maglev) – conventional ac induction type maglev and ac ampere type maglev proposed by the authors. We made up three-dimensional finite element models for these maglev methods and evaluated calculated repulsive forces in each axis of orthogonal coordinates. As a result, we achieved computer-aided visualization of eddy current in a levitated aluminum plate and magnetic flux around the plate. In addition, we found that the stability in the guidance direction is fully maintained in both methods, and the repelling force of ac ampere type maglev in the conveyance direction decrease compared to that of ac induction type maglev.

The magnetic properties of electrical steel sheet deteriorates due to residual stress, which occurs during the manufacturing process. Therefore, it is important to know the relationship between the magnetic property and the residual stress in order to utilize electrical steel sheets effectively. This paper presents the effect of residual stress on the magnetic properties of motor cores in a rotating machine. First, the local residual stress distribution of the motor core is measured using an X-ray stress measurement system. Next, the magnetic properties of the motor cores for the different residual stress distributions are measured using a single sheet tester. Based on these results, the maximum permeability and magnetic power loss differed depending on the sample, each of which had a different residual stress. In addition, we attempt to measure the inductance of the motor core in order to easily evaluate the magnetic property. The difference in the inductance of each sample was obtained based on the excitation voltage and frequency measured using an LCR meter. It is very useful to evaluate the inductance in order to easily determinine the difference in the residual stress.

Haptic devices using asymmetric drive have been attracting attention. We have been studying 2-DOF haptic devices using a 2-DOF oscillatory actuator that can independently output asymmetric acceleration waveforms in 2 axes. This paper presents a new 2-Degree-of-freedom (DOF) linear oscillatory actuator. First, its static characteristics are computed by 3-D finite element method (FEM). Then, the dynamic characteristics of the actuator under asymmetric acceleration drive are clarified through FEM analysis and finally compared with measurements on a prototype.

This paper discusses material aging diagnosis what uses a non-destructiveness evaluation system. The diagnosis is based on magnetic characteristics of material. It is well known that the magnetism of strong magnetic materials is extremely sensitive with respect to the change of microstructure and to residual-stress variation. For example, coercive force and minor-loop coefficients have shown a linear relationship with rolling reduction. We have proposed a method what is an impedance measurement of a sensor. The method needs a magnetizer with one coil and an impedance meter. The method is simpler than a method what use coercive force. We have compared the method with a method what is a measurement of coercive force. Relationship between strain of carbon steels and experimental results of using coercive force or impedance measurements has measured. Carbon steel sample specimens with some strain loading in the experiment have been used. The experimental results have shown that the method can detect strain of steel just like a method of using a coercive force measurement.

Non-destructive inspection is an important technique in the maintenance of plants and factories. It is necessary to appropriately evaluate the reliability of non-destructive inspection techniques. This study focuses on a reliability evaluation method for nondestructive inspections. The reliability method uses the probability of detection (POD) as a metric. A POD function is determined based on the thicknesses, signal responses, and a decision threshold for all pipe-wall measurements, and can be reasonably modeled by the cumulative log normal distribution function. In this study, the POD is applied to reliability evaluations of an electromagnetic acoustic transducer (EMAT), which is a non-destructive inspection device. Using the results of experimental measurements, we confirm that the POD can evaluate the reliabilities of EMATs that have different specifications.

The multi-fingered robot hand has much attention in various fields. Many robot hands have been proposed so far and we have developed a hand/arm robot with universal robot hand II. The human type robot like the hand/arm robot can be operated by imitating the human motion. Various types of the human motion capture have been developed. However, it is difficult to capture the twist motion by the conventional motion capture. This paper deals with a motion capture system with inertial measurement units (IMUs). The IMUs are used in order to estimate the joint angles of the operator's hand and arm.

In order to reduce acoustic noises and vibrations of electrical machines caused by magnetostriction, it is necessary to make clear the distribution of magnetostriction on magnetic core. The distribution of magnetostriction has been visualized by measured two-dimensional magnetostriction of electrical steel sheet and vector magnetic characteristics analysis technique. The distributions of vector magnetic characteristics and magnetostriction and the relationship between the magnetic flux density vector and two-dimensional magnetostriction have been made clear in the method.

High speed induction motors have the different design parameters and loss distribution compared with line start induction motor because of various load conditions and inverter-fed supply voltage. Especially harmonic losses and mechanical losses must be considered severely. In order to check the variation of the design parameters in inverter-fed induction motor, these values are compared with those of line start induction motor (sinusoidal supply voltage) at same rated output power. The experimental results are verified through testing prototype of two types of 30 kW induction motor for loss analysis. The amount of harmonic loss is confirmed by calculating the loss differences between operating 4.5 kW induction motor from sinusoidal and inverter-fed supply voltage.

Dissimilar material bonding has recently gained a lot of attention in automotive, marine and defense applications. Nevertheless, a major hurdle limiting the full acceptance of such structural components is the lack of non-destructive evaluation (NDE) technique to evaluate their strength, which depends on the integrity of the bonding layer. In this work, guided wave (GW) inspection with surface-mounted piezoelectric sensors (PZT) was employed along with time reversal for Structural Health Monitoring (SHM) of dissimilar material lap-joints. Baseline-free probability imaging was used to identify the location of artificial disbond. The results of GW inspection were further validated with ultrasonic C-scan. Overall, the technique shows great potential in detection of defects in bonded joints.

Hysteresis is an important nonlinear effect exhibited by the Macro Fiber Composite (MFC) that is testified from experimental study. In order to interpret the characteristic accurately, various models were proposed previously, in which the Bouc-Wen model has gained more interest because of its capability to match a wide class of hysteretic systems. However the model consists of a set of differential equations where multi parameters present need to be estimated simultaneously. In view of this, the present study sets out to propose a more efficient Genetic Algorithm (GA) and a simplified Bouc-Wen model on the one hand, and on the other, the GA is applied to the model to enhance the accuracy and efficiency of the parameter estimation. Finally a large number of experimental data are used to testify the proposed approach more efficient and accurate than the other conventional methods. Also suggested are the implications of the present study on other hysteretic models or other complex mathematical models.

This paper presents a modified Preisach model to describe the nonlinear hysteresis property of Macro Fiber Composite (MFC). In order to apply the proposed model, two necessary and sufficient inherent properties which exist in most piezoelectric materials should be met, which are referred to as the wiped-out and the congruency. By using the hysteresis properties and the identified database, the numerical expressions of the proposed modified Preisach model are presented for different inputs in detail. Then several waveforms of input excitation schemes are experimentally realized in order to demonstrate the effectiveness of the modified Preisach model. The good agreement between the measured and predicted results show that the modified Preisach model is an effective mean for predicting the hysteresis of the MFC actuator system.

Author Index Volume 45 (2014)