Hiroyuki Wakiwaka

Eddy-current testing probe with spin-valve type GMR sensor for printed circuit board inspection

This paper proposes an eddy-current testing (ECT) probe composed of a spin-valve giant magnetoresistance (SV-GMR) sensor and a meander coil for the inspection of bare printed circuit board. The SV-GMR sensor serves as a magnetic sensor for the ECT probe to sense the variation of the magnetic field distribution occurred on the printed circuit board. The SV-GMR sensor is used specifically to detect the changing magnetic field distribution occurred at the defect point. The characteristics of the proposed probe are discussed in this paper. The comparisons of signal-to-noise ratios obtained from ECT probe with SV-GMR sensor and with solenoid coil verify that the applying of SV-GMR sensor to the ECT probe can improve the PCB inspection results.

New magnetostrictive type torque sensor for steering shaft

Abstract When measuring torque, there are many demands, such as non-contact to the shaft, a small size, and a simple installation. Other critical factors include, special processing in the shaft, which is not required, and being cost-effective. Therefore, we have proposed a new magnetostrictive type torque sensor [IEEE Trans. Mag. 35 (1999) 4503] (MTS) for a steering shaft using an inverse magnetostrictive effect. Generally, a magnetostrictive type torque sensor has a large hysteresis property. With this sensor, we have shown that the hysteresis can be drastically decreased, if the excitation magnetic field double the value or more of the coercive force of the shaft material is applied.

Design of linear DC motor for high-speed positioning

Abstract Miniaturization, increased speed, and higher accuracy for industrial positioning devices have recently been the main requests for industrial upgrades. Using linear motors is an effective way to meet these requests. This paper discusses a linear DC motor (LDM) for high-speed positioning. One high-speed positioning approach decreases the mechanical time constant for LDMs. The LDM with the smallest mechanical time constant (4.1 ms) was designed and manufactured within the overall dimensions: 72×75×62 mm3. The positioning device with the manufactured LDM positions a 0.2 kg load with 10 mm stroke in 27 ms.

Performance Analysis of Long Distance Transmitting of Magnetic Signal on Cylindrical Steel Rod

The magnetic signal transmission (MST) method is a transmission system in which magnetic flux is distributed over a boring rod (cylindrical steel rod). The boring rod is provided with a transmitting coil and receiving coil. At the tip of the boring rod, a sensor is provided to obtain information from underground. The output signal of the sensor becomes the input of the transmitting coil. Magnetic flux is generated by the current in the transmitting coil. The sensor signal is transmitted to the receiving coil by electromagnetic induction. MST is being developed for long distance transmission. In this paper we describe experiments to assess the performance of MST.

Comparative Evaluation on Power-Speed Density of Portable Permanent Magnet Generators for Agricultural Application

The comparative evaluation based on the power speed density of several types of portable Permanent Magnet Generator (PMG) considered for agricultural applications is presented. These generators are purposely designed to be used in agriculture sectors and thereby it should be of lightweight, small in size and ease to use. Six difierent generator topologies are developed for investigation of such purposes. A number of design parameters are considered to analyze the performance characteristics for each type of developed PMG. Based on the power speed density factor that is used to describe better generator performance, the suitable PMG for the agricultural application is identifled through a comprehensive evaluation.

Consideration of magnetization and detection on magnetic rotary encoder using finite element method

This article shows the results of a feasibility study of a high resolution magnetic rotary encoder. The magnetization and the detection processes of a magnetic rotary encoder were simulated using the finite element method. In addition, experimental considerations have been given to the numerical effect of the parameters on a magneto-resistive (MR) output by a method of double interpolation. The optimum condition of a Z phase (i.e., original point of the rotation) signal obtained for the magneto-resistive output was a magnetization gap 0 /spl mu/m and a magnetization current of 400 mA (i.e., the magnetized state for saturation of the medium). It was analytically determined that an increase in magnetization current or a detection gap reduction saturated the magneto-resistive output voltage. The magneto-resistive output obtained using FEM showed good numerical agreement with experimental results, given conditions when the magnetization current was 200 mA or less. It was an advantage therefore, in the case of the minimum MR element being used with a double interpolation method, to achieve a wider usable detection gap range.

Effect of Inductive Coil Shape on Sensing Performance of Linear Displacement Sensor Using Thin Inductive Coil and Pattern Guide

This paper discusses the effect of inductive coil shape on the sensing performance of a linear displacement sensor. The linear displacement sensor consists of a thin type inductive coil with a thin pattern guide, thus being suitable for tiny space applications. The position can be detected by measuring the inductance of the inductive coil. At each position due to the change in inductive coil area facing the pattern guide the value of inductance is different. Therefore, the objective of this research is to study various inductive coil pattern shapes and to propose the pattern that can achieve good sensing performance. Various shapes of meander, triangular type meander, square and circle shape with different turn number of inductive coils are examined in this study. The inductance is measured with the sensor sensitivity and linearity as a performance evaluation parameter of the sensor. In conclusion, each inductive coil shape has its own advantages and disadvantages. For instance, the circle shape inductive coil produces high sensitivity with a low linearity response. Meanwhile, the square shape inductive coil has a medium sensitivity with higher linearity.

Double Side Interior Permanent Magnet Linear Synchronous Motor and Drive System

Linear motor has been applied in various fields such as factory and office automation. A linear motor differs from a rotational motor, in which it has a simpler structure. Linear Synchronous Motor is one of the types of linear motor and its application is very wide which is from the small application (i.e. industrials automation) to large application (i.e. maglev transportation) [1]. The thrust which is generated by linear motor is high, even with the size of the motor is small [2]. This is the feature of the linear motor compared to rotational motor where a gear is needed to change the rotational movement to the linear movement. Therefore the linear motor can reduce the mechanical losses. This paper discuss on the proposal of Double Side Interior Permanent Magnet of Linear Synchronous Motor (DIPM-LSM). The structure and three dimensions of magnetic circuit of DIPM-LSM are discussed. This type of DIPM-LSM can be driven by sinusoidal and pulse voltage input. The three phase two coils excitation-driving mode of open loop drive systems are also been discussed.

Index phase output characteristics of magnetic rotary encoder using a magneto-resistive element

The purpose of this paper is to develop a magnetic rotary encoder with a resolution more than 4000 pulses per revolution in a magnetic drum with a diameter of 35 mm. The required resolution is more than 2000 pulses per revolution. As the resolution increases, ever greater accuracy is needed in the index phase to detect the original position of the encoder. To stabilize the index pulse, the authors took into account the width of the magneto-resistive element and the magnetization current wave form. As a result, the index pulse has been extremely steady in the magneto-resistive element with a width of 20 /spl mu/m. It is pointed out that a pulse width of less than 6.9 /spl mu/m is necessary for 4000 pulses per revolution. Moreover, the usable detection gap could be expanded by magnetizing the drum in a wave form in which both sides of a rectangular wave curved inward.

Magnetic field analysis of a resolver with a skewed and eccentric rotor

Factory automation applications such as machine tools, etc., with high precision motion control require a feedback sensor with low speed-ripple for precise velocity control. The resolver is one of feedback sensors widely used in automation applications. Distorted signal-output related to speed fluctuations of the resolver result from permeance ripples, etc., produced by eccentricity of the rotor and stator slots in which coils are installed, and of the rotor itself. Although the permeance method has been used to analyze and determine the optimal magnetic design of a resolver, it remains an imperfect solution. This paper proposes a new magnetic field analysis method which offers the means to produce better analysis. The most significant feature of our method is that the skewed resolver rotor is divided into segments and the induced voltages of each segments are calculated and combined. Therefore, the analysis of the skew affect and the eccentricity of the rotor becomes possible by using the 2-D FEM (two-dimensional finite element method) with magnetic vector potential. The analyzed results of the spectrum in the induced dual phase voltage waveforms indicate the possibilities of close agreement with the measured values. These results confirm the validity of this method.