Tolerance Analysis of Halbach Array Magnetic Gravity Compensator Using Reluctance-corrected Magnetic Model

J. Jung(정재환),K. T. Yoon(윤경택),Y. M. Choi(최영만) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월

The magnetic spring has been used as a gravity compensator in ultra-precision positioning system or vibration isolator system for semiconductor process, which has a simple structure and can be used in vacuum without mechanical contact. The Halbach array magnetic spring, designed to have quasi-zero stiffness, generates a large levitation force for its volume, and improves control and isolation performance by having a resonance-free characteristic. In many previous studies, the magnetic springs were modeled using surface current model. However, there exists an error in estimating stiffness when compared with finite element model due to inconsideration of permanent magnet reluctance. Furthermore, the geometric tolerances of Halbach array magnetic spring greatly affect the uncertainty of stiffness and force. In this study, a magnetic model considering the magnetic permeability of permanent magnet is proposed. Additionally, tolerance analysis was performed by parametric study and Monte-carlo simulation. Compared with the conventional magnetic model, the stiffness characteristics of the magnetic spring modeled by the proposed magnetic model is closer to that of the finite element model. From the results of tolerance analysis, the dominant tolerance parameters that determines the uncertainty in performance were identified. Through Monte-carlo simulation with 5,000 iterations, statistical estimations of performance variation were obtained.

Modeling of a Dual Stator Induction Generator with and Without Cross Magnetic Saturation

Marwa Ben Slimene,Mohamed Arbi Khlifi,Mouldi Ben Fredj,Habib Rehaoulia 한국자기학회 2015 Journal of Magnetics Vol.20 No.3

This paper discusses general methods of modelling magnetic saturation in steady-state, two-axis (d & q) frame models of dual stator induction generators (DSIG). In particular, the important role of the magnetic coupling between the d-q axes (cross-magnetizing phenomenon) is demonstrated, with and without cross-saturation. For that purpose, two distinct models of DSIGs, with and without cross-saturation, are specified. These two models are verified by an application that is sensitive to the presence of cross-saturation, to prove the validity of these final methods and the equivalence between all developed models. Advantages of some of the models over the existing ones and their applicability are discussed. In addition, an alternative is given to evaluate all saturation factors (static and dynamic) by just calculating the static magnetizing inductance which is simply the magnitude of the ratio of the magnetizing flux to the current. The comparison between the simulation results of the proposed model with experimental results gives a good correspondence, especially at startup.

Modeling of a Scan Type Magnetic Camera Image Using the Improved Dipole Model

Jiseong Hwang,Jinyi Lee 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.10

The scan type magnetic camera is proposed to improve the limited spatial resolution due to the size of the packaged magnetic sensor. An image of the scan type magnetic camera, ∂B/∂x image, is useful for extracting the crack information of a specimen under a large inclined magnetic field distribution due to the poles of magnetizer. The ∂B/∂x images of the cracks of different shapes and sizes are calculated by using the improved dipole model proposed in this paper. The improved dipole model uses small divided dipole models, the rotation and relocation of each dipole model and the principle of superposition. Also for a low carbon steel specimen, the experimental results of nondestructive testing obtained by using multiple cracks are compared with the modeling results to verify the effectiveness of ∂B/∂x modeling. The improved dipole model can be used to simulate the LMF and ∂B/∂x image of a specimen with complex cracks, and to evaluate the cracks quantitatively using magnetic flux leakage testing.

초등 예비교사의 자기 모델 탐구 과정과 과학적 모델에 대한 이해 변화

윤혜경 ( Hye Gyoung Yoon ) 한국초등과학교육학회 2011 초등과학교육 Vol.30 No.3

An alternative vision for science inquiry that appears to be important and challenging is model-based inquiry in which students generate, evaluate and revise their explanatory model. Pre-service teachers should be given opportunities to develop and use their mechanistic explanatory models in order to participate in the practice of science and to have a sound understanding of science. With this view, this study described a case of pre-service elementary teachers` scientific modeling in magnetism. The aims of this study were to explore difficulties pre- service elementary teachers encountered while they engaged in a model-based inquiry, and to examine how their understandings of the nature of scientific models changed after the model-based inquiry. The data analysis revealed that the pre-service teachers had difficulties in drawing and writing their own thinking because they had little experience of expressing their own science ideas. When asked to predict what would happen, they could not understand what it meant to make a prediction "based on their model". They did not know how to use or consider their model in making a prediction. At the end of the model-based inquiry they reached a final consensus of a best model. However, they were very anxious about whether the model was the "correct" answer. With respect to the nature of scientific models, almost all of the pre-service teachers initially viewed models only as a communication tool among scientists or students and teachers to help understand others` ideas. After the model-based inquiry, however, many of them understood that they could create, test, and revise their "own" models "by themselves". They also realized the key aspects of scientific models that a model can be changed as evidence is accumulated and a model is a knowledge production tool as well as a communication tool. The results indicated that pre-service elementary teachers` understandings of the nature of scientific models and their previous school science experiences could affect their performance on a model-based inquiry, and their experience of scientific modeling could help them enhance their understandings of the nature of scientific models.

Magnetic Characteristic Analysis of Permanent Magnet Motor with Complex E&S Modeling

Zeze, Shingo,Todaka, Takashi,Enokizono, Masato Journal of International Conference on Electrical 2012 Journal of international Conference on Electrical Vol.1 No.1

This paper presents analyzed results of a permanent magnet motor by using complex E&S modeling. The calculated results are compared with ones from the conventional E&S modeling for verification. Combinations of the numbers of slots and poles are investigated to reduce total iron loss. The results demonstrate that the complex E&S modeling is very useful in design under consideration of rotational magnetic field and magnetic anisotropy.

A combined theoretical and in vitro modeling approach for predicting the magnetic capture and retention of magnetic nanoparticles in vivo

David, A.E.,Cole, A.J.,Chertok, B.,Park, Y.S.,Yang, V.C. Elsevier Science Publishers 2011 Journal of controlled release Vol.152 No.1

Magnetic nanoparticles (MNP) continue to draw considerable attention as potential diagnostic and therapeutic tools in the fight against cancer. Although many interacting forces present themselves during magnetic targeting of MNP to tumors, most theoretical considerations of this process ignore all except for the magnetic and drag forces. Our validation of a simple in vitro model against in vivo data, and subsequent reproduction of the in vitro results with a theoretical model indicated that these two forces do indeed dominate the magnetic capture of MNP. However, because nanoparticles can be subject to aggregation, and large MNP experience an increased magnetic force, the effects of surface forces on MNP stability cannot be ignored. We accounted for the aggregating surface forces simply by measuring the size of MNP retained from flow by magnetic fields, and utilized this size in the mathematical model. This presumably accounted for all particle-particle interactions, including those between magnetic dipoles. Thus, our ''corrected'' mathematical model provided a reasonable estimate of not only fractional MNP retention, but also predicted the regions of accumulation in a simulated capillary. Furthermore, the model was also utilized to calculate the effects of MNP size and spatial location, relative to the magnet, on targeting of MNPs to tumors. This combination of an in vitro model with a theoretical model could potentially assist with parametric evaluations of magnetic targeting, and enable rapid enhancement and optimization of magnetic targeting methodologies.

Modeling of a Scan Type Magnetic Camera Image Using the Improved Dipole Model

Hwang Ji-Seong,Lee Jin-Yi The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.10

The scan type magnetic camera is proposed to improve the limited spatial resolution due to the size of the packaged magnetic sensor. An image of the scan type magnetic camera, ${\partial}B/{\partial}x$ image, is useful for extracting the crack information of a specimen under a large inclined mag netic field distribution due to the poles of magnetizer. The ${\partial}B/{\partial}x$ images of the cracks of different shapes and sizes are calculated by using the improved dipole model proposed in this paper. The improved dipole model uses small divided dipole models, the rotation and relocation of each dipole model and the principle of superposition. Also for a low carbon steel specimen, the experimental results of nondestructive testing obtained by using multiple cracks are compared with the modeling results to verify the effectiveness of ${\partial}B/{\partial}x$ modeling. The improved dipole model can be used to simulate the LMF and ${\partial}B/{\partial}x$ image of a specimen with complex cracks, and to evaluate the cracks quantitatively using magnetic flux leakage testing.

Magnetization Characteristics Analysis in a Pole Changing Memory Motor Using Coupled FEM and Preisach Modeling

Jung Ho Lee,Seung Chul Lee 한국자기학회 2011 Journal of Magnetics Vol.16 No.4

This paper deals with the magnetic equivalent circuit modeling and permanent magnet (PM) performance evaluations of a pole changing memory motor (PCMM). We use a coupled transient finite element method (FEM) and Preisach modeling, which is presented to analyze the magnetic characteristics of the permanent magnets. The focus of this paper is on the evaluation of characteristics such as the magnetizing direction and the pole number of the machine under re- and de-magnetization conditions.

System Modeling and Robust Control of an AMB Spindle : Part I Modeling and Validation for Robust Control

Ahn, Hyeong-Joon,Han, Dong-Chul The Korean Society of Mechanical Engineers 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.12

This paper discusses details of modeling and robust control of an AMB (active magnetic bearing) spindle, and part I presents a modeling and validation process of the AMB spindle. There are many components in AMB spindle : electromagnetic actuator, sensor, rotor, power amplifier and digital controller. If each component is carefully modeled and evaluated, the components have tight structured uncertainty bounds and achievable performance of the system increases. However, since some unknown dynamics may exist and the augmented plant could show some discrepancy with the real plant, the validation of the augmented plant is needed through measuring overall frequency responses of the actual plant. In addition, it is necessary to combine several components and identify them with a reduced order model. First, all components of the AMB spindle are carefully modeled and identified based on experimental data, which also render valuable information in quantifying structured uncertainties. Since sensors, power amplifiers and discretization dynamics can be considered as time delay components, such dynamics are combined and identified with a reduced order. Then, frequency responses of the open-loop plant are measured through closed-loop experiments to validate the augmented plant. The whole modeling process gives an accurate nominal model of a low order for the robust control design.

Fast Analytical Modeling and Analysis of Flux Focusing Disk-Type Permanent Magnet Eddy Current Couplings

Dazhi Wang,Zhao Li 한국자기학회 2018 Journal of Magnetics Vol.23 No.2

This paper presents an improved 2-D analytical model to predict the magnetic field distributions and torque characteristics for a flux focusing disk-type permanent magnet eddy current coupling. Due to the inhomogeneous physical properties in the permanent magnet regions, based on the equivalent magnetic circuit method, a fictitious magnetization for the iron cores is introduced to simplify the complexity of modeling. The magnetic flux density distributions are derived when the eddy current generated in the copper plate and its back iron is reasonably concerned in 2-D Cartesian coordinates. Then, the explicit expression of torque is given and the torque-speed characteristics are analyzed. In the end, the calculated results of the proposed model are compared with those obtained from the magnetic equivalent circuit model and 3-D finite-element simulations.