Study of the Spinning Mechanism Resulting from Permanent Magnet Linear Actuation

Transcription

1 Materials cience Forum Online: I: , Vol. 721, pp doi:1.428/ 212 Trans Tech Publications, witzerland tudy of the pinning Mechanism Resulting from Linear Actuation Koichi OKA 1, a, Feng U 2,b Akira TURUMI 1,c and Gota AKAMURA 1,d 1 Intelligent Mechanical Engineering, Kochi University of Technology, Miyanokuchi 185, Tosayamadacho, Kamicity, Kochi, , JAPA 2 Mechanical Engineering, henyang University of Technology, 111, henliao West Road, Economic & Technological Development Zone, henyang, 11178, P. R. China a oka.koichi@kochitech.ac.jp, b sunfeng29@gmail.com, c 1454y@gs.kochitech.ac.jp, d 15534t@gs.kochitech.ac.jp Keywords: oncontact pin Drive,, Linear Actuation, IEM Analysis, Remanent Magnetism Model Abstract. This paper describes an analysis of the torque characteristics of a noncontact spinning system using linearly actuated magnets. This noncontact spinning system spins the suspended object (here, an iron ball) without contact by the remanent magnetization and the linear movement of four permanent magnets. In this paper, the remanent magnetization point is modeled, and the rotational torque of this mechanism is calculated by IEM (Integral Element Method) analysis. The rotational torque is also measured using a measurement device with strain gauges. According to the IEM analysis results and the experimental results, the rotational torque characteristics of the noncontact spinning system are discussed. Introduction Many types of noncontact suspension systems and manipulation systems have been proposed using electromagnets and permanent magnets [13]. With the development of highperformance permanent magnets, more and more researchers have focused on magnetic suspension systems using permanent magnets. For example, Oka et al. have proposed an active magnetic levitation system using a permanent magnet and a motion control mechanism [4, 5]. In this system, noncontact levitation was realized by adjusting the magnetic force via the control of the air gap between the permanent magnet and a ferromagnetic suspended object. Mizuno et al. have proposed a magnetic suspension system with a permanent magnet and three fluxpath control modules consisting of a ferromagnetic plate, a voice coil motor (VCM), and a displacement sensor [6]. Ueno and Higuchi presented a magnetic levitation technique using a flux path control method with a composite of magnetostrictive and piezoelectric forces [7]. The authors have proposed a variable flux path control suspension mechanism using a disktype permanent magnet and a rotary motor with a reducer [8]. oncontact spinning systems have been proposed. Ikuta et al. have proposed a noncontact magnetic gear acting as a transmission mechanism [9]. Okada et al. have developed a magnetic bearing mechanism combined with a motor mechanism [1]. The authors have proposed two types of noncontact spinning systems using permanent magnets. One system uses rotational disk magnets to vary the magnetic flux field around the suspended object [11]; the other system uses linearly actuated magnets to approach the suspended object [12]. Using these two spinning systems, the suspended objects (iron balls) have been spun successfully without contact. The analysis of the rotational torque characteristics of the later system using linearly actuated magnets has been performed. However, the iron ball could not be spun [13]. All rights reserved. o part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania tate University, University Park, UA9/4/16,2:36:4)

2 256 Applied Electromagnetic Engineering for Magnetic, uperconducting and ano Materials In this paper, the prototype and the spinning principle are introduced. Based on a simplification of the remanent magnetization on the surface of the iron ball, the IEM analysis model is created, and the rotational torque of the noncontact spinning system is calculated in several cases for the number and the position of the remanent points. In addition, a measurement device that is similar to the analysis model is set up using strain gauges, and the measurement experiment is carried out. The models of the remanent magnetism on the iron ball that can cause spinning are explored. Experimental Prototype and pinning Principle Fig. 1 shows the configuration of the noncontact spinning system using linearly actuated magnets. The mechanism has two parts: one is a suspension part, which consists of a permanent magnet, a voice coil motor and two eddy current sensors, and the other is a spinning part, which consists of four permanent magnets and four VCMs. The spinning part surrounds the device, as shown in Fig. 1 and consists of four of the same independent units. The magnet is installed on a linear actuator and is driven to approach and move away from the suspended iron ball. The principle of the spinning mechanism can be understood from Fig. 2. The suspended object in the center of the figure is an iron ball on which there exists remanent magnetization points. This remanent magnetization causes the ball to rotate about the vertical axis due to its attraction to the approaching magnet. The figure shows that magnet I approaches the iron ball. When the magnet is near the ball, the remanent is attracted to the nearest magnet. ext, magnet I moves away from the ball, and magnet II approaches the ball. This time, the stable point will be at the position facing magnet II. Theoretically, repetitions of this approachdepart cycle of the four magnets can make the iron ball spin. permanent magnet 1 IV I 4 2 Y X remnat remanent magnetization 3 II iron ball III movement of permanent magnet spinning movement of iron ball Fig. 1 oncontact spinning system Fig. 2 Principle of spinning The control block diagram of this spinning system is shown in Fig. 3. Four controllers are used in the block diagram, and each feedback loop is independent. Four magnets are driven to move by sine waves that have the same amplitude, the same frequency, and different phases. The phase difference between two adjacent magnets is 9 degrees. As a result, the four magnets approach the iron ball in turn. Consequently, based on the repetition of this approach and the separation, the point of magnetization continuously faces the nearest magnet, and the ball is rotated. Remanent Point Examination and Modeling Remanent Point Examination. Fig. 4 shows real remanent magnetization on the surface of the suspended iron ball. The magnetic flux density along the equator near the surface of an iron ball was measured by a Gauss meter. Before the measurement experiment, the iron ball was suspended with

3 Magnetic Flux Density [mt] a Materials cience Forum Vol the suspension system. The measurement was performed over two revolutions of the iron ball. The point with a large magnetic flux density is labeled the pole, and the point with a small magnetic flux density is labeled the pole. On the basis of this result, the existence of the remanent magnetization points on the surface of the iron ball is demonstrated. ystem (X1) ystem (Y1) 1. ystem (X2) ystem (Y2) Rotational Angle [pi rad.] Fig. 3 Block diagram of the spinning system Fig. 4 Magnetic flux density along the equator Modeling of a Remanent Point. The strength of the remanent magnetization point on the surface of the iron ball is very weak, and the rotational torque of the iron ball cannot be analyzed directly. To examine the rotational torque of the spinning mechanism, we assumed a remanent magnetization point could be represented by a permanent magnet. First, we made a model of the iron ball that has two remanent points, as shown in the right of Fig. 5. One is located on the top of the iron ball and generates the suspension force. The other is located on the equator of the iron ball and generates the rotation torque. As shown on the left side of Fig. 5, each remanent point is represented by one magnet whose one pole is located on the surface of the iron ball, and the other pole of the magnet is located at the center of the iron ball. As a result, the remanent point is modeled as if it were located on the top surface and the pole remanent point were located on the equator of the iron ball. X Z Y Remanent magnetization for suspension Permanent magnet z o x y Lsinφ II III θ I Iron ball P Remanent magnetization for rotation Fig. 5 A model of a remanent magnetization point IV Lsinφ Fig. 6 IEM analysis model IEM Analysis to Determine the Rotation Torque and the table Point IEM Analysis. For the magnetic analysis, we use the IEM analysis software ELF/MAGIC, which is produced by ELF Corporation [14]. Fig. 6 shows the analysis model with one remanent magnetization point along the equator of the iron ball. In the model, we assume that the rotational angle of the iron ball is expressed as θ and the drive angle of the magnets for rotation is expressed as

4 θ Rotational angle of ball (Degree) Rotational torque (m) Rotational torque (m) 258 Applied Electromagnetic Engineering for Magnetic, uperconducting and ano Materials φ. In addition, the movement amplitude of the magnets used for rotation is represented by L. The distance between the center of the iron ball and the movement center of the magnets is P. The diameter and the length of the magnet regarded as the remanent magnetization point are 5 mm and 15 mm, respectively. The size of the magnet used for rotation is the same as those used in the experimental prototype. Using this analysis model, the rotational torque was calculated. Because the magnets were driven by sine waves with phases of 9 degrees, the analysis started from the position when the remanent magnetization was facing the nearest magnet. When the remanent magnetization rotated in steps of 5 degrees from to 36 degrees, the rotational torque was calculated at each step. Then, the magnets were driven in steps of 3 degrees until 36 degrees had been completed. From the result of the torque, we considered the stable angle in each magnet arrangement of φ. The stable angle is fixed by the angle in which the torque is zero and the torque line is downward to the right. One Remanent Point Model. In the case of L=4 mm and P=26 mm, the results of the torque were calculated as shown Fig. 7. As shown in the figure, the stable point is concentrated at 4 points; thus, the iron ball could not be spun. In the case of L=1 mm and P=2 mm, the results of the torque lines are shown in Fig. 8, and the stable angles are shown in Fig. 9. In this case, the stable angle changes according to the magnet arrangement φ. We can spin the iron ball. However, the spinning motion may not be smooth, and cogging torque seems to be present φ Angle of permanent magnets (Degree) θ Rotational angle of iron ball (Degree) Fig. 7 IEM result (L=4 mm, P=26 mm) θ Rotational angle of iron ball (Degree) Fig. 8 IEM result (L=1 mm, P=2 mm) Fig. 9 table Points of Fig. 8 X Z Y θ A B α D D=2mm L=1mm α=45 Fig. 1 Two remanent points model Various Remanent Points Model. We examined the various remanent models. Two types of two remanent points models are introduced. One model places the two remanent points on the equator. The other model has two remanent points at 45 degrees latitude. These models are represented by Fig. 1 and Fig. 13. The results of the torque and the stable points are shown in Fig. 11 and Fig. 12 and in Fig. 14 and Fig. 15, respectively. As shown in the figures, the iron ball can be spun smoothly when the number of remanent magnetization points is equal to two.

5 Rotational torque (m) θ Rotational angle of ball (Degree) Materials cience Forum Vol θ Rotational angle of iron ball (Degree) Fig. 11 IEM analysis results of Fig. 1 Fig. 12 table point of Fig. 1 Fig. 13 Two remanent points model Fig. 14 IEM torque analysis of Fig. 13 Fig. 15. table point of Fig. 13 ummary In this paper, the prototype and the spinning principle of the noncontact spinning mechanism using linearly actuated magnets were introduced. The remanent magnetization point was simplified, and the IEM analysis for rotational torque performance was carried out with several assumed models. The IEM analysis results indicate that the large movement amplitude of linearly actuated magnets and the large distance between the iron ball and the magnets can make the iron ball spin. Moreover, the two remanent points will yield a better rotational performance. In addition, a measurement device was installed with one remanent magnetization point, and the rotational torque was measured

6 26 Applied Electromagnetic Engineering for Magnetic, uperconducting and ano Materials experimentally. The experimental results indicated that all of the IEM analysis results were available. Finally, in addition to the models discussed in this paper, there will be many complex models that can spin the iron ball successfully. References [1] B.V. Jayawant, Electromagnetic levitation and suspension techniques, Edward Arnold, London, [2]. Kurita, T. Ishikawa, and Y. Okada, Development of Lorentz Force Type Magnetic Bearing, Materials cience Forum, Vol. 67 pp , 21 [3] T. Ohji, T. hinkai, K. Amei, and M. akui, Application of Lorentz force to a magnetic levitation system for a nonmagnetic thin plate, Proceedings 4th JapaneseMediterranean Workshop, Cairo, 25 [4] K. Oka and T. Higuchi, Magnetic Levitation ystem by Reluctance Control: Levitation by Motion Control of, International Journal of Applied Electromagnetics in Materials, Vol. 4, pp , [5] K. Oka and F. un, Zero Power Control for Mechanical Magnetic uspension ystem Using pring Force, Proceedings of 6th JapaneseMediterranean Workshop, Bucharest, pp , 29 [6] T. Mizuno, Y. Hirai, Y. Ishino and T. Misuno, FluxPath Control Magnetic uspension ystem Using Voice Coil Motors, Journal of ystem Design and Dynamics, Vol.1, o.2, pp , 27 [7] T. Ueno, J. Qiu, J. Tani, Magnetic Force Control Based on the Inverse Magnetostrictive Effect, IEEE Trans. on Magnetics, Vol.4, o.3, pp , 24 [8] F. un, K. Oka, and Y. aibara, Magnetic uspension ystem by Flux Path Control Using Rotary Actuator, Proceedings of 14th International ymposium on Applied Electromagnetics and Mechanics, pp.28929, Xi an, China, 29. [9] K. Ikuta,. Makita and. Arimoto, oncontact Magnetic Gear for Micro Transmission Mechanism, Proceedings of the 1991 IEEE Micro Electro Mechanical ystem, pp.12513, ara, Japan, (1991) [1] Y. Okada, H. Miyazawa, R. Kondo and M. Enokizono, Proposal of Flux Concentrated Radial and Axial Magnetic Bearings, Materials cience Forum, Vol.67, pp , 21 [11] Feng U and Koichi OKA, oncontact pinning Mechanism Using Rotary Permanent Magnets, IEEJ Transactions on Industry Applications, Vol.13, o.7, pp , (217) [12] Y. Fujiwara, T.. Cui, L Chen and K. Oka, Manipulation by Linear Driving Permanent magnet Rotation Control of Ironball, Journal of the Japan ociety Applied Electomagnetics and Mechanics, Vol. 14, o. 1 pp , 26, (in Japanese) [13] Feng U, Akira TURUMI and Koichi OKA, Torque Analysis of a oncontact pinning ystem Using Linearly Actuated magnets, Proceeding of AsiaPacific ymposium on Applied Electromagnetics and Mechanics 21, pp.1819, Kuala Lumpur, Malaysia, (217). [14] ELF Corporation,

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