Experimental Evaluation of New Magnetic Movement Converter for Linear Oscillatory Actuator

Transcription

1 APAEM14 Journal of the Japan ociety of Applied Electromagnetics and Mechanics Vol.23, o.3 (215) Regular Paper Experimental Evaluation of ew Magnetic Movement Converter for Linear Oscillatory Actuator Fumiya KITAYAMA*1, Katsuhiro HIRATA*1, oboru IGUCHI*1 and Tatsuro YAMADA*1 In this paper, we propose a new magnetic movement converter for linear oscillatory actuators. The proposed magnetic movement converter can convert a rotational motion into a linear motion, and reduce the load torque on a rotor, and the armature is oscillated with fewer harmonics. First, the basic construction and the operation principle are described. ext, we confirm its characteristics through FEM analysis and measurement on prototypes. Keywords: Linear oscillatory actuator, magnetic movement converter, load torque reduction, harmonics reduction, FEM. (Received: 24 July 214) 1. Introduction Recently, active control engine mounts (ACMs) employing linear oscillatory actuators have been mounted between an engine and an automobile frame to reduce a frame vibration. There are many requirements for linear oscillatory actuators: high thrust, low friction losses, low manufacturing costs, low noises and small size, and various kinds of linear oscillatory actuators have been developed [1-4]. In order to reduce the costs, we proposed a simple linear oscillatory actuator using a DC motor and a magnetic movement converter (MMC). The MMC is a device converting a rotational motion into a linear motion, as shown in Fig. 1 [5,6]. The linear oscillatory actuator oscillates when the DC motor rotates. And, the linear oscillatory actuator can be cheaply manufactured because of the use of the DC motor. However, this actuator had two problems: large load torque and harmonics in the actuator s oscillation. If a load torque on the DC motor is large, the size of the DC motor has to be increased accordingly, causing an increase in the size of the overall system. Also, due to the harmonics in the actuator s oscillation, new vibration frequencies will be inadvertently added to the automobile frame. And, these problems are caused by the MMC. In this paper, these problems of the conventional MMC are evaluated, and a new MMC are proposed [7]. And, the characteristics of MMCs are verified through FEM analysis and measurement on prototypes in order to clarify the effectiveness of the proposed MMC. prings Magnets with Yokes z Fig. 1. MMC. 2. Magnetic Movement Converter As shown in Fig. 1, a conventional MMC which we Correspondence: F.KITAYAMA, Department of Adaptive Machine systems, Graduate school of Engineering, Osaka University, Yamadaoka 2-1, uita, Osaka, Japan fumiya.kitayama@ams.eng.osaka-u.ac.jp *1 first proposed (basic MMC) is composed of an armature, a rotor and springs. The rotor and the armature are faced with an initial air-gap length. The armature is composed of a 4-pole permanent magnet with a yoke and an output shaft, and the output shaft is connected to the springs. The armature is fixed so that it cannot rotate but can only move in a linear direction. The rotor is also composed of a 4-pole permanent magnet with a yoke, and it is connected to a shaft of a motor. Fig. 2 shows the operational principle of the basic MMC. The armature reciprocates in a linear direction by rotating the rotor due to attractive and repulsion forces between the permanent magnets as shown in Fig.2 (a). However, large load torques is also generated in the Osaka University (93) Attractive force s (a)when thrust is (b) When load torque generated. is generated. Fig. 2. Operational principle of the basic MMC. 527

2 日本 AEM 学会誌 Vol. 23, o.3 (215) motor when the angle difference between armature magnetic poles and rotor magnetic poles is 45 degrees as shown in Fig.2 (b). In the basic MMC, the air-gap length is changed when the armature is moved, and the thrust is also changed. Then, the thrust variation against the armature position affects the oscillation, and the oscillation contains harmonics. 3. ew Magnetic Movement Converter Fig. 3 shows the newly proposed MMC. The MMC is composed of an armature, a rotor and springs. The armature is placed inside the rotor. At an initial position, the air gap length between the armature and the rotor is 2 mm each. The armature is composed of a 4-pole permanent magnet and an output shaft as shown in Fig. 3 (b), and it is fixed so that it cannot rotate. The output prings shaft is fitted with the springs. The rotor is composed of two sets of 4-pole permanent magnets, yokes and nonmagnetic material. The rotor permanent magnets are connected to each other through the non-magnetic plates as shown in Fig. 3 (c). The rotor is directly connected to the shaft of a motor. Outer diameters of permanent magnets and yokes are 18 mm, and inner diameters of permanent magnets and yokes are 1 mm, and heights of permanent magnets and yokes are 3 mm. Fig. 4 shows the operational principle of the proposed MMC. This principle is the same as that of the basic MMC. In the proposed MMC, load torques on the motor are reduced because torques generated in the rotor A and B are cancelled with each other, as shown in Fig. 4 (b). Also, a total air-gap length of the proposed MMC is constant regardless of the armature position. From this, a constant thrust with respect to the armature position is obtained, and harmonics in the oscillation are also reduced. s (a) Overall. 4. Evaluation by Analyses In order to verify the effectiveness of the proposed MMC, the static and dynamic characteristics are investigated through FEM analysis. First, tatic thrusts and static load torques were computed by 3-D FEM [6]. Fig. 5 shows the computed ( A) z ( B) Magnet (b). on-magnetic material Magnets Yokes Attractive force Repulsive force (a) When a thrust is generated to an armature. A B (c). Fig. 3. ewly proposed actuator. s (b) When load torque are reduced. Fig. 4. Operational principle of the proposed MMC. 528

3 日本 AEM 学会誌 Vol. 23, o.3 (215) static thrusts and load torques against the rotor angle when the armature position is fixed. As we can see in Fig. 5 (a-i) and (b-i), the thrust of the basic and proposed MMCs at the initial armature position are almost the same at about 4. Additionally, the load torque of the proposed MMC is close to although that of the basic MMC is 15 mm. This is because the Table 1 pecification of prototype of basic MMC. pring constant 61.4 /mm Mass of armature 85.3 g Viscous damping coefficient 23. s/m Table 2. pecification of the proposed MMC. pring constant 58.3 /mm Mass of armature 82.6 g Viscous damping coefficient 3.6 s/m (a-i) The armature position is mm torques of rotor A and B cancel each other out. In comparison with Fig. 5 (a-ii) and (b-ii), the thrust of the proposed MMC are higher than that of the basic MMC, and the load torque of the proposed MMC is smaller that of the basic MMC. However, in the proposed MMC, the load torques on rotors A and B at shifted armature positons do not completely cancel each other out and the load torque on a motor generates because the load torques on rotors A and B are not the same with each other. The static torques became maximum when the rotor angle was 45 degree, and the static thrusts became maximum when the rotor angle was 9 degree because magnets are four poles. Fig. 6 shows the maximum load torque and the maximum thrust against the armature position. As we can see in Fig. 6, the load torque of the proposed MMC is reduced by 165 mm (maximum value) compared with that of the basic MMC at all armature positions. Also, the thrust variation against the position of the proposed MMC is reduced by 8% against that of the basic MMC, because a total air-gap length of the proposed MMC is constant. A dynamic analyses using Matlab/imulink and 3- D FEM analysis was conducted to investigate the dynamic characteristics of these MMCs [8]. In analyses, an equation of motion is calculated through Matlab/imulink when the rotor is rotated at a constant speed of about 18rpm. In this calculation, the thrusts and the load torques of MMCs are obtained using the (a-ii) The armature position is 1mm. (a) The basic MMC. (only rotor A) (only rotor B) (b-i) The armature position is mm. (only rotor A) (only rotor B) (a) Maximum torque (b-ii) The armature position is 1mm. (b) The proposed MMC. Fig. 5. tatic characteristics vs. rotation angle (b) Maximum thrust. Fig. 6. tatic characteristics vs. armature positon. 529

4 日本 AEM 学会誌 Vol. 23, o.3 (215) static characteristics calculated by 3-D FEM. The specifications of the basic and proposed actuators are shown in Tables 1 and 2. Results of the dynamic analyses are shown in Fig. 7. As shown in Fig. 7 (a) and (b), the maximum load torque of the proposed MMC is reduced by 59 %, and it is much smaller than the basic MMC. And, harmonics of the proposed MMC was less than the basic actuator because the proposed MMC has a nearly constant thrust with respect to the position. are manufactured in order to evaluate the characteristics by carrying out measurements. Fig.8 and 9 show our prototypes. These are mainly composed of armatures, rotors, stators and springs. s are composed of Bearings Linear bearing 5. Experimental Evaluation 5.1 Prototype tator prings Prototypes of the basic MMC and proposed MMC 6, (a) Overall. Magnet with Yoke (a). 1.5 PTFE part Position,mm (b) position. 15 (b). Torque,mm haft Magnet with Yoke (c). Fig. 7. Dynamic characteristics. (c). Fig. 8. Prototype of the basic MMC. 53

5 日本 AEM 学会誌 Vol. 23, o.3 (215) Magnet PTFE part Bearings haft tator (a) Overall. (b). Linear bearing prings Magnets with Yokes permanent magnets, yokes, output shafts and polytetrafluoroethylene parts (PTFE parts), and there are supported by linear bearings. PTFE parts of armatures are a square shape and slide in square shaped stators. s are composed of permanent magnets, yokes and shafts, and there are supported by bearings. hafts of rotors are connected to those of motors. A resonance frequency of the basic MMC is 133 Hz, and that of the proposed MMC is 135 Hz. 5.2 Experimental etup An experiment setup is shown in Fig. 1. First, static load torques and static thrusts were measured by a torque meter and a load cell, respectively, the position and the angle are measured by a displacement meter and a controller. econd, the dynamic armature positon is measured by a displacement meter, when the rotor of the MMC is rotated by the motor at about 18rpm. 5.3 Experimental Results Fig. 11 shows the static load torques and thrusts against the rotor angle when the armature positon is.5 mm. In the proposed MMC, the maximum load torque was 47 mm and the maximum thrust was 41. The load torques of the proposed MMC is smaller than that of the basic MMC, as same as analyzed results. This is because the torques of rotor A and B cancel each other out in the proposed MMC. Fig. 12 shows the maximum load torque and the maximum thrust against the armature position. As we can see in Fig. 12, the maximum load torque of the proposed MMC is lower, and the maximum thrust of the proposed MMC was more constant with respect to the armature position than that of the basic MMC, as same as analyzed results. This is because a total air-gap length of the proposed MMC is constant. ext, the armature position was measured when the rotor was rotated by the motor. The results are shown in Fig. 13. In the proposed MMC, the amplitude is 1.6 mm and the drive frequency is 6 Hz, and harmonics in the oscillation of the proposed MMC is smaller than those of the basic MMC because the static and maximum thrust of the proposed MMC was nearly constant with respect to the armature position, as same as analyzed results. Finally, the measured results almost agreed well with the analyzed results. Errors between the measured and the analyzed results are due to manufacturing errors of prototypes. (c). Fig. 9. Prototype of the proposed MMC. Motor Torque meter MMC Displacement meter Fig. 1. Experiment setup. 531

6 日本 AEM 学会誌 Vol. 23, o.3 (215) () Torque () () Torque () 1.5, Torque, mm Position,mm Fig. 11. tatic characteristics vs. rotation angle Fig. 13. Dynamic characteristics. actuator can oscillate with fewer harmonics. And, in the actuator, we could use a low-power and small dc motor because the new MMC did not generate high load torques. In the future, we will manufacture a new actuator by connecting the new MMC with a dc motor, and apply this actuator to vibration control devices. References (a) Maximum torque (b) Maximum thrust. Fig. 12. tatic characteristics vs. armature positon. 5. Conclusion In this paper, we proposed a new MMC that an armature is placed inside a rotor. From the analysis and the measurement, we could clearly see that the proposed MMC has lower load torques, more constant thrusts against the armature position and fewer harmonics. From these results, it could think that a linear oscillatory actuator using the new MMC and a dc motor is effective to vibration control devices because the [1] Y. akaji,. atoh, T. Kimura, T. Hamabe, Y Akatsu and H. Kawazoe, Development of an Active Control Engine Mount ystem, Vehicle ystem Dynamics, Vol.32, pp , [2] H. Matsuoka, T. Mikasa and H. emoto, V countermeasure technology for a cylinder-on-demand engine - Development of active control engine mount, AE Transactions , 24. [3] B. H. Lee and C. W. Lee, Model Based Feed-forward Control of Electromagnetic Type Active Control Engine- Mount ystem, Journal of ound And Vibration., Vol.323, pp , 29. [4] F. Kitayama, K. Hirata, and M. akai, Proposal of a Two Movers Linear Oscillatory Actuator for Active Control Engine Mounts, IEEE Trans. Magn., Vol.49, o.5, pp , 213. [5] T. Yamaguchi, Y. Kawase,. uzuki, K. Hirata, T.Ota, and Y.Hasegawa, Dynamic Analysis of Linear Resonant Actuator Driven by DC Motor Taking into Account Contact Resistance Between Brush and Commutator, Trans. IEEE Trans. Magn., Vol.44, o. 6, pp , 28. [6] T. Ota, K. Hirata, T. Yamaguchi, and Y. Kawase, ew Linear Oscillatory Actuator Using DC Motor, Trans. IEE Jpn., Vol.126-D, o. 8, pp , 26. [7] F. Kitayama, K. Hirata, M. akai and T.Yamada, Linear Oscillatory Actuator Using ew Magnetic Movement Converter, in Proceedings of IEEE International Conference on Mechatronics and Automation 213, pp , 213. [8] K. Hirata, Y. Ichii, and Y.Arikawa, Linear oscillatory actuator with dynamic vibration control, Trans. IEE Jpn., Vol.122-D, o. 4, pp , 22, (in Japanese). 532