|Yoshihisa Takayama||Last modified date：2021.06.08|
Assistant Professor / Department of Mechanical Engineering / Department of Mechanical Engineering / Faculty of Engineering
|Yoshihisa Takayama||Last modified date：2021.06.08|
|1.||Y. Takayama, S. Kijimoto, S. Ishikawa, Eddy Current Damper Model of Ring Magnet and Coaxially Moving Conducting Disk, IEEE Transactions on Magnetics , 10.1109/TMAG.2021.3058739, 2021.02, An eddy current damper comprising a magnet and a conducting plate moving perpendicularly to it is called a perpendicular-motion-type eddy current damper, whereas one with a magnet and a conducting plate moving parallel to it is called a parallel-motion-type eddy current damper. In this paper, a method of using magnetic vector potentials in a stationary-conductor coordinate system to obtain easily the damping coefficient (the A method) is proposed and applied to a perpendicular-motion-type eddy current damper comprising a ring magnet and conducting disk. The previously proposed coil method is also applied. Because both methods utilize the magnetic flux densities and magnetic vector potentials obtained using a circular current loop, they cannot be considered to be the effect of the magnetic field generated by eddy currents on the damping coefficients. However, the damping coefficients were in good agreement with those obtained using a three-dimensional finite element method (3D-FEM). Hence, the effect of the secondary magnetic field can be ignored. Moreover, the A method is as precise as the 3D-FEM, is less complicated, and does not require an air region and boundary conditions for computation. Additionally, although the errors of the damping ratios calculated from measured data and the A method were 17 %, the error of the modified damping ratios obtained by applying the equivalent mass of the disk to the A method decreased to 6 %..|
|2.||Modeling of magnetic damper composed of ring magnet and coaxially and relatively moving conducting disk considering skin effect.|
|3.||Yoshihisa Takayama, Takahiro KONDOU, Magnetic Damper Consisting of a Combined Hollow Cylinder Magnet and Conducting Disks, Transactions of the ASME, 10.1115/1.4024094, 135, 051007-1, OCTOBER 2013, Vol. 135 / 051007-1
, 2013.10, It is recognized that unstable vibration occurs at a rotating speed above the major critical
speed by a rotating-conducting-disk type magnetic damper, but not by a rotating-circular-
magnet type magnetic damper. In addition, magnetic dampers generally have
relatively poor damping performance. In the present work, two new rotating-circularmagnet
type magnetic dampers, (which consist of a combined hollow cylinder magnet
with alternating directional magnetic poles), are introduced and their design method is
presented. Applying the modeling method that the authors have been studying, a prototype
magnetic damper with a combined magnet is fabricated and the damping ratios from
the analytical results agree well with those from the experimental results. Rotating tests
are performed and it is confirmed that unstable vibration does not occur at a rotating
speed of more than twice the major critical speed. Based on these findings, an optimally
designed magnetic damper with a combined magnet is developed and a damping ratio of
0.25 (damping coefficient of 215 Ns/m) is achieved..
|4.||Study on Magnetic Damper Composed of Combined Magnets
(Magnetic Damper Composed of Basic Halbach Magnet Arrays).
|5.||Magnetic Damper Consisting of Circular Coil and Columnar Magnet.|
|6.||Yoshihisa TAKAYAMA Atsuo SUEOKA Takahiro KONDOU, Modeling of Moving-Conductor Type Eddy Current Damper, Journal of System Design and Dynamics, DOI: 10.1299/jsdd.2.1148, Vol.2, No.5, 1148-1159, Vol.2, No.5, 2008, pp.1148-1159
DOI: 10.1299/jsdd.2.1148, 2008.11.
|7.||Yoshihisa TAKAYAMA Atsuo SUEOKA Takahiro KONDOU, Magnetic Damper Consisting of Spherical Magnet and Conducting Shell, 12th Asia Pacific Vibration Conference, CD-ROM Paper No.20
APVC2007 Program and Abstracts, pp.23, 2007.08.
|8.||Yoshihisa TAKAYAMA Atsuo SUEOKA and Takahiro KONDOU, Modeling of Eddy Current Damper Composed of Spherical Magnet and Conducting Shell, 2006 ASME International Mechanical Engineering Congress and Exposition, IMECE2006-13114, 2006.11.|
|9.||Vibration Reduction of a Rotating Machinery by Magnetic Damper with Rotating Circular Magnet
(Nonoccurrence of an Unstable Vibration Caused by Magnetic Damping Force), Transactions of the Japan Society of Mechanical Engineering, Series C, Vol.70, No.696 (2004), pp.2195-2202, (in Japanese)
|10.||Y. Takayama, A. Sueoka, T. Kondou, Fundamental analysis of magnetic damping force for a rotating machine, Theoretical and Applied Mechanics Japan, Vol.52 (2003), pp.137-144,
[ https://www.jstage.jst.go.jp/article/nctam/52/0/52_0_137/_pdf ] , 2003.10.
|11.||Unstable Vibration of a Rotating Machine Caused by a Magnetic Damping Force, Transactions of the Japan Society of Mechanical Engineering, Series C, Vol.68, No.665 (2002), pp.16-23, (in Japanese)
|12.||Yoshihisa TAKAYAMA, Atsuo SUEOKA and Takahiro KONDOU, Unstable Vibrations of Rotating Machinery Caused by Magnetic Damper (Experiments and Electric Circuit Model), Proceedings of the Asia-Pacific Vibration Conference '99, Vol.1, (1999), 198 -203, 1999.12.|
|13.||Yoshihisa TAKAYAMA, Atsuo SUEOKA and Shinji FUJIMOTO, Unstable Vibrations of Rotating Machinery Generated in DC Current Electromagnet Field, Proceedings of the Asia-Pacific Vibration Conference '97, Vol.2,1027 -1032, 1997.11.|
|14.||Yutaka Yoshitake, Atsuo Sueoka and Yoshihisa Takayama, Quenching of Self-Excited Vibrations by an Impact Damper, Proceedings of the Asia-Pacific Vibration Conference '93, Vol.4,(1993),1699-1704, 1993.11.|
|15.||Atsuo SUEOKA, Yutaka YOSHITAKE, Hideyuki TAMURA, Yoshihisa TAKAYAMA, Self-excited Vibration of a Circular Plate Subjected to Frictional Forces Exerted in Two Regions on Its Outer Circumference, Bulletin of JSME, 29, 256, 3499-3504, Vol.29, No.256, October 1986, 3499-3504, 1986.10.|