高山 佳久（たかやま よしひさ） | データ更新日：2021.06.08 |

助教 ／
工学研究院
機械工学部門
力学システム講座

**原著論文**

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. | 山根甲彰, 高山 佳久, 雉本 信哉, 石川 諭, 表皮効果を考慮した導体円板とリ ング型磁石から構成された垂直運動型磁気ダンパのモデル化, 日本機械学会論文集, http://dx.doi.org/10.1299/kikaic.78.1691, 82, 837, 1-16, http://dx.doi.org/10.1299/kikaic.78.1691, 2016.01, A magnetic damper composed of a permanent magnet and a conducing plate has the advantage that the magnetic damper can generate a damping force woth no physically contact.The conducting plate needs to be thickened in or-der to obtain a stronger magnetic damping force,since the magnitude ofthe magnetic flux produced by a permanent magnet is limited.However,it is known that the magnitude ofthe magnetic damping force is limited,even ifthe conduct-ing plate ofthe magnetic damper has a large thickness.It has been considered that skin effect by eddy curents is the cause ofthis limited magnetic damping force. In addition,it is known that eddy curents have a very slight effect on the natural frequency of a structure with a magnetic damper.In this paper,the coil method considering inductances is proposed as one of the modeling methods for magnetic dampers consisting of a ring magnet and a conducting disk moving relatively in an axial direction.Applying this method,a modal analysis ofthe free and the forced vibration of a1-DOF system with a magnetic damper are performed,and the magnetic damping and the magnetic stiffness consid-ering the skin effect,are introduced.Furthermore,the experiments are performed in order to confirm the practicality ofthe method.The analytical results are found to be in agreement with the experimental results.. |

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 / 051007-1DOI: 10.1115/1.4024094 , 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. | 木村 貴裕, 高山 佳久, 近藤 孝広, 雉本 信哉, 組み合わせ磁石を用いた磁気ダンパの研究 （基本ハルバッハ配列磁石を用いた磁気ダンパ）, 日本機械学会論文集（Ｃ編）, http://dx.doi.org/10.1299/kikaic.78.1691, 78, 789, 387-396, http://dx.doi.org/10.1299/kikaic.78.1691, 2012.05, The damping force of a magnetic damper is based on the Lorentz force. That is to say, the magnetic damping forceis generated in the direction opposite to the relative motion of a conductor with respect to a magnet. Normally, a magnetic damper uses two conducting plates facing the opposite sides of a magnet. If only one side of the magnet is used, the magnetic damping force is less. In the present work, a new magnetic damper composed of Halbach magnet arrays arranged in three parallel lines is proposed. A basic Halbach magnet array consists of five magnet cubes that are glued in the specific directions relative to each other, and is characterized as having a strong magnetic field on one side and a weak field on the other. For this reason, it is possible to realize a high-performance magnetic damper using only one side of a magnet. The magnetic fields of the Halbach magnet arrays of the new magnetic damper we are proposing, together with other magnet arrays, were investigated analytically using Biot–Savart’s Law. Furthermore, the proposed magnetic damper was fabricated and tested. The experimental results were compared with the analytical results. As a result, the effectiveness of the new magnetic damper was confirmed.. |

5. | 高山 佳久, 末岡 淳男, 近藤 孝広, 中村研介, 円形コイルと円柱磁石で構成された磁気ダンパ, 日本機械学会論文集C, 076, 771, 209-215, 2010.11. |

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[ https://www.jstage.jst.go.jp/article/jsdd/2/5/2_5_1148/_pdf] 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.20APVC2007 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. | 高山佳久，末岡淳男，近藤孝広, 円形磁石回転型磁気ダンパによる回転体の制振効果 （磁気ダンピング力に起因した不安定振動の不発生）, 日本機械学会論文集, 70-696，C(2004)，2195-2202, 2004.08, he magnetic damping force is generated by not only a rotating-conductor-type magnetic damper composed of a rotating conductor and a fixed magnet but also a rotating-magnet-type magnetic damper composed of a rotating magnet and a fixed conductor. In the previous report, it was demonstrated analytically and experimentally that a rotating-conductor-type magnetic damper for a rotating machine caused unstable vibrations at a rotating speed over the critical speed. In this report, the authors show that the rotation of the axisymmetric magnet on its axisymmetric axis affects the magnetic damping force very slightly by a simple experiment, and that a rotating-magnet-type magnetic damper for a rotating machine can be modeled by considering the whirling of the magnet only. As the result, the rotating-magnet-type magnetic damper never generates unstable vibrations analytically. The analytical results agree well with the experimental ones.. |

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. | 高山佳久，末岡淳男，近藤孝広，長井直之, 磁気ダンピング力に起因した回転体の不安定振動, 日本機械学会論文集, 68-665，C(2002)，16-23, 2002.01, [URL], Using the infinitesimal loop model that is moving through the nonuniform magnetic field in space, the effective expression of the magnetic damping force is derived. This method has an advantage of calculating no scalar potential and it is easy to compute the magnetic damping force by using the static magnetic field obtained by FEM, measurements and so on. By the way, a magnetic damper used in turbo-molecular pump and so on in order to reduce vibration sometimes generates unstable vibrations. In this report, it was made clear that the Jeffcot rotor with the magnetic damper generated the unstable vibration in the experiment over a critical speed, and the present method was available for investigating the cause of the unstable vibration due to asymmetric stiffness matrix. Then a good agreement between the analytical and experimental results was confirmed. |

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. |

16. | 末岡淳男，吉武裕，田村英之，高山佳久, 外周上の２箇所に摩擦力が作用する円板の自励振動 （分布摩擦力を受ける内部共振のない円板）, 日本機械学会論文集, 52-474，C(1986,昭和61-2),704-709, 1986.02. |

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