磁碟機陣列資料存取系統(Disk Array),整合許多磁碟機在單一系統,儲存的資料量倍增,適用的範圍更廣,此存取設備必須確保能穩定的運作,若是資料存取有誤,流失大量珍貴資料,會發生無法彌補的損失。 磁碟陣列機之振動源有風扇、硬碟及電源供應器。振動源的振動訊號經由連接點,傳遞到整個系統,造成整個系統的振動。施加許多的振動源在同一個物體上,許多的刺激相互影響,使得振動問題更加複雜難解。當系統之自然頻率和外加力之激振頻率相同時,會產生共振。共振時,會使得系統有非常大的振動。振動能量會傳到整個系統,妨害磁碟之之正常運作,危及資料的安全性,甚至造成系統損壞。 為解決共振問題,須先了解系統的自然頻率,以及轉動裝置的激振頻率,才能避免產生共振。為避免振動源影響系統正常運作,須先了解振動源的振動特性、振動的傳遞方式以及各個振動源對結構的效應,才能確保系統能穩定的運作。為解決上述問題,本研究以電腦輔助工程配合實驗驗證,分析此系統的振動行為。 本研究使用有限元素分析軟體ANSYS 5.5,以模態分析功能( Modal Analysis)及簡諧分析功能( Harmonic Analysis ),分析磁碟機陣列資料存取系統之振動特性。 模態分析係求得系統特性,包括每個模態的頻率及振形。本研究同時進行模態實驗,以衝擊法求得頻率響應函數。比較實驗與分析結果,驗證分析結果與有限元素模型皆為準確。 簡諧分析係以簡諧外力激振結構,產生響應。本研究同時進行簡諧實驗,以振動測試機激振結構。比較實驗與分析結果,驗證分析方法的準確性。 磁碟陣列機之振動源有風扇、硬碟及電源供應器。本研究以實驗量得風扇、硬碟及電源供應器的振動,分析其振源特性。硬碟及電源供應器皆含旋轉機構,其激振特性皆因不平衡量所引起,為單一頻率之簡諧激振源。風扇的振動現象,除了旋轉頻率下的振幅明顯外,因葉片與流道之關係,也會出現旋轉頻率的倍頻振動。若氣流遇上流道阻礙,或流道設計不良,會出現紊流衝擊流道之現象,造成複雜的寬頻振動。 綜合上述結果,建立出系統化的分析方法,並獲得準確的有限元素模型。配合減振理論,提出減振方案,在分析軟體中修改有限元素模型,以簡諧分析方法求解簡諧振動之振幅,並與修改前的分析結果比較,驗證減振方案的成效。
The disk array under investigation comprised of six hard disks, and a large amount of data are stored frequently. Usually, the stored data are critical and valuable, so the safety and smooth operation of the disk array become an important concern in the design of this apparatus. The sources of excitation acting on the disk array consist of 2 fans, 6 hard disks and 2 power-supplies. The response of the disk array is the cross-interaction of the structure and the various excitation sources. If the frequency of any excitation coincides with one of the natural frequencies of the system, resonance will occur, and large amplitude of vibration will be harmful to the hard disks. The dynamic properties of the disk array and the characteristic of the excitation sources thus must be fully investigated in order to prevent resonance, and attenuation designs can be implemented to insure smoothly running of the data storage device. ANSYS, the FEM software, was used in the vibration study of the disk array, where the functions of modal analysis and harmonic analysis were exclusively used. The results of modal analysis provide the natural frequencies and the mode shapes of the components and structures. The results of harmonic analysis provide the response of the device under sinusoidal excitations. Extensive experiments were conducted to verify the accuracy of the FEM modeling. The modeling of junctions, like rivets and screws, in the structures, was validated by the comparison the numerical and the test results.