臺灣博碩士論文加值系統

　　本研究之目的為經由改善伺服器機殼之振動，以提升其硬碟之讀取性能，並發展出一套降低此產品振動的改善流程。

　　流程中之初必須先忠實複製客訴問題（量測性能最差之硬碟讀取值），並擬定改善後欲達到之目標讀取值（本研究之初步設定為28 IO/s，為此硬碟最佳性能的70%）；首先探討硬碟受到振動（方向、頻率、振動量的大小）與其讀取性能之關聯性；藉由硬碟之讀取性能與風扇激振頻率之相關性，找出主要使讀取性能下降之各個敏感頻率（本研究中主要敏感頻率為260 Hz）；然後藉由對結構（機殼與硬碟）進行之模態測試，評估結構之共振對於降低硬碟讀取性能的影響；接著搭配各種適當可行之減振方案（避開共振法、振動阻絕法等）進行改良，最後仍以量測硬碟之讀取值作為最終評估成效之依據。

　　本研究之實務案例可支持流程之實用性：在案例一中，將風扇轉速頻率從原本的260 Hz調降至230 Hz，由於能有效避開結構（機殼與硬碟）之共振頻率，故能使其讀取值上升至最佳讀取性能的75%；在案例二中，強化上蓋板之剛性後，其自然頻率從原本的259 Hz提升至301 Hz，已能有效避開風扇運轉頻率260 Hz，故使讀取值上升至最佳讀取性能的65%，若再加上與風扇架之間的四顆螺絲鎖固，更可提升至最佳讀取性能的70%。

　　The purpose of this research is to improve vibration of a server　chassis, in order to promote the performance of hard disk drives (HDDs). In addition, a flow chart was developed to reduce vibration of the whole sever system and to advance HDD performance.

　　In this flow chart, we must replicate the problem from the customer complaints (by measuring the reading values of the worst HDD) and set a goal for the reading values of the HDD to achieve (The goal is 28 IO/s in this study). First, the relevance between the reading values of a hard disk drive and its vibration (including direction, frequency and magnitude) was studied. By comparing the reading performance of a hard disk drive and excitation frequencies of server fans, one can find out the sensitive frequencies that cause the low performance of hard disk drives (260 Hz is the main sensitive frequency in this study). Secondly, modal testing was conducted to find out the possible influence of structural resonance onto the reading performance of the HDD. Thirdly, several feasible methods including resonance avoidance, vibration isolation, etc. were used to reduce the vibration of the HDD. As addressed in the beginning, the reading value is always the ultimate evaluation criterion for the HDD’s performance.

　　In the first case, after the fan frequency was reduced from 260 Hz to 230 Hz, the reading value was raised up to 30 due to the avoidance of structural resonance. In the second case, by stiffening the upper cover of the server chassis, the natural frequency of the cover was raised from 259 Hz to 301 Hz and the reading value went up accordingly from 10 to 26. If the four additional screws were fastened between the upper cover and the fan frame, the reading value can even go up to 28.

摘　要 I
Abstract II
誌 謝 III
目 錄 IV
圖索引 VII
表索引 XI
第一章 緒論 1
1.1 前言 1
1.2 研究動機與目的 3
1.3 文獻回顧與整理 3
第二章 硬碟之振動分析 8
2.1 初步量測 9
2.2 硬碟之振動與讀取性能之關聯性 12
2.2.1 硬碟受振方向與讀取性能之關係 12
2.2.2 旋轉振動對硬碟讀取性能之關係 15
2.2.3 硬碟敏感頻率與讀取性能之關係 21
2.2.4 硬碟之振動量與讀取性能之關係 27
第三章 伺服器之模態測試分析 29
3.1 實驗儀器介紹與實驗步驟 30
3.1.1 實驗儀器及其配置 30
3.1.2 實驗步驟 34
3.2 伺服器結構之自然頻率 37
3.3 平板數值模態之分析 40
3.4 導致最左側之硬碟讀取性能最差之因素 47
3.5 伺服器結構之振動改善 50
3.5.1 案例一：改變激振頻率 50
3.5.2 案例二：改變結構之自然頻率 53
3.5.3 案例三：避開共振與最佳懸吊的組合 68
3.6 設計準則與流程 71
3.6.1 硬碟減振之要點 71
3.6.2 風扇選用要點 71
3.6.3 機殼設計要點 72
第四章 結論與建議 73
4.1 結論 73
4.2 對未來研究方向之建議 75
參考文獻 76
附錄A　風扇之規格 78

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