近年來因為網路服務的快速發展，使得伺服器的建置量不斷地攀升並且帶來了龐大的耗電量。散熱系統的耗電量是伺服器整體耗能很大的一部分，因此各種散熱設計及散熱管理的研究的主要考量是降低冷卻系統的功率消耗。近幾年有少數的文獻開始探討以風扇速度控制的方式節省風扇散熱時的耗電量。目前所提出的最佳化風扇控制器的設計必須建立在已知的系統模式下。然而，風扇散熱系統具有強烈的交互耦合作用以至於系統模式不易獲得，而且伺服器型態種類繁多，以系統模式為基礎的控制器設計方式窒礙難行。因此，本研究論文以節能的目標為出發點，並且在不需要系統模式下提出以PID控制加上風扇權重設定實現解耦合的風扇控制方式。無系統模式的PID控制參數可經由類神經網路線上調校而得，此控制器增益值對系統而言僅可稱之為適切值，PID參數需進一步優化以節省風扇耗能。本文之PID控制器進一步的在暫態響應中以最低的風扇耗電量的方式進行PID參數的最佳化。設定風扇權重的方式可以有效的降低伺服器內部分元件因交互耦合作用而過度冷卻，可在系統處於穩態時節省風扇的耗電量。本研究以伺服器仿真系統模擬真實伺服器的行為驗證控制器的設計，實驗結果顯示控制器的設計符合伺服器系統散熱要求。透過PID控制器的最佳化，風扇在暫態時可節省14%以上的能源；而適當的風扇權重設定可節省穩態運轉中的風扇耗電量約16.8%。

Recently, the rapid development of Internet Service brings the increasing demands of servers and large amount of electricity consumption. The electricity used by the cooling system contributes a major part in the server power budget. Therefore, many researches, relating to thermal design and thermal management, aim to reduce power consumption in servers. In recent years, few studies began to explore low fan power consumption by utilizing fan speed control. To date, the design of optimal fan speed controller is based on the system model. However, server fan cooling system has strong cross-coupling effect that makes the system model hard to be obtained. Moreover, the model-based controller design may hardly be implemented because there exists many different types of servers. Concentrating on power saving, this thesis proposes a decoupled fan control, combining proportional-integral-derivative (PID) controllers and fan weighting settings, which does not need to know the system model in advance. The PID control parameters of unknown system model can be obtained through the on-line tuning using neural network. However, the tuning PID controller is only suitable to the system and needs to be optimized in advance in order to reduce the fan power consumption. The optimization of PID gains is based on low fan power consumption in the transient-state response. Furthermore, fan weighting setting is the effective method to reduce the over-cooling of electronic components due to the cross-coupling effect. It can save fan power usage when the system is in the steady state. A server mockup system simulating a real server was constructed to validate the design of the proposed control system. The experimental results show that the temperature responses satisfy the cooling requirements of the server. Furthermore, up to 14% of a server’s fan cooling power can be saved in the transient-state by optimal PID controllers and the proper fan weighting reduces power use by 16.8% in the steady-state.

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