本論文中，我們提出一個雙自由度多變數去耦合控制器的設計方法，在雙自由度控制架構中使用簡易的去耦合器，以降低環路間交互作用。此雙自由度架構允許設定點追蹤及負載擾動排除控制器被分別獨立地設計，完美解決單自由度控制器無法兼顧兩者的常見缺點。本設計法比傳統雙自由度控制器設計法更具便利性，後者必須先設計完負載擾動排除控制器，才能設計設定點追蹤控制器。
在多變數控制系統中，完美去耦合器的加入，可以產生多個獨立的單變數控制環路，但實際的去耦合器往往只能減輕卻無法完全消除環路間交互作用。因此我們採用順序設計法來決定各個控制環路的PI或PID控制器參數，以進一步降低交互作用對負載擾動排除的影響。針對設定點追蹤，我們使用基於Laguerre展開式之鑑別法將去耦合後程序近似成多個三階轉移函數，再利用轉移函數之可逆轉部份來設計相關控制器。

In this thesis, we propose a design method for two-degree-of-freedom multivariable decoupling controllers. In the two-degree-of-freedom control structure, simple decouplers are employed to reduce interactions among loops. This two-degree-of-freedom structure allows the controller for set-point tracking and the controller for load disturbance rejection to be designed independently. This perfectly resolves the common disadvantage that a one-degree-of-freedom controller cannot deal with set-point tracking and load disturbance rejection simultaneously. The proposed design method is more convenient than a traditional two-degree-of-freedom controller design method in that the latter must design the controller for load disturbance rejection first, and then design the controller for set-point tracking.
In a multivariable control system, the incorporation of perfect decouplers produces several independent single-variable control loops. However, practical decouplers can only mitigate but cannot completely eliminate interactions among loops. Therefore, we introduce a sequential design method to determine the PI/PID controller parameters of every control loop. This could further reduce the effect of interactions on load disturbance rejection. For set-point tracking, we apply an identification method based on Laguerre expansions to approximate the decoupled process by several third-order transfer functions, and then design the corresponding controller using the invertible parts of the transfer functions.

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