基於預測干擾觀測器與史密斯預測器架構控制穩定與積分時延系統

Abstract

由於時間延遲會影響系統的穩定性，並使控制更為複雜，為此本論文提出一個數位的時間延遲控制架構以提升時間延遲系統的性能與抗干擾能力，將預測干擾觀測器應用於穩定與積分的時延系統，搭配Smith predictor架構，補償輸出時間延遲(output delay)、輸入干擾(input disturbance)的影響。本論文提出的控制架構分為兩部分：內迴路為預測干擾觀測器(Predictive Disturbance Observer, PDOB)，用以抑制各種形式的確定性干擾，包括步階、斜坡、正弦干擾，並且保有干擾觀測器的特性，使系統趨近於模型，PDOB基於DOB架構額外加入預測濾波器(predictive filter)以消除估測干擾的時間延遲，由於此特性提升了傳統DOB在時延系統的干擾抑制性能，尤其對消除週期性干擾更為顯著；外迴路為史密斯預測架構，作用在於降低輸出時間延遲的影響，改善系統伺服響應。由於在現實中，模型誤差是不可避免的，並且會影響閉迴路系統的穩定性。故本論文設計一套強健的控制架構，能消除時間延遲的影響，滿足強健穩定條件抵抗不確定性，抑制已知的確定性干擾。

Significantly the dead-time has a great influence on the stability of systems, which make the process more difficult to control. Therefore, this thesis presents a discrete dead-time compensator to improve the performance and capability of disturbance rejection for dead-time systems. It applied predictive DOB and Smith predictor structure to compensate output delay and input disturbance for stable and integrating plants. The proposed structure consists of two parts: the inner loop and the outer loop. Firstly the PDOB can be designed to reject any kind of deterministic disturbances, including step disturbance, ramp disturbance and sine disturbance. Also, the property of DOB structure can approach the real plant to the nominal plant. The PDOB based on DOB structure has an additional predictive filter, which eliminate the time delay of estimated disturbance. Because of the property enhances disturbance rejection performance of traditional DOB for dead-time systems especially for periodic disturbance. Secondly, the Smith predictor structure is capable to suppress the effects of time delay. Seeing that the stability is influenced by the model mismatch and model mismatch will always exist in the process. In this thesis, we propose a robust controller which compensates the effect of time delay and reject deterministic disturbance to satisfy the robust stability.