選擇性還原觸媒(Selective Catalyst Reduction, SCR)藉由額外注入的尿素水溶液來有效地降低柴油引擎所排放的NOx污染物。由於柴油引擎的排氣流量及溫度皆會影響觸媒化學反應的變化情形，為了實現SCR應用於車輛排氣污染後處理技術，本篇論文建立一個SCR物理模型並依模型為基礎方式來進行控制器設計。控制目標為SCR觸媒系統縱使處於暫態操作期間，引擎排放的NOx污染必須被抑制，同時維持NH3的洩漏量於可接受的範圍內。由於SCR物理模型存在著多個控制目標以及逐步改變的限制條件，適合應用模型為基礎的最佳控制方式，例如模型預測控制器(Model Predictive Control, MPC)。為了達到最佳的NOx轉換效率並抑制NH3洩漏量，閉迴路模擬結果顯示出必須藉由預測模型所提供資訊來獲得系統熱動態變化。閉迴路控制結果除了自行設定的引擎操作條件外，亦包括實際引擎操作於ESC及FTP循環下的實驗數據進行測試。模擬結果分別顯示出$NO_x$平均轉化率可達到94%及93%，同時NH3的平均洩漏量少於9 ppm及10 ppm。實測部分則包含實際硬體下閉迴路控制的實際尿素噴注量與模擬計算噴注量之比較。

The urea-water-solution based selective catalyst reduction(SCR) system is one of the effective device to reduce the NOx emission of diesel engines. In order to realize the SCR technology in automotive application, a model-based approach is used for controller design in this paper. NOx emission must be regulated while NH3 slip is maintained at acceptable level even during the transient driving cycle. The existence of SCR model, pointwise-in-time constraints and multiple control objectives motivate the application of model-based optimization-control approaches such as model predictive control(MPC). The closed-loop simulation result shows that the thermal dynamics in the system must
be captured in order to achieve optimal conversion efficiency and minimum NH3 slip. The closed-loop simulation based on engine-out data in ESC and FTP test cycle show an average NO_x reduction of 94% , 93% separately, while the ammonia slip is kept at an
average value of 9 and 10 ppm. The closed-loop of hardware in the loop based on urea injection system show that the total urea injection volume same as simulation result.

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