DMCplus中關于定義斜坡變量有幾種不同的方式。這些類型的簡要描述如下。欲了解斜坡類型的更多細節，請點擊鏈接。
?未失衡的傳統斜坡
這是早期DMCplus版本提供的斜坡類型。它允許使用平均液位控制。穩態優化總是試圖平衡斜坡，若不能則控制器會處于關閉狀態。斜坡變量必須定義為對應用程序非常重要。
?失衡的傳統斜坡
該選項提供了用戶指定時間間隔允許斜坡失衡，控制失衡不是非常大。
它也允許使用平均液位控制。穩態優化總是試圖平衡斜坡;然而若不能平衡，在控制器關閉前，其將在失衡情況下繼續運行用戶指定的控制時間間隔。而若任意時刻失衡過大，不管其是否已達到用戶定義的不平衡周期，控制器都將被關閉。
該方法用于確定操作員提供的操作極限失衡容忍。斜坡變量必須定義為對應用程序非常重要。
·編程失衡斜坡
在此選項中，穩態優化并不試圖平衡斜坡;斜坡允許無限期失去平衡。任一方向上失衡容忍量是當前值接近操作限程度的函數。
當值靠近極限時，失衡容忍量降低到零。這個選項主要用于當DMCplus控制器存在一個大的激增容量時，控制器將花費幾個穩態時間到達設定液位操作限時。當某時刻流程上下游不在服務時，這是特別有用的。再次強調，斜坡變量必須定義為對應用程序非常重要。
·偽斜坡
這一選項是為那些不是真實的積分變量，但在我們感興趣的時域里表現出斜坡行為的變量提供的。最常見的例子是高純精餾塔的塔盤溫度。失衡的傳統斜坡的穩態優化總是嘗試著平衡斜坡，但如果不能平衡，控制器允許保留運行用戶指定的時間間隔。
偽斜坡與失衡的傳統斜坡的主要差別在于，前者不檢查失衡的量。盡管偽斜坡必須明確地被控制，但它們不要求對應用程序非常重要。需要注意的是偽斜坡是在DMCplus Build中定義的。
斜坡變量的RAHEDSUB選項可用于當遇到斜坡失衡時配置子控制器的行為。如果RSHEDSUB選項設置為1，控制器將只留下包含不平衡斜坡的子控制器。如果RSHEDSUB選項設置為0，整個控制器將留下。當RSHEDSUB選項處于啟用狀態時，控制器將在當前周期執行失衡方案，然后在下一控制周期開始時關閉子控制器。這將使得最新方案得到執行的同時避免重新求解導致的錯過周期或組合方案時間的問題。
附原文：
There are several different ways in which a ramp variable can be defined in DMCplus. A brief description of each of these types is listed below. For more detail about a ramp type, click its link.
·Traditional Ramp with No Imbalance
This is the ramp type that is provided in earlier versions of DMCplus.It allows averaging level control. The steady-state optimization is always trying to balance the ramp, and if it cannot, the controller is turned off. The ramp variable must be defined as critical to the application.
·Traditional Ramp with Imbalance
This option is provided to allow the ramp to be out of balance for a user-specified number of intervals, provided the imbalance is not too large.
It also allows averaging level control. The steady-state optimization is always trying to balance the ramp; however,if it cannot, the controller will continue to run out of balance for the user-specified number of control intervals before the controller is turned off.If at any time the imbalance is too large, the controller turns off anyway,regardless of whether it has reached the user-specified number of imbalanced cycles.
The method used to determine what is too much imbalance is based on the operating limits provided by the operator. The ramp variable must be defined as critical to the application.
In this option, the steady-state optimization does not attempt to balance the ramp; the ramp is allowed to be out of balance indefinitely. The amount of imbalance tolerated in either direction is a function of how near the current value is to the operating limit.
As the value approaches the limit, the amount of imbalance allowed decreases to zero. This option is used primarily when there is a large surge capacity in the middle of a DMCplus controller, where it may take several steady-state times of the controller for the level to reach the desired operating limit. This is especially useful when the upstream or downstream section of the process may be out of service sometime. Again, the ramp variable must be defined as critical to the application.
This option is provided for those variables that are not true integrators,but that act like ramps over the time domain of interest. Most commonly, these are tray temperatures in a high purity distillation tower. As with the Traditional Ramp with Imbalance, the steady-state optimization is always trying to balance the ramp, but if it cannot, the controller is allowed to remain on for a user-specified number of intervals.
The primary difference between pseudo-ramps and traditional ramps with imbalance is that for pseudo-ramps, no check is made on the amount of imbalance. And while pseudo-ramps must be explicitly controlled, they are not required to be critical to the application.Note that?pseudo-ramps are defined in DMCplus?Build.
The?RSHEDSUB?option on ramp variables can be used to configure the behavior of subcontrollers when a ramp imbalance is encountered. If the RSHEDSUB option is set to 1, the engine will only shed the subcontrollers that contain the imbalanced ramp. If the RSHEDSUB option is set to 0, the entire controller willbe shed. With the RSHEDSUB option enabled, the controller will implement the imbalanced solution at the current cycle and then shut the subcontrollers off at the beginning of the next control cycle. This allows the latest solution toget implemented while avoiding the overhead of re-solving the problem which could cause missed cycles or a Composite Suite timeout.
? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?2015.9.28
