Programmed Imbalance Ramps 程序失衡斜坡

程序失衡斜坡允许斜坡处于失去平衡的稳态。这种类型的斜坡通常表示一个大型储罐的液位。其目标是允许库存被累积或在规定的操作限制内耗尽。

在这种情况下，稳态优化的问题是基于安全区域限制和RHORIZ（上一节中讨论）制定稳态失衡上下限。两个方向上都允许失衡，其基于当前值与相应限制的接近程度。

在稳态优化计算出稳态失衡的情况下，DMCplus动作计算的设定值是一条起始于当前值（假设当前值在操作限之间），斜率等于稳态计算失衡的延伸向未来的射线（参见传统失衡斜坡章节图25）。

每当程序失衡斜坡已配置且稳态优化允许计算一个不平衡解决方案，稳态优化几乎肯定会计算一个失衡的解决方案，这样斜坡将趋向于被驱动向操作限的一侧或另一侧。

鉴于斜坡会更有可能地靠近操作限制，为确保斜坡值不会被驱动地太靠近仪器限制，安全区域在这种类型的斜坡中也得到执行。与传统失衡斜坡一样，安全区域等于操作上下限制之差的10％。这个区域作为操作限制的有效缓冲被加到工作区域的两端（参见传统失衡斜坡中的图25）。

传统失衡斜坡与该程序失衡斜坡的唯一区别在于，前者的稳态优化总是尝试平衡斜坡（稳态优化的失衡限制是0），而程序失衡斜坡的稳态优化通过使用上下失衡限允许稳态失衡解决方案。图25至30的所有应用亦适用于程序失衡斜坡。

原文：

The Programmed Imbalance Ramp allows the ramp to be out of balance at steady state. This type of ramp normally represents the level in a large tank. The objective is to allow inventory to be accumulated or depleted within specified operating limits.

In this case, the steady-state optimization problem is formulated with upper and lower limits on the steady-state imbalance, based on the Safety Zone Limits and RHORIZ (discussed in the previous section). Imbalance is allowed in both directions, based on how near the current value is to the respective limit.

In the event that the steady-state optimization calculates a steady-state imbalance, the setpoint for the DMCplus move calculation is a line starting at the current value (assuming the current value is between the operating limits) and extending into the future at a slope equal to the steady-state calculated imbalance (see Figure 25 in Traditional Ramps with Imbalance).

Whenever a Programmed Imbalance Ramp is configured, and the steady-state optimization is allowed to calculate an imbalanced solution, the steady-state optimization almost certainly will calculate an imbalanced solution so the ramp will tend to be driven toward one side of the operating limits or the other.

Since the ramp will be more likely to be near an operating limit, safety zones are implemented for this type of ramp also, to ensure that the value of the ramp is not driven too near the instrument limits. As for the Traditional Ramp with Imbalance, the SafetyZone is equal to 10% of the difference between the operating limits. This zone is applied at both ends of the operating region (see Figure 25 in Traditional Ramps with Imbalance) and effectively buffer the operating limits.

The only difference between the Traditional Ramp with Imbalance and this Programmed Imbalance Ramp is that for the Traditional Ramp, the steady-state optimization attempts to balance the ramp (imbalance limits for the steady-state optimization are zero), while for the Programmed Imbalance Ramp, the steady-state optimization uses the upper and lower imbalance limits in the steady-state optimization to allow an imbalanced steady-state solution. Figures 25 through 30 all apply to Programmed Imbalanced Ramps also.

                                                                          2015.10.6