当稳态优化返回一个非零的失衡时，DMCplus动作计算给出一个与失衡相同的设定值，设定值由延伸到未来的且斜率等于稳态失衡计算的线指定（如下图25所示）。如果当前值在操作限之间，则线起始于当前值;如果当前值超出操作限，线起始于违反操作限处。这保证了稳态优化和DMCplus动作计算之间的数学一致性。

Figure25:DMCplus Setpoint for Ramp with Imbalance

图25：失衡斜坡的DMCplus设定值

对于一失衡传统斜坡，稳态优化总是试图平衡斜坡。如果结果可以被平衡，上一节的未失衡传统斜坡已经描述了基于RAMPSP和RAMPRT的斜坡设定点计算。

然而如果稳态优化不能平衡斜坡并且用户设定MXMIMB>0（指定斜坡允许失衡的最大控制周期数目），则对失衡量进行检查以确保它不是太大。

如果失衡不是太大，控制器被允许保持'MXNIMB'个连续斜坡失衡控制周期。如果被发现失衡太大，或者'MXNIMB+1'个连续失衡周期后，控制器将关闭。

当稳态优化允许计算一个失衡方案时，斜坡将趋于驱动向操作限两端。由于斜坡将更可能处于操作限附近，通过实施安全区确保斜坡值不被驱动到太接近仪表限制。

安全区等于操作限制之差的10％。这个区域作为操作限制的有效缓冲被施加在操作区域的两端。详情参见图26.

若要设置允许的失衡限制，可通过用户输入的参数RHORIZ定义时域，它乘以稳态时间即得到域。

根据失衡值与安全区域的相对关系存在三种不同的方式定义失衡限制。

如果失衡斜坡当前值处于安全区域之间，允许失衡高线以当前值为起点，上安全区域与时域交点为终点，两点间的连线组成。这条线的斜率为高允许失衡。

如图26所示，允许失衡低线以类似的方式构成。稳态计算失衡（DMCplus设定点线斜率）必须在允许失衡高低线之间（允许失衡高低线斜率）。当斜坡当前值接近一安全区域时，相应的允许失衡值幅度减小，直到当前值到达安全区域（允许失衡变为0）。

DMCplus动作计算设定点是一条起始于当前值，如前所述斜率等于稳态计算失衡的延伸向未来的线，详见图27。

Figure26: Imbalanced Ramp between operating limits

图26：操作限制间的失衡斜坡

Figure27: DMCplus Setpoint for Imbalanced Ramp between operating limits

图27：操作限制间的DMCplus失衡斜坡设定点

附原文：

When the steady-state optimization returns a non-zero imbalance, the DMCplus move calculation is given a setpoint consistent with the imbalance, by specifying the setpoint as a line extending into the future with slope equal to the steady-state calculated imbalance (see Figure 25). If the current value is between the operating limits, the line starts at the current value; if the value is outside an operating limit, the line starts at the violated operating limit. This ensures mathematical consistency between the steady-state optimization and DMCplus move calculation.

For a Traditional Ramp with Imbalance, the steady-state optimization attempts to balance the ramp. If the event can be balanced, the previous section on Traditional Ramps with No Imbalance describes how the ramp setpoint is calculated, based on RAMPSP and RAMPRT.

If, however, the steady-state optimization cannot balance the ramp and the user has set MXMIMB>0(specifying the maximum number of control cycles the ramp is allowed to be out of balance), then the amount of imbalance is checked to be sure it is not too large.

If the imbalance is not too large, the controller is allowed to remain on for 'MXNIMB' consecutive control cycles with the ramp out of balance. If the imbalance is found to be too large,or after 'MXNIMB+1' consecutive cycles out of balance, the controller is turned off.

Whenever the steady-state optimization is allowed to calculate an imbalanced solution, 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 to ensure that the value of the ramp is not driven too near the instrument limits.

The Safety Zone is equal to 10% of the difference between the operating limits. This zone is applied at both ends of the operating region and effectively buffer the operating limits. See Figure 26.

To set the allowed imbalance limits, a time Horizon is specified by the user-entered parameter RHORIZ, which is multiplied by the steady-state time to give this Horizon.

There are three different ways in which the imbalance limits are determined depending on where the current value of the imbalanced ramp is relative to the Safety Zones.

If the current value of an imbalanced ramp is between the Safety Zones, the upper allowed imbalance line is constructed by drawing a line from the current value to intersect with the upper Safety Zone at the end of the Horizon. The slope of this line is the upper allowed imbalance.

A lower allowed imbalance line is constructed in a similar manner as shown in Figure 26.The steady-state calculated imbalance (slope of the DMCplus setpoint line) must be between the upper and lower allowed imbalance limits (slopes of the upper and lower allowed imbalance lines). As the current value of the ramp approaches one of the Safety Zones, the corresponding allowed imbalance decreases in magnitude until the current value reaches the safety zone, where that allowed imbalance becomes zero.

The DMCplus Move Calculation setpoint is a line starting at the current value, and extending into the future with a slope equal to the steady-state calculated imbalance as described previously. See Figure 27.

                                                                           2015.10.4