案例3：储罐液位控制-MV Horizon（范围）和POV Impulse Factor（脉冲因子）-8

另一方面，如果我们向所构建的Measurement_Noise DV（具有单位增益）注入一个值为1的噪声，我们认为液位CV的实际噪声只有液位测量值的1%。这就是为什么在这种情况下，因为模型的存在，标准差值为1的噪声信号自身注入到CV中比注入UNM中显得更为明显。作为给用户的推荐，在斜坡CVs的情况下你可能需要让噪声干扰拥有物理意义，然后你应该明确地将噪声建模成断开的DV。请记住在任何仿真工作已经以这种方式执行后，作为“测量噪声”的DVs在开始搭建最终的控制器之前必须从模型中移走。否则如果只需要噪音而不用其有物理意义，直接将噪音注入UNM即可获得满意的控制器整定和性能分析。
带回家的消息
MV时域是控制器性能的组成部分；然而通常我们不应该修改其默认值。只有所有其他调节选项都已经用尽，用户才应修改MV时域。只有当控制应用的目标是缓冲罐控制时才建议修改MV时域。有关的详细信息请参阅指南文件。
降低MV时域将使得控制器行为变得更为激进，而增加MV时域将使得控制更为平滑。需要考虑的一个重要事情是当用户指定一个MV时域时，以SMOCPro“太短”满足其目标而告终。当遇到这种情况时，结果可能是SMOCPro将不会做出任何动作去接近控制目标。
对于POVs斜坡，Impulse Factor是一个重要的整定参数，其有助于用户实现理想的控制性能。增加了Impulse Factor后，在计算动作时将减少用于计算POV预测的当前不可测干扰数量。Impulse Factor可以被解释为遗忘参数，其中Impulse Factor等于0意味着忘记0%的当前预测误差，Impulse Factor等于0.5意味着忘记50%的当前预测误差，Impulse Factor等于0.9意味着忘记90%的当前预测误差，等等。

---

原文：
On the other hand, if we inject a noise value of 1 into the Measurement_Noise DV that we constructed (with unity gain), we can expect the actual noise in the Level CV to be 1% of the Level measurement. This is why in this case, because of the models, a noise signal with a standard deviation value of 1 injected into the CV itself is larger than a noise signal with a standard deviation value of 1 injected into the UNM. As a recommendation to the user, should you require the noise disturbances to have physical meaning in the case of ramp CVs, then you should model the noise explicitly with a disconnected DV. Keep in mind that after any simulation work has been performed this way the DVs used for “measurement noise” must be removed from the model before proceeding to build the final controller. Otherwise, if only noise is required without physical meaning, injecting the noise directly into the UNM is satisfactory for controller tuning and performance analysis.
*Take Home Message *
The MV horizon plays an integral part in controller performance; however, generally it should never be modified from its default value. Only after all other tuning options have been exhausted should a user modify the MV horizon. The case where it is recommended to modify the MV horizon is when the goal of the control application is surge vessel control. For more details, please refer to the Guidelines document.
Decreasing the MV horizon results in more aggressive control behavior and increasing the MV horizon results in less aggressive and smoother control. An important thing to consider is the case where the user specifies an MV horizon that ends up being “too short” for SMOCPro to meet its targets. When this case gets encountered the result will be that SMOCPro will potentially not make any moves to meet its control objectives.
For ramp POVs, the Impulse Factor is an important tuning parameter which aides the user in attaining the desired control performance. Increasing the Impulse Factor decreases the amount of the current unmeasured disturbance which will be used in the POV’s prediction when calculating moves. The Impulse Factor can be interpreted as a forgetting parameter where an Impulse Factor of 0 means forget 0% of the current prediction error, an Impulse Factor of 0.5 means forget 50% of the current prediction error, an Impulse Factor of 0.9 means forget 90% of the current prediction error and so forth.

---

2016.5.25