Many QuickStudy users are familiar with the Output Weight setting on PCS blocks. This provides a means of adjusting how aggressive the control action is without changing the model.
The Output Weight can be adjusted on the fly by connecting an AI block to the “Output Weight” input of the PCS block. For example this could be used to adjust how aggressive the control action is based on the product recipe selected.
The PCS block optimization setting is a feature within the PCS that can be used to vary the Output Weight based on the value of the PV, the Rate Of Change of the PV, or the value of the PCS output. These setting are found on the “Optimization” tab of the PCS block.
Check the box for the type of optimization desired. For this example optimization based on the value of the PV will be described.
The Max Output Weight is the greatest output weight applied which is when PV is equal to setpoint. The Min Output Weight is the lowest output weight applied which is when the PV is farthest from setpoint.
This means that control will become more aggressive as PV moves away from setpoint.
When Symmetric Optimization is selected the “range” setting is the range of PV over which the Output Weight will be changed. The Output Weight is calculated using a bell curve.
The Weight Slope changes the slope of the bell curve between Shallow, Medium, or Steep.
When Asymmetric Optimization is selected the slope of the Output Weight change can be different depending on whether the PV is above or below setpoint.
Instead of a bell curve the result of Asymmetric Optimization may look something like this.
There is a tab for an Optimization Monitor. This tab allows the optimization settings and results to be monitored during runtime.
Doug Deiterman – Senior Controls Engineer