To achieve the maximum benefit, the performance monitoring tools that are installed in control systems to evaluate plant control performance should contain features to support both analysis and diagnostics.
- Process Analysis is the examination of a process, its elements, and their relationships.
- Process Diagnostics is the investigation of the cause or nature of a process condition or problem.
The assessment of control performance is an ongoing function involving both process analysis and process diagnostics, as illustrated below.
Most performance monitoring tools provide both an instantaneous view and a historic view that summarizes control loop utilization by process area. Control loop utilization (often simply called control utilization) is the percentage of time a control loop operated in its designed (“normal”) mode of operation over some specified period. If the utilization is lower than normal, the user can select a detail view of the process area that shows the utilization for each control loop. An example of a control performance monitoring tool’s functionality that was included in in Chapter 3 of Advanced Control Foundation – Tools, Techniques, and Applications is illustrated below.
This example also shows some of the information that is automatically collected about control system performance. A demonstration of this capability can be seen on the web site that accompanies the book Advanced Control Foundation – Tools, Techniques, and Applications.
Report generation is an important feature of performance monitoring tools. Reports can be used to gain the management support that is required to address low control utilization or to determine the source of excessive process variation that impacts production or product quality.