Evaluating Control System Performance

The operation of industrial process control systems often involves the control of multiple unit operations with hundreds of measurements and control loops, as illustrated below. Although these systems are designed to automatically archive operational data in an historian, it is time consuming to examine historical data to determine if there has been a change in control system performance that could impact plant throughput or the quality of the final product. Thus, in many cases process and control engineers and instrument technicians at the plant level spend a great deal of time addressing the most critical control and measurement problems that plant operations personnel have identified as being potentially disruptive to production or quality. There is usually no time or resources to examine the control performance to proactively address problems that could later impact operation efficiency or limit plant production.

This manpower limitation is especially true in many North American plants, where over the past 20 years corporate engineering staff have been virtually eliminated. Thus, the operating plants can no longer call on the resources that corporate engineering traditionally provided to analyze and correct measurement and control problems that limit plant production and efficiency. In this environment, it is important that tools are available within the control system to automatically evaluate control performance and to quickly identify and correct the source of any measurement or control problem.

As addressed in Chapter 2 of Advanced Control Foundation – Tools, Techniques, and Applications, the field-based, scalable process control systems and fieldbus devices
initially introduced in the late 1990s are designed to support embedded tools for process analysis and measurement and control problem diagnostics. These tools can be used to analyze both fast and slow processes. The core technology used in some of these systems supports continuous monitoring and detection of abnormal control and field device operation. For older distributed control systems, a similar capability can be provided by layering performance monitoring applications on top of the existing control system. My blogs over the next month will explore this capability in more detail.