Languages of Process Control

There are several fundamental laws that have been developed in the process control field as a result of many years of experience. Some of these may sound similar to some of the laws attributed to Pmkinson, but the process control laws are not intended to be humorous. 

Complex elegant control systems look great on paper but soon end up on manual in an industrial environment. Bigger is definitely not better in control 

PROCESS MODELING, SIMULATION, AND CONTROL FOR CHEMICAL ENGINEERS 

No degree of sophistication in the control system (be it adaptive control, Kalman filters, expert systems, etc.) will work if you do not know how your process works. Many people have tried to use complex controllers to overcome ignorance about the process fundamentals, and they have failed Learn how the process works before you start designing its control system. 

As you will see, several different approaches are used in this book to analyze the dynamics of systems. Direct solution of the differential equations to give functions of time is a time domain teehnique. Use of Laplace transforms to characterize the dynamics of systems is a Laplace domain technique. Frequency response methods provide another approaeh to the problem. 

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Process Control Laws / 1.4.2 Languages of Process Control / 1.4.3 Levels of Process Control... 

In the language of process control, the variables associated with an industrial drying process can be divided into two general groups ... 

LAWS, LANGUAGES, AND LEVELS OF PROCESS CONTROL 1.4.1 Process Control Laws... 

The most successful and user-friendly approach, which is now adopted by virtually all commercial systems, is the fill-in-the-forms or table-driven process control languages (PCLs). The core of these languages is a number of basic functional blocks or software modules. AU modules are defined as database points. Using a module is analogous to calhng a subroutine in conventional programs. 

Sherwin-Williams has developed such a polymer process control system. The methodology used to accommodate the contrasting requirements has two key elements. First, the software is based on a simple architecture that places the definition of changing reactor hardware elements and characteristics in easily modified configuration files (5). Second, the language uses a small number of basic commands to describe formulations and reactor control. Complex operations are described by reference to commands tables (macros) built using several basic commands or other macros. 

In the study of process dynamics and control we will use several languages. 

We will use English to solve some simple problems. But we will find that more complex problems are easier to understand and solve using Russian. As problems get even more eomplex and realistie, the use of Chinese is required. So we study in this book a number of very usefiil and practical process control languages. 

Therefore, the simplest procedure to get the stochastic description of the reaction leads to the rather complicated set of equations containing phenomenological parameters / (equation (2.2.17)) with non-transparent physical meaning. Fluctuations are still considered as a result of the external perturbation. An advantage of this approach is a useful analogy of reaction kinetics and the physics of equilibrium critical phenomena. As is well known, because of their nonlinearity, equations (2.1.40) reveal non-equilibrium bifurcations [78, 113]. A description of diffusion-controlled reactions in terms of continuous Markov process - equation (2.2.15) - makes our problem very similar to the static and dynamic theory of critical phenomena [63, 87]. When approaching the bifurcation points, the systems with reactions become very sensitive to the environment fluctuations, which can even produce new nonequilibrium transitions [18, 67, 68, 90, 108]. The language developed in the physics of critical phenomena can be directly applied to the processes in spatially extended systems. 

All process control languages contain PID control blocks of different forms. Other categories of function blocks include... 

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