CALCULATING PROCESS-CONTROL PARAMETERS FROM STEADY-STATE OPERATING DATA

This tutorial paper will show that chemical process control parameters can be obtained from steady state operating data in combination with simple algebraic equations. The parameters include steady state proces s gain, feedforward control factor and approximate process time consta nt. Hen, Lye treat 'self-regulating' processes first. Integrating proc esses and unstable processes are treated separately, unlike the standa rd method of setting up linear differential equations followed by Lapl ace transformations. With the standard method, a steady state portion of dynamic response, if then is any, appears as a part of equations of a complex variable. Many control engineers in the chemical industries who might have studied the method, do not use it because of mathemati cal difficulties. Instead, they may resort to plant tests that an ofte n time consuming and costly, The parameters obtained by this paper's m ethod will aid improvement of control systems. We will address the rel ation of this method with that of commercial software, which implement advanced process controls based on plant tests. (C) 1998 Elsevier Sci ence Ltd.