بسم الله الرحمن الرحيم Advanced Control Lecture two Mohammad Ali Fanaei Dept. of Chemical Engineering Ferdowsi University of Mashhad Reference: Smith & Corripio, “Principles and practice of automatic process control, 3 rd ed., Wiley, 2006

Empirical Modeling (Step Testing) Final Control Element Process Sensor/ Transmitter Step Change Record m(t)m(t)c(t) Process Gain:

FOPDT Model Fit 1 :

FOPDT Model Fit 2 :

FOPDT Model Fit 3 :

Control Valve Control Valve Action Control Valve Characteristics Control valve Capacity m(t)m(t)vp(t)Cv(t)Cv(t)f(t)f(t)

Control Valve 1.Control Valve Action Fail-Closed (FC) or Air-to-Open (AO) : Fail-Open (FO) or Air-to-Close (AC) :

Control Valve 2.Control Valve Characteristics Linear Quick-opening Equal percentage Rangeability parameter

Control Valve 3.Control Valve Capacity The flow in U.S. gallons per minute (gpm) of water that flows through a valve at a pressure drop of 1 psi across the valve Liquid Flow: gpm psi Gas Flow: scfh Critical flow factor ( ) Inlet pressure psia Inlet temperature o R Where

PID Control 1.Action of Controller If the action is not correctly selected, the controller will not control Reverse action (increase/decrease)

PID Control Direct action (increase/increase) To determine the action of a controller, the engineer must know: 1.The process requirement for control 2.The fail-safe action of the control valve

PID Control 2.Type of PID Controller Ideal PID: Parallel PID: Series PID: Range 0.05 to 0.2

PID Control 3.Reset Windup

PID Control 4.Reset Feedback (RFB) Internal Reset Feedback

PID Control 4.Reset Feedback (RFB)

PID Control 4.Reset Feedback (RFB) External Reset Feedback

PID Control 5.Back Calculation Back-Calculation with internal tracking Tracking Time Constant T d < T t < T i

PID Control 5.Back Calculation Back-Calculation with external tracking External tracking signal

PID Control 5.Proportional and Derivative Kick Proportional KickDerivative Kick Range: 0-1Range: 0-1, Commonly zero Two Degrees of Freedom or ISA - PID

PID Control