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بسم الله الرحمن الرحيم Advanced Control Lecture two

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 ). Step Change.

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بسم الله الرحمن الرحيم Advanced Control Lecture two

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

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

  3. FOPDT Model Fit 1 :

  4. FOPDT Model Fit 2 :

  5. FOPDT Model Fit 3 :

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

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

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

  9. Control Valve 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 psi Liquid Flow: Inlet pressure psia gpm Critical flow factor (0.6-0.95) Gas Flow: scfh Inlet temperature oR Where

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

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

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

  13. PID Control Reset Windup

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

  15. PID Control Reset Feedback (RFB)

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

  17. PID Control Back Calculation Internal tracking signal Tracking Time Constant Td < Tt < Ti Back-Calculation with internal tracking

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

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

  20. PID Control

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