Advanced Control Lecture three PID Controllers 1 Action

ﺑﺴﻢ ﺍﻟﻠﻪ ﺍﻟﺮﺣﻤﻦ ﺍﻟﺮﺣﻴﻢ Advanced Control Lecture three PID Controllers 1 - Action and types (Smith & Corripio: Chapter 5) 2 - Reset windup (Smith & Corripio: Chapter 5) 3 - Modifications (Smith & Corripio: Chapter 5 and Astrom & Hagglund: Chapter 3) Lecturer: M. A. Fanaei Ferdowsi University of Mashhad 1

PID Control 1. Action of Controller: If the action is not correctly selected, the controller will not control • Reverse action (increase/decrease) In feedback control loop, the multiplication of Process gain (Kp), Control valve gain (Kv), Sensor gain (Km) and Controller gain (Kc) must be positive. Reverse action : If Kp Kv Km > 0 → Kc > 0 2

PID Control • Direct action (increase/increase) Direct action : If Kp Kv Km < 0 → Kc < 0 To determine the action of a controller, the engineer must know: 1. The process characteristics 2. The fail-safe action of the control valve 3

PID Control 2. Type of PID Controller • Classic PID: • Parallel PID: • Series PID: Range : 0. 05 to 0. 2 (0. 1) 4

PID Control 5

PID Control 3. Reset Windup 6

PID Control 4. Reset Feedback (RFB) Mmax Mmin Internal Reset Feedback 7

PID Control 4. Reset Feedback (RFB) 8

PID Control 4. Reset Feedback (RFB) External Reset Feedback 9

PID Control 5. Back Calculation Tracking Time Constant Td < Tt < Ti Back-Calculation with internal tracking Internal tracking signal 10

PID Control 5. Back Calculation External tracking signal Back-Calculation with external tracking 11

PID Control 5. Proportional and Derivative Kick Proportional Kick Derivative Kick Two Degrees of Freedom or ISA - PID Range: 0 -1, Commonly zero 12

PID Control 13