1. 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

2. PID Control
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

3. 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:
The process characteristics
The fail-safe action of the control valve

4. PID Control Type of PID Controller Classic PID: Parallel PID:
Series PID:
Range :
0.05 to 0.2
(0.1)

5. PID Control

6. PID Control
Reset Windup

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

8. PID Control
Reset Feedback (RFB)

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

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

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

12. 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

13. PID Control