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Advanced ControlLecture threePID Controllers1- 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)1Lecturer: M. A. Fanaei Ferdowsi University of MashhadPID ControlAction 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 2PID Control Direct action (increase/increase)

To determine the action of a controller, the engineer must know:The process characteristicsThe fail-safe action of the control valveDirect action : If Kp Kv Km < 0 Kc < 0 3PID ControlType of PID Controller

Classic PID:

Parallel PID:

Series PID:

Range :0.05 to 0.2(0.1)4

PID Control

5PID ControlReset Windup

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PID ControlReset Feedback (RFB)

Internal Reset FeedbackMminMmax

MmaxMmin

7PID ControlReset Feedback (RFB)

8PID ControlReset Feedback (RFB)

External Reset Feedback

9PID ControlBack Calculation

Back-Calculation with internal tracking

Tracking Time ConstantTd < Tt < TiInternal tracking signal

10PID ControlBack Calculation

Back-Calculation with external tracking

External tracking signal11PID ControlProportional and Derivative Kick

Proportional KickDerivative KickRange: 0-1Range: 0-1, Commonly zeroTwo Degrees of Freedom or ISA - PID12PID Control

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