1. Process Control & Instrumentation MAPUA INSTITUTE OF TECHNOLOGY
PID CONTROLLER
MAPUA INSTITUTE OF TECHNOLOGY
School of Chemical Engineering & Chemistry

2. OUTLINE Important Concepts Process Time Lags PID Control Algorithms
Selection Of Control Action

3. PROCESS CONTROL Definition
the physical regulation of a process to maintain a particular process variable as close as possible to a desired value.

4. 4 BASIC COMPONENTS IN A FEEDBACK CONTROL LOOP
Operator
Set Point (SV)
3. Controller
Controller Output
Process Variable (PV)
2. Measuring Element
4. Final Control Element
Controlled Variable (CV)
Manipulated Variable (MV)
1. Process
Load Variable
Refining Process (Plant)

5. FEEDBACK CONTROL ALGORITHM
Feedback Control = PID Control
where
OUT(t) = controller output, %
OUTdesign = design (steady state) controller output
OUT = control adjustment
OUT(t) = OUTdesign + OUT

6. PID CONTROL ALGORITHM P = Proportional Control Action
I = Integral Control Action
D = Derivative Control Action

7. Proportional Control Action
control adjustment is proportional to the magnitude of the error
where
OUT = control adjustment, %
Kc = Proportionality Constant (Gain or Sensitivity)
e = ERROR = Set Point (SP) - Process Variable (PV)
OUT = (Kc)(e)

8. Integral Control Action
control adjustment is proportional to the time integral of the error
where
OUT = control adjustment, %
I = Integral Time Constant, time t
OUT = (Kc)/(I) (e)dt

9. Derivative Control Action
control adjustment is proportional to the rate of change of the error
where
OUT = control adjustment, %
D = Derivative Time Constant, time
OUT = (Kc)(D)(de/dt)

10. Types of PID Controller
P - Proportional Controller
PI - Proportional Integral Controller
PD - Proportional Derivative Controller
PID - Proportional Integral Derivative Controller

11. P - Proportional Controller
OUT(t) = OUTdesign + (Kc)(e)
only one tuning parameter ( Kc )
there is always an offset = steady state error or permanent deviation between the Set Point and the Process Variable

12. PI - Proportional Integral Controller
OUT(t) = OUTdesign + (Kc)(e) + (Kc)/(I) (e)dt
eliminates offset
more unstable compared to P Controller
two tuning parameters ( Kc , I )

13. PD - Proportional Derivative Controller
OUT(t) = OUTdesign + (Kc)(e) + (Kc)(D)(de/dt)
faster response
does not eliminates offset
susceptible to noise
two tuning parameters ( Kc , D)

14. PID - Proportional Integral Derivative Controller
OUT(t) = OUTdesign + (Kc)(e) + (Kc)/(I) (e)dt + (Kc)(D)(de/dt)
faster response
eliminates offset
susceptible to noise
three tuning parameters ( Kc , I , D)

15. Selection of Control Action