1. By Finn Aakre Haugen (finn.haugen@hit.no)
Course PEF3006 Process Control Fall 2018
Feedforward Control
By Finn Aakre Haugen
PEF3006 Process Control. USN. F. Haugen. 2018

2. Why feedforward control?
Faster disturbance compensation
and/or
Faster setpoint tracking (important only with time-varying setpoint)
PEF3006 Process Control. USN. F. Haugen. 2018

3. Control system with both feedforward and feedback:
PEF3006 Process Control. USN. F. Haugen. 2018

4. Example 1: Feedforward in level control system Simulator
Let's derive the feedforward controller (it is quite easy).
Skala: LTLine brukerforum, : Minikurs i regtek. F. Haugen.

5. Example 2: Feedforward control in a temperature control system
(We will run a simulator of this example.)
PEF3006 Process Control. USN. F. Haugen. 2018

6. Example cont.: How to derive the feedforward controller:
(1) Process modelling: Energy balance:
(2) The feedforward controller is obtained by solving for the control variable, and substituting the process variable by its setpoint:
Can it be implemented?
Find out by inspecting the right-hand side!
All terms must have known values.
Which sensors are needed?
PEF3006 Process Control. USN. F. Haugen. 2018

7. Feedforward control in temperature control system
Example cont.:
Simulator:
Feedforward control in temperature control system
PEF3006 Process Control. USN. F. Haugen. 2018

8. Example 3: Feedforward in a DP system( dynamic positioning)8
Simulator:
Feedforward in DP system
PEF3006 Process Control. USN. F. Haugen. 2018

9. PEF3006 Process Control. USN. F. Haugen. 20189
Experimental
feedforward
PEF3006 Process Control. USN. F. Haugen. 2018

10. Structure of control system:10
Structure of control system:
PEF3006 Process Control. USN. F. Haugen. 2018

11. Relation between disturbance measurement and 11
Relation between disturbance measurement and
steady-state control signal (with PID controller):
PEF3006 Process Control. USN. F. Haugen. 2018

12. Example 1: Temperature control of air heater12
PEF3006 Process Control. USN. F. Haugen. 2018

13. PEF3006 Process Control. USN. F. Haugen. 2018
Example 1 cont. 13
Pot.meter voltage
Potensio-
meter
Air flow (fan speed)
Temp at outlet
PEF3006 Process Control. USN. F. Haugen. 2018

14. Without feedforward (only feedback):14
PEF3006 Process Control. USN. F. Haugen. 2018

15. With feedforward (and feedback)15
Improvement?
PEF3006 Process Control. USN. F. Haugen. 2018

16. PEF3006 Process Control. USN. F. Haugen. 2018
Example 2: Feedforward from inlet temperatur (Tp_inn) in temp. control of heat ex.
Simulator
PEF3006 Process Control. USN. F. Haugen. 2018