1. CONTROLLER STRUCTURES
1. Mini module: Introduction to control structures
Strategic design of control systems.
Control objectives
Tom Pedersen
2. Mini module: Proces control of basic functions
and common unit processes.
Relative Gain Array.
3. Mini module: Control of large scale process
(sugar production)
Kirsten Mølgaard Nielsen
4. Mini module: Control Structure Design
Self-Optimizing Control Structure.
5. Mini module: Planning

2. CONTROLLER STRUCTURES
Unbalanced view of control
Control Theory:
The problems are designed for control (Balancing wedge etc.)
It's easy to model the process.
There is a good correlation between theory and practice.
Control in practice:
The objective of the control may be difficult to describe.
It is difficult to understand the function of the process.
Problems with instrumentation (sensors etc)
Modelling is difficult.
Tuning of controllers

4. Large scale systems In this course: Control of large scale systems:
Sugar production
Dairy
Cement production
Paper production
Power stations
Breweries
etc
These are characterised by:
Large
Multiple input/output
Non-linear
Difficult to understand the functions and to model.

5. Goals Main control objectives (main goals): Economy Product quality
Environment (Laws)
Standards
Sometimes it is possible to derive sub goals (strategic goals) from the main goals and the result is that it is necessary to keep a number of variables at constant set points
For a proper solution static optimization may bee needed as we will se in MM 4.

6. Strategic design Strategic design = how to keep certain process
variables at constant set points
Building blocks used in the strategic design
PID Controller - - The Archtype:
Proportional part provides the control
Derivative part provides anticipation and dynamic compensation
Integral part gives the steady state regulation

7. Bottom Up Design A way to view systems A number of building blocks
Ideas to combine them
What are the building blocks of control?
What principles can be used to select and combine them?
The danger: Can it be done better?
Commissioning: Close loops one by one

8. Bottom up design of control systems
Building blocks:
Feedback
Feedforward
Cascade
Large loop
Repetitive
Mid-range
Split-range
Ratio control
Decoupling
Limiters
Min/Max (selector)
Signal multiplication
Gain scheduling
Variable structur

9. Top down design of control systems
Model complete system
Design an integrated system
System concepts
- State feedback
- Observers
- Model predictive control
Commissioning:needs careful considerations

10. BUILDING BLOCKS

11. 1. FEEDBACK

12. 2. FEEDFORWARD

13. 3. CASCADE

14. 3. CASCADE

15. 4. LARGE LOOP

16. 5. REPETITIVE CONTROL

17. 5. REPETITIVE CONTROL

18. 6. MID-RANGE CONTROL

19. 6. MID-RANGE CONTROL

20. 7.SPLIT-RANGE CONTROL

21. 8. RATIO CONTROL

22. 8. RATIO CONTROL

23. 8. RATIO CONTROL

24. 9. DECOUPLING

25. 10. LIMITERS

26. 10. LIMITERS

27. 11. SELECTORS

28. 11. SELECTORS

29. 12. STATIC NONLINEARITY

30. 13. SIGNAL MULTIPLICATION

31. 13. SIGNAL MULTIPLICATION

32. 14. Gain Scheduling
May be a signal multiplication, so that the controller’s proportional gain is multiplied with a measured value.
In normal operation this multiplication factor is 1.
The multiplication may be inserted after the controller.

33. 15. VARIABLE STRUCTUR

34. EXAMPLE