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. Tom Pedersen 3. Mini module: Control of large scale process (sugar production) Kirsten Mølgaard Nielsen 4. Mini module: Control Structure Design Self-Optimizing Control Structure. Tom Pedersen 5. Mini module: Planning Kirsten Mølgaard Nielsen
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CONTROLLER STRUCTURES 1. Mini module: Introduction to control structures Strategic design of control systems. Control objectives Tom Pedersen 2. Mini module:
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CONTROLLER STRUCTURES1. Mini module: Introduction to control structures
Strategic design of control systems. Control objectives Tom Pedersen
2. Mini module: Proces control of basic functionsand common unit processes.Relative Gain Array.Tom Pedersen
3. Mini module: Control of large scale process(sugar production)Kirsten Mølgaard Nielsen
4. Mini module: Control Structure DesignSelf-Optimizing Control Structure.Tom Pedersen
5. Mini module: Planning Kirsten Mølgaard Nielsen
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
Large scale systems• In this course: Control of large scale systems:
LargeMultiple input/outputNon-linearDifficult to understand the functions and to model.
Goals
Main control objectives (main goals):EconomyProduct qualityEnvironment (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.
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 controlDerivative part provides anticipation and dynamic
compensationIntegral part gives the steady state regulation
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
Bottom up design of control systemsBuilding blocks:
Feedback
Feedforward
Cascade
Large loop
Repetitive
Mid-range
Split-range
Ratio control
Decoupling
Limiters
Min/Max (selector)
Signal multiplication
Gain scheduling
Variable structur
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
BUILDING BLOCKS
1. FEEDBACK
2. FEEDFORWARD
3. CASCADE
3. CASCADE
4. LARGE LOOP
5. REPETITIVE CONTROL
5. REPETITIVE CONTROL
6. MID-RANGE CONTROL
6. MID-RANGE CONTROL
7.SPLIT-RANGE CONTROL
8. RATIO CONTROL
8. RATIO CONTROL
8. RATIO CONTROL
9. DECOUPLING
10. LIMITERS
10. LIMITERS
11. SELECTORS
11. SELECTORS
12. STATIC NONLINEARITY
13. SIGNAL MULTIPLICATION
13. SIGNAL MULTIPLICATION
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.