1. 201452Feedback Control System for Agricultural EngineeringHandout 1 Watcharapol Chayaprasert Department of Agricultural Engineering Kasetsart University – Kamphaengsaen

2. Introduction Dynamic systems and processes to operate at certain conditions But disturbances that tend to change the operating conditions Control systems are needed Closed or Open loops? (i.e., Feedback or not?) Manual or Automatic? Sequential or Continuous controls? Analog or Digital? Linear or Non-linear? SISO, SIMO, MISO or MIMO?

3. Introduction Machine control Servo control systems Electro-hydraulic position controls Electric motor controls (e.g., on/off, forward/reverse) Process control Heat exchanging process Chemical reactions

4. Introduction Analog control Electrical Pneumatic Digital control Computer- or electronic-based controller Single-loop controller (continuous control) Programmable Logic Controller (PLC; logic control)

5. Introduction Continuous control system Dedicated control of single or multiple process parameters Temperature control in a room Motor speed control Flow rate control Sequential control system Process involves a series of tasks Fill  Mix  Heat  Drain  Repeat Time- or event-driven Make use of discrete inputs/outputs, timers, counters, logic controller

6. Terminology Controlled variable (CV) or Process variable (PV) Quantity to be measured and controlled Manipulated variable (MV) Varied by the controller so that the controlled variable is at the desired value (i.e., set-point, SP) Plants Any physical object to be controlled Processes Any operation to be controlled

7. Terminology Systems A combination of components that perform to achieve a certain objective Disturbances (or Disturbance variable, DV) Signals that adversely affect the output of the system Feedback control Operation that maintains the system at a desired set-point

8. Open-loop vs Closed-loop systems In closed-loop (i.e., feedback) control system, the difference between input and output-feedback signals is used to bring (i.e., control) the output of the system to a desired value In open-loop system, the output signal is neither measured or fed back for comparison with the input

9. Block diagram A pictorial representation of a system

10. Control system components Controller Implement the designed control algorithm Analog circuitry, microcontroller, PLC, PC Sensor Measure physical properties of the plant/process Force, flow rate, temperature, speed, concentration etc. Measured signals are sent back to the controller Actuator Convert control signals into actions that adjust the output of the plant/process Servo motor, pneumatic or hydraulic actuator Power amplifier Control signals are often times too weak to drive (i.e., move) an actuator

11. Examples What type of control is this system? What is the function of each component? Can you draw the block diagram of this system?

12. Examples What type of control is this system? What is the function of each component? Can you draw the block diagram of this system? Figure source: Ogata, K. Modern Control Engineering

13. Examples What type of control is this system? What is the function of each component? Can you draw the block diagram of this system?

14. Examples กุลธนปรีดา p.14; Ex 1 กุลธนปรีดา p.29: Ex 2

15. Math review Complex numbers Add, subtract, multiply, divide Logarithms Linear algebra Matrix multiply, inverse, sets of linear equations Ordinary Differential Equations Linearization Laplace transform

17. PID

18. Root locus

20. Steady

21. Transient

22. Stability

23. Routh-Hurwitz

24. Sensitivity

25. Frequencyresponse

26. Bode plot

27. Nyquist