Feedback control: Handout1

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Feedback control: Handout1

  1. 1. 201452Feedback Control System for Agricultural EngineeringHandout 1<br />Watcharapol Chayaprasert<br />Department of Agricultural Engineering<br />Kasetsart University – Kamphaengsaen<br />
  2. 2. Introduction<br />Dynamic systems and processes to operate at certain conditions<br />But disturbances that tend to change the operating conditions<br />Control systems are needed<br />Closed or Open loops? (i.e., Feedback or not?)<br />Manual or Automatic?<br />Sequential or Continuous controls?<br />Analog or Digital?<br />Linear or Non-linear?<br />SISO, SIMO, MISO or MIMO?<br />
  3. 3. Introduction<br />Machine control<br />Servo control systems<br />Electro-hydraulic position controls<br />Electric motor controls (e.g., on/off, forward/reverse)<br />Process control<br />Heat exchanging process<br />Chemical reactions<br />
  4. 4. Introduction<br />Analog control<br />Electrical<br />Pneumatic<br />Digital control<br />Computer- or electronic-based controller<br />Single-loop controller (continuous control)<br />Programmable Logic Controller (PLC; logic control)<br />
  5. 5. Introduction<br />Continuous control system<br />Dedicated control of single or multiple process parameters<br />Temperature control in a room<br />Motor speed control<br />Flow rate control<br />Sequential control system<br />Process involves a series of tasks<br />Fill  Mix  Heat  Drain  Repeat<br />Time- or event-driven<br />Make use of discrete inputs/outputs, timers, counters, logic controller<br />
  6. 6. Terminology<br />Controlled variable (CV) or Process variable (PV)<br />Quantity to be measured and controlled<br />Manipulated variable (MV)<br />Varied by the controller so that the controlled variable is at the desired value (i.e., set-point, SP)<br />Plants<br />Any physical object to be controlled<br />Processes<br />Any operation to be controlled<br />
  7. 7. Terminology<br />Systems<br />A combination of components that perform to achieve a certain objective<br />Disturbances (or Disturbance variable, DV)<br />Signals that adversely affect the output of the system<br />Feedback control<br />Operation that maintains the system at a desired set-point<br />
  8. 8. Open-loop vs Closed-loop systems<br />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<br />In open-loop system, the output signal is neither measured or fed back for comparison with the input<br />
  9. 9. Block diagram<br />A pictorial representation of a system<br />
  10. 10. Control system components<br />Controller<br />Implement the designed control algorithm<br />Analog circuitry, microcontroller, PLC, PC<br />Sensor<br />Measure physical properties of the plant/process<br />Force, flow rate, temperature, speed, concentration etc.<br />Measured signals are sent back to the controller<br />Actuator<br />Convert control signals into actions that adjust the output of the plant/process<br />Servo motor, pneumatic or hydraulic actuator<br />Power amplifier<br />Control signals are often times too weak to drive (i.e., move) an actuator<br />
  11. 11. Examples<br />What type of control is this system?<br />What is the function of each component?<br />Can you draw the block diagram of this system?<br />
  12. 12. Examples<br />What type of control is this system?<br />What is the function of each component?<br />Can you draw the block diagram of this system?<br />Figure source: Ogata, K. Modern Control Engineering<br />
  13. 13. Examples<br />What type of control is this system?<br />What is the function of each component?<br />Can you draw the block diagram of this system?<br />
  14. 14. Examples<br />กุลธนปรีดา p.14; Ex 1<br />กุลธนปรีดา p.29: Ex 2<br />
  15. 15. Math review<br />Complex numbers<br />Add, subtract, multiply, divide<br />Logarithms<br />Linear algebra<br />Matrix multiply, inverse, sets of linear equations<br />Ordinary Differential Equations <br />Linearization<br />Laplace transform<br />
  16. 16. Discussed topics<br />Modeling<br />Analysis<br />Design<br /><ul><li>Design specs
  17. 17. PID
  18. 18. Root locus
  19. 19. Frequency domain</li></ul>Models of systems<br />mechanical<br />electrical<br />Laplace transform<br />Transfer function<br />Linearization<br />State-space representation<br /><ul><li>Time response
  20. 20. Steady
  21. 21. Transient
  22. 22. Stability
  23. 23. Routh-Hurwitz
  24. 24. Sensitivity
  25. 25. Frequencyresponse
  26. 26. Bode plot
  27. 27. Nyquist</li>

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