Automationcontrol3

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Automationcontrol3

  1. 1. PID Controllers and introduction to PLC systems By Dr. Palitha Dassanayake
  2. 2. Control Systems Speed Time Motion profile Micro-processor control system
  3. 3. Fly ball governor Steam valve James watt (speed increases, Steam value closes) Control Systems in early days
  4. 4. Input- Voltage Output-Rotated angle Control System Voltage Voltage Amplifier Telephone line
  5. 5. Amplifications Amplifications Amplifications Telephone line amplification problem noise noise noise noise noise With the amplification, noise gets increased and increased…
  6. 6. Input voltage(a) Amplifier gain Output voltage Amplifier gain Attenuator circuit Input voltage Output voltage(b) _ +
  7. 7. - Feedback gain + Reference input(b) Controller Controlled variable Process Actuating signal Reference input (a) Controller Controlled variable Process Actuating signal Open Loop control system Closed Loop control system
  8. 8. PID controller P= proportional I=Integral D=Derivative 90%-95% closed loop automatic controllers are PID
  9. 9. Automatic Controller - Sensor + Reference input r(t) Controller PlantActuator Output y(t)
  10. 10. Step input and on and off controller r(t) Time A If y(t)<r(t) ON If y(t)>r(t) OFF Time y(t)
  11. 11. P controllers _ Sensor feedback + Set value r(t) Output y(t) P process Steady State Error ? Transient Response Time u(t) SSE )()(()( trtykptu −=
  12. 12. P controller outputs Input r(t)= step input value 2 s+ = 1 1 functionTransfer Kp=1 Kp=5 Steady state error decreases with kp for this particular application Plant
  13. 13. Reducing S.S.E _ + Set value Output P + + plant U(t) We may place an external input, but different set points have different SSE ?
  14. 14. PI Controller ))()(()( tytrte −= P _ + Set value Output I + + process U(t) e(t) ∫+= dttekitekptu )(*)(*)( Integral part
  15. 15. PI controller output Step input value =2 Kp=5 KI=1 KI=5 S.S.E exists S.S.E is zero KI=20 There is an overshoot
  16. 16. PID controllers P _ + Set value Output I D + + + plant dt tde kddttekitekptu )( *)(*)(*)( ++= ∫ ))()(()( tytrte −=
  17. 17. PID controller output Step input value =2 Kp=5 and KI=20 KD=1 KD=10 S.S.E still exists Transient response is also less
  18. 18. PID controller output contd. Kp=5, KI=20 and KD=10 input r(t)- pulse input output y(t)
  19. 19. Tuning of PID controllers PID values are different from one system to another It is required to tune a P, PD, PI or PID controller Basic industrial approaches  Design a stable tuned PID controller after modeling  Develop a simulator after modeling and tune observing the simulator result  On site tuning  Combination of all three approaches
  20. 20. PLC is similar to using a computer but has certain features that are specific to their use as controllers. These are: 1. They are rugged and designed to withstand vibrations, temperature, humidity and noise. 2. The interfacing for inputs and outputs is inside the controller. 3. They are easily programmed and have an easily understood programming language. Programming is primary concerned with logic and switching operations. Programmable Logic Controllers
  21. 21. Data bus Address bus Control bus CPU clock Memory Input/ Output unit Program panel Input channels Output channels Architecture of a Programmable Logic Controller
  22. 22. Normally opened contact Normally closed contact AND operation LADDER DIAGRAMS OR operation Output Special Instruction
  23. 23. I0.0 Q0.0 I0.1 Q0.1 I0.0 I0.1 Q0.0 Ladder diagram using S7 200 Q0.0I0.0 I0.1
  24. 24. Setting and Resetting an output I0.0 Q0.0 I0.1 Q0.0 S R Setting and Resetting a Memory I0.0 M0.0 S I0.1 M0.0 R
  25. 25. Memory Input Register I Type Symbol Example Bit I0.1 Byte IB4 Output Register O Type Symbol Example Bit Q1.1 Byte QB5
  26. 26. Variable Memory V Store intermediate results performed by the control logic in a program Type Symbol Example Bit V10.1 Byte VW100 Bit Memory M Store intermediate status of an operation or other control information Type Symbol Example Bit M26.7 Byte MD20
  27. 27. Two types of timers available 1. On Delay Timer 2. Off Delay Timer
  28. 28. On Delay Timer (T33- steps of 10ms) I0.0 T33 2000+ IN PT TON Q ET T33 Q0.0 Time onSwitch ON Bulb OFF 20s offSwitch
  29. 29. Off Delay Timer (T33- steps of 10ms) I0.0 T33 1500+ IN PT TOF Q ET T33 Q0.0 Time onSwitch ON Bulb OFF 15s offSwitch
  30. 30. Counters I0.0 C48 5+ UP R C48 Q0.0 PV I0.1
  31. 31. Logo Programming & I1 I2 Q1 AND Operation I1 I2 Q1 OR Operation 1≤
  32. 32. S7 200 Programming Techniques 1. Ladder Programming 2. Statement Lists (SLT) 3. Function Block Diagrams
  33. 33. Statement List (SLT) This programming method introduces a list of statements. Let’s look at the basic programming using SLT. Statement List (SLT) This programming method introduces a list of statements. Let’s look at the basic programming using SLT. AND Operation LD I I0.0 // Read I0.0 A I I0.1 //and with I0.1 = Q0.0 //write the value to Q0.0 Statement List (SLT) This programming method introduces a list of statements. Let’s look at the basic programming using SLT. AND Operation LD I I0.0 // Read I0.0 A I I0.1 //and with I0.1 = Q0.0 //write the value to Q0.0 OR Operation LD I I0.0 // Read I0.0 O I I0.1 //or with I0.1 = Q0.0 //write the value to Q0.0
  34. 34. On delay Timer Network 1 LD I0.0 TON T33,+2000 Network 2 LD T33 = Q0.0 Network 1 LD I0.0 LD I0.1 CTU C48,+5 Network 2 LD C48 = Q0.0 Timers Counters
  35. 35. I0.0 I0.1 AND Q0.0 Functional Block Diagrams I0.0 I0.1 OR Q0.0
  36. 36. END

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