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Control Actions

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Process control system: Block diagram & explanation of each
block.
Control actions, Discontinuous modes:
ON OFF controllers: equation, neutral zone
Continuous modes: PROPORTIONAL controllers (offset, proportional band),
INTEGRAL & DERIVATIVE controllers; o/p equations,
corresponding Laplace Transforms, Response of P,I & D
controllers
Composite controllers: PI, PD, PID controllers- O/P Equations, Response, Comparison

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Control Actions

  1. 1. KARMAVEER BHAURAO PATIL POLYTECHNIC, SATARA Rayat Shikshan Sanstha’s Department Of Electronics And Telecommunication Engineering Control Actions
  2. 2. 9/27/2016 Amit Nevase 2 Control System and PLC Amit Nevase Lecturer, Department of Electronics & Telecommunication Engineering, Karmaveer Bhaurao Patil Polytechnic, Satara EJ5G Subject Code: 17536 Third Year Entc
  3. 3. Objectives The student will be able to:  Understand classifications of control system.  Understand Steady state, time response, and frequency response analysis.  Analyze the Stability of control system using RH criteria.  Understand the fundamentals and diff. Hardware parts of PLC.  Draw ladder diagrams to program PLC 9/27/2016 Amit Nevase 3
  4. 4. Teaching & Examination Scheme  Two tests each of 25 marks to be conducted as per the schedule given by MSBTE.  Total of tests marks for all theory subjects are to be converted out of 50 and to be entered in mark sheet under the head Sessional Work (SW). 9/27/2016 Amit Nevase 4 Teaching Scheme Examination Scheme TH TU PR PAPER HRS TH PR OR TW TOTAL 03 -- 02 03 100 50# --- 25@ 175
  5. 5. Module I – Introduction to Control System  Introduction to Control systems (4 Marks)  Control System – Definition and Practical Examples  Classification of Control System : Open Loop and Closed Loop Systems – Definitions, Block diagrams, practical examples, and Comparison, Linear and Non-linear Control System, Time Varying and Time In-varying Systems  Servo System : Definition, Block Diagram, Classification (AC and DC Servo System), Block diagram of DC Servo System.  Laplace Transform and Transfer Function (4 Marks)  Laplace Transform : Signifiance in Control System  Transfer Function : Definition, Derivation of transfer functions for Closed loop Control System and Open Loop Control System, Differential Equations and transfer functions of RC and RLC Circuit  Block Diagram Algebra (8 Marks)  Order of a System : Definition, 0,1,2 order system Standard equation, Practical Examples  Block Diagram Reduction Technique: Need, Reduction Rules, Problems 9/27/2016 Amit Nevase 5
  6. 6. Module II – Time Response Analysis  Time Domain Analysis (4 Marks)  Transient and Steady State Response  Standard Test Inputs : Step, Ramp, Parabolic and Impulse, Need, Significance and corresponding Laplace Representation  Poles and Zeros : Definition, S-plane representation  First and Second order Control System (8 Marks)  First Order Control System : Analysis for step Input, Concept of Time Constant  Second Order Control System : Analysis for step input, Concept, Definition and effect of damping  Time Response Specifications (8 Marks)  Time Response Specifications ( no derivations )  Tp, Ts, Tr, Td, Mp, ess – problems on time response specifications  Steady State Analysis – Type 0, 1, 2 system, steady state error constants, problems 9/27/2016 Amit Nevase 6
  7. 7. Module III – Stability  Introduction to Stability (4 Marks)  Definition of Stability, Analysis of stable, unstable, critically stable and conditionally stable  Relative Stability  Root locations in S-plane for stable and unstable system  Routh’s Stability Criterion (8 Marks)  Routh’s Stability Criterion : Different cases and conditions  Statement Method  Numericals Problems 9/27/2016 Amit Nevase 7
  8. 8. Module IV – Control Actions  Process Control System (4 Marks)  Process Control System – Block diagram, explanation of each block  Control Actions (8 Marks)  Discontinuous Mode : On-Off Controller, Equation, Neutral Zone  Continuous modes: Proportional Controller (offset, proportional band), Integral Controllers, Derivative Controllers – output equations, corresponding Laplace transforms, Response of P, I, D controllers  Composite Controllers : PI, PD, PID Controllers – output equations, response, comparison 9/27/2016 Amit Nevase 8
  9. 9. Module V – PLC Fundamentals  Introduction (4 Marks)  Evolution of PLC in automation, need and benefits of PLC in automation  Block Diagram of PLC (12 Marks)  Block diagram and description of different parts of PLC -  CPU Function, Scanning cycle, speed of execution, Power supply function,  Memory – function , organization of ROM and RAM  Input modules – function, different input devices used with PLC and their uses  Output modules – function, different output devices used with PLC and their uses  Fixed and Modular PLCs 9/27/2016 Amit Nevase 9
  10. 10. Module VI – PLC Hardware and Programming  PLC Hardware (8 Marks)  Discrete Input Modules – Block diagram, typical wiring details, Specifications of AC input modules and DC input modules. Sinking and sourcing concept in DC input modules  Discrete Output Modules – Block diagram, typical wiring details, Specifications of AC output modules and DC output modules.  Analog Input and output modules : Block diagram, typical wiring details and specifications  PLC Programming (16 Marks)  I/O Addressing in PLC  PLC Instruction Set : Relay instructions, timer instructions, counter instructions, data handling instructions, logical and comparison instructions  PLC programming examples based on above instruction using Ladder programming 9/27/2016 Amit Nevase 10
  11. 11. Module-IV Control Actions 9/27/2016 Amit Nevase 11
  12. 12. Specific Objectives Explain the need of Control actions Differentiate between different types of Control actions Such as P, I & D Explain composite controllers; PI, PD, PID controllers 9/27/2016 Amit Nevase 12
  13. 13. Module IV – Control Actions  Process Control System (4 Marks)  Process Control System – Block diagram, explanation of each block  Control Actions (8 Marks)  Discontinuous Mode : On-Off Controller, Equation, Neutral Zone  Continuous modes: Proportional Controller (offset, proportional band), Integral Controllers, Derivative Controllers – output equations, corresponding Laplace transforms, Response of P, I, D controllers  Composite Controllers : PI, PD, PID Controllers – output equations, response, comparison 9/27/2016 Amit Nevase 13
  14. 14. Block Diagram of Process Control System 9/27/2016 Nevase Amit 14
  15. 15. Module IV – Control Actions  Process Control System (4 Marks)  Process Control System – Block diagram, explanation of each block  Control Actions (8 Marks)  Discontinuous Mode : On-Off Controller, Equation, Neutral Zone  Continuous modes: Proportional Controller (offset, proportional band), Integral Controllers, Derivative Controllers – output equations, corresponding Laplace transforms, Response of P, I, D controllers  Composite Controllers : PI, PD, PID Controllers – output equations, response, comparison 9/27/2016 Amit Nevase 15
  16. 16. Classification of Control Actions Discontinuous Continuous On-Off Controller Two Position Controller Multi Position Controller Floating Mode Controller Composite Controllers P I D PI PD PID 9/27/2016 Nevase Amit 16
  17. 17. Related Terms  Continuous Controller: Controller that responds to continuous input variables are called continuous controller.  Discrete Controller: Controller that responds to discrete signal are called discrete controllers.  Process Equation: A process equation describes the mathematical relationship among the input and output variables. 9/27/2016 Nevase Amit 17
  18. 18. Related Terms  Process Load: The term process load refers to a set of parameters that influences or bring changes in the process excluding the controlled variable.  Nominal Load: All the parameters have their normal or nominal value  Transient : A temporary or sudden change or the variation of one of the variable is called transient.  Process Lag : A process control loop responds to ensure that some finite time later, the variable returns to the set point value. Part of this time is consumed by the process itself and that time is called process lag. 9/27/2016 Nevase Amit 18
  19. 19. Related Terms  Control Lag : Control lag refers to the time for the process control loop to make necessary adjustment to the final control element.  Dead Time : Another time variable associated with process control is a function of both process control system and the process. This is the elapsed time between the instant of deviation (error) occurs and when the corrective action first occurs.  Cycling : Oscillation of error about the zero value. This means the dynamic variable cycling above and below the set point. For cycling we are interested in amplitude and period of oscillation. 9/27/2016 Nevase Amit 19
  20. 20. Module IV – Control Actions  Process Control System (4 Marks)  Process Control System – Block diagram, explanation of each block  Control Actions (8 Marks)  Discontinuous Mode : On-Off Controller, Equation, Neutral Zone  Continuous modes: Proportional Controller (offset, proportional band), Integral Controllers, Derivative Controllers – output equations, corresponding Laplace transforms, Response of P, I, D controllers  Composite Controllers : PI, PD, PID Controllers – output equations, response, comparison 9/27/2016 Amit Nevase 20
  21. 21. Synonyms: “two-position” or “bang-bang” controllers. Controller output has two possible values. e = error = set point – measured variable ON-OFF Controller- 2 Position Controller 9/27/2016 Nevase Amit 21
  22. 22. Neutral Zone Practical case (dead band) system never reaches steady-state δ = tolerance 9/27/2016 Nevase Amit 22
  23. 23. ON-OFF Controller-Multi position Controller Multimode/ Multi-position Controller: Multimode controller is a logical extension of On/Off controller. It is used to provide several intermediate, rather than two, setting of the controller output. This discontinuous control is used in an attempt to reduce the cycling behavior and overshoot and undershoot inherent in the On/Off controller. 9/27/2016 Nevase Amit 23
  24. 24. Floating Control Mode In a floating control, the specific output of the controller is not uniquely determined by the error. If the error is zero the output does not change but remains (floats) at whatever setting it was when the error went to zero. When the error moves off zero, the controller output again begins to change 9/27/2016 Nevase Amit 24
  25. 25. Floating Control Mode Floating mode controller is of two types: Single Speed: In the single-speed floating mode, the output of the control element changes at a fixed rate when the error exceeds the neutral zone. Multi Speed: In the multi-speed floating mode, not one but several possible speeds (rates) are changed by controller output. Usually, the rate increases as the deviation exceeds certain rate. 9/27/2016 Nevase Amit 25
  26. 26. Electronic ON-OFF Controller 9/27/2016 Nevase Amit 26
  27. 27. Electronic ON-OFF Controller 9/27/2016 Nevase Amit 27
  28. 28. Advantages of ON-OFF Controller Only two output states i.e. ON and OFF. Simple construction Low cost 9/27/2016 Nevase Amit 28
  29. 29. Disadvantages of ON-OFF Controller Response of ON-OFF controller is slow. Not suitable for complex system 9/27/2016 Nevase Amit 29
  30. 30. Module IV – Control Actions  Process Control System (4 Marks)  Process Control System – Block diagram, explanation of each block  Control Actions (8 Marks)  Discontinuous Mode : On-Off Controller, Equation, Neutral Zone  Continuous modes: Proportional Controller (offset, proportional band), Integral Controllers, Derivative Controllers – output equations, corresponding Laplace transforms, Response of P, I, D controllers  Composite Controllers : PI, PD, PID Controllers – output equations, response, comparison 9/27/2016 Amit Nevase 30
  31. 31. Proportional- Integral- Derivative Proportional Integral Derivative Output Response for Step Input Signal for: 9/27/2016 Nevase Amit 31
  32. 32. Proportional Control Action  In the case of the proportional controller, the actuation signal is proportional to the system deviation.  If the system deviation is large, the value of the manipulated variable is large.  If the system deviation is small, the value of the manipulated variable is small.  The time response of the P controller in the ideal state is exactly the same as the input variable 9/27/2016 Nevase Amit 32
  33. 33. Proportional Control Action 9/27/2016 Nevase Amit 33
  34. 34. Proportional Control Action In a proportional control mode, a smooth linear relationship exists between the controller output and the error. The range of error to cover the 0% to 100% controller output is called the proportional band, because the one-to-one correspondence exists only for errors in this range. 9/27/2016 Nevase Amit 34
  35. 35. Proportional Control Action The output can be expressed as: Where, Kp = proportional gain between error and controller output p0 = controller output with no error. 9/27/2016 Nevase Amit 35
  36. 36. Proportional Control Action In a proportional control mode, the proportional band is dependent on the gain and can be expressed as : 9/27/2016 Nevase Amit 36
  37. 37. The proportional band of a proportional controller depends on the inverse of the gain. 9/27/2016 Nevase Amit 37
  38. 38. Characteristics of P Control mode If error is zero, the output is a constant equal to p0. If there is an error, for every 1% of error, a correction of Kp percent is added to or subtracted from p0 depending the sign of the error. There is a band of error about zero of magnitude PB with which the output is not saturated at 0% or 100%. 9/27/2016 Nevase Amit 38
  39. 39. Why not “Proportional”? An important characteristics of proportional controller mode is that it produces a permanent residual error in the operating point of the controlled variable, when a change in load occurs. This error is referred to as offset. It can be minimized by a larger constant Kp which will also reduce the proportion band. Offset: 9/27/2016 Nevase Amit 39
  40. 40. An offset error must occur if a proportional controller requires a new zero-error output following a load change 9/27/2016 Nevase Amit 40
  41. 41. Proportional Controller Setpoint Car – steering analogy: Check distance from middle of the lane and correct steering in proportion to distance from desired position 9/27/2016 Nevase Amit 41
  42. 42. Electronic Proportional Controller 9/27/2016 Nevase Amit 42
  43. 43. Electronic Proportional Controller where Vout= output voltage Ve= error voltage Vo= output with zero error Vout GpVe Vo  2 1 R Gp gain R   9/27/2016 Nevase Amit 43
  44. 44. Advantages of Proportional Controller Construction is simple These controllers has high loop gain It has steady state tracking accuracy It improves the disturbances signal reduction It stabilizes the gain and makes the system more stable 9/27/2016 Nevase Amit 44
  45. 45. Disadvantages of Proportional Controller It cannot accommodate load change without sustained deviation. It produces the constant steady state error. For very large gain it leads to instability of the system It has a sluggish i.e. slow response for wide proportional band. It makes the system less sensitive to parameter variation 9/27/2016 Nevase Amit 45
  46. 46. Module IV – Control Actions  Process Control System (4 Marks)  Process Control System – Block diagram, explanation of each block  Control Actions (8 Marks)  Discontinuous Mode : On-Off Controller, Equation, Neutral Zone  Continuous modes: Proportional Controller (offset, proportional band), Integral Controllers, Derivative Controllers – output equations, corresponding Laplace transforms, Response of P, I, D controllers  Composite Controllers : PI, PD, PID Controllers – output equations, response, comparison 9/27/2016 Amit Nevase 46
  47. 47. Integral Control Action  The I controller adds the system deviation over time. It integrates the system deviation.  As a result, the rate of change (and not the value) of the manipulated variable is proportional to the system deviation.  This is demonstrated by the step response of the I controller: if the system deviation suddenly increases, the manipulated variable increases continuously. 9/27/2016 Nevase Amit 47
  48. 48. Integral Control Action 9/27/2016 Nevase Amit 48
  49. 49. Integral Control Action  The greater the system deviation, the steeper the increase in the manipulated variable  For this reason the I controller is not suitable for totally compensating remaining system deviation.  If the system deviation is large, the manipulated variable changes quickly.  As a result, the system deviation becomes smaller and the manipulated variable changes more slowly until equilibrium is reached. 9/27/2016 Nevase Amit 49
  50. 50. Integral Control Action  A pure I controller is unsuitable for most controlled systems, as it either causes oscillation of the closed loop or it responds too slowly to system deviation in systems with a long time response.  In practice there are hardly any pure I controllers. 9/27/2016 Nevase Amit 50
  51. 51. Integral Control Action In a integral control mode, the rate of change of controller output is proportional to the error. So the output can be expressed as: 9/27/2016 Nevase Amit 51
  52. 52. Characteristics Integral Control Action If error is zero, the output is a constant equal to p0. If there is an error, for every 1% of error, a correction of KI percent is added to or subtracted from p0 depending the sign of the error. 9/27/2016 Nevase Amit 52
  53. 53. Integral mode controller action: (a) The rate of output change depends on error, and (b) an illustration of integral mode output and error. 9/27/2016 Nevase Amit 53
  54. 54. Why not “Integral”? The problem for integral controller is that, if there is a zero change in slope, the controller output holds to a constant value. This is called integral windup. The only way to cut the wind up is to put a negative error Integral Windup: 9/27/2016 Nevase Amit 54
  55. 55. Integral Controller Integration of a curve  area under the curve Integrated input signal is multiplied by a factor, Ki 9/27/2016 Nevase Amit 55
  56. 56. Integral Controller Setpoint Car steering analogy: Look out through the back window and keep track of •how long the car has been out of desired position and •by how much. How long (sec) * how much (m) is the integral (sec*m). The longer the car was positioned away from the set point the stronger the signal Good to correct for long term and only slight deviation from set point. 9/27/2016 Nevase Amit 56
  57. 57. Integral Controller  A purely integrating controller is slow and  Error takes long time to build up  Action can become too strong  overshooting  Int controller is unaware of current position  Generally used combined with P control (looking at current position) – PI control 9/27/2016 Nevase Amit 57
  58. 58. Electronic Integral Controller 9/27/2016 Nevase Amit 58
  59. 59. Electronic Integral Controller where Vout= output voltage integration gain Ve= error voltage Vout(0)= initial output voltage 0 (0) t I eVout G V dt Vout  1 IG RC   9/27/2016 Nevase Amit 59
  60. 60. Advantages of Integral Controller It reduces steady state error i.e. effect of offset. It provides high controlled output at a particular time after the error generated is for high value of KI. It responds to the continued existence of deviation. 9/27/2016 Nevase Amit 60
  61. 61. Disadvantages of Integral Controller It is never used alone. It makes the system unstable for oscillatory response. It introduces hunting in the system response about its steady state condition. 9/27/2016 Nevase Amit 61
  62. 62. Module IV – Control Actions  Process Control System (4 Marks)  Process Control System – Block diagram, explanation of each block  Control Actions (8 Marks)  Discontinuous Mode : On-Off Controller, Equation, Neutral Zone  Continuous modes: Proportional Controller (offset, proportional band), Integral Controllers, Derivative Controllers – output equations, corresponding Laplace transforms, Response of P, I, D controllers  Composite Controllers : PI, PD, PID Controllers – output equations, response, comparison 9/27/2016 Amit Nevase 62
  63. 63. Derivative Control Action In a derivative control mode, the controller output is proportional to the derivative of the error. So the output can be expressed as: 9/27/2016 Nevase Amit 63
  64. 64. Derivative mode controller action changes depending on the rate of error. 9/27/2016 Nevase Amit 64
  65. 65. Characteristics Derivative Control Action If error is zero or the error is constant in time, the mode provides no output. If there is an error, for every 1% -per-second rate of change of error, the mode contributes an output of KD percent. For direct action, a positive rate of change of error produces a positive derivative mode output. 9/27/2016 Nevase Amit 65
  66. 66. Why not “Derivative”?  A step change in set point causes a false step error for the derivative controller. This step change causes the derivative part of the controller to saturate the overall controller output. This ultimately forces the final control element to go to hard Off mode. This is called derivative overrun. The solution to this problem is to feed the derivative controller with process variable (PV) instead of error Derivative Overrun: 9/27/2016 Nevase Amit 66
  67. 67. Derivative Controller  Examines the rate of change of the output of the process  The faster the change, the stronger the action  The derivative of the output (slope) is multiplied by a constant, Kd 9/27/2016 Nevase Amit 67
  68. 68. Derivative Controller Setpoint 9/27/2016 Nevase Amit 68
  69. 69. Derivative Controller  Differential control is insensitive to slow changes  If the variable is parallel to the setpoint, no change is made (slope = 0)  Differential control is very useful when combined with P and I control  PID control 9/27/2016 Nevase Amit 69
  70. 70. Electronic Derivative Controller 1 2 dVout dVe Vout R C R C dt dt    9/27/2016 Nevase Amit 70
  71. 71. Advantages of Derivative Controller It can overcome the overshoot and severe cycling. It has a rapid response to counter the effect of rapidly changing errors. It responds to the changes of the speed and direction to the deviation. It does not affect the steady state error directly, but anticipates the error. It increases the stability of the system by initiating an early corrective action 9/27/2016 Nevase Amit 71
  72. 72. Disadvantages of Derivative Controller It cannot be used alone, since it cannot give any output for zero or constant error. It is ineffective for slowly changing error and hence causes the drift. It amplifies the noise signal and causes a saturation effect on the system. It does not eliminate the steady state error. (offset) 9/27/2016 Nevase Amit 72
  73. 73. Module IV – Control Actions  Process Control System (4 Marks)  Process Control System – Block diagram, explanation of each block  Control Actions (8 Marks)  Discontinuous Mode : On-Off Controller, Equation, Neutral Zone  Continuous modes: Proportional Controller (offset, proportional band), Integral Controllers, Derivative Controllers – output equations, corresponding Laplace transforms, Response of P, I, D controllers  Composite Controllers : PI, PD, PID Controllers – output equations, response, comparison 9/27/2016 Amit Nevase 73
  74. 74. PI-Controller  The PI controller combines the behaviour of the I controller and P controller.  This allows the advantages of both controller types to be combined: fast reaction and compensation of remaining system deviation.  For this reason, the PI controller can be used for a large number of controlled systems.  In addition to proportional gain, the PI controller has a further characteristic value that indicates the behaviour of the I component: the reset time (integral- action time). 9/27/2016 Nevase Amit 74
  75. 75. PI-Controller 9/27/2016 Nevase Amit 75
  76. 76. PI-Controller This control mode results from a combination of the proportional mode and the integral mode. The output can be expressed as: 9/27/2016 Nevase Amit 76
  77. 77. Proportional-integral (PI) action showing the reset action of the integral contribution 9/27/2016 Nevase Amit 77
  78. 78. Characteristics of PI-Controller When error is zero, the controller output is fixed at PI(0) . If there is an error, the proportional term contributes a correction, and the integral term begins to increase/decrease the accumulated value [ initially, pI (0)], depending on the sign of the error and the direct or reverse action. 9/27/2016 Nevase Amit 78
  79. 79. Electronic PI Controller 2 2 1 1 2 0 1 ( ) ( ) (0) t e R R Vout Ve V dt Vout R R R C    9/27/2016 Nevase Amit 79
  80. 80. Advantages of PI Controller It provides better stability to the system. It provides simplicity and directness. It fully eliminates the steady state error i.e. offset. It has good transient response. It stabilizes the controller gain. 9/27/2016 Nevase Amit 80
  81. 81. Disadvantages of PI Controller It takes the longer time to stabilize the controller gain than proportional controller action. It suffers from only oscillation induced by the integral overshoot. It requires excessive stabilization, when the process has many energy elements or dead time. 9/27/2016 Nevase Amit 81
  82. 82. Module IV – Control Actions  Process Control System (4 Marks)  Process Control System – Block diagram, explanation of each block  Control Actions (8 Marks)  Discontinuous Mode : On-Off Controller, Equation, Neutral Zone  Continuous modes: Proportional Controller (offset, proportional band), Integral Controllers, Derivative Controllers – output equations, corresponding Laplace transforms, Response of P, I, D controllers  Composite Controllers : PI, PD, PID Controllers – output equations, response, comparison 9/27/2016 Amit Nevase 82
  83. 83. PD Controller This control mode results from a combination of the proportional mode and the derivative mode. The output can be expressed as: 9/27/2016 Nevase Amit 83
  84. 84. PD- Controller  The PD controller consists of a combination of proportional action and differential action.  The differential action describes the rate of change of the system deviation.  The greater this rate of change – that is the size of the system deviation over a certain period – the greater the differential component.  In addition to the control response of the pure P controller, large system deviations are met with very short but large responses.  This is expressed by the derivative-action time (rate time). 9/27/2016 Nevase Amit 84
  85. 85. Proportional-derivative (PD) action showing the offset error from the proportional mode 9/27/2016 Nevase Amit 85
  86. 86. Electronic PD Controller 2 2 3 1 3 1 3 ( ) ( ) R R dVe Vout Ve R C Vo R R R R dt      9/27/2016 Nevase Amit 86
  87. 87. Advantages of PD Controller It allows the rise of narrower proportional band with its lesser offset. It increases the controller gain during the error change. It can compensate the rapidly changing error. It can handle the fast process load change. It can compensate some of the lag in a process. 9/27/2016 Nevase Amit 87
  88. 88. Disadvantages of PD Controller It cannot eliminate the offset of proportional controller. 9/27/2016 Nevase Amit 88
  89. 89. Module IV – Control Actions  Process Control System (4 Marks)  Process Control System – Block diagram, explanation of each block  Control Actions (8 Marks)  Discontinuous Mode : On-Off Controller, Equation, Neutral Zone  Continuous modes: Proportional Controller (offset, proportional band), Integral Controllers, Derivative Controllers – output equations, corresponding Laplace transforms, Response of P, I, D controllers  Composite Controllers : PI, PD, PID Controllers – output equations, response, comparison 9/27/2016 Amit Nevase 89
  90. 90. PID- Controller  In addition to the properties of the PI controller, the PID controller is complemented by the D component.  This takes the rate of change of the system deviation into account.  If the system deviation is large, the D component ensures a momentary extremely high change in the manipulated variable.  While the influence of the D component falls of immediately, the influence of the I component increases slowly.  If the change in system deviation is slight, the behaviour of the D component is negligible 9/27/2016 Nevase Amit 90
  91. 91. PID- Controller  This behavior has the advantage of faster response and quicker compensation of system deviation in the event of changes or disturbance variables.  The disadvantage is that the control loop is much more prone to oscillation and that setting is therefore more difficult. 9/27/2016 Nevase Amit 91
  92. 92. PID- Controller 9/27/2016 Nevase Amit 92
  93. 93. PID Controller This is one of the most powerful but complex controller mode operations combines the proportional, integral and derivative modes. The output for this mode can be expressed as: 9/27/2016 Nevase Amit 93
  94. 94. The three-mode controller action exhibits proportional, integral, and derivative action. 9/27/2016 Nevase Amit 94
  95. 95. Problems with Individual Element P, I, D Setpoint P: Alarm: strong left turn needed I: No problem: Past Right and Left errors are about equal D: No problem: Direction is parallel to setpoint 9/27/2016 Nevase Amit 95
  96. 96. Time Analogy of PID Controller  P: Present time. Only considers current position. Not aware of current direction and of error history  I: Past time. Only compiles an error sum of the past. Not aware of current distance of signal from setpoint and of current direction.  D: Future time. Only considers current direction (trend). Now aware of current distance of signal from setpoint and of error history. 9/27/2016 Nevase Amit 96
  97. 97. PID Response Positive deviation Controlled variable Set-point Negative deviation Time 1. Output without control 2. Proportional action 3. Integral action 4. Proportional + integral action 5. Proportional + derivative action 6. Proportional + integral + derivative action 1 2 3 5, 6 4 9/27/2016 Nevase Amit 97
  98. 98. Electronic PID Controller 2 2 2 1 1 1 1 ( ) ( ) ( ) (0) e e D D I I R R R dV Vout Ve V dt R C Vout R R R C R dt      9/27/2016 Nevase Amit 98
  99. 99. Advantages of PID Controller It reduces the overshoot which often occurs when integral control action is added to proportional control action. It counteracts the lag characteristics introduced by the integral control action. It approaches the tendencies towards oscillations. It senses the rate of movement away from the set point and gives corrective action earlier than only with P or PI 9/27/2016 Nevase Amit 99
  100. 100. Advantages of PID Controller It is more effective for control process with many energy storage element than P+I control action used alone. It eliminates the offset i.e. steady state error introduced by proportional control action. It stabilizes the gain of the controller 9/27/2016 Nevase Amit 100
  101. 101. Car Steering Analogy
  102. 102. References Process Control and Instrumentation Technology – C. D. Johnson 9/27/2016 Amit Nevase 102
  103. 103. Online Tutorials  http://www.electrical4u.com /types-of-controllers- proportional-integral- derivative-controllers/  http://elearning.vtu.ac.in/ne wvtuelc/courses/06IT64.html  https://www.facstaff.bucknell .edu/mastascu/eControlHTM L/Intro/Intro2.html 9/27/2016 Amit Nevase 103
  104. 104. Thank You 9/27/2016 Amit Nevase 104 Amit Nevase

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