Controllers for Process Applications_7_edit.pdf

This presentation provides an overview of control systems, their importance, and applications in various industries. The content covers both open-loop and closed-loop control systems, focusing on feedback mechanisms, system stability, and performance optimization. Key topics include:

Introduction to Control Systems: An explanation of basic control system components, including sensors, actuators, controllers, and plant models.

Types of Control Systems: Comparison between open-loop and closed-loop control systems, highlighting the advantages and limitations of each type.

Mathematical Modeling: Detailed discussion on the modeling of dynamic systems using differential equations, transfer functions, and state-space representations.

System Stability: Explanation of system stability criteria, including the Routh-Hurwitz criterion, Nyquist plots, and root-locus techniques to determine stable system behavior.

PID Controllers: Overview of Proportional, Integral, and Derivative (PID) controllers, their role in regulating system performance, and tuning methods to optimize response.

Control System Applications: Real-world examples in industries like automotive (cruise control), aerospace (flight control), robotics, and manufacturing automation.

The presentation is designed for both beginners and professionals, offering insights into how control systems are implemented and improved for efficiency and reliability. It concludes with a discussion of emerging trends, such as adaptive control, model-predictive control, and the impact of machine learning on modern control systems.This presentation provides an in-depth exploration of control systems, emphasizing their significance in modern engineering and technology-driven industries. The content is designed to cater to both newcomers and professionals, bridging foundational concepts with advanced control strategies. The topics covered include:

1. Introduction to Control Systems
The presentation begins with a definition of control systems, explaining their purpose in maintaining desired outputs of various processes or devices by manipulating inputs. It discusses the role of control systems in automating processes, enhancing accuracy, and ensuring efficiency across various applications.

2. Control System Architecture
A detailed breakdown of the essential components of control systems is provided, including:

Sensors and Transducers: Devices that measure physical quantities and convert them into signals.
Controllers: Systems that determine the necessary adjustments based on feedback.
Actuators: Mechanisms that apply the required control action to influence the process.
Process/Plant: The system or operation being controlled.
3. Types of Control Systems
The distinction between open-loop and closed-loop (feedback) systems is discussed.

Open-loop Control: Systems without feedback that rely solely on the input command.
Closed-loop Control: Systems that use feedback to dynamically adjust the output based on the

1. CONTROLLERS
FOR PROCESS APPLICATIONS

2. What is a Controller??

3. What is a Controller??

4. What is a Controller??

5. What is a Controller??

6. What is a Controller??

7. What is a Controller??

8. What is a Controller??

9. Pneumatic Actuator
(0-20 mA)

13. Controllers Modes
•Continuous Controller Action
•Discontinuous Controller Action
Each of the Above Classification can be written as:
•Direct Action and
•Reverse Action

14. Types of Controllers
✓On-Off or Two Position Controller
✓Multi-Position Controller
✓Floating mode Controller
✓Proportional Controller
✓Integral Controller
✓Derivative Controller
✓PI Controller
✓PD Controller
✓PID Controller

15. Discontinuous Controller
Modes
TWO POSITION MODE:
Controller Output p is given by
WATER HEATER EXAMPLE………………

16. Neutral Zone in Two Position Controller Mode

17. Example:
Setpoint Neutral zone
(323+12) K
(323-12) K

18. MULTIPOSITION CONTROL MODE
▪An extension of two position controller mode to provide several
intermediate rather than just two settings for the controller output

19. MULTIPOSITION CONTROL MODE

20. Relationship between error and three-position controller action, including the
effects of lag due to final control element and controller
Example:

21. FLOATING CONTROL MODE
▪InthismodethespecificControlleroutputisnotuniquelydeterminedbythe
error.Here,whenerroriszerothecontrolleroutputwillnotchangebutfloats
atthevalueatwhateverSettingitwenttozero.
▪Whenerrormovesoffthezerothecontrolleroutputbeginstochange.

23. Here, Controller is Reverse Acting
Example:

24. Multispeed floating mode control:

25. ▪The rate of controller output change has a strong effect on error recovery in a
floating controller.
▪At higher rate of change of Controller output instability or Oscillations may occur
similar to ON-OFF Control
Recovering from Error in a Floating mode Controller

26. Continuous Controller Modes

27. Proportional Controller Mode:
▪Thetwo-positionmodehadthecontrolleroutputofeither100%or
0%,dependingontheerrorbeinggreaterorlessthantheneutral
zone.Inmultiple-stepmodes,moredivisionsofcontrolleroutputs
versuserroraredeveloped.
▪Thenaturalextensionofthisconceptistheproportionalmode,
whereasmooth,linearrelationshipexistsbetweenthecontroller
outputandtheerror.Thus,oversomerangeoferrorsaboutthe
setpoint,eachvalueoferrorhasauniquevalueofcontrolleroutput
inone-to-onecorrespondence.
▪Therangeoferrortocoverthe0%to100%controlleroutputiscalled
theproportionalband,becausetheone-to-onecorrespondence
existsonlyforerrorsinthisrange.Thismodecanbeexpressedby:

28. Proportional Band:

29. Direct Acting Proportional Controller

30. Reverse Acting Proportional Controller

31. Offset in a Proportional Controller: Level Control Example

32. Which actually means
that you need to change
the nominal value, after
load change: called
“manual reset”

33. ▪Ifatransienterroroccursthesystemrespondsbychangingthe
controlleroutputincorrespondencewiththetransienttoeffecta
returntozeroerror.
▪Anoffseterrormustoccurifaproportionalcontrollerrequiresanew
zero-erroroutputfollowingaloadchange.
Offset in a Proportional Controller:

34. ▪Theoffseterroroftheproportionalmodeoccursbecausethecontroller
cannotadapttochangingexternalconditions—thatis,changingloads.In
otherwords,thezero-erroroutputisafixedvalue.Theintegralmode
eliminatesthisproblembyallowingthecontrollertoadapttochanging
externalconditionsbychangingthezero-erroroutput(alsocalled
automaticresetcontrarytomanualresetintheproportionalcontroller)
▪Integralactionisprovidedbysummingtheerrorovertime,multiplying
thatsumbyagain,andaddingtheresulttothepresentcontrolleroutput.
Youcanseethatiftheerrormakesrandomexcursionsaboveandbelow
zero,thenetsumwillbezero,sotheintegralactionwillnotcontribute.
Butiftheerrorbecomespositiveornegativeforanextendedperiodof
time,theintegralactionwillbegintoaccumulateandmakechangesto
thecontrolleroutput.
Integral Controller Mode:

35. Integral Controller Mode:

37. Integral Controller Mode:

38. Derivative Controller Mode:

39. Derivative mode of control action where the output 50% has been assumed
for the zero derivative state or the nominal output is 50%

41. Derivative Controller Mode:

42. Problem 1 (linear scaling):

43. Problem 2 (Span error): :

44. Problem 3 (Controller output in percentage): :

45. Problem 4 (ON-OFF Controller): :

47. Problem 5 (Proportional Controller): :

49. Problem 6 (Integral Controller): :

51. Problem 7 (Derivative Controller): :

52. Composite Controller Modes:
Non-Interactive (Parallel):

53. A set point filter takes a step change in SP, and as shown below, forwards a
smooth transition signal to the controller.

54. Non-Interactive (Parallel) derivative of Output
Because of possible discontinuity (step change) in reference signal that are
transferred into error signal we use this configuration
Composite Controller Modes:

55. Composite Controller Modes:
Interactive (series):

56. Interactive (series):
Composite Controller Modes:

57. External Filters in Control
Composite Controller Modes:

58. Composite Controller Modes

59. PI Controller :

60. PI Controller :

62. PD Controller :

64. PID Controller :

66. Problem 8 (PI Controller): :

68. Problem 8 (PD Controller): :