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Introduction to Control Systems


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Introduction to Control Systems

  1. 1. Introduction to Control Systems Prof. Marian S. Stachowicz Laboratory for Intelligent Systems ECE Department, University of Minnesota Duluth January 19 - 21, 2010 ECE 3151 - Spring 2010
  2. 2. Outline <ul><li>1.1 Introduction </li></ul><ul><li>1.2 References for Reading </li></ul><ul><li>1.3 History of Automatic Control </li></ul><ul><li>1.4 Terms and Concepts </li></ul><ul><li>1.5 The Control System Design Process </li></ul><ul><li>1.6 Applications </li></ul><ul><li>1.7 Three Examples of the Use of Feedback </li></ul>Control Systems
  3. 3. Introduction
  4. 4. Control <ul><li>The word control is usually taken to mean : </li></ul><ul><li>- regulate, </li></ul><ul><li>- direct, </li></ul><ul><li>- command. </li></ul>Control Systems
  5. 5. Control and politicians <ul><li>Control is a sequence of decisions aimed at the attainment of specified objectives in an environment of uncertainty and presence of disturbances. </li></ul>Control Systems
  6. 6. Control system <ul><li>A control system is an arrangement of physical components connected or related in such a manner as to command, direct, or regulate itself or another system. </li></ul>Control Systems
  7. 7. Control Systems
  8. 8. Input <ul><li>The input is the stimulus, excitation or command applied to a control system. </li></ul><ul><li>Typically from external energy source, usually in order to produce a specified response from the control system. </li></ul>Control Systems
  9. 9. Output <ul><li>The output is the actual response obtained from a control system. </li></ul><ul><li>It may or may not be equal to specified response implied by the input. </li></ul>Control Systems
  10. 10. References for reading <ul><li>R.C. Dorf and R.H. Bishop, Modern Control Systems , </li></ul><ul><li>10th Edition, Prentice Hall, 2008, </li></ul><ul><li>Chapter 1.1 - 1.10 </li></ul><ul><li>2. J.J. DiStefano, A. R. Stubberud, I. J. Williams, Feeedback and Control Systems, Schaum's Outline Series, McGraw-Hill, Inc., 1990 </li></ul><ul><li>Chapters 1, 2 </li></ul>Control Systems
  11. 11. <ul><li>History of Automatic Control </li></ul>Control Systems
  12. 12. Prior to World War II <ul><li>A main impetus for the use of feedback in the United States was the development of the telephone system and electronic feedback amplifiers by Bode, Nyquist, and Black at Bell Telephone Laboratories . </li></ul>Control Systems
  13. 13. Prior to World War II <ul><li>The Russian theory tended to utilize a time-domain formulation using differential equations. </li></ul>Control Systems
  14. 14. World War II <ul><li>Design and construct: </li></ul><ul><li>automatic airplane pilots, </li></ul><ul><li>gun-positioning systems, </li></ul><ul><li>radar antenna control systems. </li></ul>Control Systems
  15. 15. Sputnik and space age <ul><li>The time-domain methods developed by Liapunov, Minorsky, and others have met with great interest in the last two decades. </li></ul>Control Systems
  16. 16. Resent time <ul><li>Recent theories of optimal control developed by L.S. Pontryagin in the former Soviet Union and R. Bellman in the United States, and studies of robust systems, have contributed to the interest in time-domain methods . </li></ul>Control Systems
  17. 17. Terms and Concepts Control Systems
  18. 18. Control system <ul><li>A control system is an interconnection of components forming a system configuration that will provide a desired system response. </li></ul>Control Systems
  19. 19. Two Types of Control Systems <ul><li>Open Loop </li></ul><ul><ul><li>No feedback </li></ul></ul><ul><ul><li>Difficult to control output with accuracy </li></ul></ul><ul><li>Closed Loop </li></ul><ul><ul><li>Must have feedback </li></ul></ul><ul><ul><li>Must have sensor on output </li></ul></ul><ul><ul><li>Almost always negative feedback </li></ul></ul>Control Systems
  20. 20. Open-loop control <ul><li>An open-loop control system utilizes an actuating device to control the process directly without using feedback. </li></ul><ul><li>A common example of an open-loop control system is an electric toaster in the kitchen. </li></ul>Control Systems
  21. 21. Control Systems
  22. 22. Closed-loop control <ul><li>A closed-loop control system uses a measurement of the output and feedback of this signal to compare it with the desired output. </li></ul>Control Systems
  23. 23. Control Systems
  24. 24. A person steering an automobile by looking at the auto’s location on the road and making the appropriate adjustments. Control Systems
  25. 25. Control Systems
  26. 26. Manual control system Intelligent Control Goal: Regulate the level of fluid by adjusting the output valve. The input is a reference level of fluid and is memorized by operator. The power amplifier is the operator. The sensor is visual. Operator compares the actual level with the desired level and opens or closes the valve ( actuator).
  27. 27. The level of fluid in a tank control. Intelligent Control
  28. 28. Multivariable control system Control Systems
  29. 29. Control Systems
  30. 30. Control Systems
  31. 31. Control system of the national income. Control Systems
  32. 32. A robot is a computer-controlled machine. Industrial robotics is a particular field of automation in which the robot is designed to substitute for human labor. The Honda P3 humanoid robot. Control Systems
  33. 33. <ul><li>Automation - The control of a process by automatic means. </li></ul><ul><li>Closed-loop feedback control system - </li></ul><ul><li>A system that uses a measurement of the output and compares it with the desired output. </li></ul>Control Systems
  34. 34. <ul><li>Design - The process of conceiving or inventing the forms, parts, and details of a system to achieve a specified purpose. </li></ul><ul><li>Feedback signal - A measure of the output of the system used for feedback to control the system. </li></ul><ul><li>Multivariable control system - A system with more than one input variable or more than one output variable. </li></ul>Control Systems
  35. 35. <ul><li>Negative feedback - The output signal is fed back so that it subtracts from the input signal. </li></ul><ul><li>Open-loop control system - A system that utilizes a device to control the process without using feedback. </li></ul><ul><li>Optimization - The adjustment of the parameters to achieve the most favorable or advantageous design. </li></ul>Control Systems
  36. 36. <ul><li>Positive feedback - The output signal is fed back so that it adds to the input signal. </li></ul><ul><li>Process - The device, plant, or system under control. </li></ul><ul><li>Productivity -The ratio of physical output to physical input of an industrial process. </li></ul>Control Systems
  37. 37. <ul><li>Robot - Programmable computers integrated with a manipulator. </li></ul><ul><li>Synthesis - The combining of separate elements or devices to form a coherent whole. </li></ul><ul><li>System - An interconnection of elements and devices for a desired purpose. </li></ul>Control Systems
  38. 38. The Control System Design Process
  39. 39. <ul><li>Design is the process of conceiving or inventing the forms, parts, and details of a system to achieve a specified purpose. </li></ul>Engineering design Control Systems
  40. 40. Engineering design <ul><li>Trade-off </li></ul><ul><li>The result of making a judgment about how to compromise between conflicting criteria. </li></ul>Control Systems
  41. 41. <ul><li>Control system engineers are concerned with understanding and controlling segments of their environment, often called systems, to provide useful economic products. </li></ul>Control Systems
  42. 42. Goals <ul><li>Twin goals of understanding and controlling are complementary because effective systems control requires that the systems be understood and modeled. </li></ul>Control Systems
  43. 43. Control engineering <ul><li>Control engineering is based on the foundations of feedback theory and linear system analysis, and it integrates the concepts of network theory and communication theory. </li></ul>Control Systems
  44. 44. Given a process, how to design a feedback control system? <ul><li>Three steps: </li></ul><ul><li>Modeling . Obtain mathematical description of the systems. </li></ul><ul><li>Analysis . Analyze the properties of the system. </li></ul><ul><li>Design . Given a plant, design a controller based on performance specifications. </li></ul><ul><li>The course spans each of these steps in that sequence. </li></ul>Control Systems
  45. 45. <ul><li>The basis for analysis of a system is the foundation provided by linear system theory, which assumes a cause-effect relationship for the components of a system. </li></ul>Control Systems
  46. 46. Control Systems
  47. 47. Design examples
  48. 48. <ul><ul><li>Rotating disk speed control </li></ul></ul>Control Systems
  49. 49. Step 1. Control goal <ul><li>Design a system that will held a rotating disk at a constant speed. Ensure that </li></ul><ul><li>the actual speed of rotation is within a specified percentage of desired speed. </li></ul>Control Systems
  50. 50. Step 2. Variable to be controlled <ul><li>Speed of rotation disc </li></ul>Control Systems
  51. 51. Step 3. Control design specification <ul><li>Design a system that will ensure that </li></ul><ul><li>the actual speed of rotation is within a specified percentage of desired speed. </li></ul>Control Systems
  52. 52. Step 4 Preliminary system configuration Control Systems
  53. 53. Step 4 Preliminary system configuration Control Systems
  54. 54. With precision components, we could expect to reduce the error of the feedback system to one-hundredth of error of the open-loop system. Control Systems
  55. 55. Insulin delivery system
  56. 56. The blood glucose and insulin concentrations for a healthy person. Control Systems
  57. 57. Step 1. Control goal <ul><li>Design a system to regulate the blood sugar concentration of a diabetic by controlled dispensing of insulin. </li></ul>Control Systems
  58. 58. Step 2. Variable to be controlled <ul><li>Blood glucose concentration </li></ul>Control Systems
  59. 59. Step 3. Control design specification <ul><li>Provide a blood glucose level for the diabetic that closely approximates the glucose level of a healthy person. </li></ul>Control Systems
  60. 60. Step 4 Preliminary system configurations Control Systems
  61. 61. A drug-delivery system implanted in the body uses an open-loop system, since miniaturized glucose sensors are not yet available. Control Systems
  62. 62. Disk drive read system Control Systems
  63. 63. Control Systems
  64. 64. Step 1. Control goal <ul><li>Design a system that will held the position the reader head to read the data stored on a track on the disk. </li></ul>Control Systems
  65. 65. Step 2. Variable to be controlled <ul><li>Position of the reader head </li></ul>Control Systems
  66. 66. Step 3. Control design specification <ul><li>Design a system that will ensure that the head : </li></ul><ul><li>- “flies” above the disk at a distance of less than 100 nm, </li></ul><ul><li>- with the position accuracy is 1  m, </li></ul><ul><li>- with speed from track to track 50 ms </li></ul>Control Systems
  67. 67. Step 4 Preliminary system configuration Control Systems
  68. 68. E 1: Controlling the position of a missile launcher from a remote location <ul><li>The input is the desired angular position of the missile launcher, </li></ul><ul><li>The control system consists: </li></ul><ul><li>of potentiometer, </li></ul><ul><li>power amplifier, </li></ul><ul><li>motor, </li></ul><ul><li>gearing between the motor and the missile launcher, </li></ul><ul><li>missile launcher. </li></ul>Control Systems
  69. 69. A position open loop control The input is the desired angular position of the missile launcher, and the control system consists of potentiometer, power amplifier, motor, gearing between the motor and missile launcher, and missile launcher. Control Systems
  70. 70. A position closed loop control Should an error exists, it is amplified and applied to a motor drive which adjusts the output-shaft position until it agrees with the input-shaft position, and the error is zero. Control Systems
  71. 71. P1.2 Manual control system Control Systems
  72. 72. Fluid-flow control <ul><li>P1.2 In the past, control systems used a human operator as part of a closed-loop control system. Sketch the block diagram of the valve control system shown in Fig. P1.2 </li></ul>Control Systems
  73. 73. P1.3 Chemical composition control <ul><li>Complete the control feedback loop, and sketch a block diagram describing the operation of the control loop. </li></ul>Control Systems
  74. 74. Control Systems
  75. 75. P1.8 Student-teacher learning process <ul><li>Construct a feedback model of the learning process and identify each block of the system. </li></ul>Control Systems
  76. 76. Inverted pendulum control <ul><li>E1.11 Sketch the block diagram of a feedback control system. Identify the process, sensor, actuator, and controller. </li></ul><ul><li>The objective is keep the pendulum in the upright position (  = 0), in the presence of disturbances. </li></ul>Control Systems
  77. 77. Control Systems
  78. 78. Applications <ul><li>Control engineering is not limited to any engineering discipline but is equally applicable to: </li></ul><ul><li>aeronautical, </li></ul><ul><li>chemical, </li></ul><ul><li>mechanical, </li></ul><ul><li>computer science and engineering , </li></ul><ul><li>civil engineering, </li></ul><ul><li>electrical engineering. </li></ul>Control Systems
  79. 79. Mechatronic systems Control Systems
  80. 80. Questions ? Control Systems
  81. 81. Control Systems
  82. 82. Control Systems
  83. 83. Control Systems
  84. 84. Control Systems The design of control systems is a specific example of engineering design. The goal of control engineering design is to obtain the configuration, specifications, and identification of the key parameters of a proposed system to meet an actual need.
  85. 85. Control Systems <ul><li>The design process consists of seven main building blocks, which are arrange into three groups: </li></ul><ul><li>Establishment of goals and variables to be controlled, and definition of specifications against which to measure performance </li></ul><ul><li>System definition and modeling </li></ul><ul><li>Control system design and integrated system simulation and analysis </li></ul>
  86. 86. Control Systems
  87. 87. Design 1 Control Systems
  88. 88. Design 2 Control Systems
  89. 89. Design 3 Control Systems
  90. 90. Open-loop and closed-loop systems