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Meeting w8 chapter 3 part 1


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Meeting w8 chapter 3 part 1

  1. 1. Chapter 3 Digital Control System Eddy Irwan Shah Bin Saadon Dept. of Electrical Engineering PPD, UTHM [email_address] 019-7017679 BS-04, G3 , FKEE Ext : 8519
  2. 2. <ul><li>Outline: </li></ul><ul><li>Introduction </li></ul><ul><li>Analog vs. Digital Control System </li></ul><ul><li>Digital Control System Selection </li></ul><ul><li>Signal in Digital Control System </li></ul><ul><li>Data Acquisition, Conversion & Distribution System </li></ul><ul><li>Example of Digital Control System </li></ul>
  3. 3. <ul><li>Intro - Objective of this chapter </li></ul><ul><li>After completing this chapter you will be able to: </li></ul><ul><li>Differentiate between analog and digital control system </li></ul><ul><li>Explain the reason for using digital control system </li></ul><ul><li>Understand the operation involved in digital conversion system </li></ul><ul><li>Describe the sampling method </li></ul>
  4. 4. Cont. <ul><li>Digital control system employs digital computer, microcontroller and microprocessor </li></ul><ul><li>Example: electromechanical servomechanism in aircraft, automobiles, mass-transit vehicle, oil refineries, paper making machine and household appliances </li></ul>
  5. 5. Cont. <ul><li>Advantages: </li></ul><ul><li>Increase flexibility of the control programs and the decision making </li></ul><ul><li>One hardware design is able to be used with many different software variations </li></ul><ul><li>Simplifying and reducing design time </li></ul>
  6. 6. 2. Analog Vs Digital <ul><li>The basic knowledge to distinguish analog and digital system is the type of signals processed </li></ul><ul><li>Analog system processes continuous signals whilst digital system processes discrete signals </li></ul><ul><li>Following is an example of block diagram for both of the systems </li></ul>
  7. 7. Cont. Analog control system Digital control system
  8. 8. 3. Digital Control System Selection <ul><li>Control system was developed from analog (continuous-time) devices such as operational amplifiers, capacitors, inductors, resistors and mechanical components. </li></ul><ul><li>However, digital control system has been used widely since it was introduced and analog control system are used nowadays for a simple applications. </li></ul>
  9. 9. Cont. <ul><li>Even though digital control system cannot perform integration of basic control system function, it has been used widely due to: </li></ul><ul><li>Cost </li></ul><ul><li>Communication </li></ul><ul><li>Flexibility </li></ul><ul><li>Digital interfacing devices </li></ul><ul><li>Performance </li></ul><ul><li>Diagnostics </li></ul>
  10. 10. Exercise 1 <ul><li>Discuss each of the aspects why digital control system are preferred compared to the analog control system. </li></ul>
  11. 11. 4. Signal in digital control system <ul><li>Type of signals: </li></ul>Continuous-time analog signal Continuous-time quantized signal Sampled-data signal Digital signal
  12. 12. Cont. <ul><li>Continuous-time analog signal = a continuous range of time signal where the amplitude is continuous range of values </li></ul><ul><li>Continuous-time quantized signal = continuous range of time signal where the amplitude is a finite number of distinct values </li></ul>
  13. 13. Cont. <ul><li>Sampled-data signal = a discrete-time signal where the amplitude is in continuous range of values </li></ul><ul><li>Digital signal = discrete-time signal with quantized amplitude and can be represented by sequence of number </li></ul>
  14. 14. Cont. <ul><li>Signal form in digital control system </li></ul>
  15. 15. Cont. <ul><li>Sample and hold (S/H) and Analog-to-digital (A/D) converter convert the continuous-time signal into a sequence of numerical coded binary words (coding/ encoding) </li></ul><ul><li>The digital computer receives the data and produces a new sequence of numbers with defined algorithm and send it to Digital-to-analog (D/A) converter </li></ul>
  16. 16. Cont. <ul><li>D/A converter will then convert the sequence of number in numerical code into a continuous-time signal </li></ul><ul><li>The-real time clock in the computer will synchronizes the event </li></ul><ul><li>The output form D/A converter is hold by Hold circuit to establish a distinct continuous-time signal </li></ul>
  17. 17. Cont. <ul><li>The signal is fed to the plant directly or through actuator to control its dynamics </li></ul><ul><li>The plant output continuous-time signal is detected by a transducer for a closed-loop system as a feedback to the system and compared to the input signal where the signal is received by S/H and A/D converter as an input </li></ul>