1. The document discusses the differences between analog and digital control systems. Digital control systems use digital computers, microcontrollers, and microprocessors to process discrete signals, while analog systems process continuous signals. 2. Digital control systems are now widely used over analog systems due to advantages like lower cost, improved communication and flexibility, easier digital interfacing, and better performance diagnostics. 3. In a digital control system, continuous signals are converted to discrete signals using sample and hold circuits and analog-to-digital converters, then processed digitally before being converted back with digital-to-analog converters.

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. Outline: Introduction Analog vs. Digital Control System Digital Control System Selection Signal in Digital Control System Data Acquisition, Conversion & Distribution System Example of Digital Control System

3. Intro - Objective of this chapter After completing this chapter you will be able to: Differentiate between analog and digital control system Explain the reason for using digital control system Understand the operation involved in digital conversion system Describe the sampling method

4. Cont. Digital control system employs digital computer, microcontroller and microprocessor Example: electromechanical servomechanism in aircraft, automobiles, mass-transit vehicle, oil refineries, paper making machine and household appliances

5. Cont. Advantages: Increase flexibility of the control programs and the decision making One hardware design is able to be used with many different software variations Simplifying and reducing design time

6. 2. Analog Vs Digital The basic knowledge to distinguish analog and digital system is the type of signals processed Analog system processes continuous signals whilst digital system processes discrete signals Following is an example of block diagram for both of the systems

7. Cont. Analog control system Digital control system

8. 3. Digital Control System Selection Control system was developed from analog (continuous-time) devices such as operational amplifiers, capacitors, inductors, resistors and mechanical components. However, digital control system has been used widely since it was introduced and analog control system are used nowadays for a simple applications.

9. Cont. Even though digital control system cannot perform integration of basic control system function, it has been used widely due to: Cost Communication Flexibility Digital interfacing devices Performance Diagnostics

10. Exercise 1 Discuss each of the aspects why digital control system are preferred compared to the analog control system.

11. 4. Signal in digital control system Type of signals: Continuous-time analog signal Continuous-time quantized signal Sampled-data signal Digital signal

12. Cont. Continuous-time analog signal = a continuous range of time signal where the amplitude is continuous range of values Continuous-time quantized signal = continuous range of time signal where the amplitude is a finite number of distinct values

13. Cont. Sampled-data signal = a discrete-time signal where the amplitude is in continuous range of values Digital signal = discrete-time signal with quantized amplitude and can be represented by sequence of number

14. Cont. Signal form in digital control system

15. Cont. 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) 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

16. Cont. D/A converter will then convert the sequence of number in numerical code into a continuous-time signal The-real time clock in the computer will synchronizes the event The output form D/A converter is hold by Hold circuit to establish a distinct continuous-time signal

17. Cont. The signal is fed to the plant directly or through actuator to control its dynamics 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