Discrete Time Control Systems Faculty of Engineering Helwan University

1. ‫ر‬َ‫ـد‬ْ‫ق‬‫ِـ‬‫ن‬،،،‫لما‬‫اننا‬ ‫نصدق‬ْْ‫ق‬ِ‫ن‬‫ر‬َ‫د‬
LECTURE (1)
Introduction To discrete-Time
Control Systems
ASCO. Prof. Amr E. Mohamed

2. Agenda
 What is Digital Control?
 Examples of Digitally Controlled Systems
 Classical Control Systems
 Digital Control Systems
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3. What is Digital Control?
 Automatic control is the science that develops techniques to steer, guide,
control dynamic systems.
 Examples of such dynamic systems are found in biology, physics, robotics,
finance, etc.
 Digital Control means that the control laws are implemented in a digital
device, such as a microcontroller or a microprocessor. Such devices are light,
fast and economical.
 Digital control systems = “Digital signals” + ”Control systems”
 The points that will be examined in these lecture notes are the following:
 transformation of an already designed continuous-time controller into a discrete-
time controller,
 discretization of continuous systems,
 direct synthesis of discrete-time control systems,
 practical considerations and precautions when implementing a digital controller.
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4. Examples of Digitally Controlled Systems
 Nowadays, digitally controlled systems are everywhere,
 automotive industry: speed regulators in cars,
 aeronautic/space industry: autopilots, automatic take off/landing, cruise
control
 chemistry: pharmaceutical industries, oil transformation, liquid level in
tanks
 robotics: robot-arm trajectory control, manipulation,
 housing: in-house temperature regulation
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5. Classical Control Systems
 Objective:
1) Closed-loop stable
2) Small steady-state error
3) Good transient response
4) Disturbance rejection
 Analog Controllers difficult to modify or redesign once implemented
in hardware
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6. Digital Control Systems
 A/D Converter: change analog signal to digital signal
 D/A Converter: change digital signal to analog signal
 Digital controller: implemented in digital computers, or in
microprocessors
 Sensors: monitors controlled variable for feedback.
 Plant: the analog system to be controlled. 6

7. Simplified version of a digital control systems
 Sampler:
 Zero-order-Hold:
 C(z): Discrete-Time Controller to be designed.
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8. Why Digital Control?
 Easy to implement complicated control algorithms
 Easy to modify the controller
 Controller parameters unchanged with variations in environment
 Low cost, low weight, and low power dissipation
 High noise tolerance
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9. Disadvantages
 Sampling and quantization process will degrade system performance
 Software errors
 Need power supply
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10. Robotic Manipulator Control
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11. Drug delivery Digital Control
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