1. Introduction Feedback is at the heart of: Thermostat:
Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Introduction
Open a window and look at nature. You may not see it but control is there
Feedback is at the heart of:
Thermostat:
Control Systems Design, Dr. Moayed Almobaied
Introduction

2. Toilet flush Islamic University of Gaza Faculty of Engineering
Electrical Engineering Department
Toilet flush
Control Systems Design, Dr. Moayed Almobaied
Introduction

3. Cruise controller Islamic University of Gaza Faculty of Engineering
Electrical Engineering Department
Cruise controller
Control Systems Design, Dr. Moayed Almobaied
Introduction

4. Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
In the early eighties it was quite common to thank the pilot for a smooth landing with applause. One morning flying into Paris, the pilot was thanked in the usual way for an outstanding landing. Promptly the captain came on the public address system not to thank the passengers but to inform them that it was the auto-pilot that had performed the landing.
Control Systems Design, Dr. Moayed Almobaied
Introduction

5. In nature, feedback is at the core of
Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
In nature, feedback is at the core of
Homeostasis: a term used to refer how in living organisms critically important variables are kept within acceptable limits; such as our body temperature or our blood glucose level for example
Control Systems Design, Dr. Moayed Almobaied
Introduction

6. Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Earth’s hydrocycle
how water evaporates, then condenses into clouds, moves around the globe, precipitates to the Earth, and flows back to the oceans, its main reservoir.
Control Systems Design, Dr. Moayed Almobaied
Introduction

7. prey-predator behavior
Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
prey-predator behavior
How a predator species feeds on its prey and therefore depends on that prey’s survival for its own survival. Most ecologies depend on feedback to maintain the balance of the species in the ecology.
Control Systems Design, Dr. Moayed Almobaied
Introduction

8. Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Parents provide feedback to their children in order to achieve a desired behavioral outcome.
Medical doctors provide feedback to their patients to assist the natural healing processes.
In a university, students are asked to provide feedback to the doctors about the quality of the instruction they have received.
Control Systems Design, Dr. Moayed Almobaied
Introduction

9. Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
What is important in this context is the direction of the flow of information. In order to provide feedback on teaching, the students have to observe or experience the teacher first.
This experience is then communicated, fed back to the teacher. The teacher then internalizes the information, and uses it to adjust the course material and presentation style for the next batch of students.
The presence of a directed information loop is the defining characteristic of feedback; without the closure of the information loop there is no feedback.
Control Systems Design, Dr. Moayed Almobaied
Introduction

10. Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
The direction associated with the information flow is of course related to causality.
First comes the experience of the teaching, then this experience is communicated to the teacher, next the teacher interprets this and reacts with improved lectures.
Control Systems Design, Dr. Moayed Almobaied
Introduction

11. University Block Diagrams, Systems, Inputs and Outputs
Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Block Diagrams, Systems, Inputs and Outputs
University
Control Systems Design, Dr. Moayed Almobaied
Introduction

12. Toilet flush Islamic University of Gaza Faculty of Engineering
Electrical Engineering Department
Toilet flush
Control Systems Design, Dr. Moayed Almobaied
Introduction

13. Earth’s hydrocycle Islamic University of Gaza Faculty of Engineering
Electrical Engineering Department
Earth’s hydrocycle
Control Systems Design, Dr. Moayed Almobaied
Introduction

14. Recording Music Islamic University of Gaza Faculty of Engineering
Electrical Engineering Department
Recording Music
Control Systems Design, Dr. Moayed Almobaied
Introduction

15. Connected Water Tanks Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Connected Water Tanks
Control Systems Design, Dr. Moayed Almobaied
Introduction

16. Examples of block diagrams: a open loop; b closed loop
Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Examples of block diagrams: a open loop; b closed loop
Control Systems Design, Dr. Moayed Almobaied
Introduction

17. Feedback and Dynamics Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Feedback and Dynamics
Control Systems Design, Dr. Moayed Almobaied
Introduction

18. Birth and Death Processes
Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Birth and Death Processes
Consider a group of rabbits enjoying an unlimited food supply and no real predators. The birth rate (percentage of new individuals in the total population) will be larger than the death rate (percentage of individuals that die). As a consequence this rabbit population will continue to grow. This case exemplifies a positive feedback loop which leads to unlimited and forever accelerating growth .
Control Systems Design, Dr. Moayed Almobaied
Introduction

19. Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Assume now that the supply of food is constant, and that the birth rate is proportional to the amount of food available to any individual. In this case as the population increases the amount of food per animal decreases and so does the birth rate. At some instant in time the birth rate will equal the death rate. At that moment equilibrium is reached and the total population remains constant.
Control Systems Design, Dr. Moayed Almobaied
Introduction

20. Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
In this case, negative feedback is at work: an increase in the population (because the birthrate is larger than the death rate) leads to a decrease in food availability, and hence a decrease in the birthrate. Also, with a similar argument, a decrease in the population will lead to an increase in the birthrate. We say that the equilibrium (birthrate equals death rate) is stable, as a small deviation away from the equilibrium leads to a response in restoring the equilibrium.
Often, negative feedback is associated with stable equilibria and positive feedback is associated with instability.
Control Systems Design, Dr. Moayed Almobaied
Introduction

21. Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Control History
18th Century James Watt’s centrifugal governor for the speed control of a steam engine.
1920s Minorsky worked on automatic controllers for steering ships.
1930s Nyquist developed a method for analyzing the stability of controlled systems
1940s Frequency response methods made it possible to design linear closed-loop control systems
1950s Root-locus method due to Evans was fully developed
1960s State space methods, optimal control, adaptive control
1980s Learning controls are begun to investigated and developed.
Present and on-going research fields. Recent application of modern control theory includes such non-engineering systems such as biological, biomedical, economic systems
Control Systems Design, Dr. Moayed Almobaied
Introduction

22. Water Clocks of the Greeks and Arabs
Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Water Clocks of the Greeks and Arabs
Control Systems Design, Dr. Moayed Almobaied
Introduction

23. Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
The elephant clock in a manuscript by Al-Jazari (1206 AD) from The Book of Knowledge of Ingenious Mechanical Devices
Control Systems Design, Dr. Moayed Almobaied
Introduction

24. Elephant clock https://www.youtube.com/watch?v=Xze9mawgxno
Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
Elephant clock
Control Systems Design, Dr. Moayed Almobaied
Introduction