1. EE 342 FEEDBACK CONTROL SYSTEMS
Department of Electrical and
Electronics Engineering
Bilkent University

3. Key Words:
Feedback Systems
Automatic Control
Estimation & Identification
Mathematical Modeling
Process Optimization
Decision Making

4. Control of a Physical System or Process
Mathematical Modeling: Determines a set of equations describing the input-output behavior the physical system
Two types of input:
Control
Disturbance/Noise
We use control input to reduce the effect of disturbance on the system output.
Example: Room temperature control
Room temperature output
Thermostat setting control input
Doors/windows opening closing disturbance

5. C A PS S Feedback Control:
Observe the output and determine the control input
Automatic Feedback Control:
Output is monitored by using a SENSOR, whose output goes to the CONTROLLER, which uses the mathematical model to determine the control input. Usually, the controller is a computer, its output is a low power signal, that gets amplified by an ACTUATOR to generate the actual control input to the PHYSICAL SYSTEM.
desired output
output C A PS S
Plant

6. Example: Automatic Steering/Car Following
wind/bumps
steering
Cars &
Road
Computer
noise
vision

7. Why Feedback Control? A blind person driving a car: open loop control
Driving a car by using vision: feedback control
In the first case driver does not have much information about the current position of the car with respect to the road.
In the second case the driver can steer the car back to the desired position despite bumps, wind and other uncontrollable effects.
So, feedback is used to cope with the uncertainty.

9. Examples of Control Applications
Aerospace Applications:
Aircraft or missile guidance and control
Space vehicles and structures

10. Examples of Control Applications
Biological Systems:
Central Nervous System is the controller for the body
Robotics:
Robots perform automated tasks in assembly lines, where precision is important (e.g. welding in automotive industry) and dangerous tasks physically impossible for humans (e.g. military operations, and space explorations)

11. Computers and Communication:
Power control in cellular wireless networks
Routing and flow control computer networks

12. Intelligent Transportation & Automotive Systems:
Marine, Land, Air vehicles
Platoon of cars in Automated Highway Systems
Warning systems for trains, railroad crossings,
Automatic landing systems for planes,
and other flight control systems
Air traffic control, highway traffic control,
Ship steering, etc…etc…

13. Electro-Mechanical Systems:
Micro actuators and sensors (MEMS)
Motor control, power electronics

14. Chemical Processes:
Oil refineries, pharmaceuticals, textiles, etc…
Home Electronics and Appliances:
DVD players, receivers, digital cameras & camcorders, washing machines, A/C and heating units, water heaters, home security and surveillance systems, etc…
Tall buildings & construction:
Lighting, elevator control, vibration suppression
Manufacturing:
Sheet metal production, pulp & paper industry, semiconductor manufacturing, assembly lines, etc…
Economy:
(no good mathematical model yet)

15. C : controller, to be designed
Basic Feedback Control System v e + u y r + C + P -
C : controller, to be designed
P : plant (process), the mathematical model is determined together with the process engineers