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

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

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

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

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

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.

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

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)

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

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…

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

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)

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