• Luck: When preparation meets opportunity.

• “Life is what happens while you are busy making other plans”. (John Lennon)

Engineering Systems Analysis

EGR 386

Fall 2003

Introduction

Introductionhistorybasic terminologyMore terminologypoint of view

Examples

Closed-loop vs Open-loop

Assignments

• Assignment: Read Chapter 1

History•17??: James Watt – centrifugal governor, speed control of steam engines•1922: Minorsky – steering ships, stability from DEs•1932: Nyquist – stability of closed-loop systems based on closed-loop response to steady-state sinusoidal inputs•1934: Hazen – introduced term servomechanism for position control systems, servomechanism capable of closely following a changing input•1940s: frequency-response methods, Bode diagram, based design methods•Late 1940s to 1950s: root locus methods due to Evans•Late 1950s – 60s – 70s: state space modeling and design, optimal control•1980s—present: H robust control

Basic TerminologyThe controlled variable is the quantity or condition that is measured and controlled.

The manipulated variable is the quantity or condition that is varied by the controller so as to affect the value of the controlled variable.

Control means measuring the value of the controlled variable of the system and applying the manipulated variable to the system to correct or limit deviation of the measured value from a desired value.

More TerminologyA plant performs a particular operation. It is the physical object to be controlled

A process is any operation to be controlled. Processes can be chemical, economic, biological, etc.

A system is a combination of components that act together and perform a certain objective.

A disturbance is a signal that adversely affects the value of the output of a system. May be internal or external.

Feedback control refers to an operation that, in the presence of disturbances, tends to reduce the difference between the output of a system and some reference input and does so on the basis of the difference.

Point of ViewControl systems are made up of components each of which

• Have input and output signal(s) (Examples of signals: position, velocity, acceleration, temperature, voltage, current, concentration, etc.)

• Process their inputs to produce their outputs (outputs are caused by the interaction of the input and the component)

• Are described by differential equations

• Engineers produce mathematical models of the components so they can design controllers.

Examples

Speed ControlTemperature ControlLight-level controlvoltage-level controlpH control etc

Closed-loop vs Open-loop Control

A system that maintains a prescribed relationship between the output and the reference input by comparing them and using the difference as a means of control is called a feedback control system.

Closed-loop control system = feedback control system. Block diagrams have loops.

Those systems in which the output has no effect on the control action are called open-loop control systems.

Block diagrams do not have loops.

Assignments1. Be able to define the following: controlled variable,

manipulated variable, plant, process, system, disturbance, feedback control, closed-loop control, open-loop control.

2. Know the Point-of-view of this course.

Quiz

Containing one of the questions above.

In class Question

One or both above.