Transcript Chapter 1: Introduction to Control Systems

• 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
• Assignment: Read Chapter 1
Introduction
history
basic terminology
More terminology
point of view
Examples
Closed-loop vs Open-loop
Assignments
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 Terminology
The 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 Terminology
A 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 View
Control 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 Control
Temperature Control
Light-level control
voltage-level control
pH 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.
Assignments
1. 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.