Lecture 1 the lecture

CONTROL ENGINEERING
(KEJURUTERAAN KAWALAN)
BMCM 3733
SEMESTER 1
SESI 2014/2015

Overview of lecture 1
 At the end of this lecture you should be able to
 Explain the definition of control system.
 Explain the basic component of control systems.
 Explain the Closed-loop and Open-loop control
system.
 Give an example of the control system.

What is control?
Fig.1 Control the water level

What is control
 http://www.merriam-webster.com
1
a archaic : to check, test, or verify by evidence or experiments
b : to incorporate suitable controls in <a controlled
experiment>
2
a : to exercise restraining or directing influence over :REGULATE
b : to have power over : RULE
c : to reduce the incidence or severity of especially to
innocuous levels <control an insect population> <control a
disease>

What is control
A term that describes the process of forcing a
system to behave in a desired way in order to
achieve certain objective(s) or goal(s).

What is system?
1 : a regularly interacting or interdependent group of items forming a unified
whole <a number system>: as
a (1) : a group of interacting bodies under the influence of related forces <a
gravitational system> (2) : an assemblage of substances that is in or tends to
equilibrium <a thermodynamic system>
b (1) : a group of body organs that together perform one or more vital
functions <the digestive system> (2) : the body considered as a functional
unit
c : a group of related natural objects or forces <a riversystem>
d : a group of devices or artificial objects or an organization forming a network
especially for distributing something or serving a common purpose <a
telephone system> <a heatingsystem> <a highway system> <a
computer system>
e : a major division of rocks usually larger than a series and including all formed
during a period or era
f : a form of social, economic, or political organization or practice <the
capitalist system>

What is system
2 : an organized set of doctrines, ideas, or principles usually intended to
explain the arrangement or working of asystematic whole <the
Newtonian system of mechanics>
3 a : an organized or established procedure <the touch systemof typing>
b : a manner of classifying, symbolizing, or schematizing <a
taxonomic system> <the decimal system>
4 : harmonious arrangement or pattern : ORDER <bring system out of
confusion — Ellen Glasgow>
5 : an organized society or social situation regarded as stultifying or
oppressive : ESTABLISHMENT 2 —usually used withthe

What is system*
 a segment of environment that is
under consideration to control.
* Can be a plant or a process

What is Control System
Control System is an interconnection of components
forming a system configuration that will provide a
desired system response.
Typically, a system process has one or more inputs and
outputs, which can be represented by a block digram as
shown below.
INPUT PROCESS OUTPUT
Fig.2 Typical representation of a process

BASIC COMPONENTS
Controlled variable Quantity or condition that is measured and controlled.
Manipulated variable Quantity or condition that is varied by the controller so as to affect
the value of the controlled variable
Plant To perform particular operation. It is the physical object to be
controlled (mechanical devices, heating furnace, etc.)
Process Is any operation to be controlled. Processes can be chemical,
economic, etc
System Is a combination of components that act together and perform
certain objective
Disturbance Is a signal that tends to adversely affect the value of the output of
a system. May internal or external
Feedback control Refers to an operation that, in the presence of disturbances,
tendsto reduce the difference between the output of a system
and some reference input.

Control System
Fig.3 Example of control system

Control Engineering
 Engineering discipline that concerned with
understanding and controlling the systems to
provide useful economics products.
 Applies control theory to design the systems
with desired behaviors.
Control Engineering is not restricted to one field
of engineering but equally applicable to
different branches of engineering such as
aeronautical, mechanical, chemical, civil,
computer, electrical etc.

OPEN-LOOP & CLOSED-LOOP
Control system can be categorized into 2
classses:
 Open-loop system
 Closed-loop system

OPEN-LOOP vs CLOSED-LOOP
Open-loop System:
utilizes a controller or actuating device to obtain
a desired response directly without using
feedback
Fig.4 Open loop control system

OPEN-LOOP vs CLOSED-LOOP
Closed-loop System:
 In contrast to an open-loop control system, a closed-loop
utilizes the additional measure of the actual output to
compare the actual output with the desired output
(reference or command).
 This additional measure of the output is called the feedback.
Fig.5 Close loop control system

Example of Control System
Fig.6 Example of control system
Room Temperature control

An open loop control system
Room temperature control.
 Control Signal / Input : the inlet vent temperature
 The output (controlled variable) : The room air
temperature.
 The actuator : comprises of the furnace and a pre-programmed
on-off switch that triggers the furnace,
which in turn activates the inlet vent temperature.
 A disturbance : The ambient temperature
Fig.7 Open loop system of Room
Temperature control

The close loop control system
 modified by incorporating the measure of the
output, i.e. the room air temperature.
 The controller is the thermostat that takes into
account a reference signal
 The output feedback in order to set the switch
position.
Fig.7 Close loop control of Room
Temperature control

The close loop control system
 Ideally, the thermostat should trigger the switch as soon as
the error is negative and switch off when the room air has
reached/exceeded the reference temperature.
 The features of this scheme are
 if room temperature < reference temperature, the furnace is switched
on automatically, until room temperature ≥ reference temperature.
 Can handle changes in the system (e.g. change in ambient
temperature).
 It is negative feedback (the measured output is subtracted from the
reference signal)
Fig.7 Close loop control of Room
Temperature control

AUTOMOTIVE AIR-CONDITIONING
SYSTEMS

Effect of Feedback on
Sensitivity
OPEN LOOP SYSTEM

Effect of Feedback on
Sensitivity
CLOSE LOOP SYSTEM

 The sensitivity is reduced as the loop gain
(i.e., K1K2) is increase.
 obvious advantage of using feedback

Motivations for Feedback
The main reasons for using feedback are :
 Reducing the sensitivity of the performance
to parameter variations of the plant and
imperfections of the plant model used for
design.
 Reducing the effects of external disturbances
and sensor noises.

Feedback can also
 Improve transient response characteristics
 Reduce steady-state errors

Output response of a control
system

A generalised feedback
system

QUIZ 1
 In group of 5(Maximum members,
less is better ),Let
 Decide one control system and define
the basic component of the control
system.
 Try to develop the block diagram for
open loop and close loop of the system.

Lecture 1 the lecture

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