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? http://www.merriam-webster.com

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 http://www.merriam-webster.com

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.

PROCESSINPUT 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 obtaina desired response directly without usingfeedback

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 systemRoom 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 systemRoom temperature control.

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 systemRoom temperature control.

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.