OPEN AND CLOSE LOOP

Open-Loop Control Systems.
Those systems in which the output has noeffect on the control action are called open-loop control systems

Closed-Loop Control Systems.

Feedback control systems are often referred to as closed-loop control systems.In a closed-loop control system the actuating error signal, which is the difference between the input signal and the feedback signal(which may be the output signal itself or a function of the output signal and its derivatives and/or integrals), is fed to the controller so as to reduce the error and bring the output of the system to a desired value.

CLOSED-LOOP CONTROL SYSTEM

Advantages of Open Loop

Simple construction and ease of maintenance.

• Less expensive than a corresponding closed-loop system.
• There is no stability problem.
• Convenient when output is hard to measure or measuring the output precisely is economically not feasible.

Disadvantages of Open Loop

• Disturbances and changes in calibration cause errors,and the output may be different from what is desired.
• To maintain the required quality in the output,recalibration is necessary from time to time.
• They are less accurate.
• If external disturbances are present, output differs significantly from the desired value.

TERMS USED IN CONTROL PROCESS

• Variable Process - proses pembolehubah
• Servo Controlled -pengawal serbo
• Feedback             -suap balik
• Process                -proses
• Set Point              -titik mula
• Error                    -ralat
• Controller            -pengawal
• Measurement      -pengukuran

Overview

This course introduce the basic concepts of control system.It includes modeling of control system in frequency and time domain,introduction of transfer function and state-space representation,study of time response,stability and steady-state errors,application of root locus technique,design via Bode Plot and root locus.

INTRO

A control system is a system by virtue or with any quantities a condition ( call controllled variable) of interest of a machine,mechanism or equipment can be controlled as per desire.Usually,the system has a command signal applied at the input and the controlled variable exhibited at the output.For example,the force applied on to an excelerator pedal causes the speed of the engine vehicle to increase.Here,force is the command signal and the speed of the engine is the controlled variable.

HISTORY

Automatic control systems were first developed over two thousand years ago. 

Control theory made significant strides in the next 100 years. New mathematical techniques made it possible to control, more accurately, significantly more complex dynamical systems than the original flyball governor.

control engineering was practiced as a part of mechanical engineering and control theory was studied as a part of electrical engineering, since electrical circuits can often be easily described using control theory techniques.  Later on, previous to modern power electronics, process control systems for industrial applications were devised by mechanical engineers using pneumatic and hydraulic control devices, many of which are still in use today.

EXAMPLED APPLICATION OF CONTROL SYSTEM

1.HUMAN CONTROL SYSTEM

-The relation between the behavior of living creatures and the functioning of CS has recently 

gained wide attention.
-Several characteristics of CS can be linked to human behavior. CS can "think" in the 

sense that they can replace to some extent, human operation

.

2.CONTROL SYSTEM IN PHYSICAL SYSTEM

-The desired temperature is set and a thermostat 

measures the actual temperature and the error. A compressor motor is utilized for power 

amplification. Other applications of control in the home are the hot-water heater, the central 

heating system, and the oven, which all work on a similar principle. We also encounter CS when 

driving our automobile. CS is used for maintaining constant speed (cruise control), constant 

temperature (climate control), steering, suspension, engine control, and to control skidding 

(antiskid system).

3.CONTROL SYSTEM IN INDUSTRIAL ROBOT

-Programmable machine tools designed in many cases 

to accomplish arduous or complex tasks.

4.CONTROL SYSTEM IN PNEUMATIC AND HYDRAULIC

-Pneumatic positioning system can be found in food industry.