introduction to the control system - Electrical Engineering Gate

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Wednesday, December 2, 2015

introduction to the control system

Control :
is that quantity responsible for activating the system for produce the output
The word  control  is  usually taken  to mean  regulate, direct,  or  command.
System :
is a combination of elements intended to act together to accomplish an objective.

A control system :
is a collection of components working together under the direction of some machine intelligence.
In most cases,
electronic circuits provide the intelligence, and
electromechanical components such as sensors and motors provide the interface to the physical world.

Examples of control systems

Problems of control  engineering
Analysis and design of control system configurations
is the investigation of the properties of an existing System.
is the choice and arrangement of control system components to perform a special task.
Objectives of analysis are:
The determination of the following system characteristic:
The degree or extent of system stability
The steady state performance
The transient performance

General procedure for analyzing a linear control system
    • Determine the equations or transfer function for each system component.
    • Choose a scheme for representing the system ( block diagram or signal flow graph ).
    • Formulate the system model by appropriately connecting the components       (blocks, or nodes and branches).
    • Determine the system response characteristics.
1.Time domain-methods:
     direct solution of the system equations to find the steady state and transient solutions.                                                                    Cumbersome for higher than second order systems.
2. Graphical methods.
           simpler and more direct.
  Bode-Plot Representations
  Nyquist diagrams
  Nichols Charts
  The Root-Locus Method

is the choice and arrangement of control system components to perform a special task.
objective of Design
meeting performance specifications.
performance specifications 
are the constraints put on system response characteristics.

Forms of specifications:
Frequency domain specifications ( pertinent quantities expressed as functions of frequency.)
Time domain specifications (in terms of time response).
These forms specify the following three important properties of dynamics systems:
Speed of response
Relative stability
System accuracy or allowable error
Types of design:
Design by analysis of system 
        is accomplished by modifying the characteristics of an existing or standard system configuration.

Design by synthesis ( direct design ) 
        is accomplished by defining the form of the system directly from its specifications

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