BASIC CONCEPTS OF CONTROL SYSTEM SEM :- V CONTROL ENGINEERING ENROLLMENT NO: GUIDED BY PROF. S.P.PATEL

ITS TERMS BASIC SYSTEM:- System – An interconnection of elements and devices for a desired purpose. Control System – An interconnection of components forming a system configuration that will provide a desired response. Process – The device, plant, or system under control. The input and output relationship represents the cause-and- effect relationship of the process.

 The interaction is defined in terms of variables. i.System input ii.System output iii.Environmental disturbances

Control System:  Control is the process of causing a system variable to conform to some desired value.  Manual control Automatic control (involving machines only).  A control system is an interconnection of components forming a system configuration that will provide a desired system response. Control System Output Signal Input Signal Energy Source

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. Plant: the portion of system which is to be controlled or regulated is called plant. Reference Input :-the input variable is generally referred as the Reference Input. Controlled output: output generally referred as the controlled output.

Classification :- I.Natural control system: II.Manmade control system: III.Combinational control system: IV.Time varying and time-invariant systems: V.Continuous time and discrete time control systems: VI.Lumped parameter and distributed parameter control systems: VII.Single input single output and multiple input multiple output control systems: VIII.Open loop and closed loop control systems: IX.Linear and non linear systems:

 Natural control system: the biological systems, systems inside human being are natural type.  Manmade control system: the various systems, we are using day to day life are designed and manufactured by human beings. (vehicles)  Combinational control system: Combinational control system is one, having combine manmade and natural control system together. (driver driving vehicle).  Time varying and time-invariant systems:

 Continuous time and discrete time control systems: in continuous time control system all system variables are the fuction of the continuous time variable ‘t’.(D.C motor using tachometer)  it is dependent in time. indiscrete time control system one or more system variables are known only certain discrete interval time.(microprocessor)  it is independent in time.  Lumped parameter and distributed parameter control systems: control system that can be describe by ordinary differential equations is called lumped parameter control system.(electric network with deferent parameter like resistance,inductions). control system that can be describe by partial differential equations is called distributed parameter control system.  Single input single output and multiple input multiple output control systems:  Open loop and closed loop control systems:

OPEN LOOP SYSTEM A system in which the control action is totally independent of the output of the system is called open loop system.

For the example:-  FAN:  AUTOMATIC TOASTER MACHINE:-

Traffic controlled system

ADVANTAGES AND DISADVANTAGES :-  Advantages: 1.They are simple in construction and design. 2.They are economic. 3.Easy for maintenance. 4.Not much problems of stability. 5.Convenient to use when output is difficult to measure.  Disadvantages: 1.Inaccurate and unreliable because accuracy is dependent on accuracy of calibration. 2.Inaccurate results are obtained with disturbances. 3.To maintain quality and accuracy, recalibration of the controller is necessary from time to time.

Closed system:-  A system in which the control action is totally dependent of the output of the system is called closed loop system.

 For example:-  Human being: Home heating system:

 Missile launchers:

 Sun seeker solar systems:-

 Ship stabilization system :

 Temperature system:

Manual controlled system:

ADVANTAGES AND DISADVANTAGES :-  Advantages:- 1.Accuracy is very high as any error arising is corrected. 2.It senses changes in output due to environmental or parametric changes, internal disturbances etc. and corrects the same. 3.Reduced effect of non-linearities. 4.High bandwidth. 5.Facilitates Automation.  Disadvantages: 1.Complicated in design and maintenance costlier. 2.System may become unstable.

Requirement of a good control system:- 1.Accuracy:- 2.Sensitivity:- 3.Noise:- 4.Stability:- 5.Bandwidth:- 6.Speed:- 7.Oscillation:-

Servo mechanisms  It is feedback control system in which controlled variable or output is mechanical position or time derivatives such as velocity, acceleration.

The design process

SOME EXAMPLE

Design Example