Basic Control System_EC
-
Upload
hiren-j-vasava -
Category
Documents
-
view
219 -
download
0
Transcript of Basic Control System_EC
-
8/12/2019 Basic Control System_EC
1/23
Basic Electronics
Ch-7
Basic Control Systems
-
8/12/2019 Basic Control System_EC
2/23
FEEDBACK CONTROL SYSTEMS
An open-loop system is one in which the
control action is independent of the output or
desired result
-
8/12/2019 Basic Control System_EC
3/23
FEEDBACK CONTROL SYSTEMS
A closed-loop (feedback) system is one in
which the control action is dependent upon
the output
-
8/12/2019 Basic Control System_EC
4/23
Feedback System Classification
According to the method of analysis and
design
Linear versus nonlinear control systems
Time-invariant versus time-varying systems
According to the types of signal found in the
system
Continuous-data and discrete-data systems
Sampled-data and digital control systems
-
8/12/2019 Basic Control System_EC
5/23
According to the type of system components
Electromechanical control systems
Hydraulic control systems
Pneumatic control systems
Biological control systems
According to the main purpose of the system
Position control systems
Velocity control systems
Regulators
Servomechanisms
Feedback System Classification
-
8/12/2019 Basic Control System_EC
6/23
Transfer Functions and Block
Diagrams
The transfer function is a mathematical formulationthat relates the output variable of a device to the inputvariable
Properties
A transfer function is defined only for a linear time-invariant system. It is meaningless for nonlinear systems
The transfer function between an input variable and anoutput variable of a system is defined as the ratio of theLaplace transform of the output to the Laplace transform
of the input All initial conditions of the system are assumed to be zero
The transfer function is independent of the input
-
8/12/2019 Basic Control System_EC
7/23
The block diagram is a pictorial representationof the equations of the system. Each blockrepresents a mathematical operation, and the
blocks are interconnected to satisfy thegoverning equations of the system
Transfer Functions and Block
Diagrams
-
8/12/2019 Basic Control System_EC
8/23
Transfer Functions and Block
Diagrams
-
8/12/2019 Basic Control System_EC
9/23
The expression for the output quantity with
negative feedback is given by
The transfer function M of the closed-loop
system is then given by
Transfer Functions and Block
Diagrams
-
8/12/2019 Basic Control System_EC
10/23
Transfer Functions and Block
Diagrams
-
8/12/2019 Basic Control System_EC
11/23
Transfer Functions and Block
Diagrams
-
8/12/2019 Basic Control System_EC
12/23
EFFECT OF FEEDBACK ON SENSITIVITY TO
PARAMETER CHANGES
The sensitivity S of a closed-loop system to a
parameter changep in the direct transmission
function G is defined as
Transfer Functions and Block
Diagrams
-
8/12/2019 Basic Control System_EC
13/23
Dynamic Response of Control Systems
-
8/12/2019 Basic Control System_EC
14/23
Maximum (or peak) overshoot A is the largest
deviation of the output over the step input during
the transient state. It is used as a measure of the
relative stability of the system.
The percentage maximum overshoot is given by
the ratio of maximum overshoot to final value,
expressed in percent. Delay time td is defined as the time required for
the step response to reach 90% of its final value.
Dynamic Response of Control Systems
-
8/12/2019 Basic Control System_EC
15/23
Rise time tr is defined as the time needed for
the step response to rise from 10% to 90% of
its final value.
Settling time ts is the time required for the
step response to decrease and stay within a
specified percentage (usually 5%) of its final
value.
Dynamic Response of Control Systems
-
8/12/2019 Basic Control System_EC
16/23
Steady-State Error of Linear Systems
If the steady-state response of the outputdoes not agree exactly with the steady state ofthe input, the system is said to have a steady-
state error
Applying the final-value theorem, the steady-state error of the system is
-
8/12/2019 Basic Control System_EC
17/23
Classification of Feedback Control
Systems by Control Action
-
8/12/2019 Basic Control System_EC
18/23
DIGITAL CONTROL SYSTEMS
Discrete-data and digital control systems differfrom the continuous-data or analog systems inthat the signals in one or more parts of thesesystems are in the form of either a pulse train or
a numerical (digital) code. Digital control systems refers to the use of a
digital computer or controller in the system;digital data usually refers to signals that are
generated by digital computers or digitaltransducers and are thus in some kind of codedform.
-
8/12/2019 Basic Control System_EC
19/23
DIGITAL CONTROL SYSTEMS
-
8/12/2019 Basic Control System_EC
20/23
Sampled data and digital control offer severaladvantages over analog systems:
More compact and lightweight
Improved sensitivity Better reliability, speed, and accuracy
More flexibility and versatility (in programming)
Lower cost
More rugged in construction no drift
Less effect due to noise and disturbance
DIGITAL CONTROL SYSTEMS
-
8/12/2019 Basic Control System_EC
21/23
DIGITAL CONTROL SYSTEMS
-
8/12/2019 Basic Control System_EC
22/23
Adaptive Control
DIGITAL CONTROL SYSTEMS
-
8/12/2019 Basic Control System_EC
23/23
DIGITAL CONTROL SYSTEMS