CONTROL SYSTEM
EEE&EE CONTROL SYSTEM QUESTION FOR PRATICE BY C KARAN SIR (PROF. GEC )
MCQ ON CONTROL SYSTEMS
1.In
an open loop control system
(a)Output is independent of control input (b) Output is dependent on
control input
(c) Only system parameters have effect on the control output (d) None of the above
Ans: a
2.For open control system
which of the following statements is incorrect ?
(a)Less expensive
(b) Recalibration is not required for maintaining the required quality of the
output
(c) Construction is simple and maintenance easy
(dErrors are caused by disturbances
Ans: b
3. A control system in
which the control action is somehow dependent on the output is known as
(a)Closed loop system
(b)Semiclosed loop system
(c) Open system
(d)None of the above
Ans: a
4.In closed loop control
system, with positive value of feedback gain the overall gain of the system
will
(a)decrease
(b)increase
(c)be unaffected
(d)any of the above
Ans: a
5.Which of the following
is an open loop control system ?
(a)Field controlled D.C. motor
(b) Ward leonard control
(c)Metadyne
(d)Stroboscope
Ans: a
6. Which of the following
statements is not necessarily correct for open control system ?
(a)Input command is the sole factor responsible for providing the control action
(b)Presence of non-linearities causes malfunctioning
(c)Less expensive
(d) Generally free from problems of non-linearities
Ans: b
7.In open loop system
(a) the control action depends on the size of the system
(b) the control action depends on system variables
(c)the control action depends on the input signal
(d)the control action is independent of the output
Ans: d
8 .has tendency to
oscillate.
(a) Open loop system
(b)Closed loop system
(c)Both (a) and (b)
(d)Neither (a) nor (b)
Ans: b
9.A good control system
has all the following features except
(a) good stability
(b) slow response
(c)good accuracy
(d)sufficient power handling capacity
Ans: b
10. A car is rtyining at a
constant speed of 50 km/h, which of the following is the feedback element for
the driver ?
(a) Clutch
(b) Eyes
(c)Needle of the speedometer
(d) Steering wheel
(e)None of the above
Ans: c
11)Which among the following
represents an illustration of closed loop system?
a. Automatic washing machine
b. Automatic electric iron
c. Bread toaster
d. Electric hand drier
12)Which among the
following is not an advantage of an open loop system?
a. Simplicity in construction & design
b. Easy maintenance
c. Rare problems of stability
d. Requirement of system
recalibration from time to time
13)Which terminology
deals with the excitation or stimulus applied to the system from an external
source for the generation of an output?
a. Input signal
b. Output signal
c. Error signal
d. Feedback signal
14)Which among the
following is a unique model of a system?
a. Transfer
function
b. State variable
c. Both a and b
d. None of the
above
st15)What should
be the nature of bandwidth for a good control syem?
a. Large
b. Small
c. Medium
d. All of the above
16)Which among the
following controls the speed of D.C. motor?
a. Galvanometer
b. Gauss meter
c. Potentiometer
d. Tachometer
17)Which system
exhibits the initiation of corrective action only after the output gets
affected?
a. Feed forward
b. Feedback
c. Both a and b
d. None of the above
18)A good control
system should be sensitive to __________
a. Internal disturbances
b. Environmental parameters
c. Parametric variations
d. Input signals (except noise)
19)What is the
value of steady state error in closed loop control systems?
a. Zero
b. Unity
c. Infinity
d. Unpredictable
20.Into which
energy signal does the position sensor convert the measured position of
servomotor in servomechanisms?
a. Mechanical
b. Electrical
c. Thermal
d. Light
21)Which among the
following represents an illustration of closed loop system?
a. Automatic washing machine
b. Automatic electric iron
c. Bread toaster
d. Electric hand drier
Ans b
22)Which notation
represents the feedback path in closed loop system representation?
a. b(t)
b. c(t)
c. e(t)
d. r(t)
23)Which among the
following is not an advantage of an open loop system?
a. Simplicity in construction & design
b. Easy maintenance
c. Rare problems of stability
d. Requirement of system
recalibration from time to time
24)Which
terminology deals with the excitation or stimulus applied to the system from an
external source for the generation of an output?
a. Input signal
b. Output signal
c. Error signal
d. Feedback signal
ANS FROM 11-31 MCQ
11-b
12-d
13-a
14-a
15-a
16-c
17-b
18-d
19-a
20-b
21-b
22-a
23-d
24-a
25-a
26-c
27-b
28-c
29-b
30-a
31-b
TWO MARKS
1.What
is meant by a system?
It is an arrangement of physical components
related in such a manner as to form an entire unit.
2.What
is a command input?
It is the excitation applied to a control
system from an external source. It is also a motivating
input
signal to the system, which is independent of the output of the system.
3. Define
output.
It is the actual response obtained from a
control system, which must be maintained at a
prescribed
value.
4.What
is an actuating signal?
It is the difference between the reference
input and feedback signal. It is also called a actuating
signal.
5.
Define plant.
It is the process/body/ machine, of which a
particular quantity or condition is to be controlled.
6.
List the two types of control systems?
The two types of control system are, open
loop systems and closed loop system.
7.What
is an open loop system?
The control system in which the output has
no effect upon the input quantity, is known as open
loop
control system.
8.What
is meant by a controller?
It is the component required to generate the
appropriate control signal applied to the plant.
9.
Define manually controlled systems?
Systems that involve continuous manual
control by a human operator are called manually
controlled
system.
10.For
what purpose feedback element is used?
It is the component required to generate
the appropriate control signal applied to the plant.
12.
What is feedback?
The feedback is a control action, in which
the output is sampled and a proportional signal is
given to
input for automatic correction of any changes in desired output.
13.
Give the types of feedback?
Negative feedback Positive feedback.
14.
When will feedback exist in a system?
Feedback is said to exist in a system,
when a closed sequence, of cause and effect relations exist between system
available.
15.Define
transfer function
Transfer function of a given system is
defined as the ratio of the laplace transform of output
variable
to laplace transform of input variables at zero input conditions.
16.Define order of the system.
The highest power of the complex variables
in the denominator of the transfer function
determines
the order of the system.
17.Define
linear system.
A system is said to be linear if it obeys
the principle of superposition and homogeneity. The
principle
of superposition states that the responseof the system to a weighted sum of the
responses
of the system to each individual input signals.
18.Give
the important characteristics of open loop control system.
Their ability to perform accurately is
determined by their calibration, which implies to establish
the
input-output relation to obtain a desired system accuracy.
19.When
will the system is said to be linear?
The system is said to be linear, if it
satisfies the following two properties: •
Adaptive
property that is for any x and y belonging to the domain of the function f,
we have
F(x+y) = f(x) +f(y) •
Homogeneous
property that is for any x belonging to the domain of the function f and for
any scalar constant
We have
F(x) =af(x)
These two
properties together constitute a principle of superposition
20.
Define differential equations.
The basic models of dynamic physical
systems are differential equations.
21.
List the steps involved in obtaining the transfer function.
To write the differential equations
governing the system.
To laplace transform the equations i.e. to
replace the terms involving d/dt by s, and integral of dt by 1/s.
To obtain the ratio of transformed output
to the input variables.
22.
Give the properties of transfer functions.
The properties of transfer function are as
follows:
The
transfer function of a system is the laplace transform of its impulse response.
i.e. if
the input
to a system with transfer function P(s) is an impulse and all initial
conditions are
zero, the
transform of the output is P(s).
The roots
of the denominator are the system poles and the roots of the numerator are
system
zeros. The system stability can be described in terms of the location of the
roots
of the
transfer function.
23.
Give the advantages of transfer function.
It helps in the stability analysis of the
system.
It helps in determining the important
information about the system Poles, zeros,
characteristic
equation etc. •Once transfer function is known, output response for any type of
reference input can be calculated.
The
system differential equation can be easily obtained by replacing variable ‘s’
by d/dt.
24.
Give the disadvantages of transfer function.
The disadvantages of transfer function
approach are:
•Only applicable to linear time invariant
systems.
•It does not provide any information
concerning the physical structure of the system. From
transfer function, physical nature of the
system, whether it is electrical, mechanical, thermal or hydraulic cannot be
judged.
•Effects arising due to initial
conditions are totally neglected. Hence initial conditions loose importance.
25.
What is the other name for closed loop control system?
The other name for closed loop control
system is feedback control system.
26.
Give the important features of feedback.
•Reduced effects of non-linearities and
distortion.
•Increased accuracy.
•Reduced sensitivity of the ratio of the
output to input to variations in system
characteristics.
•Tendency toward oscillation or
instability.
27.
What are the basic elements used for modeling mechanical translational system?
The model of mechanical translational
system can be obtained by using three basic elements
mass
spring and dashpot.
28.
What is translational system?
Consider a mechanical system in which
motion is taking place along a straight line. Such systems are of translational
type. These systems are characterized by displacement, linear velocity and
linear acceleration.
29.
Define torque.
This
is the motion about a fixed axis. In such systems, the force gets replaced by a
moment about the fixed axis. I.e. {force x distance from fixed axis} which is
called torque.
30.
Define friction.
Whenever there is a motion, there exists a
friction. Friction may be between moving element and fixed support or between
two moving surfaces. Friction is also non-linear in nature.
31. Name
the two types of electrical analogous for mechanical system.
The two types of analogies for mechanical
system are force-voltage analogy and force-current
analogy.
32.
What are analogous systems?
Systems whose differential equations are
identical form are called analogous systems.
32.
Give two types of variables in physical system.
The two variables in physical systems are
through variables and across variable. Through variables refer to a point, the
across variable is measured between two points.
34.
Give the other names for force voltage analogy, force current analogy.
The other names for force voltage analogy
and force
current
analogy are Force voltage analogy- Loop analysis. Force current analogy- nodal
analysis.
35.
What is block diagram?
A block diagram of a system is a pictorial
representation of the functions performed by each
component
of the system and shows the flow of signa ls.
36.
What are the basic components of block diagram?
The basic components of block diagram are
block, branch point, summing point, arrows.
The connection between the blocks is shown
by lines called branches.
The signal can travel along the direction
of arrow only.
37.
What is the need for block diagram reduction?
Block diagrams of some of the control
systems turn out to be complex. Such that the evaluation of their performance
requires simplification(or red
uction)
of block diagrams which is carried out by block diagram rearrangements.
38.
List the advantages of block diagram.
•Individual as well as overall performance
of the system can be studied by using transfer functions shown in the block
diagram. Overall closed loop transfer
function can be easily calculated by using block diagram rules.
•The function of individual elements can be
visualized from the block diagram.
•Very simple to construct the block diagram
for complicated systems.
39.
List the disadvantages of block diagram.
•Source of energy is generally not shown in
the block diagram. So block diagram for given system is not unique.
•Block diagram does not include any
information about physical construction of the system.
•Block diagram reduction technique is time
consuming process for complicated systems(higher order systems).
40.
List the steps to reduce the block diagram.
•Reduce the series blocks.
•Reduce the parallel blocks.
•Reduce minor feedback loops.
•As for as possible shift summing point to
the left and take-off point to the right.
•Repeat the above steps till canonical
form is obtained.
41.
What is signal flow graph?
The graphical representation of the
variables of a set of linear algebraic equations representing
the
system is called signal flow graph.
42.
Give the properties of signal flow graph?
•The signal in the system flows along the
branches and along the arrows associated with the branches.
•The value of variable represented by any
node is an algebraic sum of all the signals entering at the node.
•The signals gets multiplied by the branch
gain or branch transmittance when it travels along it.
•Applicable only to linear time invariant
systems.
43.
What are the standard test signals employed for time domain studies?
The standard test signals employed
for time domain studies are 1. step signal, ramp signal,
parabolic signal, impulse signal.
44.What
do you mean by a node in signal flow graph?
It represents a
system variable, which is equal to the sum of all incoming signals at the node,
outgoing signals from the node do not affect the value of
the node variable.
LONG QUESTIONS
(1) Derive the
expressions and draw the response of first order system for unit step input.
(2) Draw the response
of second order system for critically damped case and when input is unit
step.
(3) Measurements
conducted on a Servomechanism show the system response to be c(t)=1+0.2e 60t
-1.2 e -10t , when subjected to a unit step. Obtain an expression for closed
loop transfer function.
(4) Compare and Contrast Open loop and Closed
loop Control Systems.
(5) Explain the terminologies associated with
Signal Flow Graphs with a suitable example
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