Design and Compensation of Control
Systems
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(i)Which one of the following statements is true?
Phase lead net work is used
(a)
when fast transient response is desired.
(b)
when error constants
are specified
(c)
when system bandwidth is to be decreased.
Ans: ( a )
(ii) Which one of the following
statements is not true?
(a)The
phase lead network increases the phase margin of the system and thus provides
additional stability
(b)When
the design specifications include an error constant, the design of a phase lead
network is more readily accomplished on the Bode diagram.
(c) When an error constant is not specified but
the settling time and overshoot for a step input are specified, the design of a
phase lead network is more readily carried out on the s-plane.
(d)
Phase lead compensation decreases the system bandwidth, whereas the phase lag
compensation increases the system bandwidth.
Ans:
( d )
(iii)Which one of the following
compensators is used to increase the damping of a pair of complex roots that
are severely underdamped:
(a)
phase-lag
(b)
phase-lead
(c) phase lag-lead
(d) any one of the above
Ans: ( b )
(iv ) The time domain method of
compensation uses the following performance specifications:
(a)
Steady-state error
coefficients, phase margin and crossover frequency
(b)
Steady-state error
coefficients, location of closed loop dominant poles, and root sensitivity
(c)
Integral squared
error
Ans: ( c)
(v) The
time domain method of compensation uses the following performance
specifications:
(a)
Integral squared
error
(b)
Steady-state error
coefficients, phase margin and crossover frequency
(c)
Steady-state error coefficients, location of closed loop dominant poles,
and root sensitivity
Ans: (a)
(vi) It is
desirable to avoid the use of the differentiator in control system design,
because
(a) it is not
economical
(b)
its size is big
(c ) it develops
noise and will saturate the amplifier
Ans: (c)
(vii) In practise,
inductance is not fabricated to realize a lag network.
(a)
True
(b)
False.
Ans: (a)
(viii) The following compensator
increases the damping of a pair of complex roots that are severely
under-damped.
(a) phase-lag
(b) phase-lead
(c) phase-lag-lead
(d) none
of the above.
Ans: (d)
( ix) The following performance specifications are used in
the time domain method of compensation.
(a)
Integral squared
error
(b)
Steady-state error
coefficients, phase margin and crossover frequency
(c)
Steady-state error
coefficients, location of closed loop dominant poles, and root sensitivity
(d)
Desired closed-loop
transfer function, and sensitivity of poles to parameter variations.
(e)
Ans : (a)
(x)Which one of the following
statements is not rue?
(a)
A phase-lag
compensation network decreases the system bandwidth and slows down the
transient response.
(b)
A phase-lag network reduces
the steady-state error and suppresses high frequency noise.
(c)
A phase-lead network
increases the bandwidth and is used to obtain fast transient response.
(d)
A phase-lead network
decreases the bandwidth and slows down the transient response.
Ans: (d)
(xi ) Match List E containing A,B,C time functions with List F containing
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List E |
List F |
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A |
x(t)= 1-e-at |
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I |
x(s)= w/[(s+a)2+w2] |
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B |
x(t)= e-at sinwt |
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II |
wn2/(s2
+ 2xwn
s+ wn2) |
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C |
x(t)= wn e-jwn tsinwn.Ö(1-x2).t / Ö(1-x2). ;
x<1 |
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III |
x(s)=a/(s(s+a)) |
The correct matching is
(a) AIII BII CI
(b)AI BI ICIII
(c) AIII BI CII
(d)AI BIICIII
Ans: (c)
(xii )Match List E with List F given below.
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List E |
List F |
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A |
Analogue controller |
I |
Are
high performance controllers and are combinations of analogue & digital
controllers. |
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B |
Digital controller |
II |
Represent
the variables in the equations by continuous physical quantities and can be designed
that will serve as nondecision
making controllers |
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C |
Hybrid controller |
III |
Operate
only on numbers and are currently being used for the solution of optimal
operation of industrial plants. |
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The
correct matching is
(a)AII
BIII CI
(b)
AI BII CIII
( c ) AIII BII
CI
(d)AI
BIII CII
Ans
(a)
(xiii )
A phase lead compensating network
(a)
decreases the system
bandwidth
(b)
speeds up dynamic
response
(c)
reduces the
steady-state error
(d)
slows down transient response.
Ans: ( b)
(xiv)
A phase lag
compensating network
a.
decreases the system
bandwidth
b.
increases
susceptibility to noise
c.
increases gain at
higher frequencies
d.
is not applicable when phase decreases rapidly near
the crossover frequency.
Ans: (a)