Control System Engineering Set 4

Electrical Engineering

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This set of Control System Engineering (CSE) Multiple Choice Questions & Answers (MCQs) focuses on Control System Engineering Set 4

Q1 | Addition of zero at origin:
  • improvement in transient response
  • reduction in steady state error
  • reduction is settling time
  • increase in damping constant
Answer: improvement in transient response
Explaination:
stability of the system can be determined by various factors and for a good control system the stability of the system must be more and this can be increased by adding zero to the system and improves the transient response.
Q2 | Derivative output compensation:
  • improvement in transient response
  • reduction in steady state error
  • reduction is settling time
  • increase in damping constant
Answer: reduction is settling time
Explaination:
derivative controller is the controller that is also like high pass filter and is also phase lead controller and it is used to increase the speed of response of the system by increasing the damping coefficient.
Q3 | Derivative error compensation:
  • improvement in transient response
  • reduction in steady state error
  • reduction is settling time
  • increase in damping constant
Answer: increase in damping constant
Explaination:
damping constant reduces the gain, as it is inversely proportional to the gain and as increasing the damping gain reduces and hence the speed of response and bandwidth are both increased.
Q4 | Lag compensation leads to:
  • increases bandwidth
  • attenuation
  • increases damping factor
  • second order
Answer: attenuation
Explaination:
phase compensation can be lead, lag or lead lag compensation and integral compensation is also known as lag compensation and leads to attenuation which has least effect on the speed but the accuracy is increased.
Q5 | Lead compensation leads to:
  • increases bandwidth
  • attenuation
  • increases damping factor
  • second order
Answer: increases bandwidth
Explaination:
high pass filter is similar to the phase lead compensation and leads to increase in bandwidth and also increase in speed of response.
Q6 | Lag-lead compensation is a:
  • increases bandwidth
  • attenuation
  • increases damping factor
  • second order
Answer: second order
Explaination:
lag-lead compensation is a second order control system which has lead and lag compensation both and thus has combined effect of both lead and lag compensation this is obtained by the differential equation.
Q7 | Rate compensation :
  • increases bandwidth
  • attenuation
  • increases damping factor
  • second order
Answer: increases damping factor
Explaination:
damping factor is increased for reducing the oscillations and increasing the stability and speed of response which are the essential requirements of the control system and damping factor is increased by the rate compensation.
Q8 | Negative exponential term in the equation of the transfer function causes the transportation lag.
  • true
  • false
Answer: true
Explaination:
transportation lag is the lag that is generally neglected in systems but for the accurate measurements the delay caused to transport the input from one end to the other is called the transportation lag in the system causes instability to the system.
Q9 | Scientist Bode have contribution in :
  • asymptotic plots
  • polar plots
  • root locus technique
  • constant m and n circle
Answer: asymptotic plots
Explaination:
asymptotic plots are the bode plots that are drawn to find the relative stability of the system by finding the phase and gain margin and this was invented by scientist bode.
Q10 | Scientist Evans have contribution in :
  • asymptotic plots
  • polar plots
  • root locus technique
  • constant m and n circle
Answer: root locus technique
Explaination:
root locus technique is used to find the transient and steady state response characteristics by finding the locus of the gain of the system and this was made scientist evans .
Q11 | Scientist Nyquist have contribution in:
  • asymptotic plots
  • polar plots
  • root locus technique
  • constant m and n circle
Answer: polar plots
Explaination:
nyquist plot is used to find the stability of the system by open loop poles and zeroes and the encirclements of the poles and zeroes and satisfying the equation n=p-z and this is named under the name of scientist nyquist.
Q12 | Which one of the following methods can determine the closed loop system resonance frequency operation?
  • root locus method
  • nyquist method
  • bode plot
  • m and n circle
Answer: m and n circle
Explaination:
closed loop system resonance frequency is the frequency at which maximum peak occurs and this frequency of operation can best be determined with the help of m and n circle.
Q13 | If the gain of the open loop system is doubled, the gain of the system is :
  • not affected
  • doubled
  • halved
  • one fourth of the original value
Answer: not affected
Explaination:
gain of the open loop system is doubled then the gain of the system is not affected as the gain of the system is not dependent on the overall gain of the system.
Q14 | Constant M- loci:
  • constant gain and constant phase shift loci of the closed-loop system.
  • plot of loop gain with the variation in frequency
  • circles of constant gain for the closed loop transfer function
  • circles of constant phase shift for the closed loop transfer function
Answer: circles of constant phase shift for the closed loop transfer function
Explaination:
by definition, constant m loci are circles of constant phase shift for the closed loop transfer function.
Q15 | Constant N-loci:
  • constant gain and constant phase shift loci of the closed-loop system.
  • plot of loop gain with the variation in frequency
  • circles of constant gain for the closed loop transfer function
  • circles of constant phase shift for the closed loop transfer function
Answer: circles of constant gain for the closed loop transfer function
Explaination:
constant n loci are the circles of constant gain for the closed loop transfer function and the intersection point of the m and n is always the point (-1,0).
Q16 | Nichol’s chart:
  • constant gain and constant phase shift loci of the closed-loop system.
  • plot of loop gain with the variation in frequency
  • circles of constant gain for the closed loop transfer function
  • circles of constant phase shift for the closed loop transfer function
Answer: plot of loop gain with the variation in frequency
Explaination:
nichol’s chart are plot of loop gain with the variation in frequency and this is used to determine the stability of the system with the variation in the frequency.
Q17 | Scientist Nyquist have contribution in:
  • asymptotic plots
  • polar plots
  • root locus technique
  • constant m and n circle
Answer: polar plots
Explaination:
nyquist plot is used to find the stability of the system by open loop poles and zeroes and the encirclements of the poles and
Q18 | For a stable closed loop system, the gain at phase crossover frequency should always be:
  • < 20 db
  • < 6 db
  • > 6 db
  • > 0 db
Answer: > 0 db
Explaination:
phase crossover frequency is the frequency at which the gain of the system must be 1 and for a stable system the gain is decibels must be 0 db.
Q19 | Which principle specifies the relationship between enclosure of poles & zeros by s- plane contour and the encirclement of origin by q(s) plane contour?
  • argument
  • agreement
  • assessment
  • assortment
Answer: argument
Explaination:
argument principle specifies the relationship between enclosure of poles & zeros by s-plane contour and the encirclement of origin by q(s) plane contour.
Q20 | If a Nyquist plot of G (jω) H (jω) for a closed loop system passes through (-2, j0) point in GH plane, what would be the value of gain margin of the system in dB?
  • 0 db
  • 2.0201 db
  • 4 db
  • 6.0205 db
Answer: 6.0205 db
Explaination:
gain margin is calculated by taking inverse of the gain where the nyquist plot cuts the real axis.
Q21 | For Nyquist contour, the size of radius is
  • 25
  • 0
  • 1
  • ∞
Answer: ∞
Explaination:
for nyquist contour, the size of radius is ∞.
Q22 | According to Nyquist stability criterion, where should be the position of all zeros of q(s) corresponding to s-plane?
  • on left half
  • at the center
  • on right half
  • random
Answer: on left half
Explaination:
according to nyquist stability criterion zeroes must lie on the left half on the s plane.
Q23 | If the system is represented by G(s) H(s) = k (s+7) / s (s +3) (s + 2), what would be its magnitude at ω = ∞?
  • 0
  • ∞ c) 7/10
  • d) 21
Answer: 0
Explaination:
on calculating the magnitude
Q24 | Consider the system represented by the equation given below. What would be the total phase value at ω = 0?
  • -90°
  • -180°
  • -270°
  • -360°
Answer: -270°
Explaination:
the phase can be calculated by the basic formula for calculating phase angle.
Q25 | In polar plots, if a pole is added at the origin, what would be the value of the magnitude at Ω = 0?
  • zero
  • infinity
  • unity
  • unpredictable
Answer: infinity
Explaination:
addition of pole causes instability to the system.
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