Control Systems MCQ Questions & Answers

81

Consider the following statements with reference to frequency-domain approaches to analysis of feedback to control system
1. The approach needs and accurate mathematical description of the system
2. The method is independent of the complexity of systems
3. The method gives an approach for trial and error design
Which of the above statements are correct?

A) 1 and 2 only B) 1 and 3 only C) 2 and 3 only D) 1, 2 and 3

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Answer & Solution

Answer: Option D

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82

The transfer function of a plant is $$T\left( s \right) = \frac{5}{{\left( {s + 5} \right)\left( {{s^2} + s + 1} \right)}}.$$ The second-order approximation of T(s) using dominant pole concept is

A) $$\frac{1}{{\left( {s + 5} \right)\left( {s + 1} \right)}}$$ B) $$\frac{5}{{\left( {s + 5} \right)\left( {s + 1} \right)}}$$ C) $$\frac{5}{{{s^2} + s + 1}}$$ D) $$\frac{1}{{{s^2} + s + 1}}$$

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Answer & Solution

Answer: Option D

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83

The correct sequences of steps needed to improve system stability is:

A) Insert derivative action, use negative feedback, reduce gain B) Reduce gain, use negative feedback, insert derivative action C) Reduce gain, Insert derivative action, use negative feed back D) Use negative feedback, reduce gain, and insert derivative action

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Answer & Solution

Answer: Option D

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84

The phase-lead network function $${G_C}\left( s \right) = \frac{{s + \frac{1}{T}}}{{s + \frac{1}{{aT}}}},$$ where a < 1 would provide maximum phase-lead at a frequency of:

A) $$\frac{1}{T}$$ B) $$\frac{1}{{aT}}$$ C) $$\frac{1}{{T\sqrt a }}$$ D) $$\frac{1}{{a\sqrt T }}$$

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Answer & Solution

Answer: Option C

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85

Identify the matrix that can be a state transition matrix.

A) \[\phi = \left[ {\begin{array}{*{20}{c}} {{e^{ - t}}}&0\\ 1&{{e^{ - 2t}}} \end{array}} \right]\] B) \[\phi = \left[ {\begin{array}{*{20}{c}} {{e^t}}&t\\ 1&{2{e^{ - t}}} \end{array}} \right]\] C) \[\phi = \left[ {\begin{array}{*{20}{c}} {{e^t} + {e^{ - t}}}&0\\ 0&{2{e^{ - t}}} \end{array}} \right]\] D) \[\phi = \left[ {\begin{array}{*{20}{c}} {{e^{ - t}}}&0\\ 0&{{e^{ - 2t}}} \end{array}} \right]\]

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Answer & Solution

Answer: Option D

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86

Consider the following information regards open loop frequency response of a unity feedback system

ω	\|G(j)\|	∠G(j)
2	7.5	-118°
3	4.8	-130°
4	3.15	-140°
5	2.25	-150°
6	1.70	-157°
8	1.00	-170°
10	0.64	-180°

The gain and phase margin of the system are respectively:

A) 0 dB, -180° B) 3.86 dB, -180° C) 0 dB, -10° D) 3.86 dB, 10°

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Answer & Solution

Answer: Option D

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87

A control system has $$G\left( s \right)H\left( s \right) = \frac{{K\left( {s + 1} \right)}}{{s\left( {s + 3} \right)\left( {s + 4} \right)}}.$$ Root locus of the system can lie on the real axis

A) between s = -1 and s = -3 B) between s = 0 and s = -4 C) between s = -3 and s = -4 D) towards left of s = -4

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Answer & Solution

Answer: Option C

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88

The unit step response of a particular control system is given by c(t) = 1 - 10e^-t. Then its transfer function is:

A) $$\frac{{10}}{{s + 1}}$$ B) $$\frac{{s - 9}}{{s + 1}}$$ C) $$\frac{{1 - 9s}}{{s + 1}}$$ D) $$\frac{{1 - 9s}}{{s\left( {s + 1} \right)}}$$

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Answer & Solution

Answer: Option C

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89

Due to derivative control, the steady-state error is

A) ratio control reduced B) cascade control increased C) split range control not effected D) inferential control made zero

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Answer & Solution

Answer: Option B

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90

The characteristic equation of a closed loop system is given by s⁴ + 6s³ + 11s² + 6s + k = 0
Stable closed loop behavior can be ensured when gain k is such that

A) 0 < k < 10 B) k > 10 C) -∞ ≤ k < ∞ D) 0 < k ≤ ∞

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Answer & Solution

Answer: Option A

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Control Systems MCQ Questions & Answers | ECE