Recent questions and answers in Control Systems

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1

GATE ECE 2021 | Question: 13
The block diagram of a feedback control system is shown in the figure The transfer function $\dfrac{Y{\left ( s \right )}}{X {\left ( s \right )}}$ of the system is $\frac{G_{1}+G_{2}+G_{1}G_{2}H}{1+G_{1}H}$ $\frac{G_{1}+G_{2}}{1+G_{1}H+G_{2}H}$ $\frac{G_{1}+G_{2}}{1+G_{1}H}$ $\frac{G_{1}+G_{2}+G_{1}G_{2}H}{1+G_{1}H+G_{2}H}$

Arjun asked in Control Systems Feb 20, 2021

by Arjun

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2

GATE ECE 2020 | Question: 38
$P, Q$, and $R$ are the decimal integers corresponding to the $4$-bit binary number $1100$ considered in signed magnitude, $1$’s complement, and $2$’s complement representations, respectively. The $6$-bit $2$’s complement representation of $(P+Q+R)$ is $110101$ $110010$ $111101$ $111001$

go_editor asked in Control Systems Feb 13, 2020

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3

GATE ECE 2020 | Question: 39
The state diagram of a sequence detector is shown below. State $S_{0}$ is the initial state of the sequence detector. If the output is $1$, then the sequence $01010$ is detected. the sequence $01011$ is detected. the sequence $01110$ is detected. the sequence $01001$ is detected.

go_editor asked in Control Systems Feb 13, 2020

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4

GATE ECE 2020 | Question: 40
The characteristic equation of a system is $s^{3}+3s^{2}+\left ( K+2 \right )s+3K=0.$ In the root locus plot for the given system, as $K$ varies from $0$ to $\infty$, the break-away or break-in points(s) lie within $(-1, 0)$ $(-2, -1)$ $(-3, -2)$ $(-\infty, -3)$

go_editor asked in Control Systems Feb 13, 2020

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5

GATE ECE 2020 | Question: 41
The components in the circuit given below are ideal. If $R=2\:k \Omega$ and $C=1$ $\mu F$, the $-3$ dB cut-off frequency of the circuit in Hz is $14.92$ $34.46$ $59.68$ $79.58$

go_editor asked in Control Systems Feb 13, 2020

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6

GATE ECE 2019 | Question: 29
It is desired to find a three-tap casual filter which gives zero signal as an output to an input of the form $x[n]= c_{1}exp\left(-\dfrac{j\pi n}{2}\right)+c_{2}\left(\dfrac{j\pi n}{2}\right),$ where $c_{1}$ and $c_{2}$ are arbitrary real numbers. The desired three-tap filter is ... $n$, when $x[n]$ is as given above ? $a=1,b=1$ $a=0,b=-1$ $a=-1,b=1$ $a=0,b=1$

Arjun asked in Control Systems Feb 12, 2019

by Arjun

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7

GATE ECE 2019 | Question: 39
The state transition diagram for the circuit shown is

Arjun asked in Control Systems Feb 12, 2019

by Arjun

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8

GATE ECE 2016 Set 3 | Question: 6
Consider the signal $x(t) = \cos(6\pi t) + \sin (8\pi t)$, where $t$ is in seconds. The Nyquist sampling rate (in samples/second) for the signal $y(t) = x(2t + 5)$ is $8$ $12$ $16$ $32$

Milicevic3306 asked in Control Systems Mar 28, 2018

by Milicevic3306

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9

GATE ECE 2016 Set 3 | Question: 19
The block diagram of a feedback control system is shown in the figure. The overall closed-loop gain of $G$ of the system is $G = \large\frac{G_1G_2}{1+G_1H_1} \\$ $G = \large\frac{G_1G_2}{1+G_1G_2+G_1H_1} \\$ $G = \large\frac{G_1G_2}{1+G_1G_2H_1} \\$ $G = \large\frac{G_1G_2}{1+G_1G_2+G_1G_2H_1}$

Milicevic3306 asked in Control Systems Mar 28, 2018

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10

GATE ECE 2016 Set 3 | Question: 20
For the unity feedback control system shown in the figure, the open-loop transfer function $G(s)$ is given as $G(s) = \frac{2}{s(s+1)}$ The steady state error $e_{ss}$ due to a unit step input is $0$ $0.5$ $1.0$ $\infty$

Milicevic3306 asked in Control Systems Mar 28, 2018

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11

GATE ECE 2016 Set 3 | Question: 22
An analog baseband signal, bandlimited to $100\ Hz$, is sampled at the Nyquist rate. The samples are quantized into four message symbols that occur independently with probabilities $p_1 = p_4 = 0.125$ and $p_2 = p_3$. The information rate (bits/sec) of the message source is _______

Milicevic3306 asked in Control Systems Mar 28, 2018

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12

GATE ECE 2016 Set 3 | Question: 46
The first two rows in the Routh table for the characteristic equation of a certain closed-loop control system are given as $\begin{array}{|c|cc} \hline s^3 & 1 &(2K+3) \\ s^2 & 2K & 4 \end{array}$ The range of $K$ for which the system is stable is $-2.0<K<0.5$ $0<K<0.5$ $0<K<\infty$ $0.5<K<\infty$

Milicevic3306 asked in Control Systems Mar 28, 2018

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13

GATE ECE 2016 Set 2 | Question: 9
The $z$-parameter matrix for the two-port network shown is $\begin{bmatrix} 2j\omega &j\omega \\ j\omega & 3+2j\omega \end{bmatrix},$ where the entries are in $\Omega$. Suppose $Z_{b}\left ( j\omega \right )=R_{b}+j\omega .$ Then the value of $R_{b}$ (in $\Omega$) equals ________

Milicevic3306 asked in Control Systems Mar 28, 2018

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14

GATE ECE 2016 Set 2 | Question: 20
The number and direction of encirclements around the point $-1+j0$ in the complex plane by the Nyquist plot of $G(s)=\frac{1-s}{4+2s}$ is zero. one,anti-clockwise. one, clockwise. two, clockwise.

Milicevic3306 asked in Control Systems Mar 28, 2018

by Milicevic3306

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15

GATE ECE 2016 Set 2 | Question: 47
The asymptotic Bode phase plot of $G\left ( s \right )=\frac{k}{\left ( s+0.1 \right )\left ( s+10 \right )\left ( s+p_{1} \right )},$ with $k$ and $p_{1}$ both positive, is shown below. The value of $p_{1}$ is _______

Milicevic3306 asked in Control Systems Mar 28, 2018

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16

GATE ECE 2016 Set 1 | Question: 5
Consider the plot $f(x)$ versus $x$ as shown below. Suppose $F(x)= \int_{-5}^{x} f(y) dy$. Which one of the following is a graph of $F(x)$?

Milicevic3306 asked in Control Systems Mar 28, 2018

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17

GATE ECE 2016 Set 1 | Question: 19
Match the inferences $X$, $Y$ and $Z$ ... $X \to R, \: Y \to Q, \: Z \to P$ $X \to P, \: Y \to R, \: Z \to Q$

Milicevic3306 asked in Control Systems Mar 28, 2018

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18

GATE ECE 2016 Set 1 | Question: 20
A closed-loop control system is stable if the Nyquist plot of the corresponding open-loop transfer function encircles the $s$-plane point $(-1+j0)$ in the counter clockwise direction as many times as the number of right-half $s$-plane poles. ... plane point $(-1+j0)$ in the counterclockwise direction as many times as the number of right-half $s$-plane zeroes.

Milicevic3306 asked in Control Systems Mar 28, 2018

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19

GATE ECE 2015 Set 3 | Question: 19
Consider the Bode plot shown in the figure. Assume that all the poles and zeros are real-valued. The value of $f_{H}\: – f_{L}\:( \text{in}\: Hz)$ is ___________.

Milicevic3306 asked in Control Systems Mar 28, 2018

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20

GATE ECE 2015 Set 3 | Question: 47
For the system shown in the figure, $s=-2.75$ lies on the root locus if $K$ is _______.

Milicevic3306 asked in Control Systems Mar 28, 2018

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21

GATE ECE 2015 Set 3 | Question: 54
A $200\: m$ long transmission line having parameters shown in the figure is terminated into a load ܴ$R_{L}$. The line is connected to a $400\: V$ source having source resistance $R_{S}$ through a switch, which is closed at $t = 0.$ The transient response of the ... line $(z = 0)$ is also drawn in the figure. The value of $R_{L}\: \text{(in}\: \Omega)$ is ________.

Milicevic3306 asked in Control Systems Mar 28, 2018

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22

GATE ECE 2015 Set 2 | Question: 20
For the signal flow graph shown in the figure, the value of $\dfrac{C(s)}{R(s)}$ is $\dfrac{G_{1}G_{2}G_{3}G_{4}}{1 - G_{1}G_{2}H_{1} - G_{3}G_{4}H_{2} - G_{2}G_{3}H_{3} +G_{1}G_{2}G_{3}G_{4}H_{1}H_{2}} \\$ ... $\dfrac{1}{1 - G_{1}G_{2}H_{1} - G_{3}G_{4}H_{2} - G_{2}G_{3}H_{3} +G_{1}G_{2}G_{3}G_{4}H_{1}H_{2}}$

Milicevic3306 asked in Control Systems Mar 28, 2018

by Milicevic3306

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23

GATE ECE 2015 Set 1 | Question: 19
Negative feedback in a closed-loop control system $\textbf{ DOES NOT}$ reduce the overall gain reduce bandwidth improve disturbance rejection reduce sensitivity to parameter variation

Milicevic3306 asked in Control Systems Mar 28, 2018

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24

GATE ECE 2015 Set 1 | Question: 20
A unity negative feedback system has the open-loop transfer function $G(s) = \frac{K}{s(s+1)(s+3)}$. The value of the gain $K (>0)$ at which the root locus crosses the imaginary axis is ________

Milicevic3306 asked in Control Systems Mar 28, 2018

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25

GATE ECE 2014 Set 4 | Question: 20
In a Bode magnitude plot, which one of the following slopes would be exhibited at high frequencies by a $4$th order all-pole system? $-80$ dB/decade $-40$ dB/decade $+40$ dB/decade $+80$ dB/decade

Milicevic3306 asked in Control Systems Mar 26, 2018

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26

GATE ECE 2014 Set 2 | Question: 20
The natural frequency of an undamped second-order system is $40$ rad/s. If the system is damped with a damping ratio $0.3$, the damped natural frequency in $rad/s$ is ___________.

Milicevic3306 asked in Control Systems Mar 26, 2018

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27

GATE ECE 2014 Set 2 | Question: 30
A series LCR circuit is operated at a frequency different from its resonant frequency. The operating frequency is such that the current leads the supply voltage. The magnitude of current is half the value at resonance. If the values of L, C and R are $1$ H, $1$ F and $1 \Omega$, respectively, the operating angular frequency (in rad/s) is _________.

Milicevic3306 asked in Control Systems Mar 26, 2018

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28

GATE ECE 2014 Set 2 | Question: 47
The Bode asymptotic magnitude plot of a minimum phase system is shown in the figure. If the system is connected in a unity negative feedback configuration, the steady state error of the closed loop system, to a unit ramp input, is _________.

Milicevic3306 asked in Control Systems Mar 26, 2018

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29

GATE ECE 2014 Set 1 | Question: 18
Consider two real valued signals, $x(t)$ band-limited to $[-500\:Hz,500\:Hz]$ and $y(t)$ band-limited to $[-1\:kHz,1\:kHz].$ For $z(t) = x(t)\cdot y(t),$ the Nyquist sampling frequency (in $kHz$) is _______.

Milicevic3306 asked in Control Systems Mar 26, 2018

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30

GATE ECE 2014 Set 1 | Question: 21
Consider the feedback system shown in the figure. The Nyquist plot of $G(s)$ is also shown. Which one of the following conclusions is correct? $G(s)$ is an all-pass filter $G(s)$ is a strictly proper transfer function $G(s)$ is a stable and minimum-phase transfer function The closed-loop system is unstable for sufficiently large and positive $k$

Milicevic3306 asked in Control Systems Mar 26, 2018

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31

GATE ECE 2014 Set 1 | Question: 47
The phase margin in degrees of $G(s) = \dfrac{10}{(s+0.1)(s+1)(s+10)}$ calculated using the asymptotic Bode plot is ______.

Milicevic3306 asked in Control Systems Mar 26, 2018

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32

GATE ECE 2013 | Question: 40
The signal flow graph for a system is given below. The transfer function $\dfrac{Y(s)}{U(s)}$ for this system is $\frac{s+1}{5s^{2}+6s+2} \\$ $\frac{s+1}{s^{2}+6s+2} \\$ $\frac{s+1}{s^{2}+4s+2} \\$ $\frac{1}{5s^{2}+6s+2}$

Milicevic3306 asked in Control Systems Mar 26, 2018

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33

GATE ECE 2013 | Question: 21
Assuming zero initial condition, the response $y(t)$ of the system given below to a unit step input $u(t)$ is $u(t)$ $tu(t)$ $\frac{t^{2}}{2}u(t)$ $e^{-t}u(t)$

Milicevic3306 asked in Control Systems Mar 26, 2018

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34

GATE ECE 2013 | Question: 9
The Bode plot of a transfer function $G(s)$ is shown in the figure below. The gain $(20\log \mid G(s)\mid)$ is $32\:dB$ and $-8\:dB$ at $1\:rad/s$ and $10\:rad/s$ respectively. The phase is negative for all $\omega.$ Then $G(s)$ is $\frac{39.8}{s} \\$ $\frac{39.8}{s^{2}} \\$ $\frac{32}{s} \\$ $\frac{32}{s^{2}} \\$

Milicevic3306 asked in Control Systems Mar 26, 2018

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35

GATE ECE 2018 | Question: 5
The Nyquist stability criterion and the Routh criterion both are powerful analysis tools for determining the stability od feedback controllers. Identify which of the following statements is FALSE: Both the criteria provide information relative to the ... criterion. The closed-loop frequency response for a unity feedback system cannot be obtained from the Nyquist plot.

anonymous answered in Control Systems Feb 20, 2018

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36

GATE ECE 2017 Set 2 | Question: 48
A unity feedback control system is characterized by the open-loop transfer function $G(s)=\frac{10K(s+2)}{s^3+3s^2+10}$ The Nyquist path and the corresponding Nyquist plot of $G(s)$ are shown in the figures below. If $0 < K < 1$, then the number of poles of the closed-loop transfer function that lie in the right-half of the $s$-plane is $0$ $1$ $2$ $3$

admin asked in Control Systems Nov 25, 2017

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37

GATE ECE 2017 Set 2 | Question: 47
A second-order LTI system is described by the following state equations, $ \begin{array}{ll} \frac{d}{dt}x_1(t)-x_2(t)=0 \\ \frac{d}{dt}x_2(t)+2x_1(t)+3x_2(t)=r(t) \end{array}$ where $x_1(t)$ and $x_2(t)$ are the two state variables and $r(t)$ denotes the input. The output $c(t)=x_1(t)$. The system is undamped (oscillatory) underdamped critically damped overdamped

admin asked in Control Systems Nov 25, 2017

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38

GATE ECE 2017 Set 2 | Question: 46
A unity feedback control system is characterized by the open-loop transfer function $G(s)=\frac{2(s+1)}{s^3+ks^2+2s+1}$ The value of $k$ for which the system oscillates at $2$ rad/s is ___________

admin asked in Control Systems Nov 25, 2017

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39

GATE ECE 2017 Set 2 | Question: 34
The transfer function of a causal LTI system is $H(s)=1/s$. If the input to the system is $x(t)=[\sin(t)/\pi t] u(t)$, where $u(t)$ is a unit step function, the system output $y(t)$ as $t\to \infty$ is ____________

admin asked in Control Systems Nov 25, 2017

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40

GATE ECE 2017 Set 2 | Question: 33
Consider an LTI system with magnitude response $\mid H(f) \mid=\begin{cases} 1-\frac{\mid f \mid}{20}, & \mid f \mid \leq 20 \\ 0,& \mid f \mid > 20 \end{cases}$ and phase response $\arg \{ H(f) \}= - 2f.$ If the input to the ... $y(t)$ is ____________

admin asked in Control Systems Nov 25, 2017

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