Wednesday, September 16, 2015

Frequency Response and Bode Plots (Magnitude & Phase) - Topicwise Questions in Control Systems (1987 -2015)

2003
7. The approximate Bode magnitude plot of a minimum phase system is shown in figure.
The transfer function of the system is


Answer: A
Solution : https://www.youtube.com/watch?v=BXoIP2em_cc



2004
3. Consider the Bode magnitude plot shown in figure.
The transfer function H(s) is


Answer: C
Solution : https://www.youtube.com/watch?v=0K0Ls-_nRDQ


6. A system has poles at 0.01 Hz, 1 Hz and 80 Hz; zeros at 5 Hz, 100 Hz and 200 Hz. The approximate phase of the system response at 20 Hz is
a) - 90o
b) 0o
c) 90o
d) - 180o


Answer: A
Solution : https://www.youtube.com/watch?v=8SWwr0wlV0E



2006
3. Consider two transfer functions G1(s) = 1 / (s2 + as + b) and G2(s) = s / (s2 + as + b). The 3 dB bandwidths of their frequency responses are, respectively


Answer: C
Solution :




2007
7. The asymptotic Bode plot of a transfer function is as shown in figure.
The transfer function G(s) corresponding to this Bode plot is


Answer: D
Solution : https://www.youtube.com/watch?v=fpM5ezwr90c




2008
7. The magnitude of frequency response of an under damped second order system is 5 at 0 rad/sec and peaks to 10/√3 at 5√2 rad/sec. The transfer function of the system is


Answer: A
Solution : https://www.youtube.com/watch?v=3a4n-8XUFCg



2010
2. A system with transfer function Y(s)/X(s) = s/(s + p) has an output y(t) = cos(2t – π/3) for the input signal x(t) = p cos(2t – π/2). Then, the system parameter 'p' is
a) √3
b) 2/√3
c) 1
d) √3/2
Answer: B
Solution : https://www.youtube.com/watch?v=3WAIkGRRes4


3. For the asymptotic bode magnitude plot shown below,
the system transfer function can be


Answer: A
Solution : https://www.youtube.com/watch?v=Tt58Wfn-dsQ



2013
1. The Bode plot of a transfer function G(s) is shown in the figure below.
The gain (20log|G(s)|) is 32 dB and – 8 dB at 1 rad/sec and 10 rad/sec respectively. The phase is negative for all ω. Then G(s) is
a) 39.8/s
b) 39.8/s2
c) 32/s
d) 32/s2


Answer: B
Solution : https://www.youtube.com/watch?v=YkPfY-Gufmg




2014
11. 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 _____________
Answer: 0.5
Solution : https://www.youtube.com/watch?v=fBTMa-Ql07A


18. In a Bode magnitude plot, which one of the following slopes would be exhibited at high frequencies by a 4th order all pole system?
a) – 80 dB/decade
b) – 40 dB/decade
c) + 40 dB/decade
d) + 80 dB/decade
Answer: A
Solution : https://www.youtube.com/watch?v=bTwOnjuzVX8



2015
14. Consider the Bode plot shown in figure.
Assume that all the poles and zeros are real valued. The value of fH – fL (in Hertz) is ____________________


Answer: 8970
Solution : https://www.youtube.com/watch?v=R95T4ztuNQo

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