JNTU
JNTU B.Tech II CONTROL SYSTEMS Previous Question Paper (April/May - 2023 - R16)
Note: i) Question paper consists of Part A, Part B.
ii) Part A is compulsory, which carries 25 marks. In Part A, Answer all questions.
iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
Answer all questions.
What is the difference between a open loop control and a closed loop control system?
Answer
An open-loop control system is one in which the control action is independent of the output; it does not have feedback, making it simple and inexpensive but sensitive to external disturbances and parameter variations. In contrast, a closed-loop control system incorporates feedback by comparing the actual output with the desired input to generate an error signal, which is then used to adjust the control action. This feedback mechanism allows closed-loop systems to be more accurate, stable, and robust against disturbances, albeit at the cost of increased complexity and potential instability.
Why negative feedback is invariably preferred in a closed loop system?
Answer
Negative feedback is preferred in closed-loop systems because it significantly improves system performance by reducing sensitivity to parameter variations and suppressing external disturbances. By introducing a feedback loop with a negative sign, the system gain is reduced, which effectively increases the bandwidth and improves the transient response by providing better damping. Furthermore, negative feedback reduces the effect of non-linearities and noise within the forward path, leading to a more stable and predictable output that tracks the reference input with higher accuracy.
Define steady state response.
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Define peak time and settling time.
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Define phase margin and gain margin.
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Why bode plots are commonly used in the frequency domain design?
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What is polar plot?
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What is the basis for the selection of a compensator?
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What are the two conditions to be satisfied by the state variables?
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What are the merits of state variable technique?
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Part B
Find the overall gain C(s)/R(s) for the signal flow graph shown using Mason’s gain equation (figure 1).
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Find the transfer function of the given system using block reduction technique. Verify the result using Mason’s gain equation (figure 2).
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The forward path transfer function of a unity feedback control system is given by G(s) = 4/s(s+5). Obtain the response of the system to unit step input.
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Determine the step, ramp and parabolic error constants for the unity feedback control system. G(s) = 10 (s+2)/ (s+1)s^2.
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Determine the rise time, peak time, settling time and peak overshoot of a second order control system subjected to a unit step input. If the damping ratio is 0.5 and undamped natural frequency ωn is 6 rad/sec.
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Explain frequency domain specifications of frequency response analysis.
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The characteristic polynomial of a system is s^7+9s^6+24s^5+24s^4+24s^3+24s^2+23s+15=0. Determine the location of roots on s-plane and hence comment on the stability of the system using Routh-Hurwitz criterion.
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Plot the Bode diagram for the following transfer function and find the Gain margin and Phase margin. G(S) = 10/ S(1+0.4S) (1+0.1S)
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State and explain Nyquist stability criteria.
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What is compensation and what are the types of compensation?
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Describe the design procedure of a lead compensator.
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List out the properties of state transition matrix. Obtain the state transition matrix of A = [2 0; 1 -2].
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Define the following: (i) Eigen value (ii) Eigen vectors (iii) state (iv) state space (v) state vector.
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Construct the state model for a system characterized by differential equation d^3y/dt^3 + 6d^2y/dt^2 + 11dy/dt + 6y = u.
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