JNTU
JNTU B.Tech II CONTROL SYSTEMS Previous Question Paper (May - 2019 - R16)
Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit.
PART - A
Classify the following as open or closed loop system with valid reasons: (i) An electrical On-Off switch, (ii) Room air-conditioner.
Answer
(i) Electrical On-Off switch: Open loop system, because the output (state of the load) has no influence on the control action; the switch remains in its set position regardless of the load's performance. (ii) Room air-conditioner: Closed loop system, because it uses a thermostat to measure the actual room temperature and compares it with the set point to adjust the cooling output automatically.
Why do you need a feedback controller? Justify your answer with an example.
Answer
A feedback controller is required to reduce the sensitivity of the system to parameter variations and to reject external disturbances, ensuring the output tracks the reference input accurately. For example, in a cruise control system, feedback allows the vehicle to maintain a constant speed despite changes in road incline or wind resistance by adjusting the throttle based on the difference between actual and desired speed.
What are the effects of integral control action?
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Find the peak overshoot for unit step response of the system described by closed loop transfer function, G(s) = 64 / (s^2 + 16s + 64).
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Outline the Bode plot for a Proportional Integral controller.
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Compare between absolute stability, conditional stability and relative stability.
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Draw the polar plot for G(s)H(s) = (s+1)/(s+3).
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What is a Phase Lag compensator and why is it used?
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What are the advantages of State variable model of dynamic system?
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How do you determine the system eigen values and what is its role in the system response?
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PART - B
Determine the transfer function for the block diagram shown in Figure 1.
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Distinguish between Open loop control system and closed loop control system.
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A two phase AC servo motor has the following parameters: Starting torque = 0.166 N-m, Inertia = 1x10^-5 kg-m^2, Supply voltage = 115 V, No load angular velocity = 304 rad/sec. Assuming torque – speed curve to be linear and zero viscous friction, derive the transfer function.
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The open loop transfer function of an unity feedback control system is given as G(s) = K / s(1+sT). Determine the factor by which the gain ‘K’ should be multiplied so that the overshoot of the unity step response be reduced from 80% to 25%?
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Determine the damping ratio and natural frequency of the system if the derivative feedback is absent (K0=0) in the closed loop system shown in Figure 2. What is the steady state error resulting from unit ramp input?
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Determine the derivative feedback constant ‘K0’ which will increase the damping ratio of the system to 0.5. What is the steady state error resulting from unit ramp input with this setting of the derivative feedback constant?
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Determine the values of K and β, so that the system whose open loop transfer function is G(s) = K(s+1) / s(s^2 + 5s + β) oscillates at a frequency of oscillations of 2 rad/sec. Assume unity feedback.
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Sketch the root locus of the unity feedback system having G(s) = K / (s^2 + 2s) for positive values of K. Sketch the new root locus when a simple pole at s=-5 is added to the system loop transfer function. Hence indicate the effect of adding this pole on the root locus of the system.
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Investigate closed loop stability of a system having G(s)H(s) = K(s+4) / (s-2) using Nyquist criterion. Determine the limiting value of ‘K’ for stability.
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Design a lead compensator for the system with an open-loop transfer function G(s) = K / s(1+0.1s) for the specifications of acceleration error constant Ka = 10 and phase margin φpm = 30 degrees.
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For the system given below, obtain: a) Zero input response, b) Zero state response, c) Total response. A = [[1, 4], [-2, -5]], B = [[0], [1]], u = 1 and x(0) = [[1], [0]].
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Distinguish between Transfer function model and State Space model.
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Diagonalize the system matrix A = [[0, 1, 0], [0, 0, 1], [-2, -5, -4]].
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