JNTU
JNTU B.Tech II CONTROL SYSTEMS Previous Question Paper (August/September - 2022 - R16)
Answer any five questions. All questions carry equal marks.
Main
Explain open loop control system and closed loop control system with example.
Answer
An open-loop control system is one in which the control action is independent of the output. There is no feedback mechanism to compare the output with the desired input. The system operates based on pre-set parameters, making it simple and inexpensive but sensitive to external disturbances. An example is an automatic toaster, where the heating time is fixed regardless of the bread's actual browning level.
A closed-loop control system, or feedback control system, is one in which the control action depends on the output. It uses a feedback element to measure the actual output and compares it with the reference input via an error detector. The controller then adjusts the input to minimize the error. An example is an air conditioning system with a thermostat, which continuously monitors room temperature and adjusts cooling to maintain the set point.
Derive the transfer function of DC servo motor.
Answer
For an armature-controlled DC servo motor, the electrical circuit equation is:
Where Eb is the back EMF, proportional to angular velocity: Eb(s) = Kbsθ(s). The torque developed is proportional to armature current: T(s) = KtIa(s). The mechanical load equation is:
Substituting Ia(s) = T(s)/Kt into the electrical equation:
Assuming negligible inductance (La ≈ 0) for simplicity, the transfer function relating angular position to input voltage is:
Obtain the overall transfer functions for the signal flow graphs using mason’s gain formula.
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Explain the construction and principle of operation synchro transmitter.
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Obtain the time response of a first order system for a unit step input and plot its response.
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A unity feedback control system has an open loop transfer function, G(s) = 10 / (s(s+2)). Find the time domain specifications for unit step input.
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Find the steady-state error for unit step, unit ramp and unit acceleration inputs for the system G(s) = 100(s+1) / (s(s+10)(s+50)).
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Damping factor and natural frequency of the system are 0.12 and 84.2 rad/sec respectively. Determine the rise time (tr), peak time (tp), maximum peak overshoot (mp) and settling time (ts).
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Obtain magnitude and phase angle Bode plots for the system G(s) = 20(0.1s + 1) / (s^2(0.2s + 1)(0.02s + 1)).
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Construct Routh array, determine stability and find the location of roots for the system represented by characteristic equation: s^4 + 8s^3 + 18s^2 + 16s + 5 = 0.
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Explain about different frequency domain specifications.
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Explain the procedural steps to design a phase lag compensator using Bode analysis.
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Sketch the polar plot and discuss the stability of the system represented by G(s)H(s) = K / (s(s+1)(s+5)).
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Explain the concepts of state, state variables and state model.
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Given G(s) = 2 / (s^2 + 5s + 6), obtain the state space model of the system in the diagonal canonical form.
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