JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II CONTROL THEORY Previous Question Paper (April - 2018 - 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. Each question carries 10 marks.
PART A
Define state and state variables. List the advantages of modeling systems in state space.
Answer
The state of a dynamic system is the smallest set of variables (state variables) that determines the system's future behavior for any given input. State variables are the components of the state vector that represent the internal energy storage of the system. Advantages include the ability to model MIMO systems, handle non-linear and time-varying systems, and facilitate computer-aided analysis.
An automobile driver uses control systems to maintain the speed of a car at a prescribed level. Sketch the block diagram to illustrate this feedback control system.
Answer
The block diagram consists of a reference speed input, a comparator (error detector), a controller (driver/engine management), the plant (car dynamics), and a feedback sensor (speedometer) feeding back to the comparator.
The closed loop transfer function of a unity feedback control system is given by
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Explain the significance of static error coefficients.
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How will you find root locus on real axis?
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Draw the pole zero location of lag compensator.
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Define phase margin and gain margin.
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What are frequency domain specifications?
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List two differences between time domain and frequency domain analysis.
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Define: i) Minimum phase transfer function ii) Non minimum phase transfer function.
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Unit I
Using the Mason’s gain formula, obtain the overall transfer function whose signal flow graph is shown in figure 1.
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Determine the transfer function C(S)/R(S) for the following block diagram shown in figure 2.
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Unit II
Why derivative controller is not used in control systems? What is the effect of PI controller on the system performance?
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Derive the time response of second order under damped system due to unit step input.
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Find the Error coefficients for step, ramp and parabolic inputs for unity feed-back system having the forward transfer function G(s) = 1 / (s(s+2)(s+3)(s+5)).
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Explain with an example how the stability of system is analyzed through MATLAB.
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Unit III
Sketch the root locus plot of a unity feedback system whose open loop T.F G(S) = K(s-2) / (s(s+2)(s+3)(s+4)).
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Explain the general rules for constructing the root locus.
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Explain the effects of adding poles and zeros to G(s)H(s) on the root loci by considering one example.
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Unit IV
Sketch the Bode plot for a system G(s) = 15(s+5)/(s²+16s+100) and determine the stability of the system.
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Using Nyquist stability criterion, investigate the stability of a closed loop system whose open loop transfer function is given by G(s)H(s) = 1/(s(s+2)(s+3)(s+4)).
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Unit V
What are the characteristics of Lead compensation? When lead compensation is employed?
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Why compensation is necessary in feedback control system? Draw the lag compensator network and derive its transfer function. Also draw Pole-zero plot.
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The open loop transfer function of certain unity feedback control system is given by G(S) = K/(S+4)(S+8). It is desired to have the phase margin to be at least 33° and velocity error constant Kv = 30 Sec⁻¹. Design a lag compensator using root locus.
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