JNTU
JNTU B.Tech III CONTROL SYSTEMES ENGINEERING Previous Question Paper (May - 2018 - R15)
Note: This question paper contains two parts A and B. 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 and may have a, b, c as sub questions.
Part A
What are the feed-back characteristics?
Answer
Feedback characteristics in control systems include: 1) Increased accuracy through the reduction of steady-state error; 2) Reduced sensitivity to parameter variations and disturbances; 3) Improved transient response by allowing for the adjustment of damping and bandwidth; and 4) Noise reduction within the feedback loop, though it may introduce potential instability if not properly designed.
State and write the Mason’s gain formula.
Answer
Mason's gain formula is a mathematical method used to determine the overall transfer function of a complex control system represented by a signal flow graph. It relates the input and output variables by accounting for all possible forward paths and feedback loops within the system.
The formula is given by:
Where:
- Pk is the gain of the k-th forward path.
- Δ is the graph determinant, calculated as 1 - (sum of individual loop gains) + (sum of gain products of all possible combinations of two non-touching loops) - (sum of gain products of all possible combinations of three non-touching loops) + ...
- Δk is the cofactor of the k-th forward path, which is the value of Δ for the part of the graph that does not touch the k-th forward path.
What are the time domain specifications?
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What are the demerits of static error coefficient method?
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What is the concept of stability?
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States the Routh’s stability criterion?
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States the Nyquist stability criterion.
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What is meant by Compensation in control systems?
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States the properties of STM.
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What are the merits of state variable technique?
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Part B
What do you mean by a block diagram? What is meant by summing point and takeoff point? List the merits of block diagram representation.
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Determine the transfer function of the system given in below figure 1.
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Compare the open loop and closed loop control systems
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Using block diagram reduction technique find the transfer function for the system shown in below figure 2.
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Derive the expression for response of second order system with unit step input.
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For a negative feedback control system G(s) = 8/(s(s+0.2)) and H(s) = 3/(s+2). Using generalized error series determine the steady state error of the system when the input applied is r(t) = 1+2t+5t^2.
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What is meant by step input, ramp input and impulse input? How do you represent them graphically?
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A unity feedback control system has an open loop transfer function G(s) = 7/(s(s+2)). Determine the time domain specifications for a step input of 10 units.
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Describe the effects of adding poles and zeros to G(s)H(s) on the root loci with necessary diagrams.
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Determine the stability of a closed loop control system whose characteristic equation is s^5+s^4+6s^3+6s^2+9s+9=0.
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For a unity feedback system, the open loop transfer function is G(s) = k / (s(s+1)(s^2+4s+13)). Sketch the root locus and find the value of k to maintain the stability.
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Sketch the bode plot and determine the gain cross over frequency, phase cross over frequency, gain margin and phase margin for the transfer function G(s) = 8 / ((s+3)(s+5)).
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A unit feedback system has an open loop transfer function G(s) = k / (s(s+4)(s+2)). Design a phase lag compensator to meet the specifications, velocity error constant = 7 and phase margin >= 35 deg.
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Write the general procedure to determine the state space models of a control system.
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Check the controllability and observability of the given system state matrices.
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The state variable formulation of a system is given by matrix equations. Determine the following: a) Transfer function of the system, b) State transaction matrix, c) State equation for a unit step input under zero initial condition.
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